Type II diabetes and impaired glucose tolerance (IGT) are both associated with cognitive impairment and an increased risk of dementia, and normal aging has been shown to be accompanied by abnormalities in glucose regulation. The present study was conducted to determine if variations in cognitive performance would be observed as a function of glucose regulation in a healthy elderly population. Thus, cognitive functioning was measured in 93 healthy male and female older participants who ranged in age from 55 to 88. Participants had a glucose tolerance tests from which several biological indices were obtained including various glucose and insulin measures, and were separated into better and poorer glucoregulatory groups on the basis of these indices. Participants underwent two cognitive testing sessions, one after drinking a saccharin solution and another after drinking a glucose solution (50g). Participants with worse glucose regulation performed worse on measures of working memory, executive function, and processing speed compared to participants with better glucose regulation. Additionally, older participants with worse glucose regulation obtained the lowest scores on the majority of cognitive measures compared with younger participants and those with better regulation. A significant enhancement of cognitive performance by glucose was not clearly observed. The results suggest that cognitive functioning may be compromised before glucoregulatory impairment reaches levels consistent with IGT or Type II diabetes.

Recent studies have indicated stronger mood dependent memory (MDM) effects when subjects generate both the to-be-remembered events and the cues used in their retrieval, and when subjects who experience similar moods are compared to subjects who report a change in both pleasure and arousal, rather than others who report a change in pleasure alone. The first study was undertaken to experimentally evaluate the relationship between mood change and memory performance. Specifically, four mood manipulations were developed to compare memory performance in subjects assigned to no mood change, change in pleasure, change in arousal, or change in both pleasure and arousal. Subjects generated autobiographical events in response to neutral nouns, and were tested for free recall and recognition of these events two days later. Results demonstrated greater memory disruption after change in both pleasure and arousal than after change in pleasure alone. However, one-dimensional change in arousal led to as much memory disruption as did change in both dimensions. Separate ANOVAs compared each mood in combination with each other mood and indicated that MDM was more strongly supported in some combinations than others. Further, the pattern in free recall was different from the pattern in recognition indicating that MDM effects may vary interactively across moods and tasks. The second study was undertaken to validate prior research by employing subjects who experience large, but naturally occurring, changes in mood. Patients with rapid-cycling Bipolar Disorder performed a variety of tasks during study sessions and were tested for implicit and explicit memory during test sessions. Significant MDM effects were supported in free recall of autobiographical events and inkblot recognition, but not in implicit category production of autobiographical event probes, picture fragment completion, explicit nor implicit memory for letter associates. Results validate MDM as a real world phenomenon that impacts on explicit memory performance in subjects whose moods are not manipulated. Discussion centers on prospects for future studies that consider a wider range of manipulated moods and tasks, theories of emotion, and other clinical groups in the investigation of MDM. / Arts, Faculty of / Psychology, Department of / Graduate

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