Hormones and Behavior Hormones Modulate Behavior Hormones Can Be Necessary for a Behavior A particular level of hormone in an animal does not insure a behavior will occur. A particular level of hormone does not have the same effect in every animal.

Hormones EnvironmentNervous System

Social Behavior and Neuropeptides Oxytocin (OT) and Vasopressin (AVP) Influence a number of social behaviors including Pair bonding Maternal behavior Affiliative behaviors Generosity (?) Promiscuity (?) Where do they come from and how do they affect the nervous system?

Hypothalamus

Preoptic Supraoptic Tuberal Mammillary

Oxytocin and Vasopressin Neurons - Production Oxytocin and Vasopressin can be released directly circulation and directly into the brain Peripheral versus Central release OT and AVP receptors are localized in the limbic system

Oxytocin and Vasopressin Behavioral Effects Animal Models – Prairie Vole

California mouse (Peromyscus californicus)

Voles: A Comparative Model Prairie Voles Biparental Monogamous Mating induces changes in the brain, partner preference Meadow and Montane Voles Uniparental Polygynous

Prairie Voles OT – females Facilitates maternal behaviors Facilitates pair bond formations AVP – males Changes (cellular content/ immunoreactivity) with parental experience and cohabitation Facilitates pair bond formations and parental experience Site specific Voles: A Comparative Model

AVP in the Brain (Lateral Septum) with Parental Experience Prairie and Meadow Voles Males and Females Parental or Naive

AVP and Prairie Voles AVP and paternal responsiveness in male voles

Vasopressin Receptor: V1a Is the V1a receptor necessary for social behaviors? Prairie Voles

AVP Receptor Pattern Vasopressin Receptor Distribution varies between Prairie and Montane Voles. Montane pattern is more “typical” of other rodent species, perhaps other mammals.

Vasopressin Receptor, V1a Staining (Autoradiography) for Vasopressin Receptor Prairie Montane

Vasopressin Receptor V1a What happens if you experimentally make a mouse brain like a vole brain for AVP? Prairie Voles Mice

Oxytocin and Vasopressin in Humans Several recent studies have begun to show similar roles for these neuropeptides in human behavior Limbic system – evolutionary conservation

Vasopressin Gene sequences on alleles may predict behavior AVPR1a – Gene that codes for vasopressin receptor Longer alleles (repeat of sequence) more monogamous behavior – voles Similar sequence may predict success of opposite success relationships in humans (Walum et al., 2008) Altruistic behavior – more money is given to other participant

Vasopressin and Social Behavior Intranasal Vasopressin in Men Stimulates antagonist facial motor patterns to unfamiliar faces, decreases perception of friendliness Intranasal Vasopressin in Women Stimulates affiliative facial motor patters and increases perception of friendliness

Oxytocin and Social Behaviors Oxytocin can be released during social interactions pair bonding and sex mother – infant bonding Birth – uterine contractions Suckling - lactation Oxytocin is measured in the blood Oxytocin is also likely released in the brain

Oxytocin and Trust Oxytocin can influence Trust Trust game and monetary exchanges Oxytocin levels are higher when individuals perceive intentional trust. Oxytocin ‘correlates’ with level of perceived trust Pre- and post- measures Correlation versus causation

Oxytocin and Trust Fig. 2. OT levels and standards errors for DM2s with and without an intention to trust. In the Intention condition, DM1s voluntarily transfer money to DM2s. In the Random Draw condition, the transfer from DM1s to DM2s was determined by a public draw of a numbered ball. OT levels across conditions are statistically different at P < P.J. Zak et al. / Hormones and Behavior 48 (2005) 522–527

Oxytocin and Trust Intranasal oxytocin can influence generosity/ trust Intranasal OT and neural sites

Oxytocin and Trust Figure 2 | Transfers in the trust and the risk experiment. Each observation represents the average transfer amount (in MU) over four transfer decisions per investor. a, Relative frequency of investors’ average transfers in oxytocin (filled bars) and placebo (open bars) groups in the trust experiment (n ¼ 58). Subjects given oxytocin show significantly higher transfer levels.

Oxytocin and Trust Intranasal OT increases perception of facial attractiveness, and trustworthiness

Oxytocin Gene sequences on alleles may predict behavior OXTR Specific sequence may predict altruistic behavior and higher social values orientation

OT/AVP Implications Patterns in the AVP and OT receptor gene sequence may predict autism spectrum disorders. AVP and OT operate in similar ways in all vertebrates that have been studied. A mechanism for empathy in humans?