Neural Correlates of Trust and Adaptation in a Dynamic Neuroeconomic Task Project Presentation Adam P.R. Smith, Esther Kessler, Chiara Fiorentini, Fiona Roberts, David Skuse Behavioural and Brain Sciences Unit, Institute of Child Health

Background Social Decision Making Optimise outcome for selfOptimise outcome for group CompetitionCooperation Risk / Reward Reputation Altruism & fairness Punishment Expectation / Trust Experience / Learning Neuromodulators Appropriate social decision making key aspect of human interaction Economic models provide a model framework of interactive behaviour In real world, heavily influenced by previous interactions with others, but little done on influence of memory on social decisions

Multi-Round Trust Game Invest 100 Do not invest You have 1000 points. Your playing partner is shown below You Invest 100 Your partner returns 200 You now have 1100 points 4s3s2 – 4s (jittered) Round 1: 60 games, each with a novel partner represented by a photograph of an emotionally neutral female face. ~50% will reciprocate and return some points. If players do not invest they will still be told whether or not the partner would have reciprocated Round 2: In round 2, there is no choice as to whether or not to invest. 60 games, 30 with partners seen in round 1, 30 with novel partners. ~50% will reciprocate and return some points Round 3: In round 3, subject again has the choice whether or not to invest. 90 games - 30 from round 1 who were not in round 2, 30 from round 2 who were not in round 1 and 30 novel partners Basic structure of the trust game: Players A and B each have an amount of money (or points) for participating in the study Player A chooses to give a certain amount of their money (M A ) to Player B The money given is increased (xM A ) (e.g. if tripled x =3) Player B decides how much to return k B (xM A ) In the current study, the subject is always player A and makes a binary decision to invest money with player B or not. Player B (whose responses are pre-determined in an economics lab elsewhere) will either return nothing or half of the money.

Subjects, Scanning and Analysis 48 subjects allows counterbalancing across conditions of 120 emotionally neutral female faces representing playing partners. Each will be used an equal number of times as old/new, cooperator/defector and across the 3 rounds. To obviate effects of gender related subject/partner effects, all R handed females. Expected scanning duration ~ 1h 15m – 1h 30m / subject. Estimated total scanner time ~ 75h Experimental script implemented in Cogent. Scanning on Siemens Avanto 1.5T with 32 channel head coil. 30 slices of 2.5mm with 1.3mm gap to give near whole brain coverage (-vertex). TR ~2.5 – 3s. ?Use of pre- pulse to reduce OFC dropout. Event-related fMRI analysis in SPM 8. Key within-subject contrasts of interest: Invest vs. non-invest decision in round 1 (non-informed trust judgment) Betrayed vs. reciprocated trust in R1 Old vs. new partners in R2 (Old/New effects without need to adjust behaviour) Old co-operators vs. old defectors in R2 (Emotional memory effects without need to adjust behaviour; Conflict effects) Same contrasts from R2 in R3, where successful memory of partners behaviour should influence decision to trust Post-hoc group-wise comparison of above effects according to genetic polymorphisms affecting neuromodulation