Different patterns of local field potentials from limbic DBS targets in patients with major depressive and obsessive compulsive disorder

The role of distinct limbic areas in emotion regulation has been largely inferred from neuroimaging studies. Recently, the opportunity for intracranial recordings from limbic areas has arisen in patients undergoing deep brain stimulation (DBS) for neuropsychiatric disorders including major depressive disorder (MDD) and obsessive compulsive disorder (OCD). Here we test the hypothesis that distinct temporal patterns of local field potential (LFP) activity in the human limbic system reflect disease state and symptom severity in MDD and OCD patients. To this end, we recorded LFPs via implanted DBS electrodes from the bed nucleus of stria terminalis (BNST area) in 12 patients (5 OCD, 7 MDD) and from the subgenual cingulate cortex in 7 MDD patients (CG25 area). We found a distinct pattern of oscillatory activity with significantly higher a-power in MDD compared with OCD in the BNST area (broad a-band 8-14 Hz; P<0.01) and a similar level of alpha-activity in the CG25 area as in the BNST area in MDD patients. The mean alpha-power correlated with severity of depressive symptoms as assessed by the Beck depression inventory in MDD (n = 14, r = 0.55, P = 0.042) but not with severity of obsessive compulsive symptoms in OCD. Here we show larger alpha-band activity in MDD patients compared with OCD recorded from intracranial DBS targets. Our results suggest that a-activity in the limbic system may be a signature of symptom severity in MDD and may serve as a potential state biomarker for closed loop DBS in MDD.