A Dopaminergic Basis for Fear Extinction.

It is a joyous relief when an event we dread fails to materialize. In fear extinction, the appetitive nature of an omitted aversive event is not a mere epiphenomenon but drives the reduction of fear responses and the formation of long-term extinction memories. Dopamine emerges as key neurobiological mediator of these related processes.

Dopamine neurons drive fear extinction learning by signaling the omission of expected aversive outcomes

Extinction of fear responses is critical for adaptive behavior and deficits in this form of safety learning are hallmark of anxiety disorders. However, the neuronal mechanisms that initiate extinction learning are largely unknown. Here we show, using single-unit electrophysiology and cell-type specific fiber photometry, that dopamine neurons in the ventral tegmental area (VTA) are activated by the omission of the aversive unconditioned stimulus (US) during fear extinction. This dopamine signal occurred specifically during the beginning of extinction when the US omission is unexpected, and correlated strongly with extinction learning. Furthermore, temporally-specific optogenetic inhibition o…

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