Fast and slow extinction pathways in defensive survival circuits

Publication date: December 2018 Source:Current Opinion in Behavioral Sciences, Volume 24 Author(s): Temidayo Orederu, Daniela Schiller Threat extinction is the decline in responding to a stimulus that previously signaled danger, following repeated non-consequential exposures. The amygdala, prefrontal cortex, and hippocampus are known contributors to the neural circuits driving threat extinction, however, research has not yet resolved the precise neuronal interactions necessary for extinction success. At times, research even appears to present conflicting conclusions concerning the neurocircuitry that drives extinction learning. Here, we propose a model of threat extinction that accounts for the range of findings within the literature. Our model consists of two parallel pathways that differ in their temporal dynamics, such that a fast extinction circuit requires only one training session and exerts its effects rapidly, while a slow circuit impacts behavior only after multiple training sessions. This dual-mechanism of threat extinction circuits is rooted in a hybrid associative learning model whereby parallel fast and slow pathways differentially rely on new learning and unlearning, respectively, to optimize survival as an animal’s probabilistic beliefs concerning threat and danger evolve over repeated extinction trials.

Source: Current Opinion in Behavioral Sciences - June 30, 2018 Category: Psychiatry & Psychology Source Type: research