Eye movement control and cognition in Parkinson's disease

Abstract

Many studies have found evidence of abnormal eye movement control in Parkinson's disease. Deficits in the inhibition of unintended saccades and slowed initiation of intentional saccades have been reported in some, but not all, investigations. Also over recent years the presence of cognitive impairment in a proportion of patients with Parkinson's disease has been highlighted. Efficient use of working memory resources is thought to be involved in the performance of tasks in both domains. With a comprehensive selection of saccadic and neuropsychological tasks, the current study investigated whether aspects of abnormal oculomotor control are associated with impairment of cognitive functions. Nineteen Parkinson's disease patients and eighteen healthy age matched control subjects performed six eye movement tasks and completed a neuropsychological test battery assessing five different aspects of cognitive functioning. Deficits were found in both the oculomotor and the cognitive domain in the group of patients. As a group, the patients made more reflexive errors in antisaccade tasks, more inhibition errors in a delayed response task, and were slower to initiate intentional saccades. The three measures of abnormal oculomotor control were not consistently associated with cognitive impairments or with each other. Longer latencies of correct antisaccades and increased number of errors in a delayed response task were associated with lower scores in different cognitive tests. Reflexive errors in the antisaccade task were not associated with cognitive deficits, but with the tendency to produce very fast visually triggered responses. The results suggest that, at least in Parkinson's disease, different neural mechanisms may be involved in specific aspects of abnormal oculomotor control.