Temporary changes in large-scale memory neural networks after fear learning and extinction in healthy adults

TL;DR

This study investigates how fear learning and extinction affect large-scale brain network connectivity in healthy adults over a week, revealing specific changes in the parahippocampal and amygdala regions.

Contribution

It applies graph theory to analyze dynamic functional connectivity changes after fear extinction, highlighting new neural network patterns over time.

Findings

Increased connectivity of the left parahippocampal gyrus post-extinction.

Formation of a new subnetwork involving hippocampus and parahippocampal regions.

Connectivity changes persisted for one week after extinction.

Abstract

The analysis of the functional connectivity of brain sections associated with fear-conditioned training is one of the methods of study of memory neural networks. Before, the majority of studies focused on the functional connectivity of the brain regions that are known for emotional processing such as amygdala and areas of the ventromedial prefrontal cortex in the resting state right after the formation of a fear-conditioned reflex. In the present study authors applied the methods of the theory of graphs to search for changes in the functional connectivity at the level of the brain in the resting state in a week dynamics after the extinction of a conditioned reflex with partial reinforcement. The most significant changes were observed in the functional connectivity of the left parahippocampal area. In particular, the rostral part of the left parahippocampal gyrus became the center of a new subnetwork connected with the rostral part of the left hippocampus in all the sessions and after the extinction of a conditioned reflex and the lateral part of the left amygdala right after the extinction and a day after the extinction of a conditioned reflex. A week after the extinction of a conditioned reflex, the rostral part of the left parahippocampal gyrus also had more connections with the areas of the middle frontal gyrus in comparison with the parameters of the baseline resting state to the stimulus. Besides, these changes remained within one week from the moment of the extinction of a conditioned reflex, which could be explained by the chosen paradigm of conditioned reflex with partial reinforcement that led to a slower extinction than a paradigm with full reinforcement.