Single-trial movement intention detection estimation in patients with Parkinson's disease: a movement-related cortical potential study.

Parkinson patients often suffer from motor impairments such as tremor and freezing of movement that can be difficult to treat. To unfreeze movement, it has been suggested to provide sensory stimuli. To avoid constant stimulation, episodes with freezing of movement needs to be detected which is a challenge. This can potentially be obtained using a brain-computer interface (BCI) based on movement-related cortical potentials (MRCPs) that are observed in association with the intention to move. The objective in this study was to detect MRCPs from single-trial EEG. 
Approach: Nine Parkinson patients executed 100 wrist movements and 100 ankle movements while continuous EEG and EMG were recorded. The experiment was repeated in two sessions on separate days. Using temporal, spectral and template matching features, a random forest, linear discriminant analysis, and k-nearest neighbours classifier were constructed in offline analysis to discriminate between epochs containing movement-related or idle brain activity to provide an estimation of the performance of a BCI. Three classification scenarios were tested: 1) within-session (using training and testing data from the same session and participant), between-session (using data from the same participant from session one for training and session two for testing), and across-participant (using data from all participants except one for training and testing on the remaining participant). 
Main results: The within-session classification scenario was associated with the highest classification accuracies which were in the range of 88-89% with a similar performance across sessions. The performance dropped to 69-75% and 70-75% for the between-session and across-participant classification scenario, respectively. The highest classification accuracies were obtained for the random forest and k-nearest neighbours classifiers. 
Significance: The results indicate that it is possible to detect movement intentions in individuals with Parkinson's disease such that they can operate a BCI which may control the delivery of sensory stimuli to unfreeze movement. 
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