Biology subjects

Guerreiro, M. J. S.

Publications and source records attributed to Guerreiro, M. J. S..

3 recordsLinked to original sources

bioRxiv2024

Visual and auditory object representations in ventral visual cortex after restoring sight in humans

Visual category-selective representations in human ventral occipital temporal cortex (VOTC) seem to emerge early in infancy. Surprisingly, the VOTC of congenitally blind humans features category-selectivity for auditory and haptic objects. Yet it has been unknown whether VOTC would show category-selective visual responses if sight were restored in congenitally blind humans. Assuming competition for synaptic space during development, cross-modal activation of VOTC as a consequence of congenital blindness might interfere with visual processing in sight-recovery individuals. To test this hypothesis, we investigated adults who had suffered a transient phase of congenital blindness due to bilateral dense cataracts before their sight was restored by cataract-removal surgery. In a functional magnetic resonance imaging (fMRI) study, participants watched movies of faces, scenes, body parts and other objects in the visual condition, while in the auditory condition they listened to the corresponding sounds. The most prominent group difference was the reduced face-selectivity in individuals with reversed congenital cataracts compared to age- and sex-matched normally-sighted individuals. In addition, a double dissociation was found: only sight-recovery individuals demonstrated significant decoding accuracy of visual categories based on auditory category representations in VOTC, while only normally-sighted individuals VOTC decoded auditory categories based on visual category representations. The present results uncovered the neural mechanisms of previously observed face processing impairments in individuals with reversed congenital blindness. We suggest that lower face-selectivity in the sight recovery group might arise from selective deficits in the cortical representation of the central visual field in lower-tier visual areas. Additionally, we speculate that in higher-order visual areas cross-modal activity might facilitate - rather than interfere - with visual functional recovery after congenital blindness.

neuroscience↗

bioRxiv2021

Typical resting state activity of the brain requires visual input during an early sensitive period

Sensory deprivation, following a total loss of one sensory modality e.g. vision, has been demonstrated to result in intra- and cross-modal plasticity. It is yet not known to which extent intra- and cross-modal plasticity as a consequence of blindness reverse if sight is restored. Here, we used functional magnetic resonance imaging to acquire blood oxygen level dependent (BOLD) resting state activity during an eyes open and an eyes closed state in congenital cataract-reversal individuals, developmental cataract-reversal individuals, congenitally permanently blind individuals and sighted controls. The amplitude of low frequency fluctuations (ALFF) of the BOLD signal - a neural marker of spontaneous brain activity during rest - was analyzed. As has been shown before, in normally sighted controls we observed an increase in ALFF during rest with the eyes open compared to rest with eyes closed in visual association areas and in parietal cortex but a decrease in auditory and sensorimotor regions. In congenital cataract-reversal individuals, we found an increase of the amplitude of slow BOLD fluctuations in visual cortex during rest with eyes open compared to rest with eyes closed too but this increase was larger in amplitude than in normally sighted controls. At the same time, congenital cataract-reversal individuals lagged a similar increase in parietal regions and did not show the typical decrease of ALFF in auditory and sensorimotor cortex. Congenitally blind individuals displayed an overall higher amplitude in slow BOLD fluctuations in visual cortex compared to sighted individuals and compared to congenital cataract-reversal individuals in the eyes closed condition. Higher ALFF in visual cortex of congenital cataract-reversal individuals than in normally sighted controls during eyes open might indicate an altered excitatory-inhibitory balance of visual neural circuits. By contrast, the lower parietal increase and the missing downregulation in auditory and sensorimotor regions suggest a reduced influence of the visual system on multisensory and the remaining sensory systems after restoring sight in congenitally blind individuals. These results demonstrate a crucial dependence of multisensory neural networks on visual experience during a sensitive phase in human brain development.

neuroscience↗

bioRxiv2021

The Size-Weight Illusion is unimpaired in individuals with a history of congenital visual deprivation

Visual deprivation in childhood can lead to lifelong impairments in visual and multisensory processing. Here, the Size-Weight-Illusion was used to test whether visuo-haptic integration recovers after sight restoration. In Experiment 1, congenital (CC: 7 (3F), 8-35 years) and developmental cataract reversal individuals (DC: 9 (2F), 8-37 years), as well as congenitally blind (CB: 2 (1F), 33 and 44 years) and normally sighted individuals (SC: 10 (7F), 19-36 years) perceived larger objects as lighter than smaller objects of the same weight. In Experiment 2, CC (6 (1F), 17-44.7 years) and SC (7 (5F), 21-29 years) individuals performed identically when tested without haptic size cues. Together, this suggested that early visual experience is not necessary to perceive the Size-Weight-Illusion.

neuroscience↗