lecture 3- endocrinology- oxytocin and decision making

How do we study hormone effects on decision making?

1. Endogenous fluctuations in hormone levels correlated with decision making, or before/during a decision making task

2. Administration of exogenous hormone vs placebo- analysing decision making before and after

• variation 1 - precursor manipulation

• Variation 2 - inhibiting a hormone

3. Combined endo- & exogenous: apply a hormone but also measure baseline level.

What is decision makng?

• sequence of automatic and/or conscious processes leading to simple or complex decisions

• Areas involved: orbitofrontal, cingulate, ventromedial prefrontal etc.

What tasks are used in social decision making research?

• ultimatum game- player 1 receives £10 and gets to decide how to split it with p2. If p2 isn’t happy with amount received, they can choose for both to receive nothing.

• Dictator game- assesses generosity. P1 is given complex control on how to allocate £10 between themself and p2.

• Trust game- p1 receives £10, gets to choose how much to give to p2. Amount sent is multiplied by 3, and then p2 can return whatever they want to p1.

What is oxytocin?

• a small peptide hormone (lipid insoluble) released from the posterior pituitary

• Causes contractions of smooth muscles in breast and uterus.

• Amount increases during childbirth- signal for release of oxytocin= increased pressure on uterine cervix during later stages of childbirth

• Also during milk ejection- suckling stimulates nipple and somatosensory signals are being transmitted to hypothalamic supraoptic and paraventricular nuclei.

• A hormone of social affiliation- increases both in male and female people after the birth- promotes parenting.

How can exogenous oxytocin affect the brain?

• penetrates the blood-brain barrier at high doses

• Intranasal spraying of oxytocin increases presence in cerebrospinal fluid

• Oxytocin receptors are in limbic system, basal ganglia and cortex

• Hypothalamic neurons project to various decision making regions

Why does oxytocin promote social bonding?

• an isolated pup (mouse) issues ultrasonic distress signals.

• A dam, a female parent, but not a virgin mouse will retrieve the pup

• After injecting oxytocin, virgin mice also begin to retrieve the pups.

Relationship between oxytocin and trustworthiness in the games

• in the trust game, trustworthiness increased with oxytocin levels

• In the ultimatum game, ppts exposed to oxytocin were investing more and had increased trust

• In dictator game, ppts exposed to oxytocin were more generous.

Is there a difference between effects of oxytocin between mothers and fathers?

• no differences in oxy levels in week 1 & month 6 postpartum

• Increase in levels from week 1 to month 6 in both

• Strong correlations between mother and father’s levels

• Associated with affectionate parenting in mothers, and stimulating behaviour in fathers

How is the reward system affected when viewing infant faces?

• viewing infant faces activates hypothalamic OT region and reward system

• Oxytocin increases during playing with own baby in secure mothers

• Mothers with secure attachment style but not insecure, continue activating reward system if infant’s face is sad