title: Necessary, yet dissociable contributions of the insular and ventromedial prefrontal cortices to norm adaptation: computational and lesion evidence in humans.
abstract: Social norms and their enforcement are fundamental to human societies. The ability to detect deviations from norms and to adapt to norms in a changing environment is therefore important to individuals' normal social functioning. Previous neuroimaging studies have highlighted the involvement of the insular and ventromedial prefrontal (vmPFC) cortices in representing norms. However, the necessity and dissociability of their involvement remain unclear. Using model-based computational modeling and neuropsychological lesion approaches, we examined the contributions of the insula and vmPFC to norm adaptation in seven human patients with focal insula lesions and six patients with focal vmPFC lesions, in comparison with forty neurologically intact controls and six brain-damaged controls. There were three computational signals of interest as participants played a fairness game (ultimatum game): sensitivity to the fairness of offers, sensitivity to deviations from expected norms, and the speed at which people adapt to norms. Significant group differences were assessed using bootstrapping methods. Patients with insula lesions displayed abnormally low adaptation speed to norms, yet detected norm violations with greater sensitivity than controls. Patients with vmPFC lesions did not have such abnormalities, but displayed reduced sensitivity to fairness and were more likely to accept the most unfair offers. These findings provide compelling computational and lesion evidence supporting the necessary, yet dissociable roles of the insula and vmPFC in norm adaptation in humans: the insula is critical for learning to adapt when reality deviates from norm expectations, and that the vmPFC is important for valuation of fairness during social exchange.
authors.affiliation: Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom WC1N 3BG, Human Neuroimaging Laboratory, Virginia Tech Carilion Research Institute, Roanoke, Virginia 24016.
authors.forename: Xiaosi
authors.initials: X
authors.lastname: Gu
authors.affiliation: Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, and China National Clinical Research Center for Neurological Diseases, Beijing, China 100050.
authors.forename: Xingchao
authors.initials: X
authors.lastname: Wang
authors.affiliation: Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom WC1N 3BG.
authors.forename: Andreas
authors.identifier: http://orcid.org/0000-0003-4253-5604
authors.initials: A
authors.lastname: Hula
authors.affiliation: Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, and China National Clinical Research Center for Neurological Diseases, Beijing, China 100050.
authors.forename: Shiwei
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, and China National Clinical Research Center for Neurological Diseases, Beijing, China 100050.
authors.forename: Shuai
authors.initials: S
authors.lastname: Xu
authors.affiliation: Human Neuroimaging Laboratory, Virginia Tech Carilion Research Institute, Roanoke, Virginia 24016.
authors.forename: Terry M
authors.initials: TM
authors.lastname: Lohrenz
authors.affiliation: Helen Willis Neuroscience Institute and Department of Psychology, University of California, Berkeley, California 94720.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Knight
authors.affiliation: Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, and China National Clinical Research Center for Neurological Diseases, Beijing, China 100050.
authors.forename: Zhixian
authors.initials: Z
authors.lastname: Gao
authors.affiliation: Gatsby Computational Neuroscience Unit, University College London, London, United Kingdom WC1N 3AR, and.
authors.forename: Peter
authors.initials: P
authors.lastname: Dayan
authors.affiliation: Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom WC1N 3BG, Human Neuroimaging Laboratory, Virginia Tech Carilion Research Institute, Roanoke, Virginia 24016, Department of Physics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 read@vt.edu.
authors.forename: P Read
authors.initials: PR
authors.lastname: Montague
mesh_terms: D000223:Adaptation, Psychological; D000328:Adult; D000368:Aged; D001925:Brain Damage, Chronic / Q000503:physiopathology* / Q000523:psychology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D009928:Organ Specificity; D017397:Prefrontal Cortex / Q000502:physiology* / Q000503:physiopathology; D066262:Social Norms
keywords: brain lesion; computational modeling; decision-making; insular cortex; social norms; ventromedial prefrontal cortex