# Causal links between serotonin dynamics and cued fear learning: evidence from experimental studies

## TL;DR

This paper explores how serotonin levels dynamically influence fear learning and extinction, suggesting that models should account for continuous serotonin changes.

## Contribution

The paper emphasizes the need for theoretical models to include continuous-time serotonin dynamics based on experimental evidence.

## Key findings

- Serotonin levels show rapid responses to stimuli and a slow component during fear conditioning.
- Perturbations of serotonin dynamics affect fear expression during conditioning and extinction.
- Theoretical models should incorporate continuous serotonin dynamics for accurate predictions.

## Abstract

Serotonin is thought to regulate emotional learning and memory, but there remains much to be explored regarding its causal role in cued fear conditioning and extinction (CFC-E). Recent in vivo recording of dorsal raphe nucleus serotonin neuronal activity during CFC-E paradigm showed that the time course of serotonin level includes both rapid responses to conditioned and unconditioned stimuli and a slowly accumulating component that spans inter-trial intervals and reverses during extinction. By reviewing the studies that directly link the fear expression during CFC-E to the acute or chronic perturbations of serotonin dynamics at the organism level or within specific brain areas via pharmacological, genetic, and projection-specific manipulations, we argue that theoretical models defining the causal role of serotonin must incorporate continuous-time serotonin dynamics.