Recruiting functional brain networks to improve sight after stroke

About 150,000 people have a stroke each year in the UK. One third of stroke survivors are left with some sight loss which is caused by damage to parts of the brain that are responsible for visual perception. 

Permanent damage to the “primary” visual brain pathway is the most common and debilitating effect of stroke on visual function. This leads to a loss of conscious visual perception on one side of the visible world – so called “cortical blindness”. To date, no effective rehabilitations have been developed to treat cortical blindness.

It is known that some unconscious visual perception persists after damage to the primary visual brain pathway. Perceptual retraining can recover some of this visual loss. As the effects of perceptual retraining tend to be rather variable, they are not accepted yet as an effective method for rehabilitation.

Researchers aim to identify residual visual brain networks that survived post stroke and retrain them to detect and discriminate visual input in the cortically blind visual field.

Stroke survivors with cortical blindness and age-matched healthy controls deprived of visual input on one side of the visual field will participate in experiments to estimate the capacity of brain pathways to generate vision in the cortically blind field of stroke survivors. Magnetic resonance brain imaging will be used to measure the detailed structure and responsiveness of spared cortex in the occipital lobe. Visual stimuli will be designed to retrain visual detection and discrimination in the cortically blind field that they know elicit responses from visual cortex. Participants will practice psychophysical tasks to target perceptual retraining at residual brain networks of individual stroke survivors with the potential to generate vision in the cortically blind field.
 
This research will allow for the development of scientific tools (brain imaging and behavioural) and knowledge, to retrain the residual visual cortical networks in stroke patients. This will be the first step in a process which will require a larger scale clinical evaluation.