Deep brain stimulation increases motor cortical 1/f noise and decouples high gamma amplitude from beta phase

Deep brain stimulation (DBS) of the subthalamic nucleus is a common and effective treatment for Parkinsonian motor signs, including bradykinesia and rigidity. Recently, it was discovered that Parkinson’s Disease patients show pathological overcoupling between the beta phase and high gamma amplitude in the primary motor cortex (M1). DBS-induced decoupling may underlie improvement of Parkinsonian motor signs. In frontal and temporal regions, phase-amplitude coupling decreases with age. Empirical findings and computational simulations support the hypothesis that this reduction in coupling is caused by decreased synchrony in population spike timing. This desynchronization is also associated with increased 1/f noise, manifested as a flattening of the slope of the power spectral density. We test the hypothesis that the neurophysiological mechanism of high-frequency DBS of the STN is the desynchronization of M1 spiking. This hypothesis predicts that the decrease in M1 coupling is the result of population spike desynchronization, and thus the DBS-induced reduction in coupling should be predicted by the DBS-induced increase in 1/f noise.