Self-rated and informant-rated everyday function in comparison to objective markers of Alzheimer's disease.

It is recognized that individuals with mild cognitive impairment (MCI) already demonstrate difficulty in aspects of daily functioning, which predicts disease progression. This study examined the relationship between self- versus informant-report of functional ability, and how those reports relate to objective disease measures across the disease spectrum (i.e. cognitively normal, MCI, Alzheimer's disease). A total of 1080 subjects with self- and/or informant-rated Everyday Cognition questionnaires were included. Objective measures included cognitive functioning, structural brain atrophy, cerebrospinal fluid abnormalities, and a marker of amyloid deposition using positron emission tomography with [18F]AV45 (florbetapir). Overall, informant-report was consistently more associated with objective markers of disease than self-report although self-reported functional status may still have some utility in early disease.

Time estimation abilities in mild cognitive impairment and Alzheimer's disease.

Accurate time estimation abilities are assumed to play an important role in efficient performance of many daily activities. The authors investigated the role of episodic memory impairment in temporal perception using a prospective verbal time estimation paradigm. Verbal time estimations were made for filled intervals both within (i.e., <30 s) and beyond the time frame of working memory. In Experiment 1, the verbal time estimates of 24 individuals with mild cognitive impairment (MCI) were comparable with those of age-matched controls at both short and long (i.e., >30 s) intervals. The verbal time estimates of both older adult groups, however, deviated more significantly from true time when compared with younger adult controls. In Experiment 2, 17 individuals with Alzheimer's disease (AD) demonstrated greater error and variability in their time estimates, but no disproportionate differences emerged between short- and long-duration estimates when compared with age-matched controls. The findings did not support a noteworthy role for episodic memory impairment in temporal perception but rather elucidated a significant effect of normal aging, as well as a detrimental effect of AD on temporal perception.

Time estimation and episodic memory following traumatic brain injury.

The ability to accurately estimate the passage of time plays an important role in helping to structure daily activities. In this study, we used a prospective verbal time estimation paradigm to investigate time perception in 27 moderate to severe traumatic brain injury (TBI) participants and 27 controls. Verbal time estimations were made for filled intervals both within (i.e., <30 s) and beyond the time frame of working memory. We found that the TBI participants exhibited normal or near-normal estimates of time passage for duration up to 25 s. In contrast, for durations that exceeded working memory, the TBI group perceived less time as having passed than actually had passed as the TBI group significantly underestimated time when compared to controls. This pattern of data was interpreted as being due to episodic memory dysfunction.