Role of midline frontolimbic cortex in production of the isolation call of squirrel monkeys.

Since the separation cry of mammals serves to maintain (1) mother-offspring contact and (2) contact between members of a group, it probably ranks as a basic mammalian vocalization. The present study is part of an investigation concerned with identifying the cerebral representation of the separation call in squirrel monkeys. For this purpose, monkeys are tested for their ability to produce spontaneous calls in isolation before and after ablations of different parts of the brain. Because of the subject's auditory and visual isolation, the call emitted during testing is referred to as the isolation call. In a preceding study, it was shown that lesions at the thalamomidbrain junction and in the ventral central gray interfere with the structure and/or production of the call. The present study focuses on the rostral midline limbic cortex, known to be one of the two cortical areas where stimulation elicits vocalization in monkeys. Evidence derived by the process of elimination indicates that the spontaneous call depends on the concerted action of a continuous band of rostral limbic cortex comprising parts of areas 24, 25, and 12. The midline frontal neocortex peripheral to this limbic zone does not appear to be essential for the call.