PT  - JOURNAL ARTICLE
AU  - R.A. Seymour
AU  - G. Rippon
AU  - G. Gooding-Williams
AU  - J.M. Schoffelen
AU  - K. Kessler
TI  - Dysregulated Oscillatory Connectivity in the Visual System in Autism Spectrum Disorder
AID  - 10.1101/440586
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 440586
4099  - http://biorxiv.org/content/early/2018/10/11/440586.short
4100  - http://biorxiv.org/content/early/2018/10/11/440586.full
AB  - Autism Spectrum Disorder (ASD) is increasingly associated with atypical perceptual and sensory symptoms. Here we explore the hypothesis that aberrant sensory processing in ASD could be linked to atypical intra- (local) and inter-regional (global) brain connectivity. To elucidate oscillatory dynamics and connectivity in the visual domain we used magnetoencephalography (MEG) and a simple visual grating paradigm with a group of 18 adolescent autistic participants and 18 typically developing controls. Both groups showed similar increases in gamma (40-80Hz) and decreases in alpha (8-13Hz) frequency power in occipital cortex. However, systematic group differences emerged when analysing local and global connectivity in detail. Firstly, directed connectivity was estimated using non-parametric Granger causality between visual areas V1 and V4. Feedforward V1-to-V4 connectivity, mediated by gamma oscillations, was equivalent between ASD and control groups, but importantly, feedback V4-to-V1 connectivity, mediated by alpha (8-14Hz) oscillations, was significantly reduced in the ASD group. This reduction was correlated with autistic traits, indicating an atypical visual hierarchy in autism, with reduced top-down modulation of visual input via alpha-band oscillations. Secondly, at the local level in V1, coupling of alpha-phase to gamma amplitude (alpha-gamma PAC) was reduced in the ASD group. This implies dysregulated local visual processing, with gamma oscillations decoupled from patterns of wider alpha-band phase synchrony, possibly due to an excitation-inhibition imbalance. More generally, these results are in agreement with predictive coding accounts of neurotypical perception and indicate that visual processes in autism are less modulated by contextual feedback information.