Profiling Postural Control in Parkinson's Disease and Concussion Patients during a Virtual Reality Motion Sickness Stimulation: An EMG and Center of Pressure Data Analysis

This master’s thesis project is the culmination of six months of research conducted at the Motion Sickness and Postural Control Lab at Reykjavik University. The aim of this study is to highlight the potential utility of physiological responses to complex postural control tasks in evaluating different conditions and disabilities. For this purpose, two distinct populations are taken into consideration: individuals afflicted by Parkinson’s Disease and patients who have experienced an event of concussion. A total of 91 subjects was recruited, to participate in the BioVRSea experiment. Therefore, a comparative analysis was undertaken between each cohort and their respective healthy, age-matched control group. The goal is to discern variations in their response to a complex balancing task, which is implemented through the novel BioVRSea paradigm. The BioVRSea protocol constitutes a unique and innovative setup that employs a virtual reality environment and a moving platform, to simulate a scenario wherein the tested subject perceives themselves on a boat in the sea, exposed both to visual and motor stimuli. During the experiment different biosignals are measured, including electromyography, center of pressure, electroencephalography, electrocardiogram and electrodermal activity. This multiscale investigation particularly focuses on Electromyography and Center of Pressure data, for a mainly neuromuscular and biomechanical analysis of postural control. Subsequently to the complete acquisition of data coming from all healthy and pathological subjects, both electromyographic and force platform’s data were pre-processed implementing filtering. Furthermore, data underwent segmentation into different phases of the experiment, called baseline, PRE, MOV and POST phases. This segmentation into phases follows a subdivision dictated by the experiment’s scheduling and stimulation. The baseline corresponds to the phase in which the participant adapts to the virtual reality environment; the PRE phase follows and it is characterized by the only the visual stimuli through the sea waves scene; then in the MOV phase the platform starts moving according to the sea scene; and in the last segment called POST phase the platform stops moving and the subject is required to balance despite the induced movement provided by the previous segment. The final step into the data processing included the statistical analysis, which was performed for both Parkinson’s Disease and Concussion groups, with respect to their healthy control, in the three main phases of the experiment. Finally, a detailed discussion of the obtained results is provided. Significant variations in sway area were observed between healthy individuals and Parkinson’s patients, particularly during PRE and POST phases, while no notable difference was evident during MOV phase. In contrast, in the Concussion Study group, sway area values were comparable between healthy and pathological subjects. Nevertheless, distinct features extracted from the data exhibited significant differences between the two groups, primarily in the POST phase. Regarding muscle activity, a notable number of significant parameters were identified, particularly in the PRE and POST phases, specifically involving the tibialis anterior muscle, across both groups. Key biosignals for the differentiation of pathological subjects were identified. The inclusion of individuals with different conditions, and consequently different balance strategies, increased the relevance of collected data and obtained results. This study contributes to the validation of the BioVRSea protocols a gold standard for the quantitative measurements of motion sickness using bio-signals, advancing its recognition as a tool for the diagnostic of various conditions, and for the training and the rehabilitation for those who suffer motion sickness.