Compensatory reallocation of brain resources supporting verbal episodic memory in Alzheimer's disease

Abstract

The tight coupling of local neural activity to regional cerebral blood flow (rCBF) and the ease with which multiple whole brain images of rCBF can be obtained with¹⁵ O-water using PET has allowed the development of a powerful human brain functional mapping technique. ^[7-9] With use of cognitive and sensory tasks, this technique has been successfully applied in normal subjects, and although there have been a variety of studies of resting rCBF in AD patients, ^[10-14] few studies have examined rCBF in AD patients using activation paradigms. ^[15-18] The results of cross-sectional studies using PET ^[19,20] and SPECT ^[21-23] show decreases in blood flow in the temporal and parietal cortices early in AD, consistent with the pattern of neurodegenerative changes in these regions, although the reliability of these findings has been recently questioned. ^[24] Furthermore, longitudinal PET studies have shown that these changes may parallel or precede measurable change in cognitive function. ^[25]