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  • Title: Paola Binda
    Descriptive info: Paola Binda.. Thursday, 27 January 2011 19:06.. PisaVisionLab.. Post-Doc in Physiological Sciences, University of Pisa and University of Washington.. Contacts.. Email: pbinda1 (AT) uw.. edu.. Telephone: +39 050 3153175.. Research laboratories.. Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa, via San Zeno 31, 56123 Pisa (Italy).. Vision Cognition Group, University of Washington,Seattle, USA.. Marie Curie Fellow (International Outgoing Fellowship, Project “AWESoMe” n.. 272834, 7th Framework Programme).. Current research and interests.. Saccadic eye movements.. Numerosity.. Visual Attention.. Multisensory Integration.. 2013.. Cicchini, G.. M.. , Binda, P.. , Burr, D.. C.. & Morrone, M.. (2013).. 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.. 2012.. , Morrone, M.. & Bremmer, F.. (2012).. 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.. 2011.. , Ross, J.. & Burr, D.. (2011).. Underestimation of perceived number at the time of saccades,Vision Res, 1 (51), 34-42.. Saccadic eye movements produce transient distortions in both space and time.. Mounting evidence suggests that space and time perception are linked, and associated with the perception of another important perceptual attribute, numerosity.. Here we investigate the effect of saccades on the perceived numerosity of briefly presented arrays of visual elements.. We report a systematic underestimation of numerosity for stimuli flashed just before or during saccades, of about 35% of the reference numerosity.. The bias is observed only for relatively large arrays of visual elements, in line with the notion that a distinct perceptual mechanism is involved with enumeration of small numerosities in the 'subitizing' range.. This study provides further evidence for the notion that space, time and number share common neural representations, all affected by saccades.. Knoll, J.. 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  ...   fascinating test.. Saccades compress the perceived magnitude of spatial separations and temporal intervals to approximately half of their true value.. The question arises as to whether saccades also compress number.. They do, and compression follows a very similar time course for all three attributes: it is maximal at saccadic onset and decreases to veridicality within a window of approximately 50ms.. These results reinforce the suggestion of a common perceptual metric, which is probably mediated by the intraparietal cortex; they further suggest that before each saccade the common metric for all three is reset, possibly to pave the way for a fresh analysis of the post-saccadic situation.. Temporal auditory capture does not affect the time course of saccadic mislocalization of visual stimuli,J Vis, 2 (10), 7 1-13.. Irrelevant sounds can "capture" visual stimuli to change their apparent timing, a phenomenon sometimes termed "temporal ventriloquism".. Here we ask whether this auditory capture can alter the time course of spatial mislocalization of visual stimuli during saccades.. We first show that during saccades, sounds affect the apparent timing of visual flashes, even more strongly than during fixation.. However, this capture does not affect the dynamics of perisaccadic visual distortions.. Sounds presented 50 ms before or after a visual bar (that change perceived timing of the bars by more than 40 ms) had no measurable effect on the time courses of spatial mislocalization of the bars, in four subjects.. Control studies showed that with barely visible, low-contrast stimuli, leading, but not trailing, sounds can have a small effect on mislocalization, most likely attributable to attentional effects rather than auditory capture.. These findings support previous studies showing that integration of multisensory information occurs at a relatively late stage of sensory processing, after visual representations have undergone the distortions induced by saccades.. 2009.. , Cicchini, G.. (2009).. Spatiotemporal distortions of visual perception at the time of saccades,J Neurosci, 42 (29), 13147-13157.. Both space and time are grossly distorted during saccades.. Here we show that the two distortions are strongly linked, and that both could be 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.. 2007.. , Bruno, A.. (2007).. 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..

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  • Title: Guido Marco Cicchini
    Descriptive info: Guido Marco Cicchini.. Post-Doc in Cognitive Science, University of Florence.. Email: cicchini (AT) in.. cnr.. Telephone: +39 050 3153185.. CNR Institute of Neuroscience, Pisa.. Department of Psychology, University of Florence.. Stella Maris Foundation, Pisa, Italy.. Temporal Perception.. Eye Movements.. Clinical Psychology.. Optimal Behaviour.. Scocchia, L.. , Cicchini, G.. M.. & Triesch, J.. 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.. Anobile, G.. 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.. , 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.. 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  ...   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.. Morrone, M.. , Cicchini, M.. Spatial maps for time and motion,Exp Brain Res, 2 (206), 121-128.. In this article, we review recent research studying the mechanisms for transforming coordinate systems to encode space, time and motion.. A range of studies using functional imaging and psychophysical techniques reveals mechanisms in the human brain for encoding information in external rather than retinal coordinates.. This reinforces the idea of a tight relationship between space and time, in the parietal cortex of primates.. Shifts in spatial attention affect the perceived duration of events,J Vis, 1 (9), 9 1-13.. We investigated the relationship between attention and perceived duration of visual events with a double-task paradigm.. The primary task was to discriminate the size change of a 2 degree circle presented 10 degrees left, right, above, or below fixation; the secondary task was to judge the temporal separation (from 133 ms to 633 ms) of two equiluminant horizontal bars (10 deg x 2 deg) briefly flashed 12 degrees above or below fixation.. The stimulus onset asynchrony (SOA) between primary and secondary task ranged from -1300 ms to +1000 ms.. Temporal intervals in proximity of the onset of the primary task stimuli were perceived strongly compressed by up to 40%.. The effect was proportional to the size of the interval with a maximum effect at 100 ms SOA.. Control experiments show that neither primary-task difficulty, nor the type of primary task discrimination (form or motion, or equiluminant or luminance contrast) nor spatial congruence between primary and secondary task alter the effect.. Interestingly, the compression occurred only when the intervals are marked by bars presented in separated spatial locations: when the interval is marked by two bars flashed in the same spatial position no temporal distortion was found.. These data indicate that attention can alter perceived duration when the brain has to compare the passage of time at two different spatial positions, corroborating earlier findings that mechanisms of time perception may monitor separately the various spatial locations possibly at high level of analysis.. , Silva, O.. , Banks, M.. S.. 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.. 2008.. , Valsecchi, M.. & De'Sperati, C.. (2008).. 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..

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  • Title: Claudia Lunghi
    Descriptive info: Claudia Lunghi.. PhD Student in Cognitive Science, University of Florence.. Email: clalunghi (AT) gmail.. com.. Education.. 2010-2013:.. Doctoral School of Psychology (curriculum cognitive science), University of Florence, Italy.. Advisors: David C Burr, M Concetta Morrone.. 2006-2008:.. MA Cognitive Neuroscience, 110/110 cum laude, Department of Psychology, Libera Università Vita-Salute San Raffaele, Milano, Italy.. 2003-2006:.. BA Philosophy,110/110 cum laude, Department of Philosophy, Libera Università Vita-Salute San Raffaele, Milano, Italy.. Binocular Rilvalry.. Plasticity of the visual system.. Multi-sensory perception.. Bistable perception.. Amblyopia.. & 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  ...   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.. 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.. Conferences.. 06-11/05/2011:.. “VSS 2011” (Vision Science Society, Annual Meeting), Naples (Florida, US).. Talk, title: “ Experience-dependent plasticity in adult human visual cortex revealed by binocular rivalry”.. Link.. 08/22-26/2010:.. “ECVP 2010” (European Conference on Visual Perception), Lausanne (Switzerland).. Talk,.. title: "The effect of transient monocular deprivation on binocular rivalry".. ;.. 08/24-28/2009:.. “ECVP 2009” (European Conference on Visual Perception), Regensburg (Germany).. Poster Presentation..

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  • Title: Sofia Crespi
    Descriptive info: Sofia Crespi.. Post-Doc in Cognitive Science, Institute of Neuroscience (CNR-PISA).. Email: crespi.. sofiaallegra (AT) gmail.. Department of Psychology, Università Vita-Salute, San Raffaele.. Spatial Vision.. 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  ...   results indicate that spatial attention may play an important role in mediating spatiotopic selectivity.. 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.. 2006..

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  • Title: Francesca Tinelli
    Descriptive info: Francesca Tinelli.. Email: francesca.. tinelli (AT) inpe.. unipi.. Gori, M.. , Tinelli, F.. , Sandini, 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.. 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.. Ricci, D.. , Cesarini, L.. , Gallini, F.. , Serrao, F.. , Leone, D.. , Baranello, G.. Cortical visual function in preterm infants in the first year,J Pediatr, 4 (156), 550-555.. OBJECTIVE: To assess visual function in low-risk preterm infants at 3, 5, and 12 months corrected age to determine whether the maturation of visual function in the first year is similar to that reported in term-born infants.. STUDY DESIGN: Seventy-five low-risk infants (25.. 0-30.. 9 weeks gestation) underwent ophthalmological examinations and a battery of tests (fix and follow, visual fields, acuity, attention at distance, and fixation shift) designed to assess various aspects of visual function at 3, 5, and 12 months corrected age.. RESULTS: The results were comparable with normative data from term-born infants in all tests but fixation shift, suggesting that maturation of most aspects of visual function is not significantly affected by preterm birth.. In contrast, >25% of preterm infants failed the fixation shift test at 3 months, with a higher percentage of failing at 5 and 12 months.. CONCLUSIONS: There is a specific profile of early visual behavior in low-risk preterm infants, with a high percentage of infants failing a test that specifically assesses visual attention and provides a measure of cortical processing.. Guzzetta, A.. , D'Acunto, G.. , Rose, S.. , Boyd, R.. & Cioni, G.. Plasticity of the visual system after early brain damage,Dev Med Child Neurol, 10 (52), 891-900.. The aim of this review is to discuss the existing evidence supporting different processes of visual brain plasticity after early damage, as opposed to damage that occurs during adulthood.. There is initial evidence that some of the neuroplastic mechanisms adopted by the brain after early damage to the visual system are unavailable at a later stage.. These are, for example, the ability to differentiate functional tissue within a larger dysplastic cortex during its formation, or to develop new thalamo-cortical connections able to bypass the lesion and reach their cortical destination in the occipital cortex.. The young brain also uses the same mechanisms available at later stages of development but in a more efficient way.. For example, in people with visual field defects of central origin, the anatomical expansion of the extrastriatal visual network is greater after an early lesion than after a later one, which results in more efficient mechanisms of visual exploration of the blind field.. A similar mechanism is likely to support some of the differences found in people with blindsight, the phenomenon of unconscious visual perception in the blind field.. In particular, compared with people with late lesions, those with early brain damage appear to have stronger subjective awareness of stimuli hitting the blind visual field, reported as a conscious feeling that something is present in the visual field.. Expanding our knowledge of these mechanisms could help the development of early therapeutic interventions aimed at supporting and  ...   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.. , Pei, F.. , Mazzotti, S.. , Baldassi, 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.. 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.. Baranello, G.. , Rando, T.. , D'Acunto, M.. G.. , Epifanio, R.. , Frisone, M.. F.. (2006).. 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..

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  • Title: Kyriaki Mikellidou
    Descriptive info: Kyriaki Mikellidou.. Post-Doc in Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa.. Email: kmikellidou (AT) gmail.. Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa.. 2009 – 2013.. University of York, United Kingdom.. PhD in Psychology.. 2008 – 2009.. MSc in Cognitive Neuroscience.. 2005 – 2008 University of York, United Kingdom.. BSc (.. Hons.. ) Psychology.. Visual illusions.. Neuroimaging of vision.. 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  ...   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.. Mikellidou, K.. Simple line-length estimation not so simple.. Vision Sciences Society Annual Meeting,.. Naples, Florida.. Bisection and dissection of horizontal lines: the long and the short of the Oppel-Kundt illusion.. Journal of Vision, 11,.. 1184.. The vertical-horizontal and the Oppel-Kundt illusions: how our visual perception changes.. Perception, 40,.. 116.. Thompson,P.. (2009) The 3-D Helmholtz square illusion: more reasons to wear horizontal stripes.. Journal of Vision, 9,.. 50..

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  • Title: Graduate Students
    Descriptive info: Title Filter.. Display #.. 5.. 10.. 15.. 20.. 25.. 30.. 100.. All.. #.. Article Title.. Author.. Hits.. 1.. 1701.. 2.. 1948.. 3.. 2707.. 4.. 1564.. 5.. 174..

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  • Title: Giovanni Anobile
    Descriptive info: Giovanni Anobile.. Email: GiovanniAnobile (AT) hotmail.. 2009: Italian Master Degree in Experimental Psychology.. Summa cum laude.. University of Florence.. 2007: Italian Degree in Experimental Psychology.. Numerosity perception.. Dyscalculia.. Attention.. , 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).. & Anobile, G.. Subitizing but not estimation of numerosity requires attentional resources,J Vis, 6 (10), 20.. The numerosity of small numbers  ...   whether it requires attentional resources.. We measure subjects' accuracy and precision in making rapid judgments of numerosity for target numbers spanning the subitizing and estimation ranges while manipulating the attentional load, both with a spatial dual task and the "attentional blink" dual-task paradigm.. The results of both attentional manipulations were similar.. In the high-load attentional condition, Weber fractions were similar in the subitizing (2-4) and estimation (5-7) ranges (10-15%).. In the low-load and single-task condition, Weber fractions substantially improved in the subitizing range, becoming nearly error-free, while the estimation range was relatively unaffected.. The results show that the mechanisms operating over the subitizing and estimation ranges are not identical.. We suggest that pre-attentive estimation mechanisms works at all ranges, but in the subitizing range, attentive mechanisms also come into play.. Anobile G, Turi M, Burr D C, 2010, "Subitizing but not estimation of numerosity requires attentional resources".. Perception, 39 ECVP Abstract Supplement, page 80.. Theses..

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  • Title: Elisa Castaldi
    Descriptive info: Elisa Castaldi.. Email: elisa.. castald (AT) gmail.. Telephone: +39 050 3153172.. Colour Perception.. fMRI.. Castaldi, E.. , Frijia, F.. C.. Selectivity to spatial phase of chromatic cortical mechanisms: an fMRI study [Cavalese retreat CNR Institutes of Neuroscience 2011: Poster].. Selectivity to spatial phase of chromatic cortical mechanisms: an fMRI study.. Honours Thesis, University Vita-Salute San Raffaele Milan (2009)..

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  • Title: Michele Fornaciai
    Descriptive info: Michele Fornaciai.. PhD Student in Neuroscience, University of Florence.. Email: fornaciai (AT) hotmail.. Department of Neuroscience, Psychology, Pharmacology and Child Health.. 2007 - 2010.. Bachelor in General and Experimental Psychology, University of Florence.. 2010 - 2012.. Master degree in Psychology (Experimental Psychology), University of Florence.. 2012 - now.. PhD course in Neuroscience.. Time perception.. Motion perception.. Fornaciai M.. “Percezione visiva del movimento e meccanismi temporali”.. Visual perception of motion and temporal mechanisms.. University of Florence, Faculty of Psychology (2012)..

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  • Title: Marco Turi
    Descriptive info: Email: turimarc (AT) gmail.. Motion.. Crowding.. 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:  ...   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.. 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..

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