Differentiating Risk from Reward Motivation in Decision Making
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Risk tolerance and reward sensitivity are important phenotypes in decision making tactics and mental health. While related, these traits are distinct. When people engage in similar risky behaviors, their decision-making strategies may be reflected by different neural correlates of reward sensitivity and risk tolerance. However, few neuroimaging studies have directly compared rewards with and without risk in the same context. To fill this gap, we modified a Balloon Analogue Risk Task (BART) to include reward-only trials and modeled neural correlates of reward motivation with and without risk. During multi-echo fMRI scans of mesolimbic regions, 48 participants (28 females; M ± SD: 20.57 ± 1.92 years old ) inflated balloons across three conditions: 1) earn monetary reward but risk loss if a balloon popped (RWR); 2) earn reward without risk (RWOR); and 3) no loss or gain (neutral). Multi-echo data were preprocessed with AFNI and Tedana and sequentially analyzed with FSL GLM and permutation testing (threshold-free cluster enhancement with 5000 permutations), using the number of pumps as parametric modulator. Compared to the neutral, RWR in the decision-making phase showed greater activation in the insula, ventral- (VS) and dorsal striatum, brainstem (BS), thalamus (TH), prefrontal (PFC) and visual cortices (VC). Similarly, RWOR coincided with greater activation in the right frontal pole and middle temporal gyrus, and VC, surprisingly, not in VS. The contrast [RWR > RWOR] showed increased activity in the insula, right caudate, BS, TH, PFC, and VC. Our results suggest that RWR decision-making recruits canonical reward areas and insula, but risk involves greater recruitment of prefrontal and midbrain regions in the same task. It implies that rewards with risk recruit greater neural correlates of reward and learning. Our neuroimaging study is a first step in differentiating neural responses during risky versus simply rewarding decision making. We will further model risk-related differences in the consummatory phase to better differentiate risk tolerance from reward sensitivity.