In a previous study using a subset of the data presented here (Litvak et al., 2011a), we found that dopaminergic treatment mainly affected low-beta (∼15–20 Hz) spectral power in the STN. By contrast, coherence between STN and activity in (pre)motor cortex centred around higher beta band frequencies (∼23–28 Hz) and was not modulated by levodopa. Here we extend these findings with the observation that beta–HFO PAC within the STN was largely confined to the low-beta range. This further strengthens the notion that there might be a functional subdivision within the beta band, with beta activity at lower frequencies being more conspicuously related to the hypo-dopaminergic state of Parkinsonism (Fogelson et al., 2006, Litvak et al., 2011a, Little et al., 2013b). In contrast, communication between STN and motor cortex seems to be mediated by high-beta frequencies, and it is unresolved whether this higher frequency beta activity is a marker of parkinsonian pathophysiology (Oswal et al., 2013b), leaving the possibility that it may form part of normal physiological network activity. Although we did not find clear evidence for PAC with beta oscillations
