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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!

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.

New Research published on Current Biology!

Congratulation to Tam, David and Concetta who just published on Current Biology!

Ho, T. H., Leung, J., Burr, D., Alais, D. & Morrone, M. C. (2017). Auditory Sensitivity and Decision Criteria Oscillate at Different Frequencies Separately for the Two Ears, Current Biology, PDF

Many behavioral measures of visual perception fluctuate continually in a rhythmic manner, reflecting the influence of endogenous brain oscillations, particularly theta (~4–7 Hz) and alpha (~8–12 Hz) rhythms. However, it is unclear whether these oscillations are unique to vision or whether auditory performance also oscillates. Several studies report no oscillatory modulation in audition, while those with positive findings suffer from confounds relating to neural entrainment. Here, we used a bilateral pitch-identification task to investigate rhythmic fluctuations in auditory performance separately for the two ears and applied signal detection theory (SDT) to test for oscillations of both sensitivity and criterion (changes in decision boundary). Using uncorrelated dichotic white noise to induce a phase reset of oscillations, we demonstrate that, as with vision, both auditory sensitivity and criterion showed strong oscillations over time, at different frequencies: ~6 Hz (theta range) for sensitivity and ~8 Hz (low alpha range) for criterion, implying distinct underlying sampling mechanisms. The modulation in sensitivity in left and right ears was in antiphase, suggestive of attention-like mechanisms sampling alternatively from the two ears.


New Research published on Neuropsychologia!

Congratulation to Koulla, Roberto, Francesca, Sofia and Concetta who just published on Neuropsychologia!

Mikellidou, K., Arrighi, R., Aghakhanyan, G., Tinelli, F., Frijia, F., Crespi, S., et al. (2017). Plasticity of the human visual brain after an early cortical lesion, Neuropsychologia, PDF

In adults, partial damage to V1 or optic radiations abolishes perception in the corresponding part of the visual field, causing a scotoma. However, it is widely accepted that the developing cortex has superior capacities to reorganize following an early lesion to endorse adaptive plasticity. Here we report a single patient case (G.S.) with near normal central field vision despite a massive unilateral lesion to the optic radiations acquired early in life. The patient underwent surgical removal of a right hemisphere parieto-temporal-occipital atypical choroid plexus papilloma of the right lateral ventricle at four months of age, which presumably altered the visual pathways during in utero development. Both the tumor and surgery severely compromised the optic radiations. Residual vision of G.S. was tested psychophysically when the patient was 7 years old. We found a close-to-normal visual acuity and contrast sensitivity within the central 25 degrees and a great impairment in form and contrast vision in the far periphery (40-50 degrees ) of the left visual hemifield. BOLD response to full field luminance flicker was recorded from the primary visual cortex (V1) and in a region in the residual temporal-occipital region, presumably corresponding to the middle temporal complex (MT+), of the lesioned (right) hemisphere. A population receptive field analysis of the BOLD responses to contrast modulated stimuli revealed a retinotopic organization just for the MT+ region but not for the calcarine regions. Interestingly, consistent islands of ipsilateral activity were found in MT+ and in the parieto-occipital sulcus (POS) of the intact hemisphere. Probabilistic tractography revealed that optic radiations between LGN and V1 were very sparse in the lesioned hemisphere consistently with the post-surgery cerebral resection, while normal in the intact hemisphere. On the other hand, strong structural connections between MT+ and LGN were found in the lesioned hemisphere, while the equivalent tract in the spared hemisphere showed minimal structural connectivity. These results suggest that during development of the pathological brain, abnormal thalamic projections can lead to functional cortical changes, which may mediate functional recovery of vision.


New Research published in Scientific Reports

Congratulations to Paola who published a new paper on Scientific Reports!

Binda, P., Strasser, T., Stingl, K., Richter, P., Peters, T., Wilhelm, H., et al. (2017). Pupil response components: attention-light interaction in patients with Parinaud's syndrome, Sci Rep, 1 (7), 10283. PDF

Covertly shifting attention to a brighter or darker image (without moving one's eyes) is sufficient to evoke pupillary constriction or dilation, respectively. One possibility is that this attentional modulation involves the pupillary light response pathway, which pivots around the olivary pretectal nucleus. We investigate this possibility by studying patients with Parinaud's syndrome, where the normal pupillary light response is strongly impaired due to lesions in the pretectal area. Four patients and nine control participants covertly attended (while maintaining fixation at the center of a monitor screen) to one of two disks located in the left and right periphery: one brighter, the other darker than the background. Patients and control subjects behaved alike, showing smaller pupils when attending to the brighter stimulus (despite no eye movements); consistent results were obtained with a dynamic version of the stimulus. We interpret this as proof of principle that attention to bright or dark stimuli can dynamically modulate pupil size in patients with Parinaud's syndrome, suggesting that attention acts independently of the pretectal circuit for the pupillary light response and indicating that several components of the pupillary response can be isolated - including one related to the focus of covert attention.

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