A SINGLE-PHOTON EMISSION COMPUTERIZED-TOMOGRAPHY STUDY OF REGIONAL BRAIN-FUNCTION UNDERLYING VERBAL MEMORY IN PATIENTS WITH ALZHEIMER-TYPE DEMENTIA

Ten patients with Alzheimer-type dementia and nine age-matched normal controls were examined with SPECT, using split-dose Tc-99m-labelled ex ametazime. The baseline condition involved repetition of the word 'yes ' or 'no'. The activation condition involved recognition (indicated by a 'yes' or 'no') of words from a previously learned list presented al ong with distractor words. Patients who performed this task successful ly were selected, and efforts were made to match the patients with con trols according to their performance on the task, although this was no t fully achieved. Uptake of Tc-99m-exametazime was estimated at baseli ne and during the word-recognition task for predetermined regions of i nterest drawn from a standard neuroanatomical atlas. The baseline task appeared to normalise tracer uptake for frontal, temporal and parieta l cortex in the patient group. However, during the recognition task, c ontrols but not patients showed activation effects. These were most pr ominent in dorsolateral frontal cortex and adjacent anterior cingulate cortex. Among patients, successful performance was correlated with ac tivation of dorsolateral frontal and parietal cortex on the left side. The results confirm the central role of frontal mechanisms in a recog nition memory task. The study highlights some of the difficulties of u sing cognitive challenge tests in clinical groups.