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    Descriptive info: Lab Publications.. Monday, 11 July 2011 10:23.. PisaVisionLab.. Lab Publications.. 2013.. -.. 2012.. 2011.. 2010.. 2009.. 2008.. 2007.. 2006.. back to top.. Scocchia, L.. , Cicchini, G.. M.. & Triesch, J.. (2013).. What's "up"? Working memory contents can bias orientation processing, Vision Res, (76), 46-55.. We explored the interaction between the processing of a low-level visual feature such as orientation and the contents of working memory (WM).. In a first experiment, participants memorized the orientation of a Gabor patch and performed two subsequent orientation discriminations during the retention interval.. The WM stimulus exerted a consistent repulsive effect on the discrimination judgments: participants were more likely to report that the discrimination stimulus was rotated clockwise compared to the oblique after being presented with a stimulus that was tilted anti-clockwise from the oblique.. A control condition where participants attended to the Gabor patch but did not memorize it, showed a much reduced effect.. The repulsive effect was stable across the two discriminations in the memory condition, but not in the control condition, where it decayed at the second discrimination.. In a second experiment, we showed that the greater interference observed in the WM condition cannot be explained by a difference in cognitive demands between the WM and the control condition.. We conclude that WM contents can bias perception: the effect of WM interference is of a visual nature, can last over delays of several seconds and is not disrupted by the processing of intervening visual stimuli during the retention period.. Cicchini, G.. M.. , Binda, P.. , Burr, D.. C.. & Morrone, M.. Transient spatiotopic integration across saccadic eye movements mediates visual stability,J Neurophysiol, 4 (109), 1117-1125.. Eye movements pose major problems to the visual system, because each new saccade changes the mapping of external objects on the retina.. It is known that stimuli briefly presented around the time of saccades are systematically mislocalized, whereas continuously visible objects are perceived as spatially stable even when they undergo large transsaccadic displacements.. In this study we investigated the relationship between these two phenomena and measured how human subjects perceive the position of pairs of bars briefly displayed around the time of large horizontal saccades.. We show that they interact strongly, with the perisaccadic bar being drawn toward the other, dramatically altering the pattern of perisaccadic mislocalization.. The interaction field extends over a wide range (200 ms and 20 degrees ) and is oriented along the retinotopic trajectory of the saccade-induced motion, suggesting a mechanism that integrates pre- and postsaccadic stimuli at different retinal locations but similar external positions.. We show how transient changes in spatial integration mechanisms, which are consistent with the present psychophysical results and with the properties of "remapping cells" reported in the literature, can create transient craniotopy by merging the distinct retinal images of the pre- and postsaccadic fixations to signal a single stable object.. Binda, P.. , Pereverzeva, M.. & Murray, S.. O.. Attention to bright surfaces enhances the pupillary light reflex,J Neurosci, 5 (33), 2199-2204.. One longstanding question is how early in the visual system attention exerts its influence.. Here we show that an effect of attention can be measured at the earliest possible stage of visual information processing, as a change in the optics of the eye.. We tested human subjects and found that covertly attending to bright surfaces results in an enhanced pupillary light reflex (PLR)-the pupillary constriction that occurs in response to light increments.. The PLR optimizes the optical quality of the retinal image across illumination conditions, increasing sensitivity by modulating retinal illumination, and improving acuity by reducing spherical aberrations.. The attentional modulation of the PLR that we describe constitutes a new mechanism through which vision is affected by attention; we discuss three alternatives for the neural substrates of this effect, including the possibility that attention might act indirectly, via its well established effects in early visual cortex.. Knoll, J.. , Morrone, M.. & Bremmer, F.. Spatio-temporal topography of saccadic overestimation of time,Vision Res, (83C), 56-65.. Rapid eye movements (saccades) induce visual misperceptions.. A number of studies in recent years have investigated the spatio-temporal profiles of effects like saccadic suppression or perisaccadic mislocalization and revealed substantial functional similarities.. Saccade induced chronostasis describes the subjective overestimation of stimulus duration when the stimulus onset falls within a saccade.. In this study we aimed to functionally characterize saccade induced chronostasis in greater detail.. Specifically we tested if chronostasis is influenced by or functionally related to saccadic suppression.. In a first set of experiments, we measured the perceived duration of visual stimuli presented at different spatial positions as a function of presentation time relative to the saccade.. We further compared perceived duration during saccades for isoluminant and luminant stimuli.. Finally, we investigated whether or not saccade induced chronostasis is dependent on the execution of a saccade itself.. We show that chronostasis occurs across the visual field with a clear spatio-temporal tuning.. Furthermore, we report chronostasis during simulated saccades, indicating that spurious retinal motion induced by the saccade is a prime origin of the phenomenon.. Zimmermann, E.. , Fink, G.. R.. & Burr, D.. Spatiotopic neural representations develop slowly across saccades,Curr Biol, 5 (23), R193-194.. One of the long-standing unsolved mysteries of visual neuroscience is how the world remains apparently stable in the face of continuous movements of eyes, head and body.. Many factors seem to contribute to this stability, including rapid updating mechanisms that temporarily remap the visual input to compensate for the impending saccade [1].. However, there is also a growing body of evidence pointing to more long-lasting spatiotopic neural representations, which remain solid in external rather than retinal coordinates [2-6].. In this study, we show that these spatiotopic representations take hundreds of milliseconds to build up robustly.. Lunghi, C.. & Alais, D.. Touch Interacts with Vision during Binocular Rivalry with a Tight Orientation Tuning,PLoS One, 3 (8), e58754.. Multisensory integration is a common feature of the mammalian brain that allows it to deal more efficiently with the ambiguity of sensory input by combining complementary signals from several sensory sources.. Growing evidence suggests that multisensory interactions can occur as early as primary sensory cortices.. Here we present incompatible visual signals (orthogonal gratings) to each eye to create visual competition between monocular inputs in primary visual cortex where binocular combination would normally take place.. The incompatibility prevents binocular fusion and triggers an ambiguous perceptual response in which the two images are perceived one at a time in an irregular alternation.. One key function of multisensory integration is to minimize perceptual ambiguity by exploiting cross-sensory congruence.. We show that a haptic signal matching one of the visual alternatives helps disambiguate visual perception during binocular rivalry by both prolonging the dominance period of the congruent visual stimulus and by shortening its suppression period.. Importantly, this interaction is strictly tuned for orientation, with a mismatch as small as 7.. 5 degrees between visual and haptic orientations sufficient to annul the interaction.. These results indicate important conclusions: first, that vision and touch interact at early levels of visual processing where interocular conflicts are first detected and orientation tunings are narrow, and second, that haptic input can influence visual signals outside of visual awareness, bringing a stimulus made invisible by binocular rivalry suppression back to awareness sooner than would occur without congruent haptic input.. Long-term effects of monocular deprivation revealed with binocular rivalry gratings modulated in luminance and in color,J Vis, 6 (13),.. During development, within a specific temporal window called the critical period, the mammalian visual cortex is highly plastic and literally shaped by visual experience; to what extent this extraordinary plasticity is retained in the adult brain is still a debated issue.. We tested the residual plastic potential of the adult visual cortex for both achromatic and chromatic vision by measuring binocular rivalry in adult humans following 150 minutes of monocular patching.. Paradoxically, monocular deprivation resulted in lengthening of the mean phase duration of both luminance-modulated and equiluminant stimuli for the deprived eye and complementary shortening of nondeprived phase durations, suggesting an initial homeostatic compensation for the lack of information following monocular deprivation.. When equiluminant gratings were tested, the effect was measurable for at least 180 minutes after reexposure to binocular vision, compared with 90 minutes for achromatic gratings.. Our results suggest that chromatic vision shows a high degree of plasticity, retaining the effect for a duration (180 minutes) longer than that of the deprivation period (150 minutes) and twice as long as that found with achromatic gratings.. The results are in line with evidence showing a higher vulnerability of the P pathway to the effects of visual deprivation during development and a slower development of chromatic vision in humans.. Burr, D.. Motion Perception: Human Psychophysics.. In J.. S.. Werner & L.. Chalupa (Eds.. ),.. The New Visual Neuroscience.. : MIT Press.. Turi, M.. The "motion silencing" illusion results from global motion and crowding,J Vis, 5 (13),.. Suchow and Alvarez (2011) recently devised a striking illusion, where objects changing in color, luminance, size, or shape appear to stop changing when they move.. They refer to the illusion as "motion silencing of awareness to visual change.. " Here we present evidence that the illusion results from two perceptual processes: global motion and crowding.. We adapted Suchow and Alvarez's stimulus to three concentric rings of dots, a central ring of "target dots" flanked on either side by similarly moving flanker dots.. Subjects had to identify in which of two presentations the target dots were continuously changing (sinusoidally) in size, as distinct from the other interval in which size was constant.. The results show: (a) Motion silencing depends on target speed, with a threshold around 0.. 2 rotations per second (corresponding to about 10 degrees /s linear motion).. (b) Silencing depends on both target-flanker spacing and eccentricity, with critical spacing about half eccentricity, consistent with Bouma's law.. (c) The critical spacing was independent of stimulus size, again consistent with Bouma's law.. (d) Critical spacing depended strongly on contrast polarity.. All results imply that the "motion silencing" illusion may result from crowding.. Anobile, G.. , Cicchini, G.. (2012).. Linear mapping of numbers onto space requires attention,Cognition, 3 (122), 454-459.. Mapping of number onto space is fundamental to mathematics and measurement.. Previous research suggests that while typical adults with mathematical schooling map numbers veridically onto a linear scale, pre-school children and adults without formal mathematics training, as well as individuals with dyscalculia, show strong compressive, logarithmic-like non-linearities when mapping both symbolic and non-symbolic numbers onto the numberline.. Here we show that the use of the linear scale is dependent on attentional resources.. We asked typical adults to position clouds of dots on a numberline of various lengths.. In agreement with previous research, they did so veridically under normal conditions, but when asked to perform a concurrent attentionally-demanding conjunction task, the mapping followed a compressive, non-linear function.. We model the non-linearity both by the commonly assumed logarithmic transform, and also with a Bayesian model of central tendency.. These results suggest that veridical representation numerosity requires attentional mechanisms.. Pooresmaeili, A.. "Non-retinotopic processing" in Ternus motion displays modeled by spatiotemporal filters,J Vis, 1 (12),.. PDF.. Recently, M.. Boi, H.. Ogmen, J.. Krummenacher, T.. U.. Otto, & M.. H.. Herzog (2009) reported a fascinating visual effect, where the direction of apparent motion was disambiguated by cues along the path of apparent motion, the Ternus-Pikler group motion, even though no actual movement occurs in this stimulus.. They referred to their study as a "litmus test" to distinguish "non-retinotopic" (motion-based) from "retinotopic" (retina-based) image processing.. We adapted the test to one with simple grating stimuli that could be more readily modeled and replicated their psychophysical results quantitatively with this stimulus.. We then modeled our experiments in 3D (x, y, t) Fourier space and demonstrated that the observed perceptual effects are readily accounted for by integration of information within a detector that is oriented in space and time, in a similar way to previous explanations of other motion illusions.. This demonstration brings the study of Boi et al.. into the more general context of perception of moving objects.. , Arrighi, R.. , Cecchetti, L.. , Giusti M.. Optimal Encoding of Interval Timing in Expert Percussionists,.. J Neurosci, 3 (32), 1056-1060.. We measured temporal reproduction in human subjects with various levels of musical expertise: expert drummers, string musicians, and non-musicians.. While duration reproduction of the non-percussionists showed a characteristic central tendency or regression to the mean, drummers responded veridically.. Furthermore, when the stimuli were auditory tones rather than flashes, all subjects responded veridically.. The behavior of all three groups in both modalities is well explained by a Bayesian model that seeks to minimize reproduction errors by incorporating a central tendency prior, a probability density function centered at the mean duration of the sample.. We measured separately temporal precision thresholds with a bisection task; thresholds were twice as low in drummers as in the other two groups.. These estimates of temporal precision, together with an adaptable Bayesian prior, predict well the reproduction results and the central tendency strategy under all conditions and for all subject groups.. These results highlight the efficiency and flexibility of sensorimotor mechanisms estimating temporal duration.. Saccadic compression of symbolic numerical magnitude,PLoS One, 11 (7), e49587.. Stimuli flashed briefly around the time of saccadic eye movements are subject to complex distortions: compression of space and time; underestimate of numerosity.. Here we show that saccadic distortions extend to abstract quantities, affecting the representation of symbolic numerical magnitude.. Subjects consistently underestimated the results of rapidly computed mental additions and subtractions, when the operands were briefly displayed before a saccade.. However, the recognition of the number symbols was unimpaired.. These results are consistent with the hypothesis of a common, abstract metric encoding magnitude along multiple dimensions.. They suggest that a surprising link exists between the preparation of action and the representation of abstract quantities.. Panichi, M.. & Baldassi, S.. Spatiotemporal dynamics of perisaccadic remapping in humans revealed by classification images,J Vis, 4 (12), 11.. Visual motion distorts visual and motor space, J Vis, 2 (12),.. Taubert, J.. , Aagten-Murphy, D.. & Parr, L.. A.. A comparative study of face processing using scrambled faces,Perception, 4 (41), 460-473.. It is a widespread assumption that all primate species process faces in the same way because the species are closely related and they engage in similar social interactions.. However, this approach ignores potentially interesting and informative differences that may exist between species.. This paper describes a comparative study of holistic face processing.. Twelve subjects (six chimpanzees Pan troglodytes and six rhesus monkeys Macaca mulatta) were trained to discriminate whole faces (faces with features in their canonical position) and feature-scrambled faces in two separate conditions.. We found that both species tended to match the global configuration of features over local features, providing strong evidence of global precedence.. In addition, we show that both species were better able to generalize from a learned configuration to an entirely novel configuration when they were first trained to match feature-scrambled faces compared to when they were trained with whole faces.. This result implies that the subjects were able to access local information easier when facial features were presented in a scrambled configuration and is consistent with a holistic processing hypothesis.. Interestingly, these data also suggest that, while holistic processing in chimpanzees is tuned to own-species faces, monkeys have a more general approach towards all faces.. Thus, while these data confirm that both chimpanzees and rhesus monkeys process faces holistically, they also indicate that there are differences between the species that warrant further investigation.. Perception of duration in the parvocellular system, Front Integr Neurosci 6:14.. Both theoretical and experimental evidence suggests that duration perception is mediated preferentially by the color-blind but high temporally sensitive luminance pathway.. In this experiment we tested whether color modulated stimuli and high spatial frequency luminance modulated stimuli, which are known to be relayed mostly by the slow parvocellular system, are able to elicit reliable sense of duration.. We show that ramped color modulated stimuli seem to last less than luminance modulated stimuli matched for visibility.. The effect is large, about 200 ms and is constant at all durations tested (range 500–1100 ms).. However, high spatial frequency luminance stimuli obtain duration matches similar to those of low spatial frequency luminance modulated stimuli.. The results at various levels of contrast and temporal smoothing indicate that equiluminant stimuli have higher contrast thresholds to activate the mechanisms which time visual stimuli.. Overall the results imply that both the magnocellular and the parvocellular systems access reliably the timing mechanisms with a difference only in the way these are engaged.. Spatiotopic perceptual maps in humans: evidence from motion adaptation,Proc Biol Sci, 1740 (279), 3091-3097.. One possibility is that our brain actively constructs a spatiotopic representation of the world, which is anchored in external-or at least head-centred-coordinates.. In this study, we show that the positional motion aftereffect (the change in apparent position after adaptation to motion) is spatially selective in external rather than retinal coordinates, whereas the classic motion aftereffect (the illusion of motion after prolonged inspection of a moving source) is selective in retinotopic coordinates.. The results provide clear evidence for a spatiotopic map in humans: one which can be influenced by image motion.. , Turi, M.. The effects of cross-sensory attentional demand on subitizing and on mapping number onto space,Vision Res,.. Various aspects of numerosity judgments, especially subitizing and the mapping of number onto space, depend strongly on attentional resources.. Here we use a dual-task paradigm to investigate the effects of cross-sensory attentional demands on visual subitizing and spatial mapping.. The results show that subitizing is strongly dependent on attentional resources, far more so than is estimation of higher numerosities.. But unlike many other sensory tasks, visual subitizing is equally affected by concurrent attentionally demanding auditory and tactile tasks as it is by visual tasks, suggesting that subitizing may be amodal.. Mapping number onto space was also strongly affected by attention, but only when the dual-task was in the visual modality.. The non-linearities in numberline mapping under attentional load are well explained by a Bayesian model of central tendency.. Gori, M.. , Tinelli, F.. , Sandini, G.. , Cioni, G.. Impaired visual size-discrimination in children with movement disorders,Neuropsychologia, 8 (50), 1838-1843.. Multisensory integration of spatial information occurs late in childhood, at around eight years (Gori, Del Viva, Sandini, & Burr, 2008).. For younger children, the haptic system dominates size discrimination and vision dominates orientation discrimination: the dominance may reflect sensory calibration, and could have direct consequences on children born with specific sensory disabilities.. Here we measure thresholds for visual discrimination of orientation and size in children with movement disorders of upper limbs.. Visual orientation discrimination was very similar to the age-matched typical children, but visual size discrimination thresholds were far worse, in all eight individuals with early-onset movement disorder.. This surprising and counterintuitive result is readily explained by the cross-sensory calibration hypothesis: when the haptic sense is unavailable for manipulation, it cannot be readily used to estimate size, and hence to calibrate the visual experience of size: visual discrimination is subsequently impaired.. This complements a previous study showing that non-sighted children have reduced acuity for haptic orientation, but not haptic size, discriminations (Gori, Sandini, Martinoli, & Burr, 2010).. Together these studies show that when either vision or haptic manipulation is impaired, the impairment also impacts on complementary sensory systems that are calibrated by that one.. Tomassini, A.. , Gori, M.. Active movement restores veridical event-timing after tactile adaptation,J Neurophysiol, 8 (108), 2092-2100.. Growing evidence suggests that time in the subsecond range is tightly linked to sensory processing.. Event-time can be distorted by sensory adaptation, and many temporal illusions can accompany action execution.. In this study, we show that adaptation to tactile motion causes a strong contraction of the apparent duration of tactile stimuli.. However, when subjects make a voluntary motor act before judging the duration, it annuls the adaptation-induced temporal distortion, reestablishing veridical event-time.. The movement needs to be performed actively by the subject: passive movement of similar magnitude and dynamics has no effect on adaptation, showing that it is the motor commands themselves, rather than reafferent signals from body movement, which reset the adaptation for tactile duration.. No other concomitant perceptual changes were reported (such as apparent speed or enhanced temporal discrimination), ruling out a generalized effect of body movement on somatosensory processing.. We suggest that active movement resets timing mechanisms in preparation for the new scenario that the movement will cause, eliminating inappropriate biases in perceived time.. Our brain seems to utilize the intention-to-move signals to retune its perceptual machinery appropriately, to prepare to extract new temporal information.. Tinelli, T.. , Tosetti, M.. , Morrone M.. Blindsight in children with congenital and acquired cerebral lesions, Cortex (published online 10 August 2012).. It has been shown that unconscious visual function can survive lesions to optical radiations and/or primary visual cortex (V1), a phenomenon termed “blindsight”.. Studies on animal models (cat and monkey) show that the age when the lesion occurs determines the extent of residual visual capacities.. Much less is known about the functional and underlying neuronal repercussions of early cortical damage in humans.. We measured sensitivity to several visual tasks in four children with congenital unilateral brain lesions that severely affected optic radiations, and in another group of three children with similar lesions, acquired in childhood.. In two of the congenital patients, we measured blood oxygenation level dependent (BOLD) activity in response to stimulation of each visual field quadrants.. Results show clear evidence of residual unconscious processing of position, orientation and motion of visual stimuli displayed in the scotoma of congenitally lesioned children, but not in the children with acquired lesions.. The calcarine cortical BOLD responses were abnormally elicited by stimulation of the ipsilateral visual field and in the scotoma region, demonstrating a profound neuronal reorganization.. In conclusion, our data suggest that congenital lesions can trigger massive reorganization of the visual system to alleviate functional effects of early brain insults.. Manning, C.. & Pellicano, E.. The development of speed discrimination abilities,Vision Res, (70), 27-33.. The processing of speed is a critical part of a child's visual development, allowing children to track and interact with moving objects.. Despite such importance, no study has investigated the developmental trajectory of speed discrimination abilities or precisely when these abilities become adult-like.. Here, we measured speed discrimination thresholds in 5-, 7-, 9-, 11-year-olds and adults using random dot stimuli with two different reference speeds (slow: 1.. 5 deg/s; fast: 6 deg/s).. Sensitivity for both reference speeds improved exponentially with age and, at all ages, participants were more sensitive to the faster reference speed.. However, sensitivity to slow speeds followed a more protracted developmental trajectory than that for faster speeds.. Furthermore, sensitivity to the faster reference speed reached adult-like levels by 11 years, whereas sensitivity to the slower reference speed was not yet adult-like by this age.. Different developmental trajectories may reflect distinct systems for processing fast and slow speeds.. The reasonably late development of speed processing abilities may be due to inherent limits in the integration of neuronal responses in motion-sensitive areas in early childhood.. Morrone, M.. Plasticità ed adattabilità della visione,Giornale Italiano di Psicologia, (3), 517-522.. (2011).. Spatiotopic selectivity of adaptation-based compression of event duration, J Vis, 2 (11), 21; author reply 21a.. Bruno, I.. Ayhan, and A.. Johnston (2010) have recently challenged our report of spatiotopic selectivity for adaptation of event time (D.. Burr, A.. Tozzi, & M.. Morrone, 2007) and also our claim that retinotopic adaptation of event time depends on perceived speed.. To assist the reader judge this issue, we present here a mass of data accumulated in our laboratories over the last few years, all confirming our original conclusions.. We also point out that where Bruno et al.. made experimental measurements (rather than relying on theoretical reasoning), they too find clearly significant spatiotopically tuned adaptation-based compression of event time but of lower magnitude to ours.. We speculate on the reasons for the differences in magnitude.. Pascucci, D.. , Megna, N.. , Panichi, M.. Acoustic cues to visual detection: a classification image study,J Vis, 6 (11),.. A non-informative sound is known to improve contrast detection thresholds for a synchronous visual target (M.. Lippert, N.. K.. Logothetis, & C.. Kayser, 2007).. We investigated the spatio-temporal characteristics of the mechanisms underlying this crossmodal effect by using a classification image paradigm specifically suited to investigate perceptual templates across both space and time (P.. Neri & D.. J.. Heeger, 2002).. A bright bar was embedded in 2D (space-time) dynamic noise and observers were asked to detect its presence in both unimodal (only visual) and bimodal (audio-visual) conditions.. Classification image analysis was performed and the 1st and 2nd order kernels were derived.. Our results show that the cross-modal facilitation of detection consists in a reduction of activity of the early mechanisms elicited by the onset of the stimulation and not directly involved in the identification of the target.. In fact, the sound sharpens the 2nd order kernels (involved in target detection) by suppressing the activation preceding the target, whereas it does not influence the 1st order kernels.. These data suggest that the sound affects some non-linear process involved with the detection of a visual stimulus by, decreasing the activity of contrast energy filters temporally uncorrelated with the target, hence reducing temporal uncertainty.. , Anobile, G.. & Turi, M.. Adaptation Affects Both High and Low (Subitized) Numbers Under Conditions of High Attentional Load,Seeing and Perceiving, (24), 141-150.. It has recently been reported that, like most sensory systems, numerosity is subject to adaptation.. However, the effect seemed to be limited to numerosity estimation outside the subitizing range.. In this study we show that low numbers, clearly in the subitizing range, are adaptable under conditions of high attentional load.. These results support the idea that numerosity is detected by a perceptual mechanism that operates over the entire range of numbers, supplemented by an attention-based system for small numbers (subitizing).. Thompson, P.. & Mikellidou, K.. Applying the Helmholtz illusion to fashion: horizontal stripes won't make you look fatter,Iperception, 1 (2), 69-76.. A square composed of horizontal lines appears taller and narrower than an identical square made up of vertical lines.. Reporting this illusion, Hermann von Helmholtz noted that such illusions, in which filled space seems to be larger than unfilled space, were common in everyday life, adding the observation that ladies' frocks with horizontal stripes make the figure look taller.. As this assertion runs counter to modern popular belief, we have investigated whether vertical or horizontal stripes on clothing should make the wearer appear taller or fatter.. We find that a rectangle of vertical stripes needs to be extended by 7.. 1% vertically to match the height of a square of horizontal stripes and that a rectangle of horizontal stripes must be made 4.. 5% wider than a square of vertical stripes to match its perceived width.. This illusion holds when the horizontal or vertical lines are on the dress of a line drawing of a woman.. We have examined the claim that these effects apply only for 2-dimensional figures in an experiment with 3-D cylinders and find no support for the notion that horizontal lines would be 'fattening' on clothes.. Significantly, the illusion persists when the horizontal or vertical lines are on pictures of a real half-body mannequin viewed stereoscopically.. All the evidence supports Helmholtz's original assertion.. Lunghi C, Burr DC, Morrone C.. Brief periods of monocular deprivation disrupt ocular balance in human adult visual cortex, Curr Biol.. 2011 Jul 26;21(14):R538-9.. Neuroplasticity is a fundamental property of the developing mammalian visual system, with residual potential in adult human cortex [1].. A short period of abnormal visual experience (such as occlusion of one eye) before closure of the critical period has dramatic and permanent neural consequences, reshaping visual cortical organization in favour of the non-deprived eye [2,3].. We used binocular rivalry [4] - a sensitive probe of neural competition - to demonstrate that adult human visual cortex retains a surprisingly high degree of neural plasticity, with important perceptual consequences.. We report that 150 minutes of monocular deprivation strongly affects the dynamics of binocular rivalry, unexpectedly causing the deprived eye to prevail in conscious perception twice as much as the non-deprived eye, with significant effects for up to 90 minutes.. Apparent contrast of stimuli presented to the deprived eye was also increased, suggesting that the deprivation acts by up-regulation of cortical gain-control mechanisms of the deprived eye.. The results suggest that adult visual cortex retains a good deal of plasticity that could be important in reaction to sensory loss.. , Mazzilli, G.. Cross-Sensory Facilitation Reveals Neural Interactions between Visual and Tactile Motion in Humans,Front Psychol, (2), 55.. Many recent studies show that the human brain integrates information across the different senses and that stimuli of one sensory modality can enhance the perception of other modalities.. Here we study the processes that mediate cross-modal facilitation and summation between visual and tactile motion.. We find that while summation produced a generic, non-specific improvement of thresholds, probably reflecting higher-order interaction of decision signals, facilitation reveals a strong, direction-specific interaction, which we believe reflects sensory interactions.. We measured visual and tactile velocity discrimination thresholds over a wide range of base velocities and conditions.. Thresholds for both visual and tactile stimuli showed the characteristic "dipper function," with the minimum thresholds occurring at a given "pedestal speed.. " When visual and tactile coherent stimuli were combined (summation condition) the thresholds for these multisensory stimuli also showed a "dipper function" with the minimum thresholds occurring in a similar range to that for unisensory signals.. However, the improvement of multisensory thresholds was weak and not directionally specific, well predicted by the maximum-likelihood estimation model (agreeing with previous research).. A different technique (facilitation) did, however, reveal direction-specific enhancement.. Adding a non-informative "pedestal" motion stimulus in one sensory modality (vision or touch) selectively lowered thresholds in the other, by the same amount as pedestals in the same modality.. Facilitation did not occur for neutral stimuli like sounds (that would also have reduced temporal uncertainty), nor for motion in opposite direction, even in blocked trials where the subjects knew that the motion was in the opposite direction showing that the facilitation was not under subject control.. Cross-sensory facilitation is strong evidence for functionally relevant cross-sensory integration at early levels of sensory processing.. & Lappe, M.. Eye position effects in oculomotor plasticity and visual localization,J Neurosci, 20 (31), 7341-7348.. For visual localization to remain accurate across changes of gaze, a signal representing the position of the eye in the orbita is needed to code spatial locations in a reference frame that is independent of retinal displacements.. Here we report evidence that the localization of visual objects in space is coded in an extraretinal reference frame.. In human subjects, we used outward saccadic adaptation, which can be induced artificially by a systematic displacement of the saccade target.. This form of oculomotor plasticity is accompanied by changes in spatial perception, thus highlighting the relevance of saccade metrics for visual localization.. We tested the reference frame of outward adaptation for reactive and scanning saccades and visual localization.. For scanning saccades, adaptation magnitude was drastically reduced at positions distant from the adapted eye position.. Changes in visual localization showed a very similar modulation of eye position.. These results suggest that scanning saccade adaptation is encoded in a nonretinotopic reference frame.. Eye position effects for reactive saccade adaptation were smaller, and the induced mislocalization did not vary significantly between eye positions.. The different modulation of reactive and scanning saccade adaptation supports the idea that oculomotor plasticity can occur at multiple sites in the brain.. The findings are also consistent with previous evidence for a stronger influence of scanning saccade adaptation on the visual localization of objects in space.. Tinelli, F.. , Guzzetta, A.. , Bertini, C.. , Ricci, D.. , Mercuri, E.. , Ladavas, E.. , et al.. Greater Sparing of Visual Search Abilities in Children After Congenital Rather Than Acquired Focal Brain Damage,Neurorehabil Neural Repair,.. BACKGROUND: Visual search refers to the capacity of an individual to find a target among simultaneously presented distracters and is based on visual abilities such as a fast visual processing and an accurate control of ballistic eye movements (saccades) that guide the fovea to the target location.. OBJECTIVE: In adults, visual field defects caused by brain damage are often associated with visual search disorders; in children, little is known about the effects of early brain lesions on visual search abilities.. METHODS: To test the presence of visual search defects and to investigate the role of cortical plasticity after early brain lesions, 29 children with congenital or acquired cerebral lesions, with and without visual field defects, underwent a visual search test battery.. RESULTS: The children with acquired lesions and visual field defects had longer reaction times (RTs) in the contralesional visual field compared with the ipsilesional, whereas those with congenital lesions and visual field defects did not have differences in RTs between the contralateral and ipsilateral visual fields and had a visual search pattern similar to children without a visual field defect.. CONCLUSIONS: These findings support the hypothesis of more effective mechanisms of functional compensation and reorganization of the visual system in children with very early brain lesions, as opposed to those with later damage.. & Thompson, P.. Motion psychophysics: 1985-2010,Vision Res,.. This review traces progress made in the field of visual motion research from 1985 through to 2010.. While it is certainly not exhaustive, it attempts to cover most of the major achievements during that period, and speculate on where the field is heading.. Baldassi, S.. & Simoncini, C.. Reward sharpens orientation coding independently of attention,Front Neurosci, (5), 13.. It has long been known that rewarding improves performance.. However it is unclear whether this is due to high level modulations in the output modules of associated neural systems or due to low level mechanisms favoring more "generous" inputs? Some recent studies suggest that primary sensory areas, including V1 and A1, may form part of the circuitry of reward-based modulations, but there is no data indicating whether reward can be dissociated from attention or cross-trial forms of perceptual learning.. Here we address this issue with a psychophysical dual task, to control attention, while perceptual performance on oriented targets associated with different levels of reward is assessed by measuring both orientation discrimination thresholds and behavioral tuning functions for tilt values near threshold.. We found that reward, at any rate, improved performance.. However, higher reward rates showed an improvement of orientation discrimination thresholds by about 50% across conditions and sharpened behavioral tuning functions.. Data were unaffected by changing the attentional load and by dissociating the feature of the reward cue from the task-relevant feature.. These results suggest that reward may act within the span of a single trial independently of attention by modulating the activity of early sensory stages through a improvement of the signal-to-noise ratio of task-relevant channels.. Spatiotemporal profile of peri-saccadic contrast sensitivity,J Vis, 14 (11),.. Sensitivity to luminance contrast is reduced just before and during saccades (saccadic suppression), whereas sensitivity to color contrast is unimpaired peri-saccadically and enhanced post-saccadically.. The exact spatiotemporal map of these perceptual effects is as yet unknown.. Here, we measured detection thresholds for briefly flashed Gaussian blobs modulated in either luminance or chromatic contrast, displayed at a range of eccentricities.. Sensitivity to luminance contrast was reduced peri-saccadically by a scaling factor, which was almost constant across retinal space.. Saccadic suppression followed a similar time course across all tested eccentricities and was maximal shortly after the saccade onset.. Sensitivity to chromatic contrast was enhanced post-saccadically at all tested locations.. The enhancement was not specifically linked to the execution of saccades, as it was also observed following a displacement of retinal images comparable to that caused by a saccade.. We conclude that luminance and chromatic contrast sensitivities are subject to distinct modulations at the time of saccades, resulting from independent neural processes.. Spatiotopic coding and remapping in humans,Philos Trans R Soc Lond B Biol Sci, 1564 (366), 504-515.. How our perceptual experience of the world remains stable and continuous in the face of continuous rapid eye movements still remains a mystery.. This review discusses some recent progress towards understanding the neural and psychophysical processes that accompany these eye movements.. We firstly report recent evidence from imaging studies in humans showing that many brain regions are tuned in spatiotopic coordinates, but only for items that are actively attended.. We then describe a series of experiments measuring the spatial and temporal phenomena that occur around the time of saccades, and discuss how these could be related to visual stability.. Finally, we introduce the concept of the spatio-temporal receptive field to describe the local spatiotopicity exhibited by many neurons when the eyes move.. Crespi, S.. , Biagi, L.. , d'Avossa, G.. Spatiotopic Coding of BOLD Signal in Human Visual Cortex Depends on Spatial Attention,PLoS One, 7 (6), e21661.. The neural substrate of the phenomenological experience of a stable visual world remains obscure.. One possible mechanism would be to construct spatiotopic neural maps where the response is selective to the position of the stimulus in external space, rather than to retinal eccentricities, but evidence for these maps has been inconsistent.. Here we show, with fMRI, that when human subjects perform concomitantly a demanding attentive task on stimuli displayed at the fovea, BOLD responses evoked by moving stimuli irrelevant to the task were mostly tuned in retinotopic coordinates.. However, under more unconstrained conditions, where subjects could attend easily to the motion stimuli, BOLD responses were tuned not in retinal but in external coordinates (spatiotopic selectivity) in many visual areas, including MT, MST, LO and V6, agreeing with our previous fMRI study.. These results indicate that spatial attention may play an important role in mediating spatiotopic selectivity.. , Apthorp, D.. The role of holistic processing in face perception: evidence from the face inversion effect,Vision Res, 11 (51), 1273-1278.. A large body of research supports the hypothesis that the human visual system does not process a  ...   consequence of the transient remapping mechanisms that affect visual neurons perisaccadically.. We measured perisaccadic spatial and temporal distortions simultaneously by asking subjects to report both the perceived spatial location of a perisaccadic vertical bar (relative to a remembered ruler), and its perceived timing (relative to two sounds straddling the bar).. During fixation and well before or after saccades, bars were localized veridically in space and in time.. In different epochs of the perisaccadic interval, temporal perception was subject to different biases.. At about the time of the saccadic onset, bars were temporally mislocalized 50-100 ms later than their actual presentation and spatially mislocalized toward the saccadic target.. Importantly, the magnitude of the temporal distortions co-varied with the spatial localization bias and the two phenomena had similar dynamics.. Within a brief period about 50 ms before saccadic onset, stimuli were perceived with shorter latencies than at other delays relative to saccadic onset, suggesting that the perceived passage of time transiently inverted its direction.. Based on this result we could predict the inversion of perceived temporal order for two briefly flashed visual stimuli.. We developed a model that simulates the perisaccadic transient change of neuronal receptive fields predicting well the reported temporal distortions.. The key aspects of the model are the dynamics of the "remapped" activity and the use of decoder operators that are optimal during fixation, but are not updated perisaccadically.. , Silva, O.. Temporal mechanisms of multimodal binding,Proc Biol Sci, 1663 (276), 1761-1769.. The simultaneity of signals from different senses-such as vision and audition-is a useful cue for determining whether those signals arose from one environmental source or from more than one.. To understand better the sensory mechanisms for assessing simultaneity, we measured the discrimination thresholds for time intervals marked by auditory, visual or auditory-visual stimuli, as a function of the base interval.. For all conditions, both unimodal and cross-modal, the thresholds followed a characteristic 'dipper function' in which the lowest thresholds occurred when discriminating against a non-zero interval.. The base interval yielding the lowest threshold was roughly equal to the threshold for discriminating asynchronous from synchronous presentations.. Those lowest thresholds occurred at approximately 5, 15 and 75 ms for auditory, visual and auditory-visual stimuli, respectively.. Thus, the mechanisms mediating performance with cross-modal stimuli are considerably slower than the mechanisms mediating performance within a particular sense.. We developed a simple model with temporal filters of different time constants and showed that the model produces discrimination functions similar to the ones we observed in humans.. Both for processing within a single sense, and for processing across senses, temporal perception is affected by the properties of temporal filters, the outputs of which are used to estimate time offsets, correlations between signals, and more.. Visual aftereffects,Curr Biol, 1 (19), R11-14.. & Ross, J.. (2008).. A visual sense of number,Curr Biol, 6 (18), 425-428.. Evidence exists for a nonverbal capacity for the apprehension of number, in humans [1] (including infants [2, 3]) and in other primates [4-6].. Here, we show that perceived numerosity is susceptible to adaptation, like primary visual properties of a scene, such as color, contrast, size, and speed.. Apparent numerosity was decreased by adaptation to large numbers of dots and increased by adaptation to small numbers, the effect depending entirely on the numerosity of the adaptor, not on contrast, size, orientation, or pixel density, and occurring with very low adaptor contrasts.. We suggest that the visual system has the capacity to estimate numerosity and that it is an independent primary visual property, not reducible to others like spatial frequency or density of texture [7].. Del Viva, M.. & Gori, M.. Anti-Glass patterns and real motion perception: same or different mechanisms?,J Vis, 2 (8), 1 1-15.. A sequence of anti-Glass patterns, composed by dot pairs with opposite luminance polarity, elicits a clear perception of motion in the direction of the white dot of the pair.. This effect can be reversed by introducing a delay in the presentation of white dots, suggesting a faster processing of light dots as a cause of the motion signal (M.. Gori, & D.. Burr, 2006).. If this hypothesis is correct, anti-Glass patterns should interact with real motion signals.. In this study, we compare the motion induced by these stimuli to test whether they are analyzed by the same motion mechanism.. We found that motion induced by anti-Glass patterns annuls real motion, when they are presented simultaneously in the same display and moving in opposite directions.. By lowering the contrast of one of them, motion toward the stimulus with higher contrast prevails.. We also found sub-threshold summation of motion induced by anti-Glass patterns and real motion, when presented simultaneously and moving in the same direction.. These findings indicate that anti-Glass patterns and moving stimuli are processed by the same, contrast-dependent motion mechanism and lend further support to the proposed explanation of the effect.. Perna, A.. , Montanaro, D.. BOLD response to spatial phase congruency in human brain,J Vis, 10 (8), 15 11-15.. Human psychophysical observations, computational models, and the selectivity of neurons in primary visual cortex all suggest that an early step in visual processing is the detection of features such as lines and edges.. However, previous fMRI experiments investigating the responses of early visual areas to phase coherence have led to apparently discordant results.. We studied the human brain BOLD responses to structured periodic band-pass images of matched amplitude spectrum but of different phase spectra, arranged to create three distinct types of stimuli: pure edges; pure lines (matched global and local energy to the edges, but different phase); and random noise (random phase spectrum, hence no salient features, and a different spatial distribution of local energy from the lines and edges stimuli).. Alternation of lines against edges did not activate primary visual cortex, but did activate two higher order visual areas.. Alternation of these lines or edges against the random stimulus produced a strong activity in many visual areas, including primary visual cortex.. Interestingly, the BOLD activity was higher for the edges and lines than for the random stimuli for a wide range of stimulus contrasts, indicating the presence of non-linear gain modulation in the cell response.. These results show that phase congruency is coded at the level of primary visual cortex.. We show that a stage of response gain modulation can explain our present and previous fMRI discordant results.. , Valsecchi, M.. & De'Sperati, C.. Head movements modulate visual responsiveness in the absence of gaze shifts,Neuroreport, 8 (19), 831-834.. Visuospatial attention is strongly associated with saccades.. Given that gaze shifts are often accomplished by combined eye-head movements, attention may also be coupled to head movements.. We showed that simply turning the head without shifting the gaze is sufficient to cause a transient unbalance in responding to a visual stimulus.. Manual responses to a stimulus flashed shortly before the onset of a horizontal head movement were faster in congruent trials, when the head moved towards the stimulus, than in incongruent trials, when the head moved away from the stimulus.. These effects are similar to those observed for saccades.. We take this as evidence for a tight link between visuospatial attention and head movements, even when the gaze does not shift.. Inversion of perceived direction of motion caused by spatial undersampling in two children with periventricular leukomalacia,J Cogn Neurosci, 6 (20), 1094-1106.. We report here two cases of two young diplegic patients with cystic periventricular leukomalacia who systematically, and with high sensitivity, perceive translational motion of a random-dot display in the opposite direction.. The apparent inversion was specific for translation motion: Rotation and expansion motion were perceived correctly, with normal sensitivity.. It was also specific for random-dot patterns, not occurring with gratings.. For the one patient that we were able to test extensively, contrast sensitivity for static stimuli was normal, but was very low for direction discrimination at high spatial frequencies and all temporal frequencies.. His optokinetic nystagmus movements were normal but he was unable to track a single translating target, indicating a perceptual origin of the tracking deficit.. The severe deficit for motion perception was also evident in the seminatural situation of a driving simulation video game.. The perceptual deficit for translational motion was reinforced by functional magnetic resonance imaging studies.. Translational motion elicited no response in the MT complex, although it did produce a strong response in many visual areas when contrasted with blank stimuli.. However, radial and rotational motion produced a normal pattern of activation in a subregion of the MT complex.. These data reinforce the existent evidence for independent cortical processing for translational, and circular or radial flow motion, and further suggest that the two systems have different vulnerability and plasticity to prenatal damage.. They also highlight the complexity of visual motion perception, and how the delicate balance of neural activity can lead to paradoxical effects such as consistent misperception of the direction of motion.. We advance a possible explanation of a reduced spatial sampling of the motion stimuli and report a simple model that simulates well the experimental results.. Guzzetta, F.. , Fazzi, E.. , Biagioni, E.. , Veggiotti, P.. Neurodevelopmental evolution of West syndrome: a 2-year prospective study,Eur J Paediatr Neurol, 5 (12), 387-397.. OBJECTIVE: The aim of this study was to evaluate the epileptic and developmental evolution in infants with West syndrome.. METHODS: A prospective study of 21 infants was performed, with a follow-up at 2 years.. Serial assessment included long-term EEG monitoring, visual and auditory evaluation and assessment of neurodevelopment.. RESULTS: Neurosensory and developmental impairments at the spasm onset were transitory in seven cases, including four cryptogenic forms.. In all other cases, there was a progressive worsening in neurosensory and developmental impairments.. The epileptic evolution was generally better: in 11 of the 16 infants without seizures at outcome, spasms had already disappeared by 2 months after disease onset.. Statistic analysis of results showed a correlation between neurosensory impairment and development throughout the whole follow-up.. In addition, visual function at T1 resulted significant predictor of developmental outcome.. Among the epileptic features, disorganization of slow sleep was an unfavorable prognostic factor.. CONCLUSION: Some forms of West syndrome are confirmed to have a benign evolution: among them there are not only cryptogenic cases but also symptomatic ones without significant neurodevelopmental impairment.. Abnormalities of sleep organization, expression of the pervasive epileptic disorder, seem to play a role in determining a developmental deterioration.. Neurosensory impairment since the onset of the disease could be a relevant cause of the developmental disorder.. Gheri, C.. Non-linear integration of crowded orientation signals,Vision Res, 22 (48), 2352-2358.. Crowding of oriented signals has been explained as linear, compulsory averaging of the signals from target and flankers [Parkes, L.. , Lund, J.. , Angelucci, A.. , Solomon, J.. , & Morgan, M.. (2001).. Compulsory averaging of crowded orientation signals in human vision.. Nature Neuroscience, 4(7), 739-744].. On the other hand, a comparable search task with sparse stimuli is well modeled by a 'Signed-Max' rule that integrates non-linearly local tilt estimates [Baldassi, S.. , & Verghese, P.. (2002).. Comparing integration rules in visual search.. Journal of Vision, 2(8), 559-570], as reflected by the bimodality of the distributions of reported tilts in a magnitude matching task [Baldassi, S.. , & Burr, D.. (2006).. Visual clutter causes high-magnitude errors.. PLoS Biology, 4(3), e56].. This study compares the two models in the context of crowding by using a magnitude matching task, to measure distributions of perceived target angles and a localization task, to probe the degree of access to local information.. Response distributions were bimodal, implying uncertainty, only in the presence of abutting flankers.. Localization of the target is relatively preserved but it quantitatively falls in between the predictions of the two models, possibly suggesting local averaging followed by a max operation.. This challenges the notion of global averaging and suggests some conscious access to local orientation estimates.. , Mazzotti, S.. The assessment of visual acuity in children with periventricular damage: a comparison of behavioural and electrophysiological techniques,Vision Res, 10 (48), 1233-1241.. It has been controversial whether electrophysiology offers better precision than behavioural techniques in measuring visual acuity in children with brain damage.. We investigated the concordance between sweep VEPs and Acuity Cards (AC) in 29 children with periventricular leukomalacia (PVL), the most common type of brain damage in preterm infants.. An overall good correlation was shown but with relatively better behavioural acuity values.. VEP/AC ratio was significantly correlated to corpus callosum posterior thinning.. We propose that this result reflects the efficacy of the compensatory mechanisms following early brain damage which may differentially affect the two methods.. The knowing visual self,Trends Cogn Sci, 10 (12), 363-364.. Like all information-processing systems, biological visual systems are limited by internal and external noise; but this noise never actually impinges on our conscious perception.. An article recently published in the Journal of Vision suggests that, at least for orientation judgments, the visual system has access to its own noisiness and sets thresholds accordingly.. This could well be a general principle in perception, with important and wide ranging consequences.. Young children do not integrate visual and haptic form information,Curr Biol, 9 (18), 694-698.. Several studies have shown that adults integrate visual and haptic information (and information from other modalities) in a statistically optimal fashion, weighting each sense according to its reliability [1, 2].. When does this capacity for crossmodal integration develop? Here, we show that prior to 8 years of age, integration of visual and haptic spatial information is far from optimal, with either vision or touch dominating totally, even in conditions in which the dominant sense is far less precise than the other (assessed by discrimination thresholds).. For size discrimination, haptic information dominates in determining both perceived size and discrimination thresholds, whereas for orientation discrimination, vision dominates.. By 8-10 years, the integration becomes statistically optimal, like adults.. We suggest that during development, perceptual systems require constant recalibration, for which cross-sensory comparison is important.. Using one sense to calibrate the other precludes useful combination of the two sources.. Pellicano, E.. , Jeffery, L.. & Rhodes, G.. (2007).. Abnormal adaptive face-coding mechanisms in children with autism spectrum disorder,Curr Biol, 17 (17), 1508-1512.. In low-level vision, exquisite sensitivity to variation in luminance is achieved by adaptive mechanisms that adjust neural sensitivity to the prevailing luminance level.. In high-level vision, adaptive mechanisms contribute to our remarkable ability to distinguish thousands of similar faces [1].. A clear example of this sort of adaptive coding is the face-identity aftereffect [2, 3, 4, 5], in which adaptation to a particular face biases perception toward the opposite identity.. Here we investigated face adaptation in children with autism spectrum disorder (ASD) by asking them to discriminate between two face identities, with and without prior adaptation to opposite-identity faces.. The ASD group discriminated the identities with the same precision as did the age- and ability-matched control group, showing that face identification per se was unimpaired.. However, children with ASD showed significantly less adaptation than did their typical peers, with the amount of adaptation correlating significantly with current symptomatology, and face aftereffects of children with elevated symptoms only one third those of controls.. These results show that although children with ASD can learn a simple discrimination between two identities, adaptive face-coding mechanisms are severely compromised, offering a new explanation for previously reported face-perception difficulties [6, 7, 8] and possibly for some of the core social deficits in ASD [9, 10].. , Bruno, A.. Fusion of visual and auditory stimuli during saccades: a Bayesian explanation for perisaccadic distortions,J Neurosci, 32 (27), 8525-8532.. Brief stimuli presented near the onset of saccades are grossly mislocalized in space.. In this study, we investigated whether the Bayesian hypothesis of optimal sensory fusion could account for the mislocalization.. We required subjects to localize visual, auditory, and audiovisual stimuli at the time of saccades (compared with an earlier presented target).. During fixation, vision dominates and spatially "captures" the auditory stimulus (the ventriloquist effect).. But for perisaccadic presentations, auditory localization becomes more important, so the mislocalized visual stimulus is seen closer to its veridical position.. The precision of the bimodal localization (as measured by localization thresholds or just-noticeable difference) was better than either the visual or acoustic stimulus presented in isolation.. Both the perceived position of the bimodal stimuli and the improved precision were well predicted by assuming statistically optimal Bayesian-like combination of visual and auditory signals.. Furthermore, the time course of localization was well predicted by the Bayesian approach.. We present a detailed model that simulates the time-course data, assuming that perceived position is given by the sum of retinal position and a sluggish noisy eye-position signal, obtained by integrating optimally the output of two populations of neural activity: one centered at the current point of gaze, the other centered at the future point of gaze.. Bruno, A.. Influence of saccadic adaptation on spatial localization: comparison of verbal and pointing reports,J Vis, 5 (7), 16 11-13.. Under conditions of short-term saccadic adaptation, stimuli presented long before saccadic onset are perceptually mislocalized in space.. Here we study whether saccadic adaptation can also affect localization of objects by pointing.. We measured localization performance during fixation and after normal saccades and adapted saccades, for a bar presented well before a saccadic eye movement, for both pointing and verbal localization, under open-loop conditions generated by a transient dark period about 300 ms after the presentation of the bar.. During fixation and normal saccade, localization performance for verbal report was veridical, while for pointing there was an overestimation of the target eccentricity respect to gaze, in agreement with the idea of separate representations of space for action and perception.. During saccadic adaptation, there was a significant shift of both pointing and verbal report localization in the direction of adaptation with similar spatial selectivity for both tasks.. These results indicate that saccadic adaptation induces a similar re-calibration of the action map as well as of the perceptual map, suggesting a common site of operation in the transformation from eye-centered to gaze-centered coordinates.. Caputo, R.. , Campa, L.. , Frosini, R.. Motor coordination in children with congenital strabismus: effects of late surgery,Eur J Paediatr Neurol, 5 (11), 285-291.. BACKGROUND: Strabismus is one of the most common visual disorders in infancy.. While there is a great attention on the effects of the timing of surgery as to the development of binocular vision, little is known about the possible influence of congenital strabismus on perceptual-motor and more generally, on neuromotor development.. AIMS: Aim of this study was to investigate perceptual-motor and motor coordination abilities of 19 children with essential congenital esotropia who underwent a late surgery (after 4 years), compared to 23 age-matched controls.. METHODS: Children were tested using the Movement Assessment Battery for Children (Movement ABC) that were performed both 1-week before surgery (T1) and about 3 months (+/-2 weeks) after surgery (T2).. RESULTS AND CONCLUSIONS: At T1, abnormal or borderline results were found in more than half of the children with strabismus, as opposed to only about 17% of the controls.. At T2 none of the children showed abnormal Movement ABC total scores and there was no difference in global scores between the study and the control group.. The two groups also did not show any significant difference in individual items of the movement ABC with the exception of those assessing ball skills.. Our results suggest that surgical correction of strabismus, even when performed after the 4th year of life, appears to be effective in improving perceptual-motor and motor function.. , Tozzi, A.. Neural mechanisms for timing visual events are spatially selective in real-world coordinates,Nat Neurosci, 4 (10), 423-425.. It is generally assumed that perceptual events are timed by a centralized supramodal clock.. This study challenges this notion in humans by providing clear evidence that visual events of subsecond duration are timed by visual neural mechanisms with spatially circumscribed receptive fields, localized in real-world, rather than retinal, coordinates.. d'Avossa, G.. , Crespi, S.. Spatiotopic selectivity of BOLD responses to visual motion in human area MT,Nat Neurosci, 2 (10), 249-255.. Many neurons in the monkey visual extrastriate cortex have receptive fields that are affected by gaze direction.. In humans, psychophysical studies suggest that motion signals may be encoded in a spatiotopic fashion.. Here we use functional magnetic resonance imaging to study spatial selectivity in the human middle temporal cortex (area MT or V5), an area that is clearly implicated in motion perception.. The results show that the response of MT is modulated by gaze direction, generating a spatial selectivity based on screen rather than retinal coordinates.. This area could be the neurophysiological substrate of the spatiotopic representation of motion signals.. Ciaramelli, E.. , Leo, F.. & Ladavas, E.. The contribution of prefrontal cortex to global perception,Exp Brain Res, 3 (181), 427-434.. Recent research suggests a role of top-down modulatory signals on perceptual processing, particularly for the integration of local elementary information to form a global holistic percept.. In this study we investigated whether prefrontal cortex may be instrumental in this top-down modulation in humans.. We measured detection thresholds for perceiving a circle defined by a closed chain of grating patches in 6 patients with prefrontal lesions, 4 control patients with temporal lesions and 17 healthy control subjects.. Performance of patients with prefrontal lesions was worse than that of patients with temporal lesions and normal controls when the patterns were sparse, requiring integration across relatively extensive regions of space, but similar to the control groups for denser patterns.. The results clearly implicate the prefrontal cortex in the process of integrating elementary features into a holistic global percept, when the elements do not form a "pop-out" display.. Tozzi, A.. The effect of optokinetic nystagmus on the perceived position of briefly flashed targets,Vision Res, 6 (47), 861-868.. Stimuli flashed briefly around the time of an impending saccade are mislocalized in the direction of the saccade and also compressed towards the saccadic target.. Similarly, targets flashed during pursuit eye movements are mislocalized in the direction of pursuit.. Here, we investigate the effects of optokinetic nystagmus (OKN) on visual localization.. Subjects passively viewed a wide-field drifting grating that elicited strong OKN, comprising the characteristic slow-phase tracking movement interspersed with corrected "saccade-like" fast-phase movements.. Subjects reported the apparent position of salient bars flashed briefly at various positions on the screen.. In general, bars were misperceived in the direction of the slow-phase tracking movement.. Bars flashed around the onset of the fast-phase movements were subject to much less mislocalization, pointing to a competing shift in the direction of the fast-phase, as occurs with saccades.. However, as distinct from saccades, there was no evidence for spatial compression around the time of the corrective fast-phase OKN.. The results suggest that OKN cause perceptual mislocalizations similar to those of smooth pursuit and saccades, but there are some differences in the nature of the mislocalizations, pointing to different perceptual mechanisms associated with the different types of eye movements.. The lowest spatial frequency channel determines brightness perception,Vision Res, 10 (47), 1282-1291.. This study investigates the role played by individual spatial scales in determining the apparent brightness of greyscale patterns.. We measured the perceived difference in brightness across an edge in the presence of notch filtering and high-pass filtering for two stimulus configurations, one that elicits the perception of transparency and one that appears opaque.. For both stimulus configurations, the apparent brightness of the surfaces delimited by the border decreased monotonically with progressive (ideal) high-pass filtering, with a critical cut-off at 1 c/deg.. Using two octave ideal notch filtering, the maximum detrimental effect on apparent brightness was observed at about 1c/deg.. Critical frequencies for apparent brightness did not vary with contrast, viewing distance, or surface size, suggesting that apparent brightness is determined by the channel tuned at 1 c/deg.. Modelling the data with the local energy model [Morrone, M.. (1988).. Feature detection in human vision: a phase dependent energy model.. Proceedings of the Royal Society (London), B235, 221-245] at 1c/deg confirmed the suggestion that this channel mediates apparent brightness for both opaque and transparent borders, with no need for pooling or integration across spatial channels.. Chirimuuta, M.. The role of perceptual learning on modality-specific visual attentional effects,Vision Res, 1 (47), 60-70.. Morrone et al.. [Morrone, M.. , Denti, V.. , & Spinelli, D.. Color and luminance contrasts attract independent attention.. Current Biology, 12, 1134-1137] reported that the detrimental effect on contrast discrimination thresholds of performing a concomitant task is modality specific: performing a secondary luminance task has no effect on colour contrast thresholds, and vice versa.. Here we confirm this result with a novel task involving learning of spatial position, and go on to show that it is not specific to the cardinal colour axes: secondary tasks with red-green stimuli impede performance on a blue-yellow task and vice versa.. We further show that the attentional effect can be abolished with continued training over 2-4 training days (2-20 training sessions), and that the effect of learning is transferable to new target positions.. Given the finding of transference, we discuss the possibility that V4 is a site of plasticity for both stimulus types, and that the separation is due to a luminance-colour separation within this cortical area.. Include here the text of the publication.. A feature-tracking model simulates the motion direction bias induced by phase congruency,J Vis, 3 (6), 179-195.. Here we report a new motion illusion where the prevailing motion direction is strongly influenced by the relative phase of the harmonic components of the stimulus.. The basic stimulus is the sum of three sinusoidal contrast-reversing gratings: the first, the third, and the fifth harmonic of two square wave gratings that drift in opposite direction.. The phase of one of the fifth components was kept constant at 180 deg, whereas the phase of the other fifth harmonic was varied over the range 0-150 deg.. For each phase value of the fifth harmonic, the motion was strongly biased toward its direction, corresponding to the direction with stronger phase congruency between the three harmonics.. The strength of the prevailing motion was assessed by measuring motion direction discrimination thresholds, by varying the contrast of the third and the fifth harmonics plaid pattern.. Results show that the contrast of high harmonics had to be increased by more than a factor of 10, to achieve a balance of motion for phase differences greater than 60 deg between the 2 fifth harmonics.. We also measured the dependence on the absolute phase of harmonic components and found that it is not an important parameter, excluding the possibility that local luminance cues could be mediating the effect.. A feature-tracking model based on previous work is proposed to simulate the data.. The model computes local energy function from a pair of space-time separable front stage filters and applies a battery of directional second stage mechanisms.. It is able to simulate quantitatively the phase congruency dependence illusion and the insensitivity to overall phase.. Other energy models based on directional filters fail to simulate the phase congruency dependency effect.. Baranello, G.. , Rando, T.. , D'Acunto, M.. G.. , Epifanio, R.. , Frisone, M.. F.. Auditory attention at the onset of West syndrome: correlation with EEG patterns and visual function,Brain Dev, 5 (28), 293-299.. At the onset of West syndrome a specific impairment of visual function has been clearly demonstrated, while other aspects of sensorial development, and in particular of the auditory function, have been less studied.. The aim of this study was to evaluate auditory function and orienting responses at the onset of West syndrome, and to relate the results with EEG patterns, visual function and neurodevelopmental competence.. A prospective multicentric study was performed on 25 successively enrolled infants with West syndrome; all the patients underwent a full clinical assessment, including MRI and video-EEG, visual function and auditory orienting responses (AORs) as well as Griffiths' developmental scales.. The whole assessment performed at the onset of spasms (T0) was repeated after two months (T1).. AORs resulted significantly impaired both at T0 and T1.. At the onset of spasms a highly significant relationship of auditory attention with visual function and neurodevelopmental competence was shown in both cryptogenic and symptomatic forms, but it was no longer present after two months.. Our results may suggest a possible pervasive effect of the epileptic disorder on sensory processing, associated to a deficit of neurodevelopment.. Although we failed to show a significant correlation between auditory orienting responses and EEG patterns, some evidence seems to support at least partially an influence of the epileptic disorder per se on the genesis of the sensorial impairment.. A longer follow up and a larger cohort will be useful for a better clarification of these findings.. Combining visual and auditory information,Prog Brain Res, (155), 243-258.. Robust perception requires that information from by our five different senses be combined at some central level to produce a single unified percept of the world.. Recent theory and evidence from many laboratories suggests that the combination does not occur in a rigid, hardwired fashion, but follows flexible situation-dependent rules that allow information to be combined with maximal efficiency.. In this review we discuss recent evidence from our laboratories investigating how information from auditory and visual modalities is combined.. The results support the notion of Bayesian combination.. We also examine temporal alignment of auditory and visual signals, and show that perceived simultaneity does not depend solely on neural latencies, but involves active processes that compensate, for example, for the physical delay introduced by the relatively slow speed of sound.. Finally, we go on to show that although visual and auditory information is combined to maximize efficiency, attentional resources for the two modalities are largely independent.. Alais, D.. , Lorenceau, J.. & Cass, J.. Contour interactions between pairs of Gabors engaged in binocular rivalry reveal a map of the association field,Vision Res, 8-9 (46), 1473-1487.. A psychophysical study was conducted to investigate contour interactions (the 'association field').. Two Gabor patches were presented to one eye, with random-dot patches in corresponding locations of the other eye so as to produce binocular rivalry.. Perceptual alternations of the two rivalry processes were monitored continuously by observers and the two time series were cross-correlated.. The Gabors were oriented collinearly, obliquely, or orthogonally, and spatial separation was varied.. A parallel condition was also included.. Correlation between the rivalry processes strongly depended on separation and relative orientation.. Correlations between adjacent collinear Gabors was near-perfect and reduced with spatial separation and as relative orientation departed from collinear.. Importantly, variations in cross-correlation did not alter the rivalry processes (average dominance duration, and therefore alternation rate, was constant across conditions).. Instead, synchronisation of rivalry oscillations accounts for the correlation variations: rivalry alternations were highly synchronised when contour interactions were strong and were poorly synchronised when contour interactions were weak.. The level of synchrony between these two stochastic processes, in depending on separation and relative orientation, effectively reveals a map of the association field.. These association fields are not greatly affected by contrast, and can be demonstrated between contours that are presented to separate hemispheres.. , Brambati, S.. , Perani, D.. Development of saccadic suppression in children,J Neurophysiol, 3 (96), 1011-1017.. We measured saccadic suppression in adolescent children and young adults using spatially curtailed low spatial frequency stimuli.. For both groups, sensitivity for color-modulated stimuli was unchanged during saccades.. Sensitivity for luminance-modulated stimuli was greatly reduced during saccades in both groups but far more for adolescents than for young adults.. Adults' suppression was on average a factor of about 3, whereas that for the adolescent group was closer to a factor of 10.. The specificity of the suppression to luminance-modulated stimuli excludes generic explanations such as task difficulty and attention.. We suggest that the enhanced suppression in adolescents results from the immaturity of the ocular-motor system at that age.. & Morrone, C.. Perception: transient disruptions to neural space-time,Curr Biol, 19 (16), R847-849.. How vision operates efficiently in the face of continuous shifts of gaze remains poorly understood.. Recent studies show that saccades cause dramatic, but transient, changes in the spatial and also temporal tuning of cells in many visual areas, which may underly the perceptual compression of space and time, and serve to counteract the effects of the saccades and maintain visual stability.. , Alais, D.. Perceptual synchrony of audiovisual streams for natural and artificial motion sequences,J Vis, 3 (6), 260-268.. We investigated the conditions necessary for perceptual simultaneity of visual and auditory stimuli under natural conditions: video sequences of conga drumming at various rhythms.. Under most conditions, the auditory stream needs to be delayed for sight and sound to be perceived simultaneously.. The size of delay for maximum perceived simultaneity varied inversely with drumming tempo, from about 100 ms at 1 Hz to 30 ms at 4 Hz.. Random drumming motion produced similar results, with higher random tempos requiring less delay.. Video sequences of disk stimuli moving along a motion profile matched to the drummer produced near-identical results.. When the disks oscillated at constant speed rather than following "biological" speed variations, the delays necessary for perceptual synchrony were systematically less.. The results are discussed in terms of real-world constraints for perceptual synchrony and possible neural mechanisms.. , McKee, S.. Resolution for spatial segregation and spatial localization by motion signals,Vision Res, 6-7 (46), 932-939.. We investigated two types of spatial resolution for perceiving motion-defined contours: grating acuity, the capacity to discriminate alternating stripes of opposed motion from transparent bi-directional motion; and alignment acuity, the capacity to localize the position of motion-defined edges with respect to stationary markers.. For both tasks the stimuli were random noise patterns, low-pass filtered in the spatial dimension parallel to the motion.. Both grating and alignment resolution varied systematically with spatial frequency cutoff and speed.. Best performance for grating resolution was about 10 c/deg (for unfiltered patterns moving at 1-4 deg/s), corresponding to a stripe resolution of about 3'.. Grating resolution corresponds well to estimates of smallest receptive field size of motion units under these conditions, suggesting that opposing signals from units with small receptive fields (probably located in V1) are contrasted efficiently to define edges.. Alignment resolution was about 2' at best, under similar conditions.. Whereas alignment judgment based on luminance-defined edges is typically 3-10 times better than resolution, alignment based on motion-defined edges is only 1.. 1-1.. 5 times better, suggesting motion contours are less effectively encoded than luminance contours.. , Morrone, C.. Separate attentional resources for vision and audition,Proc Biol Sci, 1592 (273), 1339-1345.. Current models of attention, typically claim that vision and audition are limited by a common attentional resource which means that visual performance should be adversely affected by a concurrent auditory task and vice versa.. Here, we test this implication by measuring auditory (pitch) and visual (contrast) thresholds in conjunction with cross-modal secondary tasks and find that no such interference occurs.. Visual contrast discrimination thresholds were unaffected by a concurrent chord or pitch discrimination, and pitch-discrimination thresholds were virtually unaffected by a concurrent visual search or contrast discrimination task.. However, if the dual tasks were presented within the same modality, thresholds were raised by a factor of between two (for visual discrimination) and four (for auditory discrimination).. These results suggest that at least for low-level tasks such as discriminations of pitch and contrast, each sensory modality is under separate attentional control, rather than being limited by a supramodal attentional resource.. This has implications for current theories of attention as well as for the use of multi-sensory media for efficient informational transmission.. The effects of opposite-polarity dipoles on the detection of Glass patterns,Vision Res, 6-7 (46), 1139-1144.. Glass patterns--randomly positioned coherently orientated dipoles--create a strong sensation of oriented spatial structure.. On the other hand, coherently oriented dipoles comprising dots of opposite polarity ("anti-Glass" patterns) have no distinct spatial structure and are very hard to distinguish from random noise.. Although anti-Glass patterns have no obvious spatial structure themselves, their presence can destroy the structure created by Glass patterns.. We measured the strength of this effect for both static and dynamic Glass patterns, and showed that anti-Glass patterns can raise thresholds for Glass patterns by a factor of 2-4, increasing with density.. The dependence on density suggests that the interactions occur at a local level.. When the Glass and anti-Glass dipoles were confined to alternate strips (in translational and circular Glass patterns), the detrimental effect occurred for stripe widths less than about 1.. 5 degrees, but had little effect for larger stripe widths, reinforcing the suggestion that the interaction occurred over a limited spatial extent.. The extent of spatial interaction was much less than that for spatial summation of these patterns, at least 30 degrees under matched experimental conditions.. The results suggest two stages of analysis for Glass patterns, an early stage of limited spatial extent where orientation is extracted, and a later stage that sums these orientation signals.. Time perception: space-time in the brain,Curr Biol, 5 (16), R171-173.. Visual clutter causes high-magnitude errors,PLoS Biol, 3 (4), e56.. Perceptual decisions are often made in cluttered environments, where a target may be confounded with competing "distractor" stimuli.. Although many studies and theoretical treatments have highlighted the effect of distractors on performance, it remains unclear how they affect the quality of perceptual decisions.. Here we show that perceptual clutter leads not only to an increase in judgment errors, but also to an increase in perceived signal strength and decision confidence on erroneous trials.. Observers reported simultaneously the direction and magnitude of the tilt of a target grating presented either alone, or together with vertical distractor stimuli.. When presented in isolation, observers perceived isolated targets as only slightly tilted on error trials, and had little confidence in their decision.. When the target was embedded in distractors, however, they perceived it to be strongly tilted on error trials, and had high confidence of their (erroneous) decisions.. The results are well explained by assuming that the observers' internal representation of stimulus orientation arises from a nonlinear combination of the outputs of independent noise-perturbed front-end detectors.. The implication that erroneous perceptual decisions in cluttered environments are made with high confidence has many potential practical consequences, and may be extendable to decision-making in general..

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  • Title: Lab Publications
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  • Title: Risultati Esonero Percezione Attenzione 19 Aprile 2013
    Descriptive info: Message.. You are not authorised to view this resource.. Risultati Esonero Percezione Attenzione 19 Aprile 2013.. Friday, 19 April 2013 21:08.. Risultati Esonero.. Percezione ed Attenzione.. 19 Aprile 2013.. MATRICOLA.. VOTO.. 5072921.. 29.. 5079557.. 17.. 5074618.. 24.. 5074357.. 5080326.. 5082679.. 5082691.. 28.. 5069693.. 5069798.. 5082168.. 27.. 5072804.. 32.. lode.. 4929565.. 30.. 5072048.. 4763070.. 22.. 5068683.. 5074913.. 23.. 5085465.. 4744090.. 5071050.. 5114995.. 21.. 5191519.. 5082368.. 5079385.. 31.. 5082374.. 5178400.. 25.. Risultati Esonero Percezione Attenzione 19 Aprile 2013..

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  • Title: Valutazione psicofisica con esercitazioni - Modulo Tempo
    Descriptive info: Valutazione psicofisica con esercitazioni - Modulo Tempo.. Thursday, 14 March 2013 18:46.. Lesson.. Topic.. Introduzione alla studio percezione del tempo.. 463 Kb.. Un fenomeno di dilatazione temporale: Cronostasi saccadica.. 400 Kb.. 2 Art.. Action, arousal, and subjective time.. 346 Kb.. Un fenomeno di contrazione temporale al tempo delle saccadi.. 974 Kb.. 3 Art.. Saccadic eye movements cause compression of time as well as space.. 252 Kb.. 4.. Teoria modulare, binding problem e asincronie temporali.. 2 Mb.. 1 Art.. Vision:Modular analysis-or not?.. 192 Kb.. 3 Art.. Early binding of feature pairs for visual perception.. 275 Kb.. A direct demonstration of perceptual asynchrony in vision.. 419 Kb.. 5.. Asincronie temporali  ...   of Visual Attributes.. 529 Kb.. 2 Art.. Perceived timing of first- and second-order changes in vision and hearing.. 531 Kb.. 6.. Asincronie temporali e ruolo del movimento biologico nella percezione temporale.. Perceptual asynchronies for biological and non-biological visual events.. 20 Mb.. Perceptual synchrony of audio-visual streams for natural and artificial motion sequences.. 263 Kb.. 7.. L’illusione visiva del FLE e le teorie proposte sino ad ora per darne spiegazione.. 1 Mb.. Motion estrapolation in catching.. 56 Mb.. Neural processing delays are compensated in the sensorimotor branch of the visual system.. 85 Kb.. Motion integration and Postdiction in visual awareness.. 152 Kb.. Valutazione psicofisica con esercitazioni - Modulo Tempo..

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  • Title: Valutazione psicofisica con esercitazioni - Modulo Avanzato Percezione Visiva
    Descriptive info: Valutazione psicofisica con esercitazioni - Modulo Avanzato Percezione Visiva.. Friday, 29 March 2013 11:43.. Further reading.. Teaching slides.. Cenni di fisiologia.. 6 Mb.. La percezione del contrasto e della brillanza.. Spinelli:.. la visione del contrasto.. Anderson:.. Image segmentation and lightness perception.. Thompson Burr:.. Visual aftereffects.. 27 Mb.. La percezione di movimento semplice.. Burr: “.. Elementary motion mechanisms.. ”.. 3  ...   of visual processing for circular and radial motion.. Morrone et al: ".. A cortical area that responds to optic flow.. ".. 4 Mb.. La visione durante i movimenti saccadici.. Ross, Morrone, Goldberg and Burr: ".. Changes in visual percpetiona at the time of saccades.. Desperati ".. I movimenti oculari.. 18 Mb.. Valutazione psicofisica con esercitazioni - Modulo Avanzato Percezione Visiva..

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  • Title: Valutazione psicofisica con esercitazioni - Corso Matlab
    Descriptive info: Valutazione psicofisica con esercitazioni - Corso Matlab.. Monday, 03 October 2011 13:02.. Per scaricare le slides delle lezioni di porgrammazione Matlab si prega di usare la funzione "salva con nome" sui links riportati a destra.. Introduzione a Matlab.. 897 Kb.. Vettori e Matrici.. 343 Kb.. Grafici, funzioni e analisi statistica.. Es 1.. Esercitazione.. 599 Kb.. Es 2.. Gioco delle tre porte.. 4 Kb.. Valutazione psicofisica con esercitazioni - Corso Matlab..

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  • Title: Percezione e Attenzione (Modulo Percezione)
    Descriptive info: Percezione e Attenzione (Modulo Percezione).. Monday, 17 October 2011 16:55.. Qui sotto sono riportati tutti gli argomenti trattati nel modulo di "Percezione" del corso Psicologia della Percezione e dell'attenzione.. I links sulla destra permettonoo di scaricare le slide delle lezioni in formato pdf.. Si ricorda poi che per la preparazione dell'esame, il manuale di riferimento è: SENSAZIONE E  ...   visione.. 0.. La visione spaziale.. 1 Mb.. Percepire e riconoscere gli oggetti.. La percezione del colore.. Percezione dello spazio e visione binoculare.. La percezione del movimento.. 9.. Udito: fisiologia e psicoacustica.. 7 Mb.. 10.. Acustica nel mondo reale.. 5 Mb.. 11.. Percezione della musica e del linguaggio.. 12.. Il tatto.. 13.. Olfatto.. 14.. Gusto.. Percezione e Attenzione (Modulo Percezione)..

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