Local field potential (LFP) recordings obtained from DBS electrodes in the STN often contain yet another distinct spectral peak, falling in the range between 200 and 400 Hz (Foffani et al., 2003, López-Azcárate et al., 2010, Özkurt et al., 2011, Wang et al., 2014). We will refer to these as high-frequency oscillations (HFO). Its amplitude displays a clear movement-related increase that is more pronounced after levodopa administration (Foffani et al., 2003, López-Azcárate et al., 2010, Litvak et al., 2012). A small number of studies have shown that, during rest, fluctuations in the amplitude envelope of these HFO may be coupled to the phase of beta band oscillations extracted from the same LFP signal (López-Azcárate et al., 2010, Özkurt et al., 2011). Coupling strength was found to be higher before compared to after levodopa administration. Despite first observations by López-Azcárate et al. (2010) of a significant correlation between the strength of PAC and off medication Unified Parkinson’s Disease Rating Scale (UPDRS) scores, it remains to be established to what extent PAC contributes to the symptoms of Parkinson’s disease.
