Abstracts

Rationale: Functional mapping of eloquent cortex is often a necessary component of brain surgery planning, but current stimulation techniques are inefficient and can provoke unwanted seizures. Here, we present a new rapid, accurate, and practical mapping system that extracts relevant event-related cortical activity from passive electrocorticographic (ECoG) recordings while patients carry out simple behavior. Unlike previous related methodologies, this novel mapping procedure is designed to demonstrate single-trial event-related spectral alterations to localize and discriminate sensory and motor cortices. Methods: We evaluated 10 patients with epilepsy on a series of motor tasks including simple speech articulation and hand button press. Events were detected precisely with a standard analog output microphone and button press box. ECoG signal was recorded and processed in real-time (with updating every 50 ms) along with event detection. We created a user-friendly interface that displays 1) continuous spectral power, 2) single-trial event-related spectrogram, and 3) running average of event-related spectrograms. Results: For speech sounds, we could rapidly localize the motor cortex corresponding to lip and tongue articulators, as well as, sensory feedback in the lateral auditory cortex. For button press, we could easily localize the hand motor and sensory cortex. Motor function was distinguished from sensory function by evaluation of the temporal relationship of cortical activation to event onset. Finally, our passive mapping results demonstrated high concordance with results derived using blinded electrical cortical stimulation mapping. The results show that our procedure derives a complete functional motor and sensory cortical map in seconds, and usually less than 15 trials. Conclusions: In summary, we demonstrate a novel and practical cortical mapping procedure as a new tool for neuroscientific and clinical application.