Consistency of Long-Term Subdural Electrocorticography in Humans.

OBJECTIVE: Subdural electrocorticography (ECoG) can provide a robust control signal for a brain-computer interface (BCI). However, the long-term recording properties of ECoG are poorly understood as most ECoG studies in the BCI field have only used signals recorded for less than 28 days. We assessed human ECoG recordings over durations of many months to investigate changes to recording quality that occur with long-term implantation.

METHODS: We examined changes in signal properties over time from 15 ambulatory humans who had continuous subdural ECoG monitoring for 184-766 days.

RESULTS: Individual electrodes demonstrated varying changes in frequency power characteristics over time within individual patients and between patients. Group level analyses demonstrated that there were only small changes in effective signal bandwidth and spectral band power across months. High-gamma signals could be recorded throughout the study, though there was a decline in signal power for some electrodes.

CONCLUSION: ECoG-based BCI systems can robustly record high-frequency activity over multiple years, albeit with marked intersubject variability.

SIGNIFICANCE: Group level results demonstrated that ECoG is a promising modality for long-term BCI and neural prosthesis applications.