Improved short-term spatial memory but impaired reversal learning following the dopamine D₂ agonist bromocriptine in human volunteers

Abstract

Rationale: Studies in humans of cognitive effects of dopaminergic drugs have largely focused on tasks of working memory, with a few studies also examining executive function. Objectives: This study was designed to investigate the effects of 1.25 mg of the dopamine D₂ agonist bromocriptine on spatial working memory, planning and discrimination reversal learning in young healthy volunteers. Methods: Twenty volunteers were tested in a double-blind, placebo-controlled, cross-over design. The cognitive assessment included tests taken from the Cambridge Neuropsychological Test Automated Battery (CANTAB) designed to test visuo-spatial recognition memory and spatial working memory. In addition, tests of spatial planning and discrimination reversal learning were used to assess the more general effects of bromocriptine. Tests of subjective feelings and motivation were also incorporated into the battery. Results: Bromocriptine enhanced the spatial memory span of subjects, whilst impairing their ability to reverse a learned probabilistic discrimination. Tests of recognition memory and planning were unaffected by the drug. The findings were not explained by changes in subjective mood or motivational measures. Conclusions: The pattern of findings observed here mirror medication-dependent observations seen in Parkinson's disease. The results are discussed with reference to the different anatomical networks known to subserve performance of the differentially affected tasks.