Amygdala Structural Connectivity Is Associated With Impulsive Choice and Difficulty Quitting Smoking.

Ausaf A. Bari,Bayard Wilson,Simon Levinson,Hiro Sparks,Jean-Philippe Langevin,Nader Pouratian,Edythe D. London

doi:10.3389/fnbeh.2020.00117

Abstract

Introduction: The amygdala is known to play a role in mediating emotion and possibly addiction. We used probabilistic tractography (PT) to evaluate whether structural connectivity of the amygdala to the brain reward network is associated with impulsive choice and tobacco smoking.Methods: Diffusion and structural MRI scans were obtained from 197 healthy subjects (45 with a history of tobacco smoking) randomly sampled from the Human Connectome database. PT was performed to assess amygdala connectivity with several brain regions. Seed masks were generated, and statistical maps of amygdala connectivity were derived. Connectivity results were correlated with a subject performance both on a delayed discounting task and whether they met specified criteria for difficulty quitting smoking.Results: Amygdala connectivity was spatially segregated, with the strongest connectivity to the hippocampus, orbitofrontal cortex (OFC), and brainstem. Connectivity with the hippocampus was associated with preference for larger delayed rewards, whereas connectivity with the OFC, rostral anterior cingulate cortex (rACC), and insula were associated with preference for smaller immediate rewards. Greater nicotine dependence with difficulty quitting was associated with less hippocampal and greater brainstem connectivity. Scores on the Fagerstrom Test for Nicotine Dependence (FTND) correlated with rACC connectivity.Discussion: These findings highlight the importance of the amygdala-hippocampal-ACC network in the valuation of future rewards and substance dependence. These results will help to identify potential targets for neuromodulatory therapies for addiction and related disorders.

Highlights

The amygdala is known to play a role in mediating emotion and possibly addiction
Imaging studies have revealed an association between cocaine cravings and increased dopamine release in the amygdala, nucleus accumbens (NAc), orbitofrontal cortex (OFC), and anterior cingulate cortex (ACC; Koob and Volkow, 2016)
We found that connectivity with the insula, NAc, dorsolateral prefrontal cortex (DLPFC), and rostral anterior cingulate cortex (rACC) was relatively segregated with a preference toward the dorsolateral hippocampus was relatively diffuse with a localization trend amygdala

Summary

Introduction

We used probabilistic tractography (PT) to evaluate whether structural connectivity of the amygdala to the brain reward network is associated with impulsive choice and tobacco smoking. The functional disconnection between the amygdala and insula abolishes the ability to observe outcome devaluation during an instrumental conditioning task (Parkes and Balleine, 2013). Along these lines, relapse in drug addiction has been partially attributed to changes within the amygdala-hippocampus-NAc circuit. In animal models of cocaine dependence, electrical stimulation of the amygdala or the hippocampus elicits long-lasting dopamine release in the NAc which may underlie relapses in drug-seeking behavior (Blaha et al, 1997; Floresco et al, 1998; Hayes et al, 2003; Li et al, 2018). Connectivity of the amygdala with these structures likely influences addictive and reward-related behaviors through combined influences on reinforcement learning, reward valuation, and the subjective emotional experience associated with reward consumption

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