Commentary on "Neural correlates of mirth and laughter: A direct electrical cortical stimulation study" by Yamao and colleagues.

In their recent paper, Yamao and colleagues (Yamao et al., in press) report two cases of mirth during direct electrical stimulation of the basal temporal cortical surface of the left hemisphere of the brain, in patients with temporal lobe epilepsy. Here, one patient with an intact hippocampus reported mirth and exhibited laughter during stimulation, while a second patient with hippocampal sclerosis reported mirth in the absence of laughter (with the latter emerging at a delay, and only with longer and more intense stimulation). The authors argue that this is a demonstration for the dissociation of the motoric and emotional aspects of mirth, where mesial temporal lobe pathology in one patient prevented the engagement of motoric responses appropriate to the emotional experience. Moreover, the authors claim a neural commonality between language processing and mirth because the sites at which stimulation led to mirth more often also showed impairments in language task performance (compared with " no-mirth " sites). There are several aspects of these findings that should be treated with caution. First, even though there is a precedent for temporal lobe involvement in humour processing and mirthful experiences, the current study reports only two patients and there is very little behavioural detail upon which to interpret the quality of the experience reported by these individuals. In the case of Patient 1, the EMG data show that stimulation at