Effective deep brain stimulation for obsessive-compulsive disorder and Tourette Syndrome increases network-wide neural variability

IntroductionDeep brain stimulation (DBS) is an effective therapy for obsessive-compulsive disorder (OCD) and Tourette syndrome. Our previous results demonstrated disrupted circadian periodicity and increased neural variability in the region of the ventral striatum (VS) in responders to DBS for OCD. Here, we tested the hypothesis that the relationship between increased neural variability and symptom improvement is not specific to the ventral striatum alone but generalizes to another basal ganglia region, the globus pallidus internus (GPi). Materials and MethodsWe gathered chronic local field potential (LFP) recordings from four patients with OCD and comorbid Tourette syndrome implanted with bilateral dual-site DBS leads in the ventral striatum VS and GPi. We measured spectral power in the 9 Hz band in both targets continuously for over 900 days using the DBS systems on-device recording capability. We estimated neural variability using an autoregressive model applied to the continuous time series of neural power. ResultsTwo of the four patients achieved responder status for both OCD and TS. In all four patients, neural variability accurately classified responder status from LFP recordings in both VS (for OCD) and GPi (for TS) targets. Cross-correlation and Granger causal analyses between the two targets showed different lead-lag intervals and directionality, indicating non-redundant information content. ConclusionOur findings demonstrate that increased low-frequency neural variability within the VS and GPi predicts symptom improvement in OCD and TS, respectively. These findings extend our previous results in OCD alone and recapitulate the notion that biological systems function optimally with a healthy degree of physiological variability.