Altered pattern of theta and gamma oscillation to visual stimuli in patients with post-concussion syndrome.

Abstract

Purpose Although many patients with mild traumatic brain injury (mTBI) suffer from post-concussional syndrome(PCS) including abnormal emotional responses, most conventional imaging studies fail to detect any causative brain lesion. We hypothesized that event-related electroencephalography (EEG) recordings with time-frequency analysis would show a distinguishable pattern in mTBI patients with PCS compared with normal healthy controls. Methods EEG signals were collected from a total of 18 subjects: eight mTBI patients with PCS and ten healthy control subjects. The signals were recorded while the subjects were presented with affective visual stimuli, including neutral, pleasant, and unpleasant emotional cues. Event-related spectral perturbation analysis was performed to calculate frontal midline theta activity and posterior midline gamma activity, followed by statistical analysis to identify whether mTBI patients with PCS have distinct patterns of theta or gamma oscillations in response to affective stimuli. Results Compared to the healthy control group, mTBI patients with PCS did not show significant increase in the power of frontal theta activity in response to the pleasant stimuli, indicating less susceptibility towards pleasant cues. Moreover, the patient group showed attenuated gamma oscillatory activity, with no clear alteration in gamma oscillations in response to either pleasant or unpleasant cues. This study demonstrates that mTBI patients with PCS exhibited altered patterns of oscillatory activities in the theta and gamma bands in response to affective visual stimuli compared to the normal control group. Conclusion The current finding implicates that these distinguishable patterns of brain oscillation may represent the mechanism behind various psychiatric symptoms in mTBI patients.