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New Research in Journal of Vision

Congratulations to Michela, who's latest paper just got accepted for publication in JOV.

Spatiotemporal dynamics of perisaccadic remapping in humans revealed by classification images

Michela Panichi, David C. Burr, Concetta Morrone and Stefano Baldassi

We actively scan our environment with fast ballistic movements called saccades, which create large and rapid displacements of the image on the retina. At the time of saccades, vision becomes transiently distorted in many ways: Briefly flashed stimuli are displaced in space and in time, and spatial and temporal intervals appear compressed. Here we apply the psychophysical technique of classification images to study the spatiotemporal dynamics of visual mechanisms during saccades. We show that saccades cause gross distortions of the classification images. Before the onset of saccadic eye movements, the positive lobes of the images become enlarged in both space and in time and also shifted in a systematic manner toward the pre-saccadic fixation (in space) and anticipated in time by about 50 ms. The transient reorganization creates a spatiotemporal organization oriented in the direction of saccadic-induced motion at the time of saccades, providing a potential mechanism for integrating stimuli across saccades, facilitating stable and continuous vision in the face of constant eye movements.

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A royal News!

Congratulations to Marco, who's latest paper just got accepted for publication in Proceedings of the Royal Society.

Marco Turi and  David C. Burr

How our perceptual experience of the world remains stable and continuous despite the frequent repositioning eye movements remains very much a mystery. One possibility is that our brain actively constructs 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 to motion) is spatially selective in external rather than retinal coordinates, whereas the classic 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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New article in Trends in Cognitive Science

Number, texture and crowding

John Ross and  David C. Burr

A recent study shows that selectivity for numerosity emerges as a natural property in deep networks of hierarchical generative models of visual perception. These results, together with recent conceptualizations of crowding and texture, suggest that the ‘sense of number’ is a fundamental visual property, independent of texture and seemingly related attributes.

Number and Texture

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New Research in Journal of Vision

Congratulations to Eckart, who's latest paper just got accepted for publication in JOV.

Visual motion distorts visual and motor space

Eckart Zimmerman, David C. Burr and Concetta Morrone

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Much evidence suggests that visual motion can cause severe distortions in the perception of spatial position. In this study, we show that visual motion also distorts saccadic eye movements. Landing positions of saccades performed to objects presented in the vicinity of visual motion were biased in the direction of motion. The targeting errors for both saccades and perceptual reports were maximum during motion onset and were of very similar magnitude under the two conditions. These results suggest that visual motion affects a representation of spatial position, or spatial map, in a similar fashion for visuomotor action as for perception.

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New Research in Journal of Neuroscience

Congratulations to Marco and Roberto, who's latest paper just got accepted for publication in Journal of Neuroscience.

Optimal Encoding of Interval Timing in Expert Percussionists.
Marco Cicchini, Roberto Arrighi, Luca Cecchetti, Marco Giusti and David C. Burr

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.

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David Burr and Concetta Morrone award the 2011 Kurt-Koffka Award

The Kurt-Koffka award honors scientists who have advanced the fields of perception or developmental psychology to an extraordinary extent. The award is in remembrance of Kurt Koffka, who is well-known as a pioneer of Gestalt Psychology, in particular in the fields of perception and child development. Koffka worked in Giessen for 16 years, from 1911 to 1927.

This was the fifth time that the Kurt-Koffka medal was awarded. In a ceremony that took place on June 22, 2011, Profs. Concetta Morrone and David Burr were honored for their work on visual perception and its development.

(
Read more: German)

New Research in Current Biology

Congratulations to Roberto, who's latest paper just got accepted for publication in Current Biology. The paper reports a strong link between the ability of executing motor acts and having efficient perceptual sensitivity.

Reduced perceptual sensitivity for biological motion in paraplegia patients
Roberto Arrighi, Giulia Cartocci, and David C. Burr

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In the News: "That strange mechanism by which we see the world delayed"
The
visual world we perceive seems stable - despite all the changes and movements we see. Researchers (including Concetta Morrone) have proposed that this stability is the result of simultaneous modifications of both space and time neural mechanisms which are anchored in external space. Everytime we move our eyes, there could be a reorganization of the connections between neurons to ensure stability - and this results in a distortion between real and perceived time. To accommodate this change, the brain must reset both the inner and the 'real' clock at the end of each ocular movement. (Article is in Italian)
(Read more: Italian)

New Research in Current Biology
Congratulations to Claudia, who's latest paper just got accepted for publication in Current Biology.

Brief periods of monocular deprivation disrupt ocular balance in human adult visual cortex
Claudia Lunghi, David C. Burr and Concetta Morrone

Neuroplasticity is a fundamental property of the developing mammalian visual system, with residual potential in adult human cortex. 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. We used binocular rivalry — 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.

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