CEREBRAL ACTIVATION DURING PERFORMANCE OF A CARD SORTING TEST

The Wisconsin Card Sorting Test (WCST) is used clinically for evaluati ng frontal lobe function, but there is some controversy as to its spec ificity for detecting frontal lobe damage. To investigate the cerebral regions essential to the performance of the Card Sorting Test, we mea sured the regional cerebral blood pow (rCBF) in 18 normal subjects by PET under the three conditions: (i) during the Modified Card Sorting T est (MCST); (ii) during a matching-to-sample (MTS) task, based on the MCST: but with selective attention to one of three stimulus categories (colour number or shape) as a control to cancel the effects of mainte nance of sets in the MCST (iii) under resting conditions as overall co ntrol. When rCBF during the MCST was compared with that during each MT S task separately significant activations were observed during the MCS T in the left or bilateral dorsolateral prefrontal cortex (DLPFC), bil ateral inferior parietal lobes, left superior occipital gyrus and left cerebellum. Compared with all the MTS tasks inclusively, significant increase in rCBF was detected during the MCST in the bilateral DLPFC, inferior parietal lobes, striate cortex, cerebellum and left occipital cortex. These results suggest the involvement of the DLPFC and other related areas such as the inferior parietal cortex in the execution of the MCST: and may help explain why a variety of brain lesions can res ult in impaired performance on the Card Sorting Test.