Greater metabolic rate decreases in hippocampal formation and proisocortex than in neocortex in Alzheimer's disease

Neuropathological studies of Alzheimer's disease (AD) have found pathological changes in some cytoarchitectural regions and relative sparing in others. Positron emission tomography (PET) studies have also shown selective decreases in glucose metabolic rates but have generally focused on whole brain lobes or geometrically derived regions of interest. In this report, a template of Brodmann areas, derived from a whole brain histological section atlas, was used to analyze PET findings from 34 AD patients and 16 control subjects matched for age, sex, and educational level. AD patients had lowest glucose metabolic rates in limbic areas of the temporal lobe and other proisocortical areas higher rates in frontal lobe and unimodal association areas, and relative sparing of parietal/occipital lobes and motor/sensory cortices. Analysis of variance revealed larger effect sizes when AD and control subjects were compared on metabolic rate for cortical type than for lobe. These findings, which parallel neuropathological studies of regional distribution of neurofibrillary tangles in AD, suggest that vulnerability is greatest in cortical areas that are in closer synaptic contact with limbic areas.