Type 2 diabetes has been associated with a number of physiological consequences including neuropathy, retinopathy, and incidence of vascular disease. Less is known about the effect on cognition of prediabetes, a period when glucose regulation is abnormal. It is not clear which aspect of impaired glucoregulation is most predictive of cognitive deterioration. In the present experiment, we measured cognitive function in 93 healthy male and female nondiabetic older participants who ranged in age from 55 to 88 years. Various biological measures were obtained including a glucose tolerance test during which glucose and insulin were measured. Participants were evaluated twice, once after drinking a saccharin solution and on another occasion after drinking a glucose solution (50 g). The analysis of the correlations between the biological measures and the results of the cognitive tasks revealed that evoked glucose measures such as peak glucose and glucose at 1 hour were most often correlated with cognitive performance. We observed that progressively worse glucose regulation predicted poorer performance on measures of working memory and executive function-that is, on the Arithmetic, Digit Span Backward, Letter-Number Sequencing, Spatial Span Forward, Spatial Span Backward (trend), and Modified Brown-Peterson tasks. Although, there was no significant facilitative effect of glucose on cognitive performance, it reduced the association between glucose regulation and cognition, apparently by slightly improving performance. These results suggest that cognitive functions may be impaired before glucoregulatory impairment reaches levels consistent with a type 2 diabetes diagnosis.

Impaired glucoregulation is associated with neuropsychological deficits, particularly for tests that measure verbal declarative memory performance in older diabetic patients. The performances of 74 undergraduate students (mean age = 21 years) on several verbal declarative measures, including immediate and delayed paragraph recall, verbal free recall, and order reconstruction tasks, were correlated with glucoregulatory indices. The indices were obtained from glucose and insulin levels after a 75-g glucose load. In general, higher blood glucose levels were associated with poorer performance on all memory tests. Glucose ingestion did not interact with performance except on the most difficult task. Subjects with poorer glucoregulation showed higher evoked glucose and insulin, suggestive of a mild glucose intolerance accompanied by mild insulin insensitivity. Results suggest that poor peripheral glucoregulation has an impact on central nervous system functions.

No abstract

No abstract

The Rey and Taylor figures are two constructional and visual memory tests used interchangeably. The purpose of this study was to develop a scoring system for the Taylor figure based on the explicit guidelines established by Meyers and Meyers (1995) for the Rey figure. Younger (n = 97; mean age = 21 years) and older (n = 61; mean age = 72 years) participants' performance on the Taylor figure was scored according to the proposed scoring system and the original scoring system devised by Taylor (1989). Both scoring systems yielded comparable scores on the Taylor figure as well as comparable patterns of validity and good interrater reliabilities (0.85-0.98). Although the present system does not further improve scoring reliability, it renders both tests similar in methodology and simplifies training to evaluate the two figures. The present study also reveals the limitations of the use of the Taylor and the Rey in test-retest situations but suggests that administering the Taylor first would improve the comparability of the two figures in a test-retest situation.