Oscillations of pause-burst neurons in the STN correlate with the severity of motor signs in Parkinson’s disease

Abstract

BackgroundOscillatory activity in the subthalamic nucleus (STN) in Parkinson’s disease (PD) is under extensive study. While rhythmic features of local field potentials are implicated in the manifestation of PD motor signs, less is known about single unit activity (SUA). SUA parameters inside the STN show significant heterogeneity, and various firing patterns may contribute unequally to PD pathophysiology.ObjectivesWe searched for correlations between SUA parameters and PD motor signs, taking neuronal activity patterns into account.Methods829 spike trains for STN SUA were recorded during 25 DBS surgeries. We have isolated three firing patterns (tonic, irregular burst and pause-burst) and, using mixed linear models, examined several ISI parameters and burst descriptors (for the last two patterns) for their correlation with the UPDRS 3 score and bradykinesia and rigidity scores on the contralateral body side.ResultsThe predominance of pause-burst as opposed to tonic activity was associated with an increase in UPDRS 3 score. Oscillation scores in the alpha range correlated with bradykinesia and rigidity scores, and oscillation scores in the beta range correlated with bradykinesia score only for pause-burst neurons, while other patterns showed no correlation with PD motor signs. There was also significant negative correlation between bradykinesia score and theta oscillations for pause-burst pattern.ConclusionsPause-burst pattern and rhythmic neurons oscillating in the alpha range may affect motor processing in the basal ganglia more prominently than other activity patterns, probably reflecting progressive switching from tonic to burst to rhythmic activity in the parkinsonian state.