Memory deficit and regional cerebral blood flow in early Alzheimer's Disease
The purpose of the present study was to systematically investigate the cognitive and memory deficits as well as the resting and activation patterns of regional cerebral blood flow (rCBF) in early putative Alzheimer's Disease (AD). Twenty normal elderly volunteers fulfilling the inclusion criteria for early AD were compared to twenty age-matched normal subjects. Both groups were given an extensive battery of cognitive, memory, and attention measures as well as two measures of rCBF: one during a steady-state condition and another during activation via Raven's Colored Progressive Matrices. The AD group demonstrated a lowered but normal intelligence level. Performance on tests of primary memory was normal, provided that distracting stimuli were not present. The early AD group performed deficiently on both verbal and nonverbal measures of secondary memory. Deficits in acquisition, transfer between memory stores, and retrieval were implicated, but storage processes were normal. The AD group demonstrated significant reductions in resting rCBF in both hemispheres. However, with activation the AD group revealed an enhanced cerebrovascular reserve to the Raven's Matrices task such that there were no longer significant group differences during the activation run. An overlay of heightened diffuse arousal was implicated in addition to the normal regional metabolic demands of the cerebral tissue. Sex differences contributed negligibly to the between-group differences and order of rCBF runs had a marginal effect. There was little relationship between many behavioral measures of the dementing process and resting and activation levels of CBF, with the exception of Full Scale IQ.