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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 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.


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.


New Research published in Scientific Reports!

Congratulation to Eckart, Paola and Concetta who just published a new paper in Scientific Reports!

Zimmermann, E., Morrone, M. C. & Binda, P. (2018). Perception during double-step saccades, Sci Rep, 1 (8), 320. PDF

How the visual system achieves perceptual stability across saccadic eye movements is a long-standing question in neuroscience. It has been proposed that an efference copy informs vision about upcoming saccades, and this might lead to shifting spatial coordinates and suppressing image motion. Here we ask whether these two aspects of visual stability are interdependent or may be dissociated under special conditions. We study a memory-guided double-step saccade task, where two saccades are executed in quick succession. Previous studies have led to the hypothesis that in this paradigm the two saccades are planned in parallel, with a single efference copy signal generated at the start of the double-step sequence, i.e. before the first saccade. In line with this hypothesis, we find that visual stability is impaired during the second saccade, which is consistent with (accurate) efference copy information being unavailable during the second saccade. However, we find that saccadic suppression is normal during the second saccade. Thus, the second saccade of a double-step sequence instantiates a dissociation between visual stability and saccadic suppression: stability is impaired even though suppression is strong.

Interesting dispatch in Current Biology by Marco Tamietto and David Leopold on the recent study by Koulla, Jan, David and Concetta about Area Prostriata in the Human Brain! PDF

Human area Prostriata is a small, unstudied portion of the visual brain set deep in the calcarine sulcus, next to V1. A recent neuroimaging study in humans indicates that this area is specialized to respond to rapidly moving stimuli in the far periphery, consistent with single-unit responses in other mammals.


Congratulations to Koulla, Roberto, FrancescaSofia and Concetta for having the research recommended in F1000Prime!

Your article: Plasticity of the human visual brain after an early cortical lesion., Neuropsychologia, 2017 (DOI: 10.3410/f.732073581.793538629), has been recommended in F1000Prime as being of special significance in its field by F1000 Faculty Member Marlene Behrmann.


New Research published in Scientific Reports!

Congratulation to David who just published a new paper in Scientific Reports!

Alexi, J., Cleary, D., Dommisse, K., Palermo, R., Kloth, N., Burr, D., et al. (2018). Past visual experiences weigh in on body size estimation, Scientific Reports, 1 (8), PDF

Body size is a salient marker of physical health, with extremes implicated in various mental and physical health issues. It is therefore important to understand the mechanisms of perception of body size of self and others. We report a novel technique we term the bodyline, based on the numberline technique in numerosity studies. One hundred and three young women judged the size of sequentially presented female body images by positioning a marker on a line, delineated with images of extreme sizes. Participants performed this task easily and well, with average standard deviations less than 6% of the total scale. Critically, judgments of size were biased towards the previously viewed body, demonstrating that serial dependencies occur in the judgment of body size. The magnitude of serial dependence was well predicted by a simple Kalman-filter ideal-observer model, suggesting that serial dependence occurs in an optimal, adaptive way to improve performance in size judgments.


New Research published on Journal of Numerical Cognition!

Congratulation to Giovanni, Marco, Antonella and David who just published a new paper on Journal of Numerical Cognition! A special congratulation to Antonella for her first publication!

Anobile, G., Cicchini, G. M., Pomè, A. & Burr, D. (2017). Connecting Visual Objects Reduces Perceived Numerosity and Density for Sparse but not Dense Patterns, Journal of Numerical Cognition, 4 (3), PDF

How is numerosity encoded by the visual system? – directly, or derived indirectly from texture density? We recently suggested that the numerosity of sparse patterns is encoded directly by dedicated mechanisms (which have been described as the “Approximate Number System” ANS). However, at high dot densities, where items become “crowded” and difficult to segregate, “texture-density” mechanisms come into play. Here we tested the importance of item segmentation on numerosity and density perception at various stimulus densities, by measuring the effect of connecting visual objects with thin lines. The results confirmed many previous studies showing that connecting items robustly reduces the apparent numerosity of patterns of moderate density. We further showed that the apparent density of moderate-density patterns is also reduced by connecting the dots. Crucially, we found that both these effects are strongly reduced at higher numerosities. Indeed for density judgments, the effect reverses, so connecting dots in dense patterns increases the apparent density (as expected from the physical characteristics). The results provide clear support for the three-regime framework of number perception, and suggest that for moderately sparse stimuli, numerosity – but not texture-density – is perceived directly.

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