The neuroscience of pessimism.

Ann Graybiel and collaborators offer a fascinating study showing that stimulation of the brain's caudate nucleus induces persistent and repetitive negative decision making. They devised a cost-benefit situation in which monkeys were offered a reward of juice paired with an unpleasant puff of air to the face. When the caudate nucleus was stimulated the animals began to avoid choosing the reward, when previously they would have put up with the unpleasant stimulus. This suggests that pessimistic decision-making can be tied to an overactive caudate nucleus. Work is now beginning with human patients suffering from anxiety and depression to find out whether abnormal activity in the caudate nucleus can be seen during negative decision making.

Highlights

Caudate nucleus stimulation induces persistent state change affecting value evaluation 

CN stimulation produces repetitive choices, whereas pACC stimulation does not 

CN beta oscillations parallel negative states influencing repetitive decisions 

Abnormal CN beta oscillations are correlated with persistency in OCD-like states

Summary P

ersistent thoughts inducing irrationally pessimistic and repetitive decisions are often symptoms of mood and anxiety disorders. Regional neural hyperactivities have been associated with these disorders, but it remains unclear whether there is a specific brain region causally involved in these persistent valuations. Here, we identified potential sources of such persistent states by microstimulating the striatum of macaques performing a task by which we could quantitatively estimate their subjective pessimistic states using their choices to accept or reject conflicting offers. We found that this microstimulation induced irrationally repetitive choices with negative evaluations. Local field potentials recorded in the same microstimulation sessions exhibited modulations of beta-band oscillatory activity that paralleled the persistent negative states influencing repetitive decisions. These findings demonstrate that local striatal zones can causally affect subjective states influencing persistent negative valuation and that abnormal beta-band oscillations can be associated with persistency in valuation accompanied by an anxiety-like state.