Parkinson's disease, aging, and visual cognition

Normal ageing results in a multitude of physiological changes that could contribute to sensory impairments not necessarily caused by a disease process. A distinction between aging and disease has a diagnostic and potential therapeutic relevance in Parkinson's disease (PD). In parallel with retinal deficits, a dopaminergic dysregulation of the fronto-striatal circuits may occur in PD. Several visual and visuo-cognitive deficits are not yet demarcated in PD from ageing. Nevertheless, select impairment of retinal spatio-temporal visual processing and specific visual categorization deficits in PD are the result of the disease, not of aging per se.