Cortical stimulation mapping (CSM) is a type of electrocorticography which is used a method to determine the location in the brain where information of a certain kind is processed. Different parts of the brain are used for different functions; CSM attempts to find which part of the brain is responsible for certain behaviors in humans and other animals by briefly electrocuting a given part of the brain and determining what effect it has on the patient's behavior.
For instance, it's been observed that stimulation in Broca's area can result in aphasia symptoms even in individuals who do not have a speech impairment.[1] Aphasia is a speech impairment which is caused by brain lesions in Broca's area and other areas of the brain. Stimulation to Broca's area disrupts its normal function, which causes the temporary aphasia.