Dopamine and the motivation of cognitive control.

The major ascending neuromodulator dopamine has long been implicated in cognitive control. Effects of dopamine-related disorders and the treatment of the cognitive control deficits associated with these disorders are commonly attributed to modulation of the prefrontal cortex. However, many disorders that are accompanied by cognitive control deficits also implicate abnormal dopamine transmission in the striatum, which has been associated more readily with value-based learning, choice, and motivation. We put forward the hypothesis that effects of dopamine on cognitive control reflect, in part, indirect modulation of value-based learning and choice computations that alter the motivation to exert control. This hypothesis is grounded in accumulating evidence from work with experimental animals as well as neurochemical PET, pharmacologic fMRI, and computational modeling work with healthy volunteers and patients with addictive disorders, ADHD, and Parkinson's disease. Consistent with an "inverted-U"-shaped relationship between dopamine and value-based learning, this evidence suggests that dopaminergic drugs might paradoxically increase our drive away from cognitive control in individuals with high baseline levels of dopamine, perhaps by "overdosing" dopamine levels, and thus reducing the value of cognitive control. The hypothesis has implications for the many dopamine-related disorders, which are often accompanied by either apathy or problems with impulse control, and their pharmacotreatment with dopaminergic drugs. For example, the cognitive deficits that are commonly associated with prefrontal cortex dysfunctioning might instead reflect modulation of striatal dopamine and its role in the willingness rather than the ability to exert control.