AGE-RELATED-CHANGES IN CEREBRAL BLOOD-FLOW ACTIVATION DURING A CARD SORTING TEST

To determine the age-related changes in the neural processing involved in the Modified Card Sorting Test (MCST), we measured cerebral blood flow (CBF) during performance of the MCST and of the number-matching t ask in young and elderly subjects using positron emission tomography. Compared with that during the number-matching task, CBF during the MCS T was increased in the left dorsolateral prefrontal cortex (DLPFC), le ft inferior parietal lobule, and left striate and prestriate cortices in both age groups. However, CBF ac tivation in these areas was signif icantly lower in the elderly subjects than the young subjects. Further more, CBF activation was reduced in the left DLPFC, right parahippocam pal gyrus, and prestriate cortex in proportion to the increase in the number of perseverative errors with aging. These results suggest that the impaired MCST performance in elderly subjects may be due, in part, to dysfunction of the network involving certain cortical areas such a s the prefrontal and parahippocampal cortices, although the essential neural circuits for MCST performance were still preserved even in the elderly subjects.