Neocortical and limbic lesion effects on primate phonation

Five monkeys were individually trained to emit a relatively prolonged call of specified loudness in order to obtain a preferred food. At the completion of training each animal gave the required call in response to a signal cue light and withheld calls during periods in which no cue light was present. Sequential bilateral removal of the homolog of Broca's area, transitional parieto-occipital cortex, and temporal association cortex in 3 monkeys had no influence on performance of the discriminative call. There was no change in sound spectral properties of the call as a result of surgery. Bilateral removal of anterior cingulate/subcallosal gyrus in the remaining two monkeys was accompanied by loss of phonatory performance. Postoperative calls given by each of these animals in the test situation were weak and infrequent. The data indicate that control over learned, discriminative phonation in monkeys is not mediated by neorcortical regions homologous to human 'speech' areas.