COGNITIVE OPERATIONS IN THE HUMAN CAUDATE-NUCLEUS

We have addressed the role of the head of caudate nucleus in tasks of lexical decision, semantic categorization, reading aloud, memory retri eval and object naming by recording neuronal activity from depth elect rodes in parkinsonism patients. The firing rate of cells was increased within 400-600 ms when semantic processing was required, Phonological differences increased firing from 1000 to 1200 ms. These responses we re similar to those described earlier in Broca's area. Both reading al oud and explicit memory retrieval tasks elicited an inhibition in firi ng of the same cells with an onset around 800 ms. The results confirm earlier lesion and stimulation studies, and provide a basis for relati ng cellular activity to studies of blood flow and scalp electrical act ivity in similar cognitive tasks thus helping us to understand the cel lular mechanisms involved in human cognition. (C) 1997 Elsevier Scienc e Ireland Ltd.