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Phase-Amplitude Cross-Frequency Coupling in the Globus Pallidus Internus and Motor Cortex of Patients with Parkinson's Disease

  • Author(s): Tsiokos, Christos
  • Advisor(s): Pouratian, Nader
  • et al.
Abstract

Different models of the cortico-basal ganglia thalamocortical circuit are currently in existence, pointing to an incomplete understanding of those nuclei. Decades long research efforts have established the presence of oscillations in the basal ganglia and their link to functional and pathological states. More recently, hierarchical relations between those oscillations have also been shown to be functionally relevant. Phase-amplitude cross frequency coupling (PACFC), in particular, has been shown to exist within and between the human subthalamic nucleus (STN) and motor areas of the cortex. In our study we report high levels of PACFC in the human GPi of patients with Parkinson's disease (PD) and show its high correlation to local spectral power as well as coherence across GPi and motor cortex. Cross-site bidirectional PACFC was also shown to exist between the two sites in a small number of subjects. Contralateral finger movement seemed to significantly decrease coupling only in some subjects, possibly manifesting a deficiency in the diseased BG. The angle of modulation was about 28% the period of the slow oscillation and one subject had unusually high coupling (z-score = 148). The coupling was the strongest for the beta-gamma band pair, while there were also beta - (200-300 Hz) and theta - beta coupling to a lesser extent in a subset of subjects. The findings mark advances in our understanding of a nucleus that has received little attention compared to the STN, as well as its relation to the motor cortex.

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