The majority of subjects showed clear significant beta–HFO PAC in either left or right STN, OFF or ON medication state. PAC averaged across all sides and subjects was higher in the OFF state compared to the ON state, due to the appearance of a high peak for phase frequencies in the lower beta range (Fig. 1A). The frequency of the phase modulated HFO was also lower in the OFF than ON medication state. The same pattern can be observed when looking at the percentage of cases showing significant PAC (Fig. 1B), as determined by our parametric estimation of PAC (see van Wijk et al., 2015). These medication-induced modulations suggest that both the strength of PAC and the combination of phase and amplitude frequencies at which it occurs could be important markers for the severity of motor impairment.
