Title:
Coordination of extracellular dopamine and serotonin signals in human striatum during conscious decision-making.

Abstract:
How the human brain generates conscious experience is a fundamental problem. In particular, it is unknown how highly variable and dynamic changes in subjective experience are driven by interactions with objective phenomena. We hypothesize a ‘dynamic affective core’ that requires not only dynamic representations of the contents and context of conscious experiences but also their value. The latter, ‘representations of value’, have begun to be well characterized by computational reinforcement learning models and empirical data that support the idea that dopamine neurons signal ‘better (or worse) than expected’ experiences by encoding ‘reward prediction errors’ in changes in their firing rate. However, whether first-person subjective experiences  align with dopaminergic encoding of better or worse than expected ‘reward prediction errors’ has, to our knowledge, not been directly tested. Recently developed technology allows, for the first time ever, high temporal resolution (i.e., sub-second) measurements of the neurotransmitters dopamine and serotonin from deep within the human brain during conscious decision-making and behavior. I will present recent work that supports the hypotheses that dopamine and serotonin encode reward and punishment prediction errors, respectively; that these signals coordinate and drive human behaviors; and, that sub-second fluctuations in dopamine and serotonin levels may drive moment-to-moment changes in the valence of self-reported subjective experiences. Together, our results support the idea that dopamine and serotonin provide valuation update signals in the human brain that guide behavior and may also be critical modulators of subjective phenomenal experience.