The Effects of Glucose on Nonmemory Cognitive Functioning in the Elderly

The present study evaluated the role of glucose in the performance of a series of memory and nonmemory neuropsychological tasks. Each of the 28 healthy (no evidence of diabetic or dementing disease), elderly (mean age = 73), subjects participating in the study were tested under each of two conditions (50 g glucose or 27.3 mg saccharin) in a counterbalanced fashion. While actively manipulating glucose levels in participants, blood glucose (BG) levels were monitored to evaluate the effectiveness of individual subject's regulation of ingested glucose. It was hypothesized that glucose would enhance performance on a memory measure (Rey/Taylor Figure) as well as other nonmemory measures (e.g. design fluency, trail making test, etc.). A repeated measures, counterbalanced design was used to evaluate the direct manipulation of glycemic condition. Results reveal an enhancement effect on both the recall of the Rey/Taylor Figure as well as verbal fluency and figural fluency. A significant correlation between glycemic regulation and performance on a test of divided attention (dichotic listening) was also evident (r = -0.47). These findings suggest that a specific facilitation of retrieval mechanisms may account for enhancement of both memory and fluency performance.