Cognitive reserve among highly intelligent older individuals makes detection of early Alzheimer's disease (AD) difficult. We tested the hypothesis that mild memory impairment determined by IQ-adjusted norms is associated with single photon emission computed tomography (SPECT) perfusion abnormality at baseline and predictive of future decline. Twenty-three subjects with a Clinical Dementia Rating (CDR) score of 0, were reclassified after scores were adjusted for IQ into two groups, 10 as having mild memory impairments for ability (IQ-MI) and 13 as memory-normal (IQ-MN). Subjects underwent cognitive and functional assessments at baseline and annual follow-up for 3 years. Perfusion SPECT was acquired at baseline. At follow-up, the IQ-MI subjects demonstrated decline in memory, visuospatial processing, and phonemic fluency, and 6 of 10 had progressed to a CDR of 0.5, while the IQ-MN subjects did not show decline. The IQ-MI group had significantly lower perfusion than the IQ-MN group in parietal0precuneus, temporal, and opercular frontal regions. In contrast, higher perfusion was observed in IQ-MI compared with IQ-MN in the left medial frontal and rostral anterior cingulate regions. IQ-adjusted memory impairment in individuals with high cognitive reserve is associated with baseline SPECT abnormality in a pattern consistent with prodromal AD and predicts subsequent cognitive and functional decline. (JINS, 2007, 13, 821-831.)

This study presents normative data of commonly used neuropsychological tests administered to 75 individuals with high levels of intelligence (estimated IQ > or = 120). Participants were living independently in the community with ages ranging from 44 to 86. To avoid including individuals with an incipient dementia, we selected subjects who scored within the normal range on all cognitive tests for at least a two-year period. The norms are presented in table format to help clinicians easily identify a typical cognitive performance in highly intelligent individuals and to provide a useful guide for detecting abnormal cognitive decline in individuals at risk for progressive dementia.

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