Local field potentials of the bed nucleus of stria terminalis in patients with major depressive and obsessive compulsive disorder

Introduction: Deep brain stimulation (DBS) is evolving as a promising treatment for major depressive disorder (MDD) and obsessive compulsive disorder (OCD). However, the optimal target area is still under investigation. Modulation of pathological network activity has been suggested as a possible mechanism of DBS. Here, we recorded local field potentials (LFP) from the bed nucleus of stria terminalis (BNST) in patients with OCD and MDD. Methods: LFP were recorded from adjacent contacts of the DBS electrodes from five OCD patients and seven MDD patients. Spectral power was analyzed from ˜130 s rest recordings for each patient, normalized and expressed as percentage of 3 – 97 Hz total power. Relative power spectra were compared between OCD and MDD using permutation tests (5000 replications). Results: In patients with MDD, distinct low frequency peaks (5 – 16 Hz; mean frequency 9.5 ± 3.6 Hz) were present in all patients (39 of 42 contact pairs). Power spectra from OCD patients showed alpha low frequency peaks (mean frequency: 9.7 ± 2.9 Hz) in 9 of 10 hemispheres (14 of 30 contact pairs). Additionally, distinct peaks in a 16 – 30 Hz range were present in four of five OCD patients (mean frequency 21 ± 2.4 Hz) and six of seven MDD patients (mean frequency 22.6 ± 6.1 Hz). A significant difference between the groups occurred in a broad alpha band range (8 – 16 Hz) with higher power in the MDD patients (permutation test, 8 – 16 Hz, p < 0.05). Conclusion: Our data suggests that synchronized oscillatory activity in the BNST, the main output nucleus of the amygdala, shows a disease-specific pattern with increased alpha band power in patients with MDD. Neuroimaging studies in MDD have shown increased amygdala activity compared to healthy controls and treatment-induced reduction in MDD. It could be speculated that BNST DBS may work by suppression of enhanced oscillatory alpha activity in patients with depression.