ECoG gamma activity during a language task: differentiating expressive and receptive speech areas.
Electrocorticographic (ECoG) spectral patterns obtained during language tasks from 12 epilepsy patients (age: 12-44 years) were analysed in order to identify and characterize cortical language areas. ECoG from 63 subdural electrodes (500 Hz/channel) chronically implanted over frontal, parietal and temporal lobes were examined. Two language tasks were performed. During the first language task, patients listened to a series of 50 words preceded by warning tones, and were asked to repeat each word. During a second memory task, subjects heard the 50 words from the first task randomly mixed with 50 new words and were asked to repeat the word only if it was a new word. Increases in ECoG gamma power (70-100 Hz) were observed in response to hearing tones (primary auditory cortex), hearing words (posterior temporal and parietal cortex) and repeating words (lateral frontal and anterior parietal cortex). These findings were compared to direct electrical stimulation and separate analysis of ECoG gamma changes during spontaneous inter-personal conversations. The results indicate that high-frequency ECoG reliably differentiates cortical areas associated with receptive and expressive speech processes for individual patients. Compared to listening to words, greater frontal lobe and decreased temporal lobe gamma activity was observed while speaking. The data support the concept of distributed functionally specific language modules interacting to serve receptive and expressive speech, with frontal lobe 'corollary discharges' suppressing low-level receptive cortical language areas in the temporal lobe during speaking.
Towle
Vernon L
VL
Department of Neurology, MC-2030, The University of Chicago, 5841 S. Maryland Avenue, Chicago, IL 60637, USA. towle@uchicago.edu
Yoon
Hyun-Ah
HA
Castelle
Michael
M
Edgar
J Christopher
JC
Biassou
Nadia M
NM
Frim
David M
DM
Spire
Jean-Paul
JP
Kohrman
Michael H
MH
D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D002648:Child; D003142:Communication; D004558:Electric Stimulation; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D006801:Humans; D007802:Language; D007807:Language Tests; D008297:Male; D012372:ROC Curve; D012815:Signal Processing, Computer-Assisted; D013060:Speech / Q000502:physiology*; D013067:Speech Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*; D014741:Video Recording