FUNCTIONAL MAPPING OF HUMAN-MEMORY USING PET - COMPARISONS OF CONCEPTUAL AND PERCEPTUAL TASKS

An experiment is reported in which regional cerebra blood flow (rCBF) was measured using positron emission tomography (PET) as participants performed conceptual and perceptual memory tasks. Blood flow during tw o conceptual tests of semantic cued recall and semantic association wa s compared to a control condition in which participants made semantic associations to nonstudied words. Analogously, rCBF during two percept ual tasks of word fragment cued recall and word fragment completion wa s compared to a word fragment nonstudied control condition. A direct c omparison of conceptual and perceptual tasks showed that conceptual ta sks activated media and lateral left hemisphere in frontal and tempora l regions as well as the lateral aspect; of bilateral inferior parieta l lobule. Perceptual tasks, in contrast, produced relatively greater a ctivation in right frontal and temporal cortex as well as bilateral ac tivation in more posterior regions. Comparisons of the memory tasks wi th their control conditions revealed memory-specific deactivations in left media and superior temporal cortex as well as left frontal cortex for both conceptual tasks. In contrast, memory-specific deactivations for both perceptual fragment completion tests were localized in poste rior regions including occipital cortex. Results from this and other f unctional imaging experiments provide evidence that conceptual and per ceptual memory processes are subserved, at least in part, by different neurological structures in the human brain.