Covert visuospatial attentional mechanisms in Parkinson's disease.

Orienting and focusing of attention were assessed in 32 Parkinson's disease and 32 control subjects. No differences were found in the covert orienting of attention, suggesting that the Parkinson's disease subjects of the current study were not impaired in the ability to orient attention towards an expected source of stimulation. However, with the process of modulating the attentional focus or of managing more than one attentional task, dysfunction in Parkinson's disease subjects became apparent. The observed results are explained in terms of deficits in the relationship between task-related distribution of attentional resources and time efficiency of processing.