Feng. (2014) Oxytocin and vasopressin effects on the neural response to social cooperation are modulated by sex in humans. Flashcards
Describe the patients in the Feng (2014) study
153 men and 151 women from Emory University between the ages of 18 and 22
What was the design of the experiment, i.e. within subjects, between subjects, double-blind?
between subjects, double-blind study
How were OT and AVP administered?
Instranasal administration
Each participant self-administered either 24 IU OT, 20 IU AVP or 1nasal puffs of either OT vehicle or AVP vehicle
Describe how the PDG was played in the fMRI scanner when participants acted as player 1.
- Stimuli were projected onto a screen that subjects could view through a mirror mounted on the head coil
subjects’ responses were recorded using a response box - At the beginning of each round, the round number and partner’s photo were displayed for 2s.
- Player 1 then had 4s to either cooperate or defect (participants were told that if they did not decide within 4s their choice would default to defection)
- Player 1 then waited for player 2 to response (they were given 4s as well) and then the outcome was displayed to both players
How was social cooperation defined? Using the timeline in fig. 1, identify the part of the interaction that defined social cooperation.
social cooperation was defined by both players cooperating as opposed to defecting.
the part of the interaction that defines social cooperation is player 2s choice, assuming that player 1 chooses to cooperate
What were the effects of OT and AVP on choices in the PDG?
- Two way ANOVA revealed no effects of drug treatment or interaction with sex on either CC outcome frequency or the probabilty of cooperating after a CC outcome in the previous round
- within AVP group, the probability of cooperating after a CC outcome was higher for males than females
As in all functional brain imaging experiments, the results are based on the subtraction method. In these experiments, what contrast was used to identify brain areas in which OT & AVP produced different effects in men and women?
the contrast used in this experiment was the brain activation produced by those in the placebo group
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the BOLD response to the PDG in the placebo treatments was subtracted from the BOLD response to the PDG in the drug treatments
Name 3 brain areas in which OT effects were influenced by gender.
1) left and right caudate/putamen
2) the right frontal pole
3) the left medial part of the superior medial frontal cortex
Name 3 brain areas in which AVP effects were influenced by gender.
activation was found in the
1) left insula
2) right insula
3) left supramarginal gyrus
in each of these regions, AVP augmented activation relative to the placebo in males but, attenuated activation relative to placebo in females
The authors found a sex difference in the effects of OT on the BOLD response to cooperation in the caudate/putamen.
Describe what they found.
for both right and left caudate/putamen, OT increased activation in males while decreasing activation in females
In their Discussion, the authors also point out that there was a sex difference in this response “at baseline”, i.e. when the male and female placebo groups were compared, such that the female placebo group showed a larger BOLD signal than the male placebo group. This suggested that the OT-sensitive network that responds to social cooperation is operating at a higher level at baseline in women and that giving OT to men can bring its activity closer to what is seen in women at baseline. Given these findings, what explanation was offered for the finding that OT decreased activation in women?
they suggest the possibility of an inverted U-shaped dose response function between the brains OT levels and neural activity, that would would already be at the peak of that curve around baseline, and that you would have to administer OT to males for them to reach the same level of activation
conversely, if woman already have max activation (at peak of inverted U curve) then administering more OT would push them beyond the peak of activation, and actually produce deactivation (in comparison to the optimal activation they experienced at baseline) of the caudate/putamen
What do you think might explain why different results were seen when participants thought they were playing with a human vs. a computer partner? The authors don’t discuss this, but I’d like you to think about it and discuss possible reasons after you answer the following two questions about methods. You don’t need to provide more than a few sentences of speculation.
people may more than likely be at a disadvantage to a computer program than another person.
if the player defects, they are guaranteed some money, but they run the risk of the computer program defecting if they choose to cooperate at first, which would result in the player not receiving any money
the perception of playing against a computer program changes the game in the sense that is becomes all about the monetary reward, instead of trying to cooperate with another person to produce a “win-win” situation.
OT and AVP act on social cooperation and people realize that you can’t hurt a computer’s feelings, or screw them over.
How did the authors lead the participants to believe they were playing with human partners?
they introduced them to two same-sex individuals and told them that they would be playing the game together; one would play with the subject when the subject acted as player 1, and other other would play with the subject when they subject acted as player 2.
What was different about the timeline of the PDG task when participants thought their partner was human, vs. when they thought it was a computer?
Player 3 chooses did not happen, so that 0-4s would be cut out of the timeline
it does not explicitly say in the paper but, one can assume they were as consistent as possible so they could directly compare the results of the human vs. computer tasks
What function did the authors attribute to activation of the following structures during reciprocated cooperation?
caudate/putamen
the current findings may indicated that OT enhances the reward from reciprocated cooperation and/or facilitates learning that another person can be trusted to reciprocate cooperation among males, whereas OR may have the opposite effects among females.
the striatum is also involed in salience detection, so the results might also imply that OT enhances the salience of positive social interactions among men, while decreasing their salience among women
