Many functions of the brain are performed by several areas of the brain working together (networks), not by a single area in the brain. Damage to these networks can cause aphasia, apraxia, agnosia, or amnesia.
Usually, doctors can diagnose the type of dysfunction by examining the person. They ask questions designed to evaluate specific brain functions. Imaging tests, such as computed tomography (CT) and magnetic resonance imaging (MRI), are usually needed to identify the cause of the damage.
Last full review/revision October 2013 by Juebin Huang, MD, PhD