title: Learning to obtain reward, but not avoid punishment, is affected by presence of PTSD symptoms in male veterans: empirical data and computational model.
abstract: Post-traumatic stress disorder (PTSD) symptoms include behavioral avoidance which is acquired and tends to increase with time. This avoidance may represent a general learning bias; indeed, individuals with PTSD are often faster than controls on acquiring conditioned responses based on physiologically-aversive feedback. However, it is not clear whether this learning bias extends to cognitive feedback, or to learning from both reward and punishment. Here, male veterans with self-reported current, severe PTSD symptoms (PTSS group) or with few or no PTSD symptoms (control group) completed a probabilistic classification task that included both reward-based and punishment-based trials, where feedback could take the form of reward, punishment, or an ambiguous "no-feedback" outcome that could signal either successful avoidance of punishment or failure to obtain reward. The PTSS group outperformed the control group in total points obtained; the PTSS group specifically performed better than the control group on reward-based trials, with no difference on punishment-based trials. To better understand possible mechanisms underlying observed performance, we used a reinforcement learning model of the task, and applied maximum likelihood estimation techniques to derive estimated parameters describing individual participants' behavior. Estimations of the reinforcement value of the no-feedback outcome were significantly greater in the control group than the PTSS group, suggesting that the control group was more likely to value this outcome as positively reinforcing (i.e., signaling successful avoidance of punishment). This is consistent with the control group's generally poorer performance on reward trials, where reward feedback was to be obtained in preference to the no-feedback outcome. Differences in the interpretation of ambiguous feedback may contribute to the facilitated reinforcement learning often observed in PTSD patients, and may in turn provide new insight into how pathological behaviors are acquired and maintained in PTSD.
authors.affiliation: Department of Veterans Affairs, VA New Jersey Health Care System, East Orange, New Jersey, United States of America ; Stress & Motivated Behavior Institute, Department of Neurology and Neurosciences, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey, United States of America ; Department of Psychology, Rutgers, The State University of New Jersey, Newark, New Jersey, United States of America ; Graduate School of Biomedical Sciences, Rutgers, The State University of New Jersey, Newark, New Jersey, United States of America.
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Myers
authors.forename: Ahmed A
authors.initials: AA
authors.lastname: Moustafa
authors.forename: Jony
authors.initials: J
authors.lastname: Sheynin
authors.forename: Kirsten M
authors.initials: KM
authors.lastname: Vanmeenen
authors.forename: Mark W
authors.initials: MW
authors.lastname: Gilbertson
authors.forename: Scott P
authors.initials: SP
authors.lastname: Orr
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Beck
authors.forename: Kevin C H
authors.initials: KC
authors.lastname: Pang
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Servatius
mesh_terms: D000328:Adult; D003198:Computer Simulation; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011678:Punishment; D012201:Reward; D013313:Stress Disorders, Post-Traumatic / Q000503:physiopathology / Q000523:psychology; D014728:Veterans