Network-wide oscillations in the parkinsonian state: alterations in neuronal activities occur in the premotor cortex in parkinsonian nonhuman primates.

A number of studies suggest that Parkinson's disease (PD) is associated with alterations of neuronal activity patterns in the basal-ganglia-thalamocortical circuit. There are limited electrophysiological data, however, describing how the premotor cortex, which is involved in movement and decision-making, is likely impacted in PD. In this study, spontaneous local field potential (LFP) and single unit neuronal activity were recorded in the dorsal premotor area of nonhuman primates in both the naïve and parkinsonian state using the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of parkinsonism. In both animals, we observed a shift of power in LFP power spectral densities (1-350 Hz) from higher to lower frequency bands; parkinsonism resulted in increased power in frequencies <8 Hz and decreased power at frequencies >30 Hz. A comparable but not identical trend was observed in the power spectral analysis of single unit spike trains: alpha power increased in both animals and gamma power decreased in one; power in other frequency bands remaining unchanged. Although not consistent across animals, we also observed changes in discharge rates and bursting activity. Overall, the LFP and single unit analysis suggest that abnormalities in premotor neural activity are a feature of parkinsonism, although specific details of those abnormalities may differ between subjects. This study further supports the concept that PD is a network disorder that induces abnormal spontaneous neural activities across the basal-ganglia-thalamocortical circuit including the premotor cortex and provides foundational knowledge for future studies regarding the relationship between changes in neuronal activity in this region and the development of motor deficits in PD. NEW & NOTEWORTHY This study begins to fill a gap in knowledge regarding how Parkinson's disease (PD) may cause abnormal functioning of the premotor cortex. It is novel as the premotor activity is examined in both the naïve and parkinsonian states, in the same subjects, at the single unit and LFP level. It provides foundational knowledge on which to build future studies to explore the relationships between premotor activities and specific parkinsonian motor and cognitive deficits.