These studies examine the neuroanatomical and neuropharmacological mechanisms related to production of the isolation call and related vocalizations in nonhuman primates, as a model for understanding the neurology and physiology of the vocal expression of affect in human infants. Major findings this year were as follows: 1) Attempts to confirm in a primate model a role for the neuropeptide cholecystokinin in mediating panic attacks were unsuccessful. However, during the course of these experiments we discovered a clear difference in the reactivity profile of male and female squirrel monkeys to the mildly stressful contexts of brief social separation and exposure to alarm-raking visual stimuli. Males show greater locomotor activity than females during both test situations, and more vocal activity during separation. Females vocalize more during alarm-provoking testing. Furthermore, males and females exhibit different responsivity to administration of the anticholinergic drug benactyzine, in that males decrease locomotor activity and increase alarm-provoked vocal activity to levels of untreated females, whereas females show no change in locomotor activity but do increase alarm-provoked vocal activity to levels 2-3 times above vehicle trials. 2) the role of the amygdala and inferotemporal cortex in regulating male and female vocal responses to brief periods of social separation was clarified in infant rhesus macaques. The tendency for male infants to produce more tonal and less variable vocalizations in this context disappears following bilateral ablation of the inferotemporal cortex. Conversely, bilateral ablations of the amygdala, which receives input from IT cortex, result in a more severe acoustic alteration in the separation calls of female infants. 3) analysis of the cries of premature infants with intraventricular hemorrhage (IVH) indicates a hyporesponsiveness to routine manipulations, manifested by weak, poorly elaborated cry patterns. Following these infants after discharge from the intensive care nursery will permit assessment of cry acoustic pattern changes in association with resolution of the IVH diagnosis.
