Neuronal activity related to faces and matching in human right nondominant temporal cortex

Neuronal activity was recorded from 13 sites in right nondominant superior and middle temporal gyrus during matching of faces (FM), matching of complex figures (CM), labelling of facial emotional expression (FE) and object naming (N) in 11 patients undergoing craniotomy under local anaesthesia. These extracellular recordings were divided into 21 neuronal populations of one to a few cells, using amplitude window discriminators. Sixty-two percent of those populations showed statistically significant changes in activity during FM; 52% during FE; 38% during N and 38% during CM. Fifty-one percent of changes were in the first 1.3 s of each task and 33% in the next 1.3 s, when overt speech responses to the tasks occurred. Significant changes lasting throughout the 4 s allotted to each task were not seen. Functional correlates of some populations were derived from patterns of changes during FM and other tasks: four populations were related to 'matching', in that significant changes occurred with FM and CM. One of these populations, and six other populations were related to face perception, with significant change with FM and FE, confirming the presence in man of neuronal activity related to faces, as previously described from primate cortex. Six populations increased activity with overt speech; four of these showed greater increases when overt speech was in response to a visuospatial task compared with the lexical task.