Visuo-cognitive dysfunctions in Parkinson’s disease

Of all human senses, vision is crucial among sensory functions in shaping our perceptions and accurate actions. We need satisfactory visual processing for navigation; for recognizing faces, objects, buildings, and places; for writing and counting; and for a wide range of motor actions starting from eye movements to the execution of a motor response. Accurate visual information processing is also necessary for the satisfactory functioning of the visual memory. The processing and transfer of primary visual input to higherorder cortical areas is fast, almost automatic. Due to this proficient transfer process, most of our daily activities require little effort. However, when processing is impaired at a stage of the visual information Ÿow, even simple actions may be significantly delayed and distorted. In many neurological disorders, impaired vision is not the primary dominant symptom; however, unsatisfactory visual processing may contribute to difficulties in daily living. Frequently studied relevant problems include consciously controlled visual information processing, sustained and selective attention, visuo-spatial orientation, planning, problem-solving, response selection, and decision making.