Toward a Mechanistic Understanding of Human Decision Making: Contributions of Functional Neuroimaging

ABSTRACT— This article considers the contribution of functional neuroimaging toward understanding the computational underpinnings of human decision making. We outline the main processes likely underlying the capacity to make simple choices and describe their associated neural substrates. Relevant processes include the ability to encode a representation of the expected value or utility associated with each option in a decision problem, to learn such expectations through experience, and to modify action selection in order to choose those actions leading to the greatest reward. We provide several examples of how functional neuroimaging data have helped to shape and inform theories of decision making over and above results available from traditional behavioral measures.     

Associations Among Smoking,Anhedonia, and Reward Learning in Depression

Depression and cigarette smoking co-occur at high rates. However, the etiological mechanisms that contribute to this relationship remain unclear. Anhedonia and associated impairments in reward learning are key features of depression, which also have been linked to the onset and maintenance of cigarette smoking. However, few studies have investigated differences in anhedonia and reward learning among depressed smokers and depressed nonsmokers. The goal of this study was to examine putative differences in anhedonia and reward learning in depressed smokers (n = 36) and depressed nonsmokers (n = 44). To this end, participants completed self-report measures of anhedonia and behavioral activation (BAS reward responsiveness scores) and as well as a probabilistic reward task rooted in signal detection theory, which measures reward learning (Pizzagalli, Jahn, & O'Shea, 2005). When considering self-report measures, depressed smokers reported higher trait anhedonia and reduced BAS reward responsiveness scores compared to depressed nonsmokers. In contrast to self-report measures, nicotine-satiated depressed smokers demonstrated greater acquisition of reward-based learning compared to depressed nonsmokers as indexed by the probabilistic reward task. Findings may point to a potential mechanism underlying the frequent co-occurrence of smoking and depression. These results highlight the importance of continued investigation of the role of anhedonia and reward system functioning in the co-occurrence of depression and nicotine abuse. Results also may support the use of treatments targeting reward learning (e.g., behavioral activation) to enhance smoking cessation among individuals with depression.     

肥胖成因的解释——基于食物奖赏研究的视角

肥胖的形成和发展受生物、心理和社会因素的共同作用,其中食物奖赏对肥胖的产生有重要的作用。食物是一种自然奖赏,它指机体天生对食物的渴望和依赖。食物奖赏包括"wanting"、"liking"以及"learningreinforcement"三个成分,每个成分由相应的神经通路表征。食物奖赏调控机体的摄食行为并以此调控体重变化。目前,关于肥胖与食物奖赏关系的理论模型主要有刺激—敏感化理论、奖赏过度理论以及奖赏不足理论。采用横断面设计、前瞻研究设计和纵向被试内重复测量设计,使用食物图片线索和直接给予美味奶昔的技术方法,人类脑成像研究从不同侧面为以上三个理论模型提供了证据。除此之外,食物奖赏还受基因的调控。目前,研究者关注较多的是多巴胺D2受体基因Taq IA rs1800497的多态性和FTO基因rs9939609的多态性对食物奖赏及体重改变的调控。     

奖惩中枢与学习

奖惩现象及实验揭示了:兴奋了奖赏中枢的思想、行为(神经通路)能被奖赏中枢强烈易化,而兴奋了惩罚中枢的思想、行为能被惩罚中枢强烈抑制。在此基础上,通过讨论奖惩中枢在学习中的作用得出:思想、行为的动力由奖惩中枢影响产生;奖惩中枢在思想、行为(神经兴奋)习惯的选择、形成过程中起着主要作用。     

Reward Processing and Decision-Making in Posttraumatic Stress Disorder

Theory suggests that, in those with posttraumatic stress disorder (PTSD), positive emotion is likely dampened due to reexperiencing of trauma-related stimuli. Prior research has extended positive emotion experiencing to reward processing research but has not yet examined how trauma cues affect reward processing (i.e., the anticipation of and satisfaction with reward) and decision-making in individuals with PTSD. We compared 24 individuals diagnosed with PTSD to 29 trauma-exposed controls in passive and decision-making phases of a wheel-of-fortune task, following both neutral and trauma inductions. Three types of spinners were used in the task: spinners that were obviously advantageous spinners, obviously disadvantageous spinners, and ambiguously advantageous spinners with outcomes averaging to a net gain. We hypothesized that the PTSD group would report lower reward expectation and lower outcome satisfaction and make less advantageous decisions, differences that would be exacerbated following a trauma prime. The PTSD group reported lower reward expectation than controls for the ambiguous spinners only, suggesting that the reduced anticipation of reward associated with PTSD may be specific to ambiguous stimuli. Reward expectation was not affected by the type of prime. Outcome satisfaction was not affected by PTSD or type of prime. Although only marginally significant, the PTSD group played the ambiguous spinners less often than controls, and played the obviously disadvantageous spinners significantly less often than controls, suggesting that those with PTSD are more aversive to loss. Our findings suggest that PTSD-related deficits are more robust for reward expectation than outcome satisfaction, and support future research examining the role of reward-related decision-making in PTSD.