Visuo-Spatial Attention in Non-Demented Patients with Parkinson’s Disease

Abstract

The P3(00) event-related potentials (ERPs) elicited with visual stimuli were assessed in 53 non-demented patients with Parkinson’s disease (PD) and 20 age-matched normal controls. PD patients were classified as having normal cognitive function (NC) (n = 39) or patients with cognitive deficit (CD) (n = 14), defined by basic psychometric data. We used visual tasks with various cognitive difficulties: simple visual tasks with central or displaced targets (SV/ct and SV/dt), visual oddball tasks with central or displaced targets (VO/ct and VO/dt). P3 changes in patient groups were related to the cognitive demands.The amplitude of P3 was larger for the NC group in the VOlct task and for the CD group in the SV/dt and VOlct tasks. It was lower than contoIs for CD patients for the VOldt task. Estimates ofcognitive load in each task by the difference waves (ERPs to dt minus ERPs to ct) demonstrated that DLP (difference late positivity, component related to P3) was negative for the CD group in the VO task, whereas DLP was positive and greater than the controls in both the NC and CD groups inthe SV task. Prolongation of P3 latency for patient groups was also related to task demands. There were significantdifferences betweenpatients and controls for NC patients in the SV/dt, VOlct and VOldt tasks, and for CD patients in all four sets of experimental conditions. The results suggest that the amplitude of P3 reflects the use ofthe attentional resources available for the task, and P3 latency, the time required for cognitive processing.