Young and nondemented older adults were tested on a continuous recognition memory task requiring visual pattern separation. During the task, some objects were repeated across trials and some objects, referred to as lures, were presented that were similar to previously presented objects. The lures resulted in increased interference and an increased need for pattern separation. For each object, the participant was asked to indicate whether (1) this was the first time the object was seen (new), (2) the object was seen previously (old), or (3) the object was similar to a previous object (similar). Older adults were able to correctly identify objects as old or new as well as young adults; however, older adults were impaired when identifying lures as similar. Therefore, pattern separation may be less efficient in older adults resulting in poorer recognition memory performance when interference is increased.A primary region of the brain affected by normal aging is the hippocampus in humans (Good et al. 2001;Allen et al. 2005;Driscoll and Sutherland 2005;Raz et al. 2005;Walhovd et al. 2005) and animal models (Rosenzweig and Barnes 2003;Driscoll et al. 2006). However, the subregions of the hippocampus may be differentially affected by normal aging (Small et al. 2002(Small et al. , 2004. The dentate gyrus (DG) subregion may be particularly susceptible to age-related changes in both humans (Small et al. 2002) and animal models (Small et al. 2004;Patrylo and Williamson 2007), whereas aging may have less of an impact on pyramidal cells in the CA subregions (Small et al. 2002(Small et al. , 2004. In contrast, the CA subregions of the hippocampus may be more vulnerable to pathological aging associated with Alzheimer's disease (Braak and Braak 1996;Price et al. 2001;West et al. 2001). Therefore, tasks sensitive to dysfunction in particular subregions of the hippocampus may help to differentiate cognitive impairment associated with normal aging from pathological changes associated with Alzheimer's disease. Although hippocampal-dependent tasks are highly sensitive to age-related changes in the brain (for review, see Rosenzweig and Barnes 2003), behavioral studies in humans have not examined the performance of nondemented older adults on tasks shown to be particularly sensitive to DG function. As described in detail below, a key function of the DG may be to support pattern separation. Age-related changes in the DG may impair the ability to reduce similarity among new input patterns, resulting in decreased pattern separation (Wilson et al. 2006). Therefore, decreased efficiency in pattern separation may be a critical, but relatively unexamined, processing deficit in nondemented older humans.Pattern separation is described as a mechanism for separating partially overlapping patterns of activation so that one pattern may be retrieved as separate from other patterns (Gilbert et al. 2001;Gilbert and Kesner 2006;Kirwan and Stark 2007). The operation of a pattern separation mechanism is critical for reducing potential interference among ...

Performance-based measures of IADLs, particularly medication management ability, are sensitive to subtle functional declines in PD-MCI. Although impairment in performance-based measures is associated with cognitive status in PD, IADLs may be a separate domain of functioning from cognitive functioning in PD-MCI as these measures did not correlate with performance on the neuropsychological measures. Overall, performance-based assessment of IADLs may add to the clinical evaluation of PD-MCI.

Although individuals with Parkinson’s disease (PD) evidence moderate deficits in prospective memory (PM), it is not known whether PM deficits confer an increased risk of poorer everyday functioning. In the current study, 33 individuals with PD and 26 demographically similar normal controls (NC) were administered performance-based and self-report measures of PM and everyday functioning, including medication and financial management. As compared to NC, PD participants demonstrated significantly lower scores on performance-based measures of PM and financial capacity, worse performance at a trend level on performance-based medication management and endorsed significantly greater self-reported declines in PM and instrumental activities of daily living (iADLs). In the PD sample, the laboratory measure of PM significantly correlated with performance-based measures of financial capacity and medication management and a self-report measure of medication management. Self-reported PM failures significantly correlated with perceived declines in iADLs, worse medication management, and poorer health-related quality of life. Although future studies are needed to examine the incremental ecological validity of PM in PD, findings from this study extend prior research by providing preliminary evidence that PM impairment may play a significant role in a range of critical everyday functions in PD.

Young and nondemented older adults completed a visual object continuous recognition memory task in which some stimuli (lures) were similar but not identical to previously presented objects. The lures were hypothesized to result in increased interference and increased pattern separation demand. To examine variability in object pattern separation deficits, older adults were divided into impaired and unimpaired groups based on performance on a standardized serial list-learning task. Impaired older adults showed intact recognition memory, but were impaired relative to young and unimpaired older adults when identifying similar lure stimuli, demonstrating that object pattern separation varies in older adults.