Oxytocin (OT) and vasopressin (AVP) are closely related neuropeptides synthesized in the hypothalamus and then released into the bloodstream via axon terminals located in the posterior pituitary gland (Gainer & Wray, 1994). The traditional view of the neurohypophyseal peptides acting as endocrine hormones only in peripheral organs has been replaced by new evidence demonstrating that the brain is also a target organ for these peptides (Barberis & Tribollet, 1996). Moreover, three aspects of the central pathways for these peptides deserve special consideration in relation to social behavior and communication: 1) specific vasopressin pathways appear to be sexually dimorphic; 2) neurotransmission for both peptides depends largely on an unusual variability in their receptors; 3) both peptides receptors are developmentally regulated and expressed more in the immature brain, and both peptides have been shown to have effects on neural development (Johnson et al., 1991; Boer, 1993; Wang et al., 1997). Finally, strong evidence exists involving both peptides with important cognitive and behavioral effects during development, including learning and memory processes (Tinius et al., 1987), recognition of a familiar conspecific and development of attachment (Nelson & Panksepp, 1998), communication skills (Ferris et al., 1993), and development of ritual and stereotyped behaviors (van Wimersma Greidanus et al., 1996). Therefore, animal models indicate that both oxytocin and vasopressin have an active role in influencing key behaviors in the animal repertoire, including social, cognitive, and communications skills as well as motor stereotypes. However, we still have scanty evidence directly assessing oxytocin and vasopressin characteristics in primates, although a few studies in humans have found a significant reduction of repetitive behaviors in a small sample of adults via infusion of oxytocin (Hollander et al., 2003). In this project we will be able to test the hypothesis that either oxytocin or vasopressin affect social and communication functioning in marmosets. In particular, we will test the hypotheses that (a) low levels of oxytocin is related to deficits in social skills and stereotyped behaviors, whereas increased oxytocin production is related to increased affiliation and attachment, and (b) vasopressin facilitates the consolidation of social skills and communication patterns. Moreover, the synergic interaction of these neuropeptides with stress hormones will be assessed, and advanced statistical techniques (such as fractal analysis) will be used to identify patterns of variations in behavioral sequences that are not discernible with more traditional analytical methods.
Massimo Bardi (b. 1967) studied marmosets and tamarins at the New England Regional Primate Center of Harvard University, Cambridge, MA, from 1993 to 1998, with projects related to social behavior, communication, infant development and maternal behavior. He obtained the Ph.D. in Physical Anthropology on May 1998. From 1999 to 2002 he was appointed as Research Fellow and then as Visiting Associate Professor at the Primate Research Institute of Kyoto University, Japan, where he studied neurohormonal correlates of infant development and social and maternal behavior in macaques. Since 2003 he was appointed as Staff Scientist at the Southwest Foundation for Biomedical Research, San Antonio, TX, where he continued his research on neurohormonal correlates of social behavior in baboons. Recent most notable publications Bardi M., French J.A., Ramirez S.M., Brent L. (2004). The role of the endocrine system in baboon maternal behavior. Biological Psychiatry 55: 724-732. Bardi M., Bode A.E., Ramirez S.M., Brent L. (2005). Maternal care and development of stress responses in baboons. American Journal of Primatology 66.