Dr. Gerwin Schalk, Director of the Chen Frontier lab for Applied Neurotechnology, was part of a team of researchers who were investigating the feasibility of passive functional mapping in the receptive language cortex during general anesthesia using electrocorticographic (ECoG) signals. The paper, entitled, “Passive functional mapping of receptive language cortex during general anesthesia using electrocorticography” was published in the March 2023 edition of the journal Clinical Neurophysiology.
Using subdurally placed ECoG grids to record cortical responses to speech stimuli during awake and anesthesia conditions, the researchers identified the cortical areas with significant responses to the stimuli using the spectro-temporal consistency of the brain signal in the broadband gamma (BBG) frequency band (70–170 Hz).
The team found that ECoG BBG responses during general anesthesia effectively identify cortical regions associated with receptive language function. Their analyses demonstrated that the ability to identify receptive language cortex varies across different states and depths of anesthesia. We confirmed these results by comparing them to receptive language areas identified during the awake condition. Quantification of these results demonstrated an average sensitivity and specificity of passive language mapping during general anesthesia to be 49±7.7% and 100%, respectively.
The results demonstrate that mapping receptive language cortex in patients during general anesthesia is indeed feasible and the team’s proposed protocol could greatly expand the population of patients that can benefit from passive language mapping techniques, which could eliminate the risks associated with electrocortical stimulation during an awake craniotomy.