Brain Imaging Studies of Negative Reinforcement in Humans

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A major challenge to treating drug addiction is understanding how learned associations to aversive reinforcers promote avoidant behavior and trigger the onset and relapse of drug use. Studies in non-human animals have begun to elucidate the neurobehavioral mechanisms of avoidance learning, but there have been few efforts to translate these findings to human populations. Neuroplastic brain mechanisms that support long-term memory formation are hypothesized to alter the representations of stimuli and strengthen contextual associations as a function of their incentive properties. The proposed research adopts a cognitive neuroscience perspective to characterize how motivational brain systems modulate declarative memory formation in humans and lead to behavioral avoidance. Although human declarative memory is traditionally probed using list- learning paradigms, recent advances in computer graphics interfaces and immersive virtual reality (VR) technology permit the development of novel navigational avoidance tasks that provide a tighter link with the animal literature and more closely model real-world avoidant behaviors exhibited by drug addicts in response to environmental stressors. Healthy participants will undergo a series of functional magnetic resonance imaging studies that present reinforcing stimuli within the context of both traditional list-learning and novel VR-based navigational learning and memory tasks. The first series of experiments compares the influence of appetitive versus aversive instrumental reinforcers on declarative memory systems. The second series of experiments determines how negative mood states amplify the mnemonic effects of the incentive properties of instrumental reinforcers and motivate reward-seeking ("relief") as a form of mood repair. The third series of experiments develops a multisensory, immersive VR paradigm that simulates stress-induced avoidance and escape on a naturalistic memory task that combines navigational and list-learning approaches. Functional connectivity modeling, in combination with multiple regression and independent components analyses, will characterize the interactions of motivational and memory systems and their relationship to individual differences in behavioral performance indices and trait markers of avoidance. The proposed studies thus represent a systematic and innovative approach to human avoidance learning that combines cutting-edge VR technology and functional neuroimaging methods. The research findings will bridge a translational gap in understanding how positive reinforcers, mood states, and stressors modify the impact of aversive behavioral consequences on learning and memory systems that help establish internal maps of salient features of the environment.