Association of Neural Beta-Oscillations of the Subthalamic Nucleus with Clinical Symptoms of Parkinson’s Disease

Beta oscillations within the subthalamic nucleus (STN) are proposed to serve as biomarker for Parkinson’s disease. A wealth of data indicate essential functional differences between two subbands—low beta (13–19 Hz) and high beta (20–30 Hz), but full understanding of their specialization is still missing. We collected postoperative LFP data using externalized leads from 6 PD patients with implanted bilateral STN DBS electrodes before and after levodopa administration. We studied the relationship between parameters of low and high beta activity and motor symptom scales (UPDRS III, bradykinesia and rigidity). Mean PSD in both subbands decreased after levodopa administration. Low beta mean PSD was positively correlated with all three inspected motor scales (UPDRS III, rigidity and bradykinesia), while high beta mean PSD correlated only with rigidity. Most of the oscillatory peaks were concentrated within the high beta band. Their number decreased after levodopa administration, still leaving a prominent part unaffected. After levodopa administration, almost all of the low beta peaks compiling small initial number have disappeared, thus we analyzed only high beta peak parameters. High beta peak frequency and amplitude changed with OFF-ON transition and were correlated only with rigidity scores. Our findings indicate that, although both low and high beta respond to medication state, there are functional differences between the subbands: low beta reflects motor symptoms non-specifically, while high beta is more specialized and reflects rigidity.