Impaired visuospatial associative memory and attention in obsessive compulsive disorder but no evidence for differential dopaminergic modulation
Patients with obsessive compulsive disorder (OCD) demonstrate impaired cognition in some selected domains. Although serotoninergic dysfunction has been implicated in OCD, recent evidence suggests that dopamine may play a role as well. The aim of the study was to evaluate learning and working memory in OCD and to determine the effects of dopaminergic manipulations on these capacities. Visuospatial associative memory and spatial and verbal working memory were examined in 18 nondepressed patients with OCD and 18 matched healthy controls. The study further investigated whether acute administration of dopamine D2/D3 receptor agonist and antagonist would differentially modulate cognition in OCD. Each participant underwent the cognitive battery three times in a randomized double-blind, placebo-controlled crossover design. Significant impairments in patients compared with controls were noted on the Cambridge Neuropsychological Test Automated Battery (CANTAB) paired associates learning (PAL) and a measure of sustained attention (rapid visual information processing, RVIP) that persisted across all sessions, with deficient strategy in the CANTAB spatial working memory task in the first session alone. Although the dopamine D2/D3 agonist, pramipexole, led to poorer performance on the PAL and RVIP tasks, no differential effects were noted between the two groups. No significant effects were noted for the D2/D3 antagonist, amisulpride. The results are consistent with a specific associative memory deficit in OCD that remained robust despite possible practice effects and compensatory strategies and point to abnormal medial temporal lobe involvement in OCD in addition to the previously implicated frontostriatal loops, with no clear evidence of D2 receptor mediation.