Abstract
RationaleInsular cortex supports the representation of motivational feelings through the integration of interoceptive information concerning bodily physiology. Compromised insular integrity is implicated in alcohol and drug use disorders. Alcohol-associated insular dysfunction may arise through aberrant glutamatergic neurotransmission associated with selective neuronal death and atrophy.ObjectiveIn a sample of alcohol users, we combined magnetic resonance spectroscopy (MRS) with voxel and surface-based morphometry (VBM, SBM) to test the hypothesis that the neurochemical and structural properties of the insula relate to alcohol use.MethodsTwenty-three healthy individuals were characterized by measures of alcohol use and subjective craving. Right mid-insula glutamate/glutamine (Glx) and total N-acetylaspartate/N-acetyl-aspartylglutamate (TNAA) concentrations were measured using MRS. Right insular structure was quantified using VBM and SBM parameters. We tested for predictive associations between these neuroimaging and behavioral/psychometric measures using Bayesian statistics.ResultsReduced insular Glx concentration was associated with increased alcohol compulsions and, to a lesser extent, with greater alcohol use severity. Anecdotal evidence for a negative relationship between alcohol use severity and levels of insular gyrification was also observed.ConclusionsThis study is, to date, the first characterization of the neurochemical and morphological integrity of insular cortex in alcohol users. Our data seem to reveal a negative relationship between alcohol use and the neurochemical and structural integrity of the insula, a critical substrate for motivational behavior. These neurobiological characteristics might contribute to loss of control toward compulsive drinking with prolonged and excessive alcohol use.
Highlights
The insular cortex is implicated in the neurocircuitry of addiction: Interoceptive components of drug seeking are proposed to originate within the insula (Craig 2002; Gray and Critchley 2007; Naqvi et al 2007)
Insular volume is preferentially reduced in alcohol use disorder, in the context of more diffuse gray matter shrinkage (Yang et al 2016), and the volume and thickness of anterior insular cortex are negatively correlated to impulsivity and compulsions in alcohol-dependent individuals (Grodin et al 2017)
Combining magnetic resonance spectroscopy (MRS) with behavioral and psychometric ratings, we explored the relationship between alcohol-related measures, craving, and compulsion and right middle insular cortex neurochemistry in alcohol users
Summary
The insular cortex is implicated in the neurocircuitry of addiction: Interoceptive components of drug seeking (notably craving states) are proposed to originate within the insula (Craig 2002; Gray and Critchley 2007; Naqvi et al 2007). Conscious access to bodily sensations has been shown to be dependent on the right insular cortex (Craig 2002, 2009, 2010; Critchley et al 2004). Damage to insular cortex can change addictive behaviors (Naqvi et al 2014). Individuals with alcohol dependence show a reduction in functional interactions between insular cortex and prefrontal regions during emotional processing, indicating a generalized dysregulation of motivational and affective processes (O’Daly et al 2012)
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