Dissociable brain signatures of choice conflict and immediate reward preferences in alcohol use disorders

Abstract

Impulsive delayed reward discounting (DRD) is an important behavioral process in alcohol use disorders (AUDs), reflecting incapacity to delay gratification. Recent work in neuroeconomics has begun to unravel the neural mechanisms supporting DRD, but applications of neuroeconomics in relation to AUDs have been limited. This study examined the neural mechanisms of DRD preferences in AUDs, with emphasis on dissociating activation patterns based on DRD choice type and level of cognitive conflict. Heavy drinking adult men with (n = 13) and without (n = 12) a diagnosis of an AUD completed a monetary DRD task during a functional magnetic resonance imaging scan. Participant responses were coded based on choice type (impulsive versus restrained) and level of cognitive conflict (easy versus hard). AUD+ participants exhibited significantly more impulsive DRD decision-making. Significant activation during DRD was found in several decision-making regions, including dorsolateral prefrontal cortex (DLPFC), insula, posterior parietal cortex (PPC), and posterior cingulate. An axis of cognitive conflict was also observed, with hard choices associated with anterior cingulate cortex and easy choices associated with activation in supplementary motor area. AUD+ individuals exhibited significant hyperactivity in regions associated with cognitive control (DLPFC) and prospective thought (PPC) and exhibited less task-related deactivation of areas associated with the brain's default network during DRD decisions. This study provides further clarification of the brain systems supporting DRD in general and in relation to AUDs.

Keywords: Alcohol use disorders; delay discounting; neuroeconomics.

Figure 1

Delay Discounting by AUD Status. Hyperbolic temporal discounting curves corresponding to the average k values for AUD+ (solid line) and AUD- (dashed line) groups. Note: *p < .05; AUD = alcohol use disorder.

Figure 2

Neurocognitive Correlates of Delay Discounting. Panel A depicts activation during control trials versus rest. Panels B and C reflect activations and deactivations, respectively, for the impulsive/restrained categorization (red = impulsive choices; blue = restrained choices; yellow = both impulsive and restrained choices). Panels D and E reflect activations and deactivations, respectively, for the easy/hard categorization (red = easy choices; blue = hard choices; yellow = both easy and hard choices). Images thresholded at p < .001; cluster extent 11 voxels. All images shown in radiological convention (Left = Right) with corresponding Z coordinates given in Talairach space. Note: ACC = anterior cingulate; DLPFC = dorsolateral prefrontal cortex; IFG = inferior frontal gyrus; INS = insula; MEFG = medial frontal gyrus; MTG = middle temporal gyrus; PCC = posterior cingulate; PCN = precuneus; PoCG = postcentral gyrus; SMA = supplementary motor area; L = left; R = right.

Figure 3

Neural Axis of Cognitive Conflict during Easy and Hard Intertemporal Choice Decisions. Sagittal image depicting dissociation of medial prefrontal cortex region identified in the easy/hard analysis (red = easy choices; blue = hard choices; yellow = both easy and hard choices). Image thresholded at p < .001, cluster extent = 11 voxels. X coordinate given in Talairach space. Note: ACC = anterior cingulate cortex; SMA = supplementary motor area.

Figure 4

Hyperactivity in AUD+ Individuals. Significant differences between AUD groups were found in precuneus (top row), right DLPFC (middle row), and left DLPFC (bottom row). Axial slices depict the location of each region in radiological convention (Left = Right) with corresponding Z coordinates given in Talairach space. Bar graphs depict corresponding mean BOLD activation (+ standard error) per condition for AUD- (black bars) and AUD+ (gray bars). Note. *p<.05; **p<.01; AUD = alcohol use disorder; L = left.