Clinical Applications of Electrophysiological Approaches Based on Cortical Modularity in Autism

Abstract

Autism spectrum disorder (ASD) consists of a set of pervasive developmental problems marked by measurable deficits in social interaction and communication, often coupled with specific and repetitive patterns of behavior. Featured restrictions in the capability to communicate and remain attentive can directly relate to the individual’s ability to interact with others within societal norms. Comparing ASD subjects to neurotypical (NT) controls, and other developmental disorders such attention deficit/hyperactivity disorder (ADHD), previous investigations had shown that evoked electroencephalographic (EEG) gamma oscillations and event-related potentials (ERPs) to sensory stimuli do display certain aberrations in latency or amplitude in the ASD individuals. To investigate the aforementioned phenomena the series of studies by our group employed EEG recording technology while subjects participated in several oddball-paradigm reaction time tests. The paper reports on the differences in behavioral reactions as well as variances in amplitude and latency of ERP in autistic individuals and age-matched matched NT controls and children with ADHD. Subjects were evaluated using various ERP components as well as power of EEG gamma oscillations recorded at fronto-central and parietal sites. Findings of our studies suggest that the irregularities arise from deficits in the perception, integration and cognitive processing of sensory inputs. Previous research investigating the neuropathology of autism has identified abnormalities in the structure, number and activity of the cortical minicolumns. The minicolumns of ASD individuals appear in greater number coupled with increased neuronal density due to a reduction in the volume of peripheral neuropil space and neuronal cell bodies. Such a cortical and cellular arrangement favors the formation of short intralobular connections between neurons at the expense of longer interlobular fibers. Our studies propose that aberrations in sensory processing and functional cortical binding, as evidenced by EEG recordings related to the tasks, further reflect the underlying abnormalities of minicolumns in ASD individuals. Thus, the results of our studies suggest that dysfunction of sensory information processing by way of minicolumn irregularity may in turn lead to symptoms commonly associated with ASD.