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Published on: August 11, 2015
Deep Brain Stimulation Modulates Gamma Oscillations and Theta-Gamma Coupling in Treatment Resistant Depression
Yinming Sun1, Peter Giacobbe2, Chris W Tang2
1Temerty Centre for Therapeutic Brain Intervention, Centre for Addiction and Mental Health, University of Toronto, 1001 Queen Street West, Unit 4-1, Toronto, Ontario M6J 1H4, Canada.
Background:
Deep brain stimulation (DBS) in the subcallosal cingulate gyrus (SCG) is becoming an effective therapeutic option for treatment resistant depression (TRD).
Objective/Hypothesis:
Identifying the neurophysiological mechanisms altered by DBS may lead to more tailored treatment parameters and enhanced efficacy.
Methods:
Twenty TRD patients with implanted DBS in the SCG were recruited. Patients participated in three EEG recording sessions, one with DBS ON, one with DBS randomized to ON or OFF, and one with DBS OFF. During each session, subjects performed N-back working memory tasks, namely the 0-back and 3-back. Fourteen subjects with valid EEG were included in the analysis. Changes in frontal gamma oscillations (30-50 Hz) and coupling between theta (4-7 Hz) and gamma oscillations as a result of DBS stimulation were quantified and correlated with depressive symptoms.
Results:
DBS stimulation resulted in suppression of frontal oscillations in the ON state relative to the OFF state during the N-back tasks. Greatest suppression was demonstrated in beta and gamma oscillations and most pronounced during the 3-back. Suppression of gamma oscillations in the 3-back correlated with a reduction in depressive symptoms. DBS ON relative to OFF in the 3-back also resulted in an increase in theta-gamma coupling that correlated with a reduction in depressive symptoms.
Conclusion:
Suppression of gamma oscillations and increased theta-gamma coupling through DBS is likely mediated by both SCG activation of inhibitory circuits and an enhancement of plasticity in the frontal cortex. Activation of both pathways may explain the therapeutic properties of DBS in TRD.
