Casartelli, L. | Search bioRxiv

bioRxiv2020

Altered beta-band oscillations and connectivity underlie detail-oriented visual processing in autism

Sensory and perceptual anomalies have been increasingly recognized as core phenotypic markers for autism spectrum disorders (ASD). A neurophysiological characterization of these anomalies is of utmost importance to understand more complex behavioural manifestations within the spectrum. The present study employed electroencephalography (EEG) to test whether detail-oriented visual perception, a recognized hallmark of ASD, is associated with altered neural oscillations and functional connectivity in beta (and alpha) frequency bands, considering their role in feedback and top-down reentrant signalling in the typical population. A sample of children with diagnosis of ASD (N=18) and typically developing peers (TD; N=20) performed a visual crowding task, where they had to discriminate a peripheral target letter surrounded by flankers at different distances, together with a control condition with no flankers. In TD participants the amplitude of the target-locked N1 component and its cortical sources was significantly modulated as a function of visual crowding, whereas such modulation was absent in the ASD group, suggesting that their visual scene analysis takes place without a flexible neural computation. The comparison between groups showed a decreased activity in the ASD group in occipital, infero-temporal and inferior/middle frontal regions in conditions requiring detail-oriented perception as opposed to conditions requiring the discrimination of target in isolation. Moreover, in TD participants detail-oriented perception was associated with an event-related beta power reduction (15-30 Hz), which was not evident in the ASD group. A data-driven functional connectivity analysis highlighted in the ASD sample an increased connectivity in the beta frequency range between occipital and infero-temporal regions. Notably, individual hyperconnectivity indexes correlated to less severe ASD symptomatology and to a diminished detail-oriented perception, suggesting a potential compensatory mechanism. Overall, these results show that altered communication in the beta frequency band may explain atypical perception in ASD, reflecting aberrant feedback connectivity within the visual system with potential cascade effects in visual scene parsing and higher-order functions.

neuroscience↗

bioRxiv2019

Anomalous Perception Of Biological Motion In Autism: A Conceptual Review And Meta-Analysis

Despite its popularity, the construct of biological motion (BM) and its putative anomalies in autism spectrum disorder (ASD) are not completely clarified. Here, we propose a new model describing distinct levels of BM processing, and we present a meta-analysis investigating BM perception in ASD. We screened 114 articles testing BM perception in ASD and typical developing peers. A general meta-analysis including all the selected studies (N=27) showed BM processing moderate deficit in ASD, but high heterogeneity. This heterogeneity was explored in different additional meta-analyses where studies were grouped according to different levels of BM processing (first-order/direct/instrumental) and the manipulation of low-level perceptual features (spatial/temporal). Results suggest that the most severe deficit in ASD is evident when perception of BM is serving a secondary purpose (e.g., inferring intentionality/action/emotion) and, interestingly, that temporal dynamics could be an important factor in determining BM processing anomalies in ASD. In conclusion, this work questions the traditional understanding of BM anomalies in ASD and claims for a paradigm shift that deconstructs BM into distinct levels of processing and specific spatio-temporal subcomponents. Public Significance statementSince the seminal study by Johansson (1973), the construct of "biological motion" (BM) has gained a considerable success in a wide range of disciplines. In particular, BM processing has been considered a putative marker for social difficulties in neurodevelopmental conditions such as autism spectrum disorder (ASD). Our work aims to quantitatively test the solidity of this view through a meta-analytic approach and also to better define anomalies in BM perception according to distinct levels of complexity and specific spatio-temporal features. Interestingly, we do it by challenging the traditional approach to the conception of BM. This novel conceptualization has intriguing clinical and theoretical insights.

neuroscience↗