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New Research in Journal Of Neuroscience

Congratulations to Concetta, whose latest paper has just been accepted for publication in JN.

Selective tuning for contrast in macaque area V4

Ilaria Sani, Elisa Santandrea, Ashkan Golzar, Maria Concetta Morrone and Leonardo Chelazzi

Visually responsive neurons typically exhibit a monotonic-saturating increase of firing with luminance contrast of the stimulus, and are able to adapt to the current spatiotemporal context by shifting their selectivity, being therefore perfectly suited for optimal contrast encoding and discrimination. Here we report the first evidence of the existence of neurons showing selective tuning for contrast in area V4d of the behaving macaque (Macaca mulatta), i.e. narrow band-pass filter neurons with peak activity encompassing the whole range of visible contrasts and pronounced attenuation at contrasts higher than the peak. Crucially, we found that contrast tuning emerges after a considerable delay from stimulus onset, likely reflecting the contribution of inhibitory mechanisms. Selective tuning for luminance contrast might support multiple functions, including contrast identification and the attentive selection of low contrast stimuli.

(Read More - PDF)

New Research in BRAIN

Congratulations to Monica, whose latest paper has just been accepted for publication in BRAIN.

Impairment of auditory spatial localization in congenitally blind human subjects

Monica Gori, Giulio Sandini, Cristina Martinoli and David C. Burr

Several studies have demonstrated enhanced auditory processing in the blind, suggesting that they compensate their visual impairment in part with greater sensitivity of the other senses. However, several physiological studies show that early visual deprivation can impact negatively on auditory spatial localization. Here we report for the first time severely impaired auditory localization in the congenitally blind: thresholds for spatially bisecting three consecutive, spatially-distributed sound sources were seriously compromised, on average 4.2-fold typical thresholds, and half performing at random. In agreement with previous studies, these subjects showed no deficits on simpler auditory spatial tasks or with auditory temporal bisection, suggesting that the encoding of Euclidean auditory relationships is specifically compromised in the congenitally blind. It points to the importance of visual experience in the construction and calibration of auditory spatial maps, with implications for rehabilitation strategies for the congenitally blind.

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New Research in Journal of Vision

Congratulations to Claudia, whose latest paper has just been accepted for publication in JOV.

Long-term effects of monocular deprivation revealed with binocular rivalry gratings modulated in luminance and in color

Claudia Lunghi, Concetta Morrone and David C. Burr

During development, within a specific temporal window called the critical period, the mammalian visual cortex is highly plastic and literally shaped by visual experience; to what extent this extraordinary plasticity is retained in the adult brain is still a debated issue. We tested the residual plastic potential of the adult visual cortex for both achromatic and chromatic vision by measuring binocular rivalry in adult humans following 150 minutes of monocular patching. Paradoxically, monocular deprivation resulted in lengthening of the mean phase duration of both luminance-modulated and equiluminant stimuli for the deprived eye and complementary shortening of nondeprived phase durations, suggesting an initial homeostatic compensation for the lack of information following monocular deprivation. When equiluminant gratings were tested, the effect was measurable for at least 180 minutes after reexposure to binocular vision, compared with 90 minutes for achromatic gratings. Our results suggest that chromatic vision shows a high degree of plasticity, retaining the effect for a duration (180 minutes) longer than that of the deprivation period (150 minutes) and twice as long as that found with achromatic gratings. The results are in line with evidence showing a higher vulnerability of the P-pathway to the effects of visual deprivation during development and a slower development of chromatic vision in humans.

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New Research in Journal of Neuroscience

Congratulations to Paola, whose latest paper has just been accepted for publication in JN.

ReflexAttention to Bright Surfaces Enhances the Pupillary Light

Paola Binda, Maria Pereverzeva and Scott O. Murray

One longstanding question is how early in the visual system attention exerts its influence. Here we show that an effect of attention can be measured at the earliest possible stage of visual information processing, as a change in the optics of the eye.We tested human subjects and found that covertly attending to bright surfaces results in an enhanced pupillary light reflex (PLR)—the pupillary constriction that occurs in response to light increments. The PLR optimizes the optical quality of the retinal image across illumination conditions, increasing sensitivity by modulating retinal illumination, and improving acuity by reducing spherical aberrations. The attentional modulation of the PLR that we describe constitutes a new mechanism through which vision is affected by attention; we discuss three alternatives for the neural substrates of this effect, including the possibility that attention might act indirectly, via its well established effects in early visual

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New Research in Journal of Neuroscience

Congratulations to Eckart, whose latest paper has just been accepted for publication in JN.

Spatial position information accumulates steadily over time

Eckart Zimmerman, Concetta Morrone and David C. Burr

The acquisition of sensorimotor parameters that control goal-directed motor behaviours occurs by observing another person. During such observation, biological motion properties associated with the observed person are coded into a representation that controls motor learning. Understanding the underlying mechanisms, specifically associated with coding biological motion, has theoretical and practical significance. In this study, we examined the following questions: are the underlying velocity characteristics associated with observed biological motion kinematics imitated? (Experiment 1); is attention involved in imitating biological motion kinematics? (Experiment 2); can selective attention modulate how biological motion kinematics are imitated/represented? (Experiment 3). Having completed practice during which participants observed a model displaying a movement sequence, and thus did not overtly generate any motor signals, kinematic analyses confirmed that biological motion kinematics were imitated. Using a dual-task tone counting protocol, we attenuated the coding of biological motion kinematics (Experiment 2), and subsequently augmented coding using a selective attention protocol (Experiment 3). These findings confirmed velocity characteristics of biological motion kinematics are coded during observation, most likely through bottom-up sensorimotor processes. The fact that we influenced coding using two different attentional protocols indicated these bottom-up processes are influenced by input modulation, which is consistent with top-down control during observational practice.

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In the News: "The Plasticity Potential of Young Brain"

Recent research from the lab focussed on the plasticity potential of young visual brain. The paper by Tinelli et al shows that the effects of the lesions to visual regions of the brain are functionally compensated for, at least partially, when the brain damage occurs perinatally. In addition the authors show that in these cases the non-lesioned visual cortex respondeds not only to stimuli presented to the spared visual field, but also to the blind field. This shows that the brain responds to the lesion with a profound reorganization of the anatomical visual pathways.

Original Article:

Blindsight in children with congenital and acquired cerebral lesions PDF
Cortex, Volume 49, Issue 6, June 2013, Pages 1636-1647
Francesca Tinelli, Guido Marco Cicchini, Roberto Arrighi, Michela Tosetti, Giovanni Cioni, Maria Concetta Morrone

Press Coverage:

Le Scienze [Italian] Read more

La Nazione [Italian] Read more

Il Tirreno [Italian] Read more

click here for a full list of News Articles

Constructing stable spatial maps of the world

New review article by Dave and Concetta summarizing the latest results of on stability across eye movements.

CicchiniBindaBurrMorrone

To interact rapidly and effectively with our environment, our brain needs access to a neural representation—or map—of the spatial layout of the external world. However, the construction of such a map poses major challenges to the visual system, given that the images on our retinae depend on where the eyes are looking, and shift each time we move our eyes, head, and body to explore the world. Much research has been devoted to how the stability is achieved, with the debate often polarized between the utility of spatiotopic maps (that remain solid in external coordinates), as opposed to transiently updated retinotopic maps. Our research suggests that the visual system
uses both strategies to maintain stability.

The review accompanies Dave's Perception Lecture at last ECVP in Alghero and puts in a wider context recent work from the lab. (PDF)

See Also:

Turi and Burr, Proc Roy Soc, 2012 (PDF)

Cicchini, Binda, Burr and Morrone, J Neurophys, 2013 (PDF)

Zimmermann, Morrone, Fink and Burr Current Biology, 2013 (PDF)

New Perspectives on Autism published in Trends in Cognitive Sciences

When the world becomes ‘too real’: a Bayesian explanation of autistic perception

Liz Pellicano and David Burr

Perceptual experience is influenced both by incoming sensory information and prior knowledge about the world, a concept recently formalised within Bayesian decision theory. We propose that Bayesian models can be applied to autism, a neurodevelopmental condition with atypicalities in sensation and perception, to pinpoint fundamental differences in perceptual mechanisms. We suggest specifically that attenuated Bayesian priors, ‘hypo-priors’, may be responsible for the unique perceptual experience of autistic people, leading to a tendency to perceive the world more accurately rather than modulated by prior experience. In this account, we consider how hypo-priors might explain key features of autism, the broad range of sensory and other non-social atypicalities, in addition to the phenomenological differences in autistic perception.

(Read More - PDF)

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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