Online Detection of Gamma Oscillations in Ongoing Intracerebral Recordings: From Functional Mapping to Brain Computer Interfaces

The human brain displays rhythmic neural activity in a variety of frequencies and various spatial distributions in correlation with behavior. A growing body of evidence suggests that specific classes of oscillations can be modified voluntarily by the subject. Such endogenous modulation of brain oscillations is in principle a promising mechanism for direct brain-computer communication provided that it can be detected and decoded in real-time. Here, we investigate the utility of online spectral analysis of intracerebral recordings in an implanted epilepsy patient both from the perspective of functional brain mapping and brain-computer interfaces (BCIs). We found that mental calculation tasks elicited sustained increases in high gamma (30-150 Hz) oscillatory power at electrodes in the right inferior parietal lobule in the vicinity of the right intraparietal sulcus (IPS). Most importantly, the induced gamma modulations were visible online in single trial epochs. Beyond providing novel evidence for the utility of real-time spectral analysis as an additional clinical functional exploration tool, our results also demonstrate, as a proof of concept, the feasibility of a BCI system based on oscillatory gamma activity triggered by higher order cognitive processes such as those involved in mental calculation.