Age differences in perseveration: cognitive and neuroanatomical mediators of performance on the Wisconsin Card Sorting Test

Abstract

Aging effects on the Wisconsin Card Sorting Test (WCST) are fairly well established but the mechanisms of the decline are not clearly understood. In this study, we examined the cognitive and neural mechanisms mediating age-related increases in perseveration on the WCST. MRI-based volumetry and measures of selected executive functions in conjunction with the WCST were obtained in a sample of 117 healthy young and older adults. Path analysis indicated that age-related increase in perseveration is completely accounted for by declines in processing speed and temporal processing, deficits in working memory mediated by decreased prefrontal cortical volume, and the indirect influence of prefrontally-mediated declines in inhibition via working memory. We conclude that age-related increase in perseveration is indeed differentially dependent on the integrity of prefrontal cortex and on declines in selected cognitive processes dependent on this region.

Figure 1

Path model of Reduced Model III with relationships among age, brain volumes, and cognition. Numbers at paths are path coefficients; three-digit numbers at variable boxes are residuals. See text for model fit indices. LPFC=lateral prefrontal cortex; FWM=prefrontal white matter; Cd=caudate nucleus; HC=hippocampus; VC=visual cortex; PS=processing speed; IC=inhibitory control; WM=working memory; TP=temporal processing; TS=task-switching; Persev=perseverative behavior.