EEG Coherence Abnormalities in Autistic Children Triggered by the Processing of Complex Visual Stimuli in Motion

Background: Autistics show a diminished ability to integrate complex information. This may relate to altered functional connectivity. EEG coherence measures electrocortical synchrony of oscillatory brain rhythms across neural networks, which is hypothesized as a mechanism for functional connectivity, binding of neural activity and integration of cognitive processes. Objectives: We sought to test the hypothesis that there would be greater coherence differences between autistic children and controls in a complex visual input condition when compared to the differences seen in a simple or minimal visual input condition. Methods: Resting EEG was obtained, using a 128 electrode net, for 3 conditions presented for 5 minutes each: 1) complex visual stimulus: a movie, 2) simple visual stimulus: flashes of light in a visual evoked potential (VEP) paradigm, and 3) no visual stimulus: eyes closed/lights out (EC/LO) in 5 children (4.4-9.8yrs): 2 autistic, 2 autistic spectrum (ASD) and 1 typically developing control. Coherence was computed between all channel pairs for each frequency band. Power and coherence were then averaged for each condition. Results: Autistics showed broadly increased low frequency (delta/theta) coherence in the “movie” condition compared to control. Coherence differences for VEP and EC/LO were far less significant. ASD children showed the same effect but to a lesser degree. Interhemispheric higher frequency (alpha) coherence was somewhat decreased in the “movie” condition when compared to VEP and EC/LO condition in preliminary data. Conclusions: Our data suggest that autistic children show coherence abnormalities that are not static but dynamic and produced by exposure to complex visual stimuli in motion. This abnormality appears to be proportionate to the severity of the autism. Whether motion or complexity is the critical factor in producing these coherence differences remains to be determined. These data suggest that processing of complex visual images in motion alters functional connectivity in autism.