ELECTROCORTICOGRAPHIC CHANGES WITH HUMAN HIGHER FUNCTION

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Electrocorticographic (ECoG) changes accompanying human higher functions involving language are recorded directly from cortex in awake, behaving patients during the unique opportunity that occurs with the surgical treatment of epilepsy. ECoG changes are sought that are anatomically specific to those cortical sites independently identified as essential to that function by electrical stimulation mapping, and there, behaviorally specific, that is, absent on tasks using the same sensory input but processed with different higher functions. This proposal is an extension of our previous work where changes were visually identified in the averaged ECoG that had anatomic and behavioral specificity to silent naming: slow evoked potentials (EP's) at frontal language sites and desynchronization at posterior language sites. That desynchronization has been measured with spectral density techniques on ECoG during individual trials of silent naming, and the specificity confirmed statistically. An EP of unique morphology with anatomic and behavioral specificity to short-term verbal memory has been identified, measured, and that specificity confirmed statistically. Preliminary observations of ECoG changes during silent word reading have been made with some differences compared to changes with silent naming. The present posposal extends these studies by: Measurement of EP's related to motor speech function, determining if the EP related to memory also occurs at frontal sites, confirming ECoG changes with anatomic and behavioral specificity to reading, and identifying ECoG events with such specificity to auditory naming, word repetition and speech sound identification. The population variability in the occurrence of these events (identified to date in individuals patients) will be determined. The details of the extent and behavioral correlation of these ECoG events will test the hypothesis that language cortex is organized in mosaics of considerable behavioral specificity. The timing of events at different sites in the same patient will determine the degree of serial or parallel processing of a particular function. The morphology of these events may suggest underlying neurobiologic mechanisms. These studies will increase our understanding of where in the human brain language functions occur, and the neurobiologic mechanisms operative there during those behaviors.