Neural Substrates Of Social Amotivation In Late Adolescent Schizophrenia Patients

Late adolescence(18-24)is a peak period when patients get the diagnosis as schizophrenia.Social amotivation,defined as the decline in motivation to participate in social activities,is considered to be the psychopathological mechanism of social withdrawal in schizophrenia(SCZ)patients.However,the neural substrates of social avolition remains largely unclear in the late adolescent patients with SCZ.Based on the Model of Temporal Emotional Experience,the present study mainly focused on the anticipation process,which is antecedent to motivated behaviors.There were three experiments which were conducted to investigate the neural response associated with anticipation towards social reward/punishment in healthy adolescents as well as group differences between schizophrenia patients and healthy controls in their univariate and multivariate pattern associated anticipation processing.In the Experiment 1,twenty-four healthy adolescents underwent social incentive delay task during fMRI scanning.It was found that anticipation of social reward and punishment significantly activated the thalamus,the caudate nucleus,the putamen,pallidum,the insula and the cerebellum.Moreover,stronger activation of the putamen and the orbitofrontal cortex was significantly correlated with shorter reaction time towards the targets in the SID task and higher scores on the Achievement Motivation Scale.This suggests as close relationship between social motivation and the limbicmesolimbic circuit activities during anticipation.Regarding the Experiment 2,a comparative analysis of 27 SCZ patients and healthy controls found that SCZ patients displayed prolonger reaction time towards the target for social reward and punishment condition.Meanwhile,they exhibited attenuated neural activity in the thalamus in anticipation of rewarding and punishment contingencies.Interestingly,SCZ patients showed reduced activities in the pallium and putamen when anticipating social rewards,but did not display any differences from healthy controls while anticipating social punishments.It may reflect anticipatory pleasure and motivational deficit in schizophrenia.In the Experiment 3,we applied support vector machine(SVM)modeling to explore multi-voxel patterns of neural responses associated with reward/punishment anticipation.We found that,the brain activation pattern during punishment anticipation can significantly classify between schizophrenia patients and healthy controls(sensitivity=0.92,p<0.001;specificity=0.77,p<0.001).And subtle neural dysfunction pattern in the process of social anticipation was revealed in the orbitofrontal cortex and the cerebellar vermis.In conclusion,these findings suggest SCZ patients demonstrated impaired approach and avoidance motivation in response to reward and punishment cues on the behavioral level,which is associated with abnormality in "the thalamus-dorsal striatum-the orbitofrontal cortex-cerebellar vermis" circuit.This may shed light on underlying neural mechanisms of social amotivation,thereby providing new insight on its psychological pathology interpretation and clinical intervention.