Abnormal medial prefrontal cortex activity in heavy cannabis users during conscious emotional evaluation

Abstract

Rationale Long-term heavy cannabis users (cannabis users) who are not acutely intoxicated have diminished subconscious neural responsiveness to affective stimuli. Objective This study sought to determine if abnormal processing extends to the conscious evaluation of emotional stimuli. Methods Functional Magnetic Resonance Imaging (fMRI) was used to examine brain activity as cannabis users (N=16) and non-cannabis using controls (N=17) evaluated and categorized standardized International Affective Picture System (IAPS) stimuli. Individual judgments were used to isolate activity during the evaluation of emotional (i.e., emotional evaluation) or neutral (i.e., neutral evaluation) stimuli. Within- and between-group analyses were performed. Results Both groups judged the same stimuli as emotional and had activations in visual, midbrain, and middle cingulate cortices during emotional evaluation, relative to neutral. Within-group analyses also revealed amygdalar and inferior frontal gyrus activations in controls, but not cannabis users, and medial prefrontal cortex (mPFC) deactivations in cannabis users, but not controls, during emotional evaluation, relative to neutral. Between-group comparisons found that mPFC activity during positive and negative evaluation was significantly hypoactive in cannabis users, relative to controls. Conclusions Abnormal neural processing of affective content extends to the level of consciousness in cannabis users. The hypoactive mPFC responses observed resembles the attenuated mPFC responses found during increased non-affective cognitive load in prior research. These findings suggest that abnormal mPFC singling in cannabis users during emotional evaluation might be associated with increased non-affective cognitive load.

Neurophysiological capacity in a working memory task differentiates dependent from nondependent heavy drinkers and controls

“…To evaluate alcohol use history, psychiatric conditions, and intelligence, potential participants completed the Alcohol Use Disorders Identification Test (AUDIT) (Babor et al, 2001), the Structured Clinical Interview for DSM-IV Disorders (SCID) (First et al, 2002) and the Wechsler Abbreviated Scale for Intelligence (WASI) (Wechsler, 1999), respectively. Consistent with previous methods (Wesley et al, 2011; Wesley et al, 2016), individuals with current Axis I disorders (excluding alcohol use disorder) or an IQ of less than 80 were excluded from further participation.…”

Emotion regulation deficits in regular marijuana users

“…Becker et al [2010]). Furthermore, studies have reported altered emotional experience and associated neural activity in regular marijuana users in the amygdala [Gruber et al, 2009], and frontal nodes critically engaged in emotion regulation, such as the medial prefrontal [Wesley et al, 2015] and orbitofrontal [Filbey et al, 2016] cortex. Moreover, regular marijuana users show impaired automatic emotion regulation in the domains of inhibitory and behavioral control [Battisti et al, 2010].…”

Heavy cannabis use and attentional avoidance of anxiety-related stimuli

“…Therefore, due to the association between cannabis and anxiety, it is particularly important to provide evidence which may increase our understanding toward how this association manifests. Previously research has indicated altered affective response and emotional evaluation in cannabis users (see Gruber et al, 2009 , Wesley et al, 2015 ). Cannabis would appear to decrease reactivity to negative affective stimuli whilst also acutely inducing anxiety (see Powell et al, 2002 , Salamone, 1994 ).…”