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Dissociable Learning Processes Underlie Human Pain Conditioning.


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Authors

Mano, Hiroaki 
Ganesh, Gowrishankar 

Abstract

Pavlovian conditioning underlies many aspects of pain behavior, including fear and threat detection [1], escape and avoidance learning [2], and endogenous analgesia [3]. Although a central role for the amygdala is well established [4], both human and animal studies implicate other brain regions in learning, notably ventral striatum and cerebellum [5]. It remains unclear whether these regions make different contributions to a single aversive learning process or represent independent learning mechanisms that interact to generate the expression of pain-related behavior. We designed a human parallel aversive conditioning paradigm in which different Pavlovian visual cues probabilistically predicted thermal pain primarily to either the left or right arm and studied the acquisition of conditioned Pavlovian responses using combined physiological recordings and fMRI. Using computational modeling based on reinforcement learning theory, we found that conditioning involves two distinct types of learning process. First, a non-specific "preparatory" system learns aversive facial expressions and autonomic responses such as skin conductance. The associated learning signals-the learned associability and prediction error-were correlated with fMRI brain responses in amygdala-striatal regions, corresponding to the classic aversive (fear) learning circuit. Second, a specific lateralized system learns "consummatory" limb-withdrawal responses, detectable with electromyography of the arm to which pain is predicted. Its related learned associability was correlated with responses in ipsilateral cerebellar cortex, suggesting a novel computational role for the cerebellum in pain. In conclusion, our results show that the overall phenotype of conditioned pain behavior depends on two dissociable reinforcement learning circuits.

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Keywords

Adult, Amygdala, Association Learning, Avoidance Learning, Brain, Cerebellum, Conditioning, Classical, Conditioning, Psychological, Cues, Fear, Female, Humans, Magnetic Resonance Imaging, Male, Pain, Ventral Striatum

Journal Title

Curr Biol

Conference Name

Journal ISSN

0960-9822
1879-0445

Volume Title

26

Publisher

Elsevier BV
Sponsorship
Wellcome Trust (097490/Z/11/Z)
Research was supported by National Institute for Information and Communications Technology (Japan), the Japanese Society for the Promotion of Science (JSPS) and The Wellcome Trust (UK). S.Z. was supported by the WD Armstrong Fund and the Cambridge Trust. G.G. was partially supported by the Kakenhi Research Grant B #13380602 from the Japan Society for the Promotion of Science. We thank the imaging team at the Center for Information and Neural Networks for their help in performing the study. The authors declare that there are no conflicts of interest.