Analysis of Brain Signals from Patients with Parkinson’s Disease using Self-Supervised Learning

Sammanfattning: Parkinson’s disease (PD) is one of the most common neurodegenerative brain disorders, commonly diagnosed and monitored via clinical examinations, which can be imprecise and lead to a delayed or inaccurate diagnosis. Therefore, recent research has focused on finding biomarkers by analyzing brain networks’ neural activity to find abnormalities associated with PD pathology. Brain signals can be measured using Magnetoencephalography (MEG) or Electroencephalogram (EEG), which have demonstrated their practical use in decoding neural activity. Nevertheless, interpreting and labeling human neural activity measured using MEG/EEG is yet a challenging task requiring vast of time and expertise. In addition, there is a risk of introducing bias or omitting important information not recognizable by humans. This thesis investigates whether it is possible to find meaningful features relevant to PD by uncovering the brain signals’ underlying structure using self-supervised learning (SSL), requiring no labels or hand-crafted features. Four experiments on one EEG and one MEG dataset were conducted to evaluate if the features found during the SSL were meaningful, including t-SNE, silhouette coefficient, Kolmogorov-Smirnov test, and classification performance. Additionally, transfer learning between the two datasets was tested. The SSL model, TS-TCC, was employed in this thesis due to its outstanding performance on two other EEGdatasets and its training efficiency. The evaluation of the EEG dataset inferred it was feasible to find meaningful features to distinguish PD from healthy controls to some extent using SSL. However, more investigations of reusing the features in a downstream task are needed. The evaluation of the MEG dataset did not reach the same satisfying result, the proposed reason, among others, was the amount of data. Lastly, transfer learning was unsuccessful in the setting of transforming knowledge from the EEG to the MEG dataset.