Vocalization-correlated respiratory movements in the squirrel monkey

Respiratory abdominal movements associated with vocalization were recorded in awake squirrel monkeys. Several call types, such as peeping, trilling, c ackling, and err-chucks, were accompanied by large vocalization-correlated respiratory movements (VCRM) that started before vocalization. During purri ng, in contrast, only small VCRM were recorded that started later after voc al onset. VCRM during trill calls, a vocalization type with repetitive freq uency modulation, showed a modulation in the rhythm of the frequency change s. A correlation with amplitude modulation was also present, but more varia ble. As high frequencies need a higher lung pressure for production than lo w frequencies, the modulation of VCRM seems to serve to optimize the lung p ressure in relation to the vocalization frequency. The modulation, furtherm ore, may act as a mechanism to produce different trill variants. During err -chucks and staccato peeps, which show a large amplitude modulation, a nonm odulated VCRM occurred. This indicates the existence of a laryngeal amplitu de-controlling mechanism that is independent from respiration. (C) 2000 Aco ustical Society of America. [S0001-4966(00)00610-X].