People who see only a half of their visual world after brain trauma, such as stroke, have a problem in a specific brain area.
Around one in ten of stroke survivors have a bizarre visual problem. They see only a half of what is around them. So they will eat only half of a plate of food. Or, if asked to draw a scene, they will only draw half. There is no obvious damage to the visual areas of the cerebral cortex of the brain in these patients - so the condition has been a puzzle up to now.

Researchers at the Wake Forest University Baptist Medical Center carried out electrophysiology studies on a group of patients with the 'half world' visual problem. This involves inserting microelectrodes into areas of the brain and looking at the electrical response. The study revealed how cells in the basal ganglia - at the base of the brain - were no longer sending the correct messages to the visual area. Hence, half of the patient's world was not perceived through the visual circuits. Targetting the damaged cell circuits in the basal ganglia might one day lead to a cure - currently lacking - for people who can only see one half of the world around them.