[not in handout, see intranet]
Singer, T., Seymour, B., O'Doherty, J. P., Stephan, K. E., Dolan, R. J., & Frith, C. D. (2006). Empathic neural responses are modulated by the perceived fairness of others. Nature, 439(7075), 466-469.
Brief details -
Subjects first played a reciprocal money-giving game with a confederate ('Prisoner's dilemma'). In some cases the confederates player fairly - after first being given money by the participant, the confederates gave money to the participant when it was their turn. An alternative confederate played unfairly, by refusing to return the favour.
After this there was a brain scanning phase, when subjects in the fMRI scanner could see (via mirrors) their own hand and a hand of each of the 2 confederates receiving a painful electric shock (visual cues indicated which hand would be shocked, and the onset and intensity of the shock).
Brain scans showed that the same areas of the brain were activated when the subjects received shocks themselves, and when they observed others being shocked (interpreted as empathy).
An exception was that this effect was reduced when male participants observed unfair confederates being shocked (reward areas were activated instead, correlating with a post-scan questionnaire finding indicating a desire for revenge).
The pain-related brain areas are fronto-insular and anterior cingulate cortices and the main reward area is in the ventral striatum i.e. the nucleus accumbens.