The magnitude of PAC and spectral power detected in our recorded signals might have depended on the positioning of the electrodes with respect to the generating source. It is even possible that beta oscillations and HFO may originate in slightly different spatial locations (Wang et al., 2014). Variability across subjects in targeting the right compartment of the STN could have influenced both absolute and relative spectral values. PAC on the other hand, might be less sensitive to this issue as it is a normalised measure based on the variance of amplitude fluctuations present in the signal. Given that the difference in correlations coefficients for the relation with UPDRS scores were relatively small between PAC and beta power, the predominance of one over the other should be carefully interpreted.
