Spatial patterns of SSSEP under the selective attention to tactile stimuli in each hand

Steady-state somatosensory evoked potential (SSSEP) is a recently developing brain-computer interface (BCI) paradigm where the brain response to tactile stimulation of a specific frequency is used. Generally, SSSEP-based BCI classifies whether the subjects focus on the tactile stimulation at the fingers in the left or right hand. In this paper, we examine the spatial pattern difference in SSSEP from each kind of focuses. The experimental results showed that when the subjects focus to the stimulation at one hand, SSSEP response in the contralateral side decreases. These results could be related to the neurological background, that the sensory cortices for each hand is located in the contra lateral sides of the hands. We also investigate the spatial patterns obtained from common spatial pattern (CSP). In the survey results, the spatial filters, whose corresponding spatial pattern vectors emphasize the left and right parietal lobes, where the somatosensory cortices for each hand are located, made clearly separable clusters of the feature values for each class.