Electrocorticographic (ECoG) correlates of language. I. Desynchronization in temporal language cortex during object naming.

The electrocorticogram (ECoG) was recorded during a language task, silent naming, from sites identified as essential for naming by electrical stimulation mapping and from surrounding cortex of left dominant temporal cortex at craniotomies under local anesthesia. The ECoG was analyzed quantitatively for a reduction in spectral density in 7-12 Hz frequencies indicating 'desynchronization.' These measurements were made on the averaged ECoG in 3 subjects and on individual ECoG segments in 4. Statistically significant increases in desynchronization were identified during silent naming at most sites essential for language, most often in the epoch from 700 to 1200 msec after presentation of the item to be named. During silent naming, there was a greater degree of desynchronization at those sites than in surrounding cortex. At several sites essential for language in several subjects, significantly less desynchronization was evident during a spatial task using physically identical stimuli. Thus, localized desynchronization in temporal cortex is an ECoG change with temporal, anatomic, and sometimes behavioral specificity to a language task. This finding provides insights into cortical physiologic mechanisms active during human language.