Jung Ho Hyun of Johns Hopkins University School of Medicine will present a lecture entitled: Neural mechanism that regulates the modification of brain circuits when switching between learned tasks.
Abstract: Appropriate choice based on expected outcomes determined by previous experience in similar environments is important in everyday life. However, when the outcomes of decisions consistently violate expectations, new learning is necessary to maximize rewards. Cognitive flexibility, such as reversal learning - the ability to adapt to new rule when an previously rewarded stimulus is no longer rewarded - is dependent on the serotonergic system and impaired by lesions to the orbitofrontal cortex (OFC) in humans and primates (Clarke et al., 2004). Nevertheless, the circuitry and the mechanism controlling serotonergic neurons during reversal learning remains uncharacterized. Here, we found serotonin release from dorsal raphe nucleus (DRN) to the OFC promotes reversal learning. Also, we identified and functionally confirmed a long-range connectivity defining the monosynaptic inputs onto OFC projecting serotonergic neurons of DRN based on genetically defined retrograde tracing strategy. We further show that spatiotemporally precise serotonergic action enhances the excitability of OFC neurons and offers the enhanced spike probability of OFC network as well. In summary, our findings propose a role for serotonergic action on the cellular mechanism for cognitive flexibility in a neural circuit within DRN-OFC area during reversal learning.