Memory Patterns and Executive Functioning in Mild Cognitive Impairment and Alzheimer's Disease

Abstract

The present study examined the similarities in the pattern of cognitive loss in Alzheimer's Disease (AD) and Mild Cognitive Impairment (MCI). We administered a battery of neuropsychological tests to individuals with these disorders as well as to a group of cognitively intact controls. The battery included measures of memory acquisition, consolidation, and retrieval, as well as tests of language, visuospatial ability, psychomotor speed, and executive functioning. All subjects (N =62) were evaluated in a memory disorder clinic and were diagnosed by a consensus procedure. Multivariate and univariate statistical methods were used to examine differences in level of performance on all neuropsychological tests and in the pattern of performance for memory measures. We found a significant difference between controls and the MCI and AD groups in terms of consolidation, but not in acquisition or retrieval. The MCI and AD groups did not differ in the pattern of memory processing. Also, the only non-memory neurocognitive domain in which MCI group differed significantly from the control group was executive functioning. Our findings suggest that the pattern of loss of memory function of MCI patients parallels that of AD patients. Also, our finding that executive functioning was the only other neurocognitive domain in which the control and MCI groups differed significantly is in contrast to traditional clinical lore that implicates language dysfunction and/or visuospatial deficits early in AD. These findings provide preliminary evidence that consolidation deficits and subtle declines in executive functioning may be the most useful cognitive markers for the early direction of AD.