When the brain is working well, the different parts are connected by long fibers called axons. But when the brain is damaged (as in this image from a patient who suffered a stroke in a part of the brain called the thalamus), the connections break down.

When the brain is working well, the different parts are connected by long fibers called axons. But when the brain is damaged (as in this image from a patient who suffered a stroke in a part of the brain called the thalamus), the connections break down.