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...... Paula Andrea Maldonado Moscoso Cecilia Steinwurzel Paola Binda Luca Lo Verde Irene Togoli Alessandro Benedetto Akshatha Bhat Roberto Arrighi Maria Concetta Morrone David Burr Guido Marco Cicchini Tam Ho Giovanni Anobile Antonella Pomè Claudia Lunghi Francesca Tinelli Kyriaki Mikellidou Jan Kurzawski Marco Turi Elisa Castaldi ERC ECSPLAIN About PisaVisionLab ....

New Research published on Neuropsychologia!

Congratulation to Giovanni, Marco and David who just published a new paper on Neuropsychologia!

Anobile, G., Cicchini, G. M., Gasperini, F. & Burr, D. (2018). Typical numerosity adaptation despite selectively impaired number acuity in dyscalculia, Neuropsychologia, PDF

It has been suggested that a core deficit of the “number sense” may underlie dyscalculia. We test this idea by measuring perceptual adaptation and discrimination thresholds for numerosity and object size in a group of dyscalculic and typical preadolescents (N=71, mean age 12). We confirmed that numerosity discrimination thresholds are higher in evelopmental dyscalculia, while size thresholds are not affected. However, dyscalculics adapted to numerosity in a similar way to typicals. This suggests that although numerosity thresholds are selectively higher in dyscalculia, the mechanisms for perceiving numerosity are otherwise similar, suggesting that that have a similar, but perhaps noisier, number sense.

2018 giovanniNeuropsychologia

 

 

New Research published on the Proceedings of the Royal Society of London B!

Congratulation to Marco, Koulla and David who just published a new paper on Proc. R. Soc. B!

Cicchini, G. M., Mikellidou, K. & Burr, D. (2018). The functional role of serial dependence, Proceedings of the Royal Society of London B, PDF

The world tends to be stable from moment to moment, leading to strong serial correlations in natural scenes. As similar stimuli usually require similar behavioral responses, it is highly likely that the brain has developed strategies to leverage these regularities. A good deal of recent psychophysical evidence is beginning to show that the brain is sensitive to serial correlations, causing strong drifts in observer responses towards previously seen stimuli. However, it is still not clear that this tendency leads to a functional advantage. Here we test a formal model of optimal serial dependence and show that as predicted, serial dependence in an orientation reproduction task is dependent on current stimulus reliability, with less precise stimuli, such as low spatial frequency oblique Gabors, exhibiting the strongest effects. We also show that serial dependence depends on the similarity between two successive stimuli, again consistent with behavior of an ideal observer aiming at minimizing reproduction errors. Lastly, we show that serial dependence leads to faster response times, indicating that the benefits of serial integration go beyond reproduction error. Overall our data show that serial dependence has a beneficial role at various levels of perception, consistent with the idea that the brain exploits temporal redundancy of the visual scene as an optimization strategy

cicchini2018SerialProcRB

 

Congratulations to David who has been elected a Fellow of the Academy of the Social Sciences in Australia.

His election to Fellowship is in recognition of his contribution to the advancement of social science knowledge and the impact he has made. 

L'immagine può contenere: testo

New Review published in Annual Review of Vision Science!

Congratulations to Paola and Concetta for the new publication!

Binda, P. & Morrone, M. C. (2018). Vision During Saccadic Eye Movements, Annual Review of Vision Science, 1 (4), 193-213. PDF

The perceptual consequences of eye movements are manifold: Each large saccade is accompanied by a drop of sensitivity to luminance-contrast, low-frequency stimuli, impacting both conscious vision and involuntary responses, including pupillary constrictions. They also produce transient distortions of space, time, and number, which cannot be attributed to the mere motion on the retinae. All these are signs that the visual system evokes active processes to predict and counteract the consequences of saccades. We propose that a key mechanism is the reorganization of spatiotemporal visual fields, which transiently increases the temporal and spatial uncertainty of visual representations just before and during saccades. On one hand, this accounts for the spatiotemporal distortions of visual perception; on the other hand, it implements a mechanism for fusing pre- and postsaccadic stimuli. This, together with the active suppression of motion signals, ensures the stability and continuity of our visual experience.

New Research published in Scientific Reports!

Congratulations to Giovanni, David and Marco  for the new publication!

Anobile, G., Burr, D. C., Iaia, M., Marinelli, C. V., Angelelli, P. & Turi, M. (2018). Independent adaptation mechanisms for numerosity and size perception provide evidence against a common sense of magnitude, Sci Rep, 1 (8), 13571. PDF

How numerical quantity is processed is a central issue for cognition. On the one hand the "number sense theory" claims that numerosity is perceived directly, and may represent an early precursor for acquisition of mathematical skills. On the other, the "theory of magnitude" notes that numerosity correlates with many continuous properties such as size and density, and may therefore not exist as an independent feature, but be part of a more general system of magnitude. In this study we examined interactions in sensitivity between numerosity and size perception. In a group of children, we measured psychophysically two sensory parameters: perceptual adaptation and discrimination thresholds for both size and numerosity. Neither discrimination thresholds nor adaptation strength for numerosity and size correlated across participants. This clear lack of correlation (confirmed by Bayesian analyses) suggests that numerosity and size interference effects are unlikely to reflect a shared sensory representation. We suggest these small interference effects may rather result from top-down phenomena occurring at late decisional levels rather than a primary "sense of magnitude".

41598 2018 31893 Fig1 HTML

New Research published in Scientific Reports

Congratulations to Koulla, Dave and Concetta who published a new paper on Scientific Reports!


Mikellidou, K., Frijia, F., Montanaro, D., Greco, V., Burr, D. C. & Morrone, M. C. (2018). Cortical BOLD responses to moderate- and high-speed motion in the human visual cortex, Sci Rep, 1 (8), 8357. PDF

We investigated the BOLD response of visual cortical and sub-cortical regions to fast drifting motion presented over wide fields, including the far periphery. Stimuli were sinusoidal gratings of 50% contrast moving at moderate and very high speeds (38 and 570 degrees /s), projected to a large field of view (~60 degrees ). Both stimuli generated strong and balanced responses in the lateral geniculate nucleus and the superior colliculus. In visual cortical areas, responses were evaluated at three different eccentricities: central 0-15 degrees ; peripheral 20-30 degrees ; and extreme peripheral 30-60 degrees . "Ventral stream" areas (V2, V3, V4) preferred moderate-speeds in the central visual field, while motion area MT+ responded equally well to both speeds at all eccentricities. In all other areas and eccentricities BOLD responses were significant and equally strong for both types of moving stimuli. Support vector machine showed that the direction of the fast-speed motion could be successfully decoded from the BOLD response in all visual areas, suggesting that responses are mediated by motion mechanisms rather than being an unspecific preference for fast rate of flicker. The results show that the visual cortex responds to very fast motion, at speeds generated when we move our eyes rapidly, or when moving objects pass by closely.


KoullaScientificReps2018 figure pisavisionlab

New Research published on Journal of Vision!

Congratulation to Michele, Paola e Marco who just published a new paper on Journal of Vision!

Fornaciai, M., Binda, P. & Cicchini, G. M. (2018). Trans-saccadic integration of orientation information, J Vis, 4 (18), 9. PDF

Does visual processing start anew after each eye movement, or is information integrated across saccades? Here we test a strong prediction of the integration hypothesis: that information acquired after a saccade interferes with the perception of images acquired before the saccade. We investigate perception of a basic visual feature, grating orientation, and we take advantage of a delayed interference phenomenon-in human participants, the reported orientation of a target grating, briefly presented at an eccentric location, is strongly biased toward the orientation of flanker gratings that are flashed shortly after the target. Crucially, we find that the effect is the same whether or not a saccade is made during the delay interval even though the eye movement produces a large retinotopic separation between target and flankers. However, the trans-saccadic effect nearly vanishes when flankers are displaced to a different screen location even when this location matches the retinotopic coordinates of the target. We conclude that information about grating orientation is integrated across saccades within a spatial region that is defined in external coordinates and thereby is stable in spite of the movement of the eyes.

transaccadiIntegration

New Research published on Cortex!

Congratulation to Elisa, Francesca, Marco and Concetta who just published a new paper on Cortex!

Castaldi, E., Tinelli, F., Cicchini, M. & Morrone, M. C. (2018). Supramodal agnosia for oblique mirror orientation in patients with periventricular leukomalacia, Cortex, PDF

Periventricular leukomalacia (PVL) is characterized by focal necrosis at the level of the periventricular white matter, often observed in preterm infants. PVL is frequently associated with motor impairment and with visual deficits affecting primary stages of visual processes as well as higher visual cognitive abilities. Here we describe six PVL subjects, with normal verbal IQ, showing orientation perception deficits in both the haptic and visual domains. Subjects were asked to compare the orientation of two stimuli presented simultaneously or sequentially, using both a two alternative forced choice (2AFC) orientation-discrimination and a matching procedure. Visual stimuli were oriented gratings or bars or collinear short lines embedded within a random pattern. Haptic stimuli comprised two rotatable wooden sticks. PVL patients performed at chance in discriminating the oblique orientation, both for visual and haptic stimuli. Moreover when asked to reproduce the oblique orientation, they often oriented the stimulus along the symmetric mirror orientation. The deficit generalized to stimuli varying in many low level features, was invariant for spatiotopic object orientation, and also occurred for sequential presentations. The deficit was specific to oblique orientations, and not for horizontal or vertical stimuli. These findings show that PVL can affect a specific network involved with the supramodal perception of mirror symmetry orientation.

obliqueMirrorDef



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