From Value to Saliency: Neural Computations of Subjective Value under Uncertainty in PTSD

Abstract

Combat soldiers are vulnerable to Posttraumatic Stress Disorder (PTSD), following traumatic experiences in the battlefield. Studies have often used fear-related design to unravel the underlying neural deficits of learning and emotion regulation in PTSD patients. However, the role of individual uncertainty attitudes in the development of trauma-related psychopathology has hardly been examined, especially that uncertainty is highly related to the traumatic experiences from the battlefield. Through a monetary gambling paradigm inspired by behavioral economics, we explore the neural markers of PTSD symptoms of combat veterans in the realm of decision making, focusing on the subjective valuation of uncertain monetary gains and losses. We identify increased behavioral aversion to risky monetary gains and ambiguous monetary losses related to higher PTSD symptom severity. We find the key role of the emotional numbing cluster of PTSD symptoms in influencing the general activities of ventromedial prefrontal cortex (vmPFC) during valuation.We further suggest that a shift from value-to saliency-encoding pattern of subjective values across rewards and punishments in the valuation neural system, especially in ventral striatum, exist in combat veterans with PTSD, compared with trauma-exposed controls. Our results elucidate the increased neural sensitivity to highly salient rewards and punishments related to PTSD symptoms, and at the same time, point to the fundamental differences in brain regions involved in reward-and punishment-processing. We also identify

Differential Roles of Positive and Negative Valence Systems in the Development of Post-Traumatic Stress Psychopathology

“…This can be interpreted as over-emphasized NVS and reduced engagement of the PVS in decision-making processes. Such imbalance between the two valence systems is in line with previous work in chronic PTSD patients reporting increased behavioral aversion to risky monetary gains and ambiguous monetary losses 24,26 . This further corresponds to the idea that trauma exposure might alter the homeostatic balance in motivation behavior towards less approach and more avoidance, which in turn might lead to the development of chronic PTSD 15 .…”

“…symptom provocation, fearful faces) 18,19 among PTSD patients, potentially reflecting clinical symptoms of hyperarousal and intrusion (i.e., re-experiencing) 20–23 . Furthermore, studies using decision-making tasks demonstrated an association between PTSD and increased behavioral aversion to risk 24,25 and ambiguous losses 26 , possibly reflecting the generalized (not only trauma-specific) oversensitivity of the NVS, often seen in PTSD patients. At the neural level, the role of the NVS in PTSD has been repeatedly documented as abnormally heightened amygdala activation and hyperactive salience network (e.g., anterior insula, dorsal anterior cingulate cortex) in response to negative stimuli 20,27–29 .…”

Distinct neural dynamics underlying risk and ambiguity during valued‐based decision making

“…Anticipatory ERP components (the cue-P3 and the SPN) were uniquely modulated by decision riskiness, whereas consummatory ERP components (the RewP and the fb-P3) were more affected by decision ambiguity. Given that forms of abnormal decision making are common across a variety of psychiatric and neurological disorders (Euteneuer et al, 2009;Jia et al, 2020;Pushkarskaya, Tolin, et al, 2015), our findings of the dissociable neural dynamics between risk and ambiguity should be extended to relevant clinical populations to facilitate a deeper understanding of their heterogenous mechanisms underlying uncertainty processing.…”