Brain correlates of memory processes in patients with dementia of Alzheimer's type: a SPECT Activation Study

Task-induced changes in regional cerebral blood flow (rCBF) during verbal episodic memory activation were compared in 17 right-handed patients with dementia of the Alzheimer's type (DAT) and 20 healthy volunteers. Regional cerebral blood flow was assessed using single photon emission computed tomography (SPECT) and an injection of 133Xe (xenon, isotope of mass 133) in 21 regions of interest (ROI) during rest, passive listening to 36 words, and memorizing of a 12-word list repeated three times. In healthy subjects, memory-listening comparison showed activation of a distributed system involving several left-sided ROI, especially the posterior inferior frontal region. In patients with DAT, the same pattern of activation was found for listening-rest comparison, and no significant changes were found in memory-listening comparison. During listening compared with rest, significant activation was observed in left-sided hypoperfused regions. A significant correlation between memory performance and rCBF recorded in patients with DAT during the memory task was found only in the right lateral frontal region, a region that was not hypoperfused significantly in patients. The involvement of this region might relate to either retrieval effort or actual performance of patients with DAT on the memory task.