Gamma Frequency Oscillations
Research Papers
TMS-based neuromodulation of evoked and induced gamma oscillations and event-related potentials in children with autism
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.
View Full Paper →Low-Frequency Repetitive Transcranial Magnetic Stimulation (rTMS) Modulates Evoked-Gamma Frequency Oscillations in Autism Spectrum Disorder (ASD)
Introduction It has been reported that individuals with Autism Spectrum Disorder (ASD) have abnormal reactions to the sensory environment and visuo-perceptual abnormalities. Electrophysiological research has provided evidence that gamma band activity (30-80 Hz) is a physiological indicator of the co-activation of cortical cells engaged in processing visual stimuli and integrating different features of a stimulus. A number of studies have found augmented and indiscriminative gamma band power at early stages of visual processing in ASD; this may be related to decreased inhibitory processing and an increase in the ratio of cortical excitation to inhibition. Low frequency or ‘slow’ (≤1HZ) repetitive transcranial magnetic stimulation (rTMS) has been shown to increase inhibition of stimulated cortex by the activation of inhibitory circuits.
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