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.

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There is an ongoing debate whether or not multisensory interactions require awareness of the sensory signals. Static visual and tactile stimuli have been shown to influence each other even in the absence of visual awareness. However, it is unclear if this finding generalizes to dynamic contexts. In the present study, we presented visual and tactile motion stimuli and induced fluctuations of visual awareness by means of binocular rivalry: two gratings which drifted in opposite directions were displayed, one to each eye. One visual motion stimulus dominated and reached awareness while the other visual stimulus was suppressed from awareness. Tactile motion stimuli were presented at random time points during the visual stimulation. The motion direction of a tactile stimulus always matched the direction of one of the concurrently presented visual stimuli. The visual gratings were differently tinted, and participants reported the color of the currently seen stimulus. Tactile motion delayed perceptual switches that ended dominance periods of congruently moving visual stimuli compared to switches during visual-only stimulation. In addition, tactile motion fostered the return to dominance of suppressed, congruently moving visual stimuli, but only if the tactile motion started at a late stage of the ongoing visual suppression period. At later stages, perceptual suppression is typically decreasing. These results suggest that visual awareness facilitates but does not gate multisensory interactions between visual and tactile motion signals.

Children with autism spectrum disorders (ASDs) often exhibit altered representations of the external world. Consistently, when localizing touch, children with ASDs were less influenced than their peers by changes of the stimulated limb's location in external space [Wada et al., Scientific Reports 2015, 4(1), 5985]. However, given the protracted development of an external‐spatial dominance in tactile processing in typically developing children, this difference might reflect a developmental delay rather than a set suppression of external space in ASDs. Here, adults with ASDs and matched control‐participants completed (a) the tactile temporal order judgment (TOJ) task previously used to test external‐spatial representation of touch in children with ASDs and (b) a tactile‐visual cross‐modal congruency (CC) task which assesses benefits of task‐irrelevant visual stimuli on tactile localization in external space. In both experiments, participants localized tactile stimuli to the fingers of each hand, while holding their hands either crossed or uncrossed. Performance differences between hand postures reflect the influence of external‐spatial codes. In both groups, tactile TOJ‐performance markedly decreased when participants crossed their hands and CC‐effects were especially large if the visual stimulus was presented at the same side of external space as the task‐relevant touch. The absence of group differences was statistically confirmed using Bayesian statistical modeling: adults with ASDs weighted external‐spatial codes comparable to typically developed adults during tactile and visual‐tactile spatio‐temporal tasks. Thus, atypicalities in the spatial coding of touch for children with ASDs appear to reflect a developmental delay rather than a stable characteristic of ASD. Autism Res 2019, 12: 1745–1757. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. Lay Summary A touched limb's location can be described twofold, with respect to the body (right hand) or the external world (right side). Children and adolescents with autism spectrum disorder (ASD) reportedly rely less than their peers on the external world. Here, adults with and without ASDs completed two tactile localization tasks. Both groups relied to the same degree on external world locations. This opens the possibility that the tendency to relate touch to the external world is typical in individuals with ASDs but emerges with a delay.