Visual Selective Attention in Parkinson's Disease

Parkinson's disease (PD), which is generally considered to be a motor disorder, is now known to be accompanied in many instances by a variety of cognitive defects. This can be explained considering that PD is a neurodegenerative and progressive disorder of the basal ganglia system, which works modulating not only motor, but also cognitive and emotional behaviours. Concerning this, some studies suggest that non-demented PD patients may suffer from a voluntary selective visual attention orienting deficit, showing a reduced skill in focusing upon one target, and may be easily distracted from irrelevant but salient stimuli, with a consequent negative impact on their physical health, social interactions and quality of life. Up to now, the evidence of the role of the basal-ganglia system in modulating visual attention functions is poor and indirect and the effects of dopaminergic and subthalamic nucleus (STN) stimulation (two usual and effective treatments in PD) on attention performances are controversial. The main objectives of the project are: 1) to assess the visual selective attention as well as the distractibility in PD patients; 2) to study the effects of patient's usual antiparkinsonian treatments, that is dopaminergic and STN stimulation, on visual attention performances. Secondly, from a clinical and neurophysiologic point of view, the investigators want to study the respective role of the dopaminergic pathways and the sensorimotor and associative/limbic cortico-basal ganglia loops passing across the STN in the visual attention performances. To precisely answer the objectives of the protocol, the investigators will record the performances of participants during the administration of 3 computerized tests, which are suitable to study visual attention, decision making and motor performances. The investigators will compare the performances on the computerized tests of two groups of PD patients, one evaluated in different sets of electrical (without stimulation