The dynamics of language-related high-gamma activity assessed on a spatially-normalized brain

ObjectiveWe developed a novel technique of spatial normalization of subdural electrode positions across subjects and assessed the spatial–temporal dynamics of high-gamma activity (HGA) in the dominant hemisphere elicited by three distinct language tasks.MethodsThe normalization process was applied to 1512 subdural electrodes implanted in 21 patients with intractable epilepsy. We projected each task-related HGA profile onto a normalized brain.ResultsThe word interpretation task initially elicited HGA augmentation in the bilateral fusiform gyri at 100 ms after stimulus onsets, subsequently in the left posterior middle temporal gyrus, in the left ventral premotor cortex at 200 ms and in the left middle and left inferior frontal gyri at 300 ms and after. The picture naming task elicited HGA augmentation in few sites in the left frontal lobe. The verb generation task elicited HGA in the left superior temporal gyrus at 100–600 ms. Common HGA augmentation elicited by all three tasks was noted in the left posterior-middle temporal and left ventral premotor cortices.ConclusionsThe spatial–temporal dynamics of language-related HGA were demonstrated on a spatially-normalized brain template.SignificanceThis study externally validated the spatial and temporal dynamics of language processing suggested by previous neuroimaging and electrophysiological studies.

► We made spatial normalization of 1512 intracranial electrodes in 21 patients with intractable epilepsy to identify typical dynamics of semantic processing. ► Word interpretation task evoked high gamma activity (HGA) at 200 ms after stimulus onset on the posterior temporal language area and alternatively at 400 ms on the frontal language area, following the initial HGA of bilateral fusiform gyri. ► The novel ECoG-normalization technique evolved visualization of electrophysiological dynamics related to semantic processing among individual subjects.