Higher visual functions: How to improve visual perception in patients with unilateral brain lesion
Visual perception can be defined as the integration of a series of cognitive processes, including reception, organization, and assimilation of the visual information sent to the cerebral cortex. The visual information is processed in two streams: a ventral stream for object recognition and a dorsal stream for perception of motion. A lesion in the ventral stream can cause impairment in recognition of visually presented objects (visual agnosias), deficit in reading (alexia). Lesions on the dorsal stream can lead to difficulties in perceiving visual motion (akinetopsia). These higher visual functions are of key importance for daily living activities. However, in patients with hemispheric brain lesions, impaired higher visual functions are not always detected in classical neurological examinations. Therefore, we developed a series of new tests to assess higher visual functions (i.e. visual perception of motion, size, shape, and pattern). In this study, the performances of patients with unilateral brain lesions after stroke or traumatic brain injury, as well as age-matched healthy controls are measured. We plan to use tDCS (transcranial direct current stimulation) to stimulate the impaired region of the brain to enhance the higher visual functions and, therefore, improve the level of performances at the proposed tasks.