Mirth, laughter and gelastic seizures.

Little is known about what pathways subserve mirth and its expression laughter. We present three patients with gelastic seizures and laughter elicited by electrical stimulation of the cortex who provide some insight into the mechanisms of laughter and its emotional concomitants. The first patient had seizures manifested by laughter without a subjective feeling of mirth. Magnetic resonance imaging showed a cavernous haemangioma in the left superior mesial frontal region. Ictal subdural electrode recording showed the seizure onset to be in the left anterior cingulate gyrus. Removal of the lesion and of the seizure focus rendered the patient virtually seizure free over 16 months of follow-up. The other two patients had complex partial seizures of temporal lobe origin. Electrical stimulation of the fusiform gyrus and parahippocampal gyrus produced bursts of laughter accompanied by a feeling of mirth. These cases reveal a high likelihood of cingulate and basal temporal cortex contribution to laughter and mirth in humans, and suggest the possibility that the anterior cingulate region is involved in the motor act of laughter, while the basal temporal cortex is involved in processing of laughter's emotional content in man.