And on the Mahayana side, there is this study which looked at Vietnam war vetrans with brain leisons in various parts of the brain. The veterens were given exercises involving either donating or punishing a cause with money that they were granted at the beginning of the experiment. Both actions constitute some moral action but only donation is altruistic. Vetrans preferring one or the other kind of action had leisons in different parts of the brain (punish: dorsomedial prefrontal cortex, donate: dorsomedial parietal cortex)