Amplitude modulated gamma oscillations as electrophysiological markers for repetitive transcranial magnetic stimulation efficacy in treatment-resistant depression: a randomized sham-controlled study.

BACKGROUND

Gamma oscillations play an important role in cognitive processes, including emotional processing in humans. Abnormal gamma oscillations may reflect certain psychiatric disorders, such as major depressive disorder (MDD). However, less attention has been paid to the role of gamma oscillations in treatment-resistant depression (TRD) and their association with the response to repetitive transcranial magnetic stimulation (rTMS).

METHODS

A total of 61 TRD patients were recruited for a two-week rTMS treatment consisting of ten sessions. Clinical assessments and eyes-closed resting-state electroencephalogram (EEG) recordings were conducted before and after treatment. Participants were randomly assigned to one of three treatment groups: prolonged intermittent theta burst stimulation (piTBS), 10-Hz rTMS, or a Sham group. Adaptive nonlinear analysis using Holo-Hilbert spectral analysis (HHSA) was applied to extract nonlinear information from the EEG data.

RESULTS

Gamma oscillations were found to be positively correlated with scores on the Hamilton Depression Rating Scale (HDRS-17). Additionally, changes in alpha-beta amplitude modulation (AM) modulated gamma oscillations were significantly larger in the Sham group compared to the two active stimulation groups. Furthermore, alpha-beta AM modulated gamma activity was significantly lower in responders compared to non-responders prior to rTMS treatment, irrespective of the specific rTMS protocol.

CONCLUSIONS

Gamma oscillations may serve as an electrophysiological marker for the severity of depression in TRD. Additionally, alpha-beta AM could represent a potential predictor of response to rTMS treatment, identifiable prior to the treatment.

CLINICAL TRIALS REGISTRY NUMBER

UMIN000020892.