Movement Related Cortical Potentials in Parkinson's Disease Patients with Freezing of Gait

Parkinson's disease (PD) is a complex neurode-generative disorder that results into poverty of movements. Freezing of gait (FOG) is a common and severely incapacitating symptom of PD. However, the underlying neurophysiological mechanism of FOG is still unclear. Electroencephalogram (EEG) as a non-invasive brain signal measurement method has been repeatedly used to reveal the pathological reasons behind PD. Since PD affects movement abilities, one particular type of EEG pattern called Movement-related cortical potential (MRCP), which was shown to be related to the generation of movement intention, can be a useful tool in PD research. However, most MRCP studies in PD area focus on the upper-limb movement like finger movement, to the best knowledge of the authors, no study explored MRCP characteristics during lower extremity movement in PD patients, particularly PD patients with FOG. This paper intends to investigate the relationship between the characteristics of MRCP and FOG by comparing MRCP signals among three groups: healthy controls group, PD patients without FOG group, and PD patients with FOG group. These three groups of participants were recruited based on age-matching and gender proportion matching criteria. During the experiment, the Electromyography (EMG) from the tibialis anterior (TA) muscle and EEG were recorded when performing ankle dorsiflexion (AD) by the dominant foot. MRCP signals were extracted from EEG data based on the muscle activities in the TA muscle of the dominant foot. The results of this study show that, during lower limb activities, MRCP shares considerable similarities between PD patients and healthy participants. However, the amplitude of MRCP in PD patients (with and without FOG) is lower compared to the healthy participants. In addition, direct observations from the results show that MRCP from PD patients with FOG has higher amplitude but more variability in terms of amplitude and latency than those from PD patients without FOG.