Area of Monkey Brain Keeps Tally of Altruistic Acts
…monkeys have a specific area in their brains to keep track of altruistic acts…They used electrodes to directly record neuronal activity in three areas of the prefrontal cortex, an area that is known to be involved in social decision-making while the monkey performed reward-related tasks.…. in two out of the three brain areas being recorded, neurons fired in the presence or absence of the juice reward only. By contrast, the area known as the anterior cingulate gyrus responded only when the monkey allocated the juice to the neighbor and observed it being received. The scientists suggest that the neurons in the ACG respond to and record the act simultaneously.
The ACG is known to be a region specialized for social decision-making in primates, and it is located in the same area of the brain as that associated with the generation of feelings of empathy in humans.
The most basic form of ACC theory states that the ACC is involved with error detection. Evidence has been derived from studies involving a Stroop task. However, ACC is also active during correct response and this has been shown using a letter task, whereby participants had to respond to the letter X after an A was presented and ignore all other letter combinations with some letters being more competitive than others. They found that for more competitive stimuli ACC activation was greater.
A similar theory poses that the ACC’s primary function is the monitoring of conflict. In Eriksen flanker task, incompatible trials produce the most conflict and, the most activation by the ACC. Upon detection of a conflict, the ACC then provides cues to other areas in the brain to cope with the conflicting control systems.
Using a computer screen to allocate juice rewards, the monkeys:
- preferred to reward themselves first and foremost
- But they also chose to reward the other monkey when it was either that or nothing for either of them.
- They also were more likely to give the reward to a monkey they knew over one they didn’t, preferred to give to lower status than higher status monkeys
- had almost no interest in giving the juice to an inanimate object.
Calculating the social aspects of the reward system seems to be a combination of action by two centers involved in calculating all sorts of rewards and a third center that adds the social dimension
- The orbital frontal cortex, right above the eyes, was activated when calculating rewards to the self.
- The anterior cingulate sulcus in the middle of the top of the brain seemed to calculate giving up a reward. But both centers appear “divorced from social context,”
- A third area, the anterior cingulate gyrus (ACCg), seemed to “care a lot about what happened to the other monkey,”
…. it would appear that neurons in the ACCg encode both the giving and receiving of rewards, and do so in a remarkably similar way.