Incidental and intentional recall in Parkinson's disease: an account based on diminished attentional resources.

The recall of common objects and their spatial location was examined in 65 patients with Parkinson's disease (PD) under conditions in which available attentional resources were manipulated by secondary task demands. PD patients were impaired at item recall particularly under intentional learning conditions but were unimpaired at recall of spatial location. These findings were similar in newly diagnosed, untreated cases as well as patients who had suffered with the disease for an average of 9.6 years. Test performance was not improved by levodopa therapy, despite it benefiting motor control, and was not impaired by anticholinergic medication. Item recall correlated significantly with other memory measures (particularly tasks of working memory) but only weakly with indices of physical disability and traditional frontal-lobe measures. Spatial recall, by contrast, correlated with memory quotient but no other cognitive measure and depression and disease duration failed to correlate significantly with performance on either recall task. These results are attributed to a deficit in attentional resources in PD that impairs performance most markedly for tasks and conditions that make the greatest demands upon effort.