Electrical stimulation of the pregenual anterior cingulate cortex (pACC) in monkeys increases negative decision making, an effect blocked by anti-anxiety drugs, reports a study published online this week in Nature Neuroscience. This area of the brain has previously been implicated in human anxiety disorders and depression, and these results suggest how it could cause pathological behaviour.
Graybiel and colleagues offered monkeys choices between large rewards that came along with an annoying air puff, and small rewards without the air puff. They found that some of the neurons in the pACC fired before the monkey chose the large reward despite the air puff and some fired before the monkey chose the small reward to avoid the air puff. Both kinds of neurons were mostly intermingled, but in one area of the pACC, there were more neurons that fired when monkeys chose the small reward to avoid the air puff. Stimulating the neurons in this area increased the likelihood that the monkey would choose to avoid the air puff, but this effect was blocked when the animals received an anti-anxiety drug.
People with anxiety disorders and depression are known to have difficulty making decisions in which they have to trade off costs and benefits. These results suggest that the pACC could be critical for regulating negative emotional states and anxiety in decision-making.