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

Environment Nervous 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

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

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) withParental Experience

Prairie and Meadow VolesMales and FemalesParental 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 anintention to trust. In the Intention condition, DM1s voluntarily transfermoney to DM2s. In the Random Draw condition, the transfer from DM1s toDM2s was determined by a public draw of a numbered ball. OT levelsacross conditions are statistically different at P < 0.05.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 observationrepresents the average transfer amount (in MU) over four transfer decisionsper 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?