No abstract

A subtle decline in episodic memory often occurs prior to the emergence of the full dementia syndrome in nondemented older adults who develop Alzheimer's disease (AD). The APOE-epsilon4 genotype may engender a more virulent form of AD that hastens this decline. To examine this possibility, we compared the rate of decline in episodic memory during the preclinical phase of AD in individuals with or without at least one APOE epsilon4 allele. Nondemented normal control (NC; n = 84) participants, nondemented older adults who subsequently developed dementia within 1 or 2 years (i.e., preclinical AD; n = 20), and patients with mild AD (n = 53) were examined with 2 commonly employed tests of episodic memory, the Logical Memory subtest of the Wechsler Memory Scale-Revised and the California Verbal Learning Test. Results revealed a precipitous decline in verbal memory abilities 1 to 2 years prior to the onset of the dementia syndrome, but there was little effect of APOE genotype on the rate of this memory decline. The presence of an APOE-epsilon4 allele, however, did have a differential effect on the sensitivity of the 2 types of memory tests for tracking progression and made an independent contribution to the prediction of conversion to AD.

The ability to generate words from phonemic (i.e., words beginning with 'F,' 'A,' and 'S') and semantic (i.e., animals, fruits, and vegetables) categories was assessed longitudinally in patients with Alzheimer's disease (AD; N 5 59) and normal controls (NC; N 5 59). Patients with AD performed worse than NC participants on both tasks at each of 4 annual evaluations and exhibited greater impairment relative to controls on the semantic-category task than on the phonemic-category task. In addition, the performance of the patients with AD declined over time on both tasks, but the rate of decline was faster on the semantic-category than on the phonemic-category task. Examination of individual responses across the annual evaluations revealed that patients with AD were more consistent than NC participants in failing to generate previously produced semantic-category, but not phonemic-category, items in all years following the 1st year in which the item was not produced. These results are consistent with the notion that patients with AD suffer a gradual deterioration of the organization and content of semantic memory as the disease progresses. (JINS, 1999, 5, 692-703.)

Background-Chronic elevations in cortisol associated with prolonged stress have been associated with memory loss, as has the APOE-ε4 genotype. The combined effects of stress and APOE status on memory and cortisol in humans have not been studied.

No abstract

Previous studies have examined the impact of subcortical hyperintensities (SH), a proxy measure of cerebrovascular disease, on the cognitive abilities of otherwise healthy older adults. However, there remains a limited understanding as to what extent this MRI marker of pathological processes explains the decline in specific cognitive functions that occur nearly ubiquitously with advanced age, especially in relation to other age-related imaging markers. In the present study we compared cognitive abilities between a sample of 53 older healthy adults (age range=50-79) and a sample of 53 younger adults (age range=21-40). As expected, the older group performed significantly worse on most cognitive measures compared to the younger group. Frontal volume and total grey matter volume were also significantly reduced among the older individuals compared to the younger individuals. SH volume was consistently associated with cognitive function in older adults, though, this relationship was evident only for a relatively small subset of older individuals with the most severe SH. These data suggest that the relationship between SH and cognition in the elderly is driven by a subset of individuals who may be in the earliest stages of vascular cognitive impairment. Further, the findings suggest that cognitive aging is largely determined by factors other than SH for most older adults.

There are many conflicting results concerning the effects of age and Alzheimer's disease (AD) on word-stem completion priming. To examine potential sources of this variability, the authors examined the influences on such priming of age, cognitive status, and encoding in a large sample of young, old, and AD individuals. At study, words were processed aloud by reading, reading and rating likeability, or generating from definition. Old participants had less priming than young participants and more priming than AD patients. For the healthy old participants, priming decreased with advancing age and with cognitive loss following generation only. For AD patients, priming decreased as dementia severity increased; patients with the mildest dementia did not differ from healthy old participants. Thus, age, cognitive status, and encoding differentially influenced the magnitude of priming in healthy aging and AD.

The contributions of text meaning, new between-word associations, and single-word repetition to priming in text rereading in younger and older adults, and in patients with Alzheimer's disease. (AD), were assessed in Experiment 1. Explicit recognition memory for text was also assessed. Equivalent single-word and between-word priming was observed for all groups, even though patients with AD showed impaired explicit memory for individual words in the text. The contribution of generalized reading task skill to priming in meaningless text rereading in younger adults was assessed in Experiment 2. Generalized reading task skill was also found to contribute to priming. These results reveal 3 mechanisms of priming: new between-word associations for meaningful and meaningless text, individual word repetition for meaningless text, and general task or skill factors for meaningless text. All priming mechanisms appear to be intact in older adults and in patients with AD.