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    Archived pages: 251 . Archive date: 2013-07.

  • Title: Marco Turi
    Descriptive info: Thursday, 27 January 2011 19:06.. PisaVisionLab.. PhD Student in Cognitive Science, University of Florence.. Contacts.. Email: turimarc (AT) gmail.. com.. Telephone: +39 050 3153175.. Research laboratories.. CNR Institute of Neuroscience, Pisa.. Department of Psychology, University of Florence.. Stella Maris Foundation, Pisa, Italy.. Current research and interests.. Numerosity perception.. Multi-sensory perception.. Motion.. Crowding.. Attention.. 2013.. Turi, M.. & Burr, D.. (2013).. 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.. 2012.. (2012).. 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  ...   modality.. The non-linearities in numberline mapping under attentional load are well explained by a Bayesian model of central tendency.. 2011.. Burr, D.. , Anobile, G.. & Turi, M.. (2011).. 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).. 2010.. & Anobile, G.. (2010).. Subitizing but not estimation of numerosity requires attentional resources,J Vis, 6 (10), 20.. The numerosity of small numbers of objects, up to about four, can be rapidly appraised without error, a phenomenon known as subitizing.. Larger numbers can either be counted, accurately but slowly, or estimated, rapidly but with errors.. There has been some debate as to whether subitizing uses the same or different mechanisms than those of higher numerical ranges and 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.. Conferences.. Theses..

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  • Title: PisaVisionLab
    Descriptive info: Close Window.. E-mail this link to a friend.. E-mail to:.. Sender:.. Your E-mail:.. Subject:.. Send.. Cancel..

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  • Title: Monica Gori
    Descriptive info: Monica Gori.. Thursday, 02 May 2013 16:05.. Redirect.. Redirect in corso..

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  • Title: Faculty
    Descriptive info: Title Filter.. Display #.. 5.. 10.. 15.. 20.. 25.. 30.. 50.. 100.. All.. #.. Article Title.. Author.. Hits.. 1.. 91.. 2.. David Burr Extended Publications.. 2496.. 3.. Concetta Morrone Extended Publications.. 1932.. 4.. 13012.. 5.. 7954.. 6.. 2433..

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  • Title: PisaVisionLab
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  • Title: Liz Pellicano
    Descriptive info: Liz Pellicano..

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  • Title: PisaVisionLab
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  • Title: Eckart Zimmermann
    Descriptive info: Eckart Zimmermann.. Post-Doc in Cognitive Science, University of Florence.. Email: Eckart (AT) in.. cnr.. Eye Movements.. Visual Stability.. Saccadic Adaptation.. Zimmermann, E.. , Morrone, M.. Visual motion distorts visual and motor space, J Vis, 2 (12),.. 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.. & 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.. Zimmerman, E.. , Burr D.. C.. , and Morrone, M.. (2011) Spatiotopic Visual Maps Revealed by Saccadic Adaptation in Humans, Curr Biol.. 2011 Aug 23;21(16):1380-4.. Saccadic adaptation is a powerful experimental paradigm to probe the mechanisms of eye movement control and spatial vision, in which saccadic amplitudes change in response to false visual feedback.. The adaptation occurs primarily in the motor system, but there is also evidence for visual adaptation, depending on the size and the permanence of the postsaccadic error.. Here we confirm that adaptation has a strong visual component and show that the visual component of the adaptation is spatially selective in external, not retinal coordinates.. Subjects  ...   probe location.. These findings are consistent withthe assumption that oculomotor space and perceptual space are linked to each other.. Motor signals in visual localization,J Vis, 6 (10), 2.. We demonstrate a strong sensory-motor coupling in visual localization in which experimental modification of the control of saccadic eye movements leads to an associated change in the perceived location of objects.. Amplitudes of saccades to peripheral targets were altered by saccadic adaptation, induced by an artificial step of the saccade target during the eye movement, which leads the oculomotor system to recalibrate saccade parameters.. Increasing saccade amplitudes induced concurrent shifts in perceived location of visual objects.. The magnitude of perceptual shift depended on the size and persistence of errors between intended and actual saccade amplitudes.. This tight agreement between the change of eye movement control and the change of localization shows that perceptual space is shaped by motor knowledge rather than simply constructed from visual input.. , Schnier, F.. The contribution of scene context on change detection performance,Vision Res, 20 (50), 2062-2068.. The gist of a visual scene is perceived in a fraction of a second but in change detection tasks subjects typically need several seconds to find the changing object in a visual scene.. Here, we report influences of scene context on change detection performance.. Scene context manipulations consisted of scene inversion, scene jumbling, where the images were cut into 24 pieces and randomly recombined, and scene configuration scrambling, where the arrangement of the objects in the scene was randomized.. Reaction times, where significantly lower in images with normal scene context.. We conclude that scene context structures scene perception.. 2009.. (2009).. Mislocalization of flashed and stationary visual stimuli after adaptation of reactive and scanning saccades,J Neurosci, 35 (29), 11055-11064.. When we look around and register the location of visual objects, our oculomotor system continuously prepares targets for saccadic eye movements.. The preparation of saccade targets may be directly involved in the perception of object location because modification of saccade amplitude by saccade adaptation leads to a distortion of the visual localization of briefly flashed spatial probes.. Here, we investigated effects of adaptation on the localization of continuously visible objects.. We compared adaptation-induced mislocalization of probes that were present for 20 ms during the saccade preparation period and of probes that were present for >1 s before saccade initiation.. We studied the mislocalization of these probes for two different saccade types, reactive saccades to a suddenly appearing target and scanning saccades in the self-paced viewing of a stationary scene.. Adaptation of reactive saccades induced mislocalization of flashed probes.. Adaptation of scanning saccades induced in addition also mislocalization of stationary objects.. The mislocalization occurred in the absence of visual landmarks and must therefore originate from the change in saccade motor parameters.. After adaptation of one type of saccade, the saccade amplitude change and the mislocalization transferred only weakly to the other saccade type.. Mislocalization of flashed and stationary probes thus followed the selectivity of saccade adaptation.. Since the generation and adaptation of reactive and scanning saccades are known to involve partially different brain mechanisms, our results suggest that visual localization of objects in space is linked to saccade targeting at multiple sites in the brain..

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  • Title: PisaVisionLab
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  • Title: Michela Panichi
    Descriptive info: Michela Panichi.. Email: MichelaPanichi (AT) gmail.. Education.. Visual stability.. Eye movements.. Classification Images analysis.. Time perception.. Pascucci, D.. , Megna, N.. , Panichi, M.. & Baldassi, S.. 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  ...   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.. Panichi M, Morrone MC, Burr DC, Baldassi S.. (2010) “Spatiotemporal mechanisms of perisaccadic vision revealed by psychophysical reverse correlation”.. Perception 39 ECVP Abstract Supplement 2010.. European Conference on Visual Perception 2010.. Lausanne (CH).. [Talk].. Panichi M, Megna N, Baldassi S.. (2009) “Spatial frequency affects perceived temporal duration”.. Perception 38 ECVP Abstract Supplement 2009.. European Conference on Visual Perception 2009.. Regensburg, GE.. [Poster].. Pascucci D, Megna N, Panichi M, Baldassi S.. (2009) “How does sound improve vision? A classification image study”.. Panichi M.. “Studio della soppressione saccadica attraverso una tecnica comportamentale di monitoraggio dei movimenti oculari”.. Investigating saccadic suppression through the usage of a behavioral paradigm to control eye movements.. Honours Thesis, University of Florence (2008)..

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  • Title: All Publications
    Descriptive info: Message.. You are not authorised to view this resource.. Autism TICS.. 198.. Lab Publications.. 5752..

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  • Archived pages: 251