Abstract
Functional brain development is characterized by sensitive periods during which experience must be available to allow for the full development of neural circuits and associated behavior. Yet, only few neural markers of sensitive period plasticity in humans are known. Here we employed electroencephalographic recordings in a unique sample of twelve humans who had been blind from birth and regained sight through cataract surgery between four months and 16 years of age. Two additional control groups were tested: a group of visually impaired individuals without a history of total congenital blindness and a group of typically sighted individuals. The EEG was recorded while participants performed a visual discrimination task involving intact and scrambled biological motion stimuli. Posterior alpha and theta oscillations were evaluated. The three groups showed indistinguishable behavioral performance and in all groups evoked theta activity varied with biological motion processing. By contrast, alpha oscillatory activity was significantly reduced only in individuals with a history of congenital cataracts. These data document on the one hand brain mechanisms of functional recovery (related to theta oscillations) and on the other hand, for the first time, a sensitive period for the development of alpha oscillatory activity in humans.
Highlights
A model in humans[14,15,16] and allow uncovering sensitive periods analogous to the extensive work in animals[17,18]
Strong evidence in favor of a sensitive period for the emergence of the neural mechanisms underlying alpha oscillatory activity would be if it could be shown that alpha oscillations do not or not fully recover after restoring sight following a congenital blindness while alpha oscillations would be recorded in visually impaired individuals who had had some vision at birth
The present study evaluated neural mechanisms of sensitive period plasticity in humans
Summary
A model in humans[14,15,16] and allow uncovering sensitive periods analogous to the extensive work in animals[17,18]. Strong evidence in favor of a sensitive period for the emergence of the neural mechanisms underlying alpha oscillatory activity would be if it could be shown that alpha oscillations do not or not fully recover after restoring sight following a congenital blindness while alpha oscillations would be recorded in visually impaired individuals who had had some vision at birth. By studying alpha activity we were able to assess neural mechanisms related to the control of the excitatory/inhibitory balance of neural ciricuits. Since the latter crucuially rely on GABA-mediated mechanisms, we consider alpha oscillatory activity as an index for the functionality of inhbitory circuits whose establishment has often been postulated to constitute a hallmark of brain development[21]. Alpha activity was hypothesized to depend on visual input from birth
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