Coherent Activity in Bilateral Parieto-Occipital Cortices during P300-BCI Operation.

Kouji Takano,Hiroki Ora,Kenji Kansaku,Kensuke Sekihara,Sunao Iwaki

doi:10.3389/fneur.2014.00074

Abstract

The visual P300 brain–computer interface (BCI), a popular system for electroencephalography (EEG)-based BCI, uses the P300 event-related potential to select an icon arranged in a flicker matrix. In earlier studies, we used green/blue (GB) luminance and chromatic changes in the P300-BCI system and reported that this luminance and chromatic flicker matrix was associated with better performance and greater subject comfort compared with the conventional white/gray (WG) luminance flicker matrix. To highlight areas involved in improved P300-BCI performance, we used simultaneous EEG–fMRI recordings and showed enhanced activities in bilateral and right lateralized parieto-occipital areas. Here, to capture coherent activities of the areas during P300-BCI, we collected whole-head 306-channel magnetoencephalography data. When comparing functional connectivity between the right and left parieto-occipital channels, significantly greater functional connectivity in the alpha band was observed under the GB flicker matrix condition than under the WG flicker matrix condition. Current sources were estimated with a narrow-band adaptive spatial filter, and mean imaginary coherence was computed in the alpha band. Significantly greater coherence was observed in the right posterior parietal cortex under the GB than under the WG condition. Re-analysis of previous EEG-based P300-BCI data showed significant correlations between the power of the coherence of the bilateral parieto-occipital cortices and their performance accuracy. These results suggest that coherent activity in the bilateral parieto-occipital cortices plays a significant role in effectively driving the P300-BCI.

Highlights

The brain–machine interface (BMI) or brain–computer interface (BCI) is an interface technology that uses neurophysiological signals from the brain to control external machines or computers [1,2,3]
When comparing functional connectivity between the right and left parieto-occipital channels, significantly greater functional connectivity in the alpha band was observed under the GB flicker matrix condition than under the WG flicker matrix condition
When comparing functional connectivity between the right and left occipital channels, significantly greater functional connectivity in the alpha band was observed under the GB than under the WG flicker matrix condition

Summary

INTRODUCTION

The brain–machine interface (BMI) or brain–computer interface (BCI) is an interface technology that uses neurophysiological signals from the brain to control external machines or computers [1,2,3]. Our fMRI–EEG study suggested the importance of the parietal and occipital regions, especially in the right hemisphere, for the operation of P300-BCI with the GB flicker matrix. We used 306-channel whole-head magnetoencephalography (MEG), which has high spatial resolution compared with EEG, to investigate coherent activity in these areas during the P300-BCI operation. In our previous EEG–fMRI study, we showed that greater activity was elicited in the right inferior parietal lobule by GB than by WG flicker [11]. We reanalyzed some previous EEG-based P300-BCI data, and further investigated the coherence of the power spectrum between bilateral parieto-occipital cortices and performance accuracy. Each row/column of the matrix was intensified in random order (Figure 1)

MATERIALS AND METHODS

RESULTS

DISCUSSION