The effects of galvanic vestibular stimulation on motor cortical related potentials in Parkinson's disease

A recent study showed that vestibular stimulation can produce long-lasting alleviation of motor and non-motor symptoms in Parkinson’s disease (PD) sample. The mechanisms of action behind the alleviation of PD symptoms through vestibular stimulation are currently unknown. An electrophysiological marker known to be abnormal in PD is a particular movement-related cortical potential (MRCP) known as the Bereitschaftpotential (BP). The aim of this thesis was to observe the effects of galvanic vestibular stimulation (GVS) on reaction time and MRCPs in PD using electroencephalograph (EEG) to better understand its underlying physiological mechanisms. All Seventeen participants with a diagnosis of Parkinson’s disease completed a voluntary finger and foot tapping task and seven participants also completed a simple reaction time task whilst receiving both active and sham GVS. Analysis revealed that active GVS did not influence any of the mean amplitudes of the MRCPs nor participants reaction time. Exploratory correlation analysis revealed certain clinical characteristics modulated participants responsivity to GVS, however post-hoc manipulation of these correlations did not find them significant. It is unclear whether these null effects were observed due to a lack of sample size and neurologically healthy control group for baseline comparison. It is speculated whether a different GVS technique is needed in order to understand the previous literatures findings, and this is considered through GVS type and frequency.