TMS-based neuromodulation of evoked and induced gamma oscillations and event-related potentials in children with autism

Yao Wang,Manuel Casanova,Estate Sokhadze,Ayman El-Baz,Heba Elsayed Farag,Xiaoli Li

doi:10.15540/nr.3.3.101

Abstract

Gamma oscillations are important for the integration of information and are involved in a variety of perceptual, cognitive, and motor process that are affected in autism spectrum disorder (ASD). We used gamma oscillations along with event-related potentials (ERP) as functional markers of response to repetitive transcranial magnetic stimulation (rTMS). The subjects were age- and gender-matched ASD and typically developing children (TDC). Behavioral evaluations along with evoked and induced gamma and ERPs during oddball task were collected at pre- and post-TMS in ASD group (N = 23) and at baseline in TDC (N = 21). ASD subjects were assigned to 18 sessions of rTMS over the dorsolateral prefrontal cortex. Baseline test showed significant differences between ASD and TDC groups in terms of responses to non-targets where ASD showed excessive gamma oscillations and larger ERPs as compared to the TDC group. Behavioral response differences were manifested in a lower accuracy of motor responses. The rTMS resulted in improved accuracy of response, attenuated evoked gamma responses to non-targets, and increased induced gamma to targets. Behavioral outcomes showed decreased irritability and hyperactivity scores and decreased repetitive and stereotype behaviors. There is discussed utility of gamma oscillations as biomarkers for functional diagnostics and predictions of TMS outcomes in ASD.

Highlights

The cerebral cortex inherent hyperexcitability demands the presence of dampening mechanisms that maintain a proper set point when acquiring and processing stimuli from other parts of the nervous system
We found a significant decrease in stereotype, repetitive and restricted behavior patterns following repetitive transcranial magnetic stimulation (rTMS) course as measured by the repetitive behavior scale (RBS)-R (Bodfish et al, 1999) and analyzed them using a paired sample Student’s t-test
Differences between autism spectrum disorder (ASD) and typically developing (TD) children in RT, event-related potentials (ERP) and gamma band responses In our study children with ASD did not differ from typical children in terms of reaction time, though they committed more errors, mostly commission errors, and did not show normative post-error RT slowing as TD children did

Summary

Introduction

The cerebral cortex inherent hyperexcitability demands the presence of dampening mechanisms that maintain a proper set point when acquiring and processing stimuli from other parts of the nervous system. Inappropriate regulation of our excitatory-inhibitory (E/I) bias creates abnormal responsiveness. It is known, for example, that contusions and hemorrhages involving the cerebral cortex interfere with the action of its dampening mechanisms, facilitating an epileptogenic environment. The carefully crafted E/I bias of the cerebral cortex depends on the coordinated action of both pyramidal cells and interneurons. Cell fate specification studies have shown that a variety of different interneurons develop at specific laminar locations and at different times during neurodevelopment. These cells migrate to the cortex during the entire period of corticogenesis using multiple tangential routes in order to reach their final destination

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