Neuroanatomical foundations of delayed reward discounting decision making

Abstract

Resolving tradeoffs between smaller immediate rewards and larger delayed rewards is ubiquitous in daily life and steep discounting of future rewards is associated with several psychiatric conditions. This form of decision-making is referred to as delayed reward discounting (DRD) and the features of brain structure associated with DRD are not well understood. The current study characterized the relationship between gray matter volume (GMV) and DRD in a sample of 1038 healthy adults (54.7% female) using cortical parcellation, subcortical segmentation, and voxelwise cortical surface-based group analyses. The results indicate that steeper DRD was significantly associated with lower total cortical GMV, but not subcortical GMV. In parcellation analyses, less GMV in 20 discrete cortical regions was associated with steeper DRD. Of these regions, only GMV in the middle temporal gyrus (MTG) and entorhinal cortex (EC) were uniquely associated with DRD. Voxelwise surface-based analyses corroborated these findings, again revealing significant associations between steeper DRD and less GMV in the MTG and EC. To inform the roles of MTG and EC in DRD, connectivity analysis of resting state data (N = 1003) using seed regions from the structural findings was conducted. This revealed that spontaneous activity in the MTG and EC was correlated with activation in the ventromedial prefrontal cortex, posterior cingulate cortex, and inferior parietal lobule, regions associated with the default mode network, which involves prospection, self-reflective thinking and mental simulation. Furthermore, meta-analytic co-activation analysis using Neurosynth revealed a similar pattern across 11,406 task-fMRI studies. Collectively, these findings provide robust evidence that morphometric characteristics of the temporal lobe are associated with DRD preferences and suggest it may be because of their role in mental activities in common with default mode activity.

Keywords: Behavioral economics; Delayed reward discounting; Gray matter; MRI; Morphometry.

Figure 1

Partial regressions of mean delayed reward discounting area under the curve in relation to bilateral middle temporal gyrus (Panel A) and bilateral entorhinal cortex (Panel B); sex, age, income and intracranial volume are included in the models.

Figure 2

Whole brain correlation of gray matter volume and area under the curve. All clusters represent a positive correlation of mean area under the curve and regional gray matter volume. Panel A presents a lateral view of the left hemisphere, panel B presents a medial view of left hemisphere, panel C represents lateral view of the right hemisphere, panel D represents medial view of the right hemisphere. aMTG = anterior middle temporal gyrus; pMTG = posterior middle temporal gyrus.

Figure 2

Whole brain correlation of gray matter volume and area under the curve. All clusters represent a positive correlation of mean area under the curve and regional gray matter volume. Panel A presents a lateral view of the left hemisphere, panel B presents a medial view of left hemisphere, panel C represents lateral view of the right hemisphere, panel D represents medial view of the right hemisphere. aMTG = anterior middle temporal gyrus; pMTG = posterior middle temporal gyrus.

Figure 3

Resting state functional connectivity for seeds based on the structural analyses in the Human Connectome Project (N=1003) total sample. Each image shows a voxelwise correlation of all voxels on the cortical surface (no subcortical regions) with a seed identified from the voxelwise cortical surface analysis of GMV and mAUC (shown as a white sphere). Seeds were A) left middle temporal gyrus B) right middle temporal gyrus C) left entorhinal cortex D) right entorhinal cortex. Panel E displays the color scale used.

Figure 3

Resting state functional connectivity for seeds based on the structural analyses in the Human Connectome Project (N=1003) total sample. Each image shows a voxelwise correlation of all voxels on the cortical surface (no subcortical regions) with a seed identified from the voxelwise cortical surface analysis of GMV and mAUC (shown as a white sphere). Seeds were A) left middle temporal gyrus B) right middle temporal gyrus C) left entorhinal cortex D) right entorhinal cortex. Panel E displays the color scale used.

Figure 4

Neurosynth co-activation meta-analysis of MTG and EC, thresholded at false discovery rate criterion of p < .05. Neurosynth had 11,406 studies, 150,000 brain locations, and 413,429 activations at time of analysis (April 18^th, 2017). Red activation represents positive co-activation with seed region (white corresponds with the seed). No negative co-activation was found in any of the analyses completed. Maps show co-activation of the following seed regions: A) left middle temporal gyrus; B) right middle temporal gyrus; C) left entorhinal cortex D) right entorhinal cortex.

Figure 4

Neurosynth co-activation meta-analysis of MTG and EC, thresholded at false discovery rate criterion of p < .05. Neurosynth had 11,406 studies, 150,000 brain locations, and 413,429 activations at time of analysis (April 18^th, 2017). Red activation represents positive co-activation with seed region (white corresponds with the seed). No negative co-activation was found in any of the analyses completed. Maps show co-activation of the following seed regions: A) left middle temporal gyrus; B) right middle temporal gyrus; C) left entorhinal cortex D) right entorhinal cortex.

Figure 4

Neurosynth co-activation meta-analysis of MTG and EC, thresholded at false discovery rate criterion of p < .05. Neurosynth had 11,406 studies, 150,000 brain locations, and 413,429 activations at time of analysis (April 18^th, 2017). Red activation represents positive co-activation with seed region (white corresponds with the seed). No negative co-activation was found in any of the analyses completed. Maps show co-activation of the following seed regions: A) left middle temporal gyrus; B) right middle temporal gyrus; C) left entorhinal cortex D) right entorhinal cortex.