Spatiotemporal dynamics of electrocorticographic high gamma activity during overt and covert word repetition

• Published in: NeuroImage (Orlando, Fla.) Vol. 54; no. 4; pp. 2960 - 2972
• Main Authors: Pei, Xiaomei, Leuthardt, Eric C., Gaona, Charles M., Brunner, Peter, Wolpaw, Jonathan R., Schalk, Gerwin
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 14.02.2011; Elsevier Limited
• Subjects: Acoustics; Adolescent; Adult; Brain - physiology; Brain Mapping; Brain research; electrocorticography (ECoG); Electrodes; Electroencephalography; Female; high gamma activity; Humans; Language; Male; Medical imaging; Middle Aged; Monitoring systems; Signal Processing, Computer-Assisted; Studies; temporal lobe; Verbal Behavior - physiology; verbal response; word processing; high gamma activity; verbal response; electrocorticography (ECoG); temporal lobe; word processing
• DOI: 10.1016/j.neuroimage.2010.10.029
• ISSN: 1053-8119; 1095-9572

Language is one of the defining abilities of humans. Many studies have characterized the neural correlates of different aspects of language processing. However, the imaging techniques typically used in these studies were limited in either their temporal or spatial resolution. Electrocorticographic (ECoG) recordings from the surface of the brain combine high spatial with high temporal resolution and thus could be a valuable tool for the study of neural correlates of language function. In this study, we defined the spatiotemporal dynamics of ECoG activity during a word repetition task in nine human subjects. ECoG was recorded while each subject overtly or covertly repeated words that were presented either visually or auditorily. ECoG amplitudes in the high gamma (HG) band confidently tracked neural changes associated with stimulus presentation and with the subject's verbal response. Overt word production was primarily associated with HG changes in the superior and middle parts of temporal lobe, Wernicke's area, the supramarginal gyrus, Broca's area, premotor cortex (PMC), primary motor cortex. Covert word production was primarily associated with HG changes in superior temporal lobe and the supramarginal gyrus. Acoustic processing from both auditory stimuli as well as the subject's own voice resulted in HG power changes in superior temporal lobe and Wernicke's area. In summary, this study represents a comprehensive characterization of overt and covert speech using electrophysiological imaging with high spatial and temporal resolution. It thereby complements the findings of previous neuroimaging studies of language and thus further adds to current understanding of word processing in humans. ►ECoG gamma activity reflects spatiotemporal dynamics during a word repetition task. ►Overt word repetition involves ECoG gamma changes in a widely distributed network. ►Activity during overt but not covert tasks rely on motor cortical networks.