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New Research published in Journal of Cognitive Neuroscience!

Congratulation to Luca, Concetta and Claudia who just published a new paper on the Journal of Cognitive Neuroscience!

Lo Verde, L., Morrone, M. C. & Lunghi, C. (2016). Early Cross-modal Plasticity in Adults, J Cogn Neurosci, 1-10. PDF

It is known that, after a prolonged period of visual deprivation, the adult visual cortex can be recruited for nonvisual processing, reflecting cross-modal plasticity. Here, we investigated whether cross-modal plasticity can occur at short timescales in the typical adult brain by comparing the interaction between vision and touch during binocular rivalry before and after a brief period of monocular deprivation, which strongly alters ocular balance favoring the deprived eye. While viewing dichoptically two gratings of orthogonal orientation, participants were asked to actively explore a haptic grating congruent in orientation to one of the two rivalrous stimuli. We repeated this procedure before and after 150 min of monocular deprivation. We first confirmed that haptic stimulation interacted with vision during rivalry promoting dominance of the congruent visuo-haptic stimulus and that monocular deprivation increased the deprived eye and decreased the nondeprived eye dominance. Interestingly, after deprivation, we found that the effect of touch did not change for the nondeprived eye, whereas it disappeared for the deprived eye, which was potentiated after deprivation. The absence of visuo-haptic interaction for the deprived eye lasted for over 1 hr and was not attributable to a masking induced by the stronger response of the deprived eye as confirmed by a control experiment. Taken together, our results demonstrate that the adult human visual cortex retains a high degree of cross-modal plasticity, which can occur even at very short timescales.


castaldi2016_Neuroimage

New Research in Scientific Report

Congratulations to David whose latest paper has just been published in Scientific Reports!

Taubert, J., Alais D., Burr, D. (2016). Different coding strategies for the perception of stable and changeable facial attributes, Sci. Rep., 6.
PDF

Perceptual systems face competing requirements: improving signal-to-noise ratios of noisy images, by integration; and maximising sensitivity to change, by differentiation. Both processes occur in human vision, under different circumstances: they have been termed priming, or serial dependencies, leading to positive sequential effects; and adaptation or habituation, which leads to negative sequential effects. We reasoned that for stable attributes, such as the identity and gender of faces, the system should integrate: while for changeable attributes like facial expression, it should also engage contrast mechanisms to maximise sensitivity to change. Subjects viewed a sequence of images varying simultaneously in gender and expression, and scored each as male or female, and happy or sad. We found strong and consistent positive serial dependencies for gender, and negative dependency for expression, showing that both processes can operate at the same time, on the same stimuli, depending on the attribute being judged. The results point to highly sophisticated mechanisms for optimizing use of past information, either by integration or differentiation, depending on the permanence of that attribute.

New Research published in PLoS Biology!

Congratulation to Elisa, Guido Marco and Concetta who just published a new paper on PLoS Biology!

Castaldi, E., Cicchini, G. M., Cinelli, L., Biagi, L., Rizzo, S. & Morrone, M. C. (2016). Visual BOLD Response in Late Blind Subjects with Argus II Retinal Prosthesis, PLoS Biol, 10 (14), e1002569. PDF

Retinal prosthesis technologies require that the visual system downstream of the retinal circuitry be capable of transmitting and elaborating visual signals. We studied the capability of plastic remodeling in late blind subjects implanted with the Argus II Retinal Prosthesis with psychophysics and functional MRI (fMRI). After surgery, six out of seven retinitis pigmentosa (RP) blind subjects were able to detect high-contrast stimuli using the prosthetic implant. However, direction discrimination to contrast modulated stimuli remained at chance level in all of them. No subject showed any improvement of contrast sensitivity in either eye when not using the Argus II. Before the implant, the Blood Oxygenation Level Dependent (BOLD) activity in V1 and the lateral geniculate nucleus (LGN) was very weak or absent. Surprisingly, after prolonged use of Argus II, BOLD responses to visual input were enhanced. This is, to our knowledge, the first study tracking the neural changes of visual areas in patients after retinal implant, revealing a capacity to respond to restored visual input even after years of deprivation.



castaldi2016_Neuroimage

New Research published in Neuroimage!

Congratulation to Elisa, David Aagten-Murphy, David Burr and Concetta who just published a new paper on Neuroimage!

Castaldi, E., Aagten-Murphy, D., Tosetti, M., Burr, D. & Morrone, M. C. (2016). Effects of adaptation on numerosity decoding in the human brain, Neuroimage, (143), 364-377. PDF

Psychophysical studies have shown that numerosity is a sensory attribute susceptible to adaptation. Neuroimaging studies have reported that, at least for relatively low numbers, numerosity can be accurately discriminated in the intra-parietal sulcus. Here we developed a novel rapid adaptation paradigm where adapting and test stimuli are separated by pauses sufficient to dissociate their BOLD activity. We used multivariate pattern recognition to classify brain activity evoked by non-symbolic numbers over a wide range (20-80), both before and after psychophysical adaptation to the highest numerosity. Adaptation caused underestimation of all lower numerosities, and decreased slightly the average BOLD responses in V1 and IPS. Using support vector machine, we showed that the BOLD response of IPS, but not in V1, classified numerosity well, both when tested before and after adaptation. However, there was no transfer from training pre-adaptation responses to testing post-adaptation, and vice versa, indicating that adaptation changes the neuronal representation of the numerosity. Interestingly, decoding was more accurate after adaptation, and the amount of improvement correlated with the amount of perceptual underestimation of numerosity across subjects. These results suggest that numerosity adaptation acts directly on IPS, rather than indirectly via other low-level stimulus parameters analysis, and that adaptation improves the capacity to discriminate numerosity.



castaldi2016_Neuroimage

Professor Adriana Fiorentini: 1/11/1926 – 29/2/2016

Nicoletta Berardi, Concetta Morrone, Donatella Spinelli - Perception - in press

Adriana Fiorentini was for many decades a pillar of the CNR Institute for Neurophysiology (then Neuroscience). On the 29th February 2016 she passed away peacefully in her sleep, with a smile. A whole generation of vision scientists remembers her with love and respect. Her wisdom, intelligence, dedication to science, enthusiasm for research and love of knowledge set an example to us all. She was a role model of respect, generosity, patience, collaboration and true humility: discrete and reserved, always there for her students and colleagues. Born and schooled in Milan, she graduated in Physics in 1948 at the University of Florence, studying optics under Professor Giuliano Toraldo di Francia at the National Institute of Optics in Arcetri.

Adriana and Lamberto

During her studies she noticed a strange contrast phenomenon, which she correctly interpreted as the visual illusion known as “Mach Bands”: this observation was fundamental in shifting her research interests towards visual perception. In her early post-graduate years at Arcetri (1948-1968), Adriana published many innovative studies on physiological optics and perception, which are cited to this day. To mention just two: the seminal demonstration of human receptive fields (or “perceptive fields”) defined by antagonistic center‐surround interactions; and her first (but not last) Nature paper (with Donald MacKay of Keele), demonstrating a neural (VEP) correlate of a perceptual phenomenon ...[PDF]

New Research published in Investigative Ophthalmology & Visual Science!

Congratulation to Claudia and Concetta who just published a new paper on Investigative Ophthalmology & Visual Science!

Lunghi, C., Morrone, M. C., Secci, J. & Caputo, R. (2016). Binocular Rivalry Measured 2 Hours After Occlusion Therapy Predicts the Recovery Rate of the Amblyopic Eye in Anisometropic Children, Invest Ophthalmol Vis Sci, 4 (57), 1537-1546. PDF


PURPOSE. Recent studies on adults have shown that short-term monocular deprivation boosts the deprived eye signal in binocular rivalry, reflecting homeostatic plasticity. Here we investigate whether homeostatic plasticity is present also during occlusion therapy for moderate amblyopia. METHODS. Binocular rivalry and visual acuity (using Snellen charts for children) were measured in 10 children (mean age 6.2 ± 1 years) with moderate anisometropic amblyopia before the beginning of treatment and at four intervals during occlusion therapy (2 hours, 1, 2, and 5 months). Visual stimuli were orthogonal gratings presented dichoptically through ferromagnetic goggles and children reported verbally visual rivalrous perception. Bangerter filters were applied on the spectacle lens over the best eye for occlusion therapy. RESULTS. Two hours of occlusion therapy increased the nonamblyopic eye predominance over the amblyopic eye compared with pretreatment measurements, consistent with the results in adults. The boost of the nonamblyopic eye was still present after 1 month of treatment, steadily decreasing afterward to reach pretreatment levels after 2 months of continuous occlusion. Across subjects, the increase in nonamblyopic eye predominance observed after 2 hours of occlusion correlated (rho = -0.65, P = 0.04) with the visual acuity improvement of the amblyopic eye measured after 2 months of treatment. CONCLUSIONS. Homeostatic plasticity operates during occlusion therapy for moderate amblyopia and the increase in nonamblyopic eye dominance observed at the beginning of treatment correlates with the amblyopic eye recovery rate. These results suggest that binocular rivalry might be used to monitor visual cortical plasticity during occlusion therapy, although further investigations on larger clinical populations are needed to validate the predictive power of the technique.



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New Research published in Scientific Reports and Cognition!

Double achievement for Michele and David! Congratulations to Roberto and Marco, too!

Fornaciai, M., Arrighi, R. & Burr, D. C. (2016). Adaptation-Induced Compression of Event Time Occurs Only for Translational Motion, Scientific Reports, (6), 23341. PDF

Adaptation to fast motion reduces the perceived duration of stimuli displayed at the same location as the adapting stimuli. Here we show that the adaptation-induced compression of time is specific for translational motion. Adaptation to complex motion, either circular or radial, did not affect perceived duration of subsequently viewed stimuli. Adaptation with multiple patches of translating motion caused compression of duration only when the motion of all patches was in the same direction. These results show that adaptation-induced compression of event-time occurs only for uni-directional translational motion, ruling out the possibility that the neural mechanisms of the adaptation occur at early levels of visual processing.


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Fornaciai, M., Cicchini, G. M. & Burr, D. C. (2016). Adaptation to number operates on perceived rather than physical numerosity, Cognition, (151), 63-67. PDF

Humans share with many animals a number sense, the ability to estimate rapidly the approximate number of items in a scene. Recent work has shown that like many other perceptual attributes, numerosity is susceptible to adaptation. It is not clear, however, whether adaptation works directly on mechanisms selective to numerosity, or via related mechanisms, such as those tuned to texture density. To disentangle this issue we measured adaptation of numerosity of 10 pairs of connected dots, as connecting dots makes them appear to be less numerous than unconnected dots. Adaptation to a 20-dot pattern (same number of dots as the test) caused robust reduction in apparent numerosity of the connected-dot pattern, but not of the unconnected dot-pattern. This suggests that adaptation to numerosity, at least for relatively sparse dot-pattern, occurs at neural levels encoding perceived numerosity, rather than at lower levels responding to the number of elements in the scene.

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Adriana Fiorentini (1/11/1926 - 29/2/2016)

Adriana Fiorentini passed away peacefully in her sleep last Monday. Adriana was an inspirational pillar of the Pisa Vision Laboratory and leading international visual scientist for over half a century. She was well loved by all her colleagues and students who had the privilege to work with and learn from her. We will miss her.

Adriana

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