Separating individual finger activity when performing force tasks using EEG source localization methods

Abstract

Electroencephalography (EEG) source localization has been applied in the development of braincomputer interfaces to control hand prostheses. When performing fine movements, our brain uses sensory feedback regarding position, velocity, and force to improve performance. Understanding the cortical mechanisms underlying individual finger movements can lead to a higher number of degrees of freedom (DoF) when developing BCI-controlled hand prostheses. Our goal was to test the efficacy of separating the activity of two individual fingers during a pinch-and-hold motor task using EEG source localization. EEG data from three healthy participants performing the motor task using different fingers were collected and analyzed using two parametric and two non-parametric source localization methods. A statistical analysis was performed on the source space to test whether it is possible to distinguish between the two fingers. We were able to measure the cortical response to the perturbations on the channel level during the hold phase of the motor task. However, source power in the primary motor (M1) and somatosensory (S1) cortices was low for all conditions. The most active sources were found in the frontal cortex over Brodmann area 8. A cluster-based permutation test performed on the source space results did not reveal differences between the two fingers on the cortical area. Statistically significant (p < 0:05) source differences are reported in one case, however, the locations of the sources indicate this effect is irrelevant to the motor task. Our findings indicate that there are no measurable source-level differences regarding the motor activity of individual fingers during the hold phase of the motor task, independently of the source localization method used.