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Associability-modulated loss learning is increased in posttraumatic stress disorder.

ABSTRACT: Disproportionate reactions to unexpected stimuli in the environment are a cardinal symptom of posttraumatic stress disorder (PTSD). Here, we test whether these heightened responses are associated with disruptions in distinct components of reinforcement learning. Specifically, using functional neuroimaging, a loss-learning task, and a computational model-based approach, we assessed the mechanistic hypothesis that overreactions to stimuli in PTSD arise from anomalous gating of attention during learning (i.e., associability). Behavioral choices of combat-deployed veterans with and without PTSD were fit to a reinforcement learning model, generating trial-by-trial prediction errors (signaling unexpected outcomes) and associability values (signaling attention allocation to the unexpected outcomes). Neural substrates of associability value and behavioral parameter estimates of associability updating, but not prediction error, increased with PTSD during loss learning. Moreover, the interaction of PTSD severity with neural markers of associability value predicted behavioral choices. These results indicate that increased attention-based learning may underlie aspects of PTSD and suggest potential neuromechanistic treatment targets.

SUBMITTER: Brown VM

PROVIDER: S-EPMC5760201 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Associability-modulated loss learning is increased in posttraumatic stress disorder.

Brown Vanessa M VM Brown Vanessa M VM Zhu Lusha L Wang John M JM Frueh B Christopher BC King-Casas Brooks B Chiu Pearl H PH

eLife 20180109

Disproportionate reactions to unexpected stimuli in the environment are a cardinal symptom of posttraumatic stress disorder (PTSD). Here, we test whether these heightened responses are associated with disruptions in distinct components of reinforcement learning. Specifically, using functional neuroimaging, a loss-learning task, and a computational model-based approach, we assessed the mechanistic hypothesis that overreactions to stimuli in PTSD arise from anomalous gating of attention during lea ...[more]

PMID: 29313489

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Project description:IntroductionImprovement in posttraumatic stress disorder (PTSD) is associated with better health behavior such as better medication adherence and greater use of nutrition and weight loss programs. However, it is not known if reducing PTSD severity is associated with smoking cessation, a poor health behavior common in patients with PTSD.Aims and methodsVeterans Health Affairs (VHA) medical record data (2008-2015) were used to identify patients with PTSD diagnosed in specialty care. Clinically meaningful PTSD improvement was defined as ≥20 point PTSD Checklist (PCL) decrease from the first PCL ≥50 and the last available PCL within 12 months and at least 8 weeks later. The association between clinically meaningful PTSD improvement and smoking cessation within 2 years after baseline among 449 smokers was estimated in Cox proportional hazard models. Entropy balancing controlled for confounding.ResultsOn average, patients were 39.4 (SD = 12.9) years of age, 86.6% were male and 71.5% were white. We observed clinically meaningful PTSD improvement in 19.8% of participants. Overall, 19.4% quit smoking in year 1 and 16.6% in year 2. More patients with versus without clinically meaningful PTSD improvement stopped smoking (n = 36, cumulative incidence = 40.5% vs. 111, cumulative incidence = 30.8%, respectively). After controlling for confounding, patients with versus without clinically meaningful PTSD improvement were more likely to stop smoking within 2 years (hazard ratio = 1.57; 95% confidence interval: 1.04-2.36).ConclusionsPatients with clinically meaningful PTSD improvement were significantly more likely to stop smoking. Further research should determine if targeted interventions are needed or whether improvement in PTSD symptoms is sufficient to enable smoking cessation.ImplicationsPatients with PTSD are more likely to develop chronic health conditions such as heart disease and diabetes. Poor health behaviors, including smoking, partly explain the risk for chronic disease in this patient population. Our results demonstrate that clinically meaningful PTSD improvement is followed by greater likelihood of smoking cessation. Thus, PTSD treatment may enable healthier behaviors and reduce risk for smoking-related disease.

Project description:Fear conditioning is an established model for investigating posttraumatic stress disorder (PTSD). However, symptom triggers may vaguely resemble the initial traumatic event, differing on a variety of sensory and affective dimensions. We extended the fear-conditioning model to assess generalization of conditioned fear on fear processing neurocircuitry in PTSD. Military veterans (n=67) consisting of PTSD (n=32) and trauma-exposed comparison (n=35) groups underwent functional magnetic resonance imaging during fear conditioning to a low fear-expressing face while a neutral face was explicitly unreinforced. Stimuli that varied along a neutral-to-fearful continuum were presented before conditioning to assess baseline responses, and after conditioning to assess experience-dependent changes in neural activity. Compared with trauma-exposed controls, PTSD patients exhibited greater post-study memory distortion of the fear-conditioned stimulus toward the stimulus expressing the highest fear intensity. PTSD patients exhibited biased neural activation toward high-intensity stimuli in fusiform gyrus (P<0.02), insula (P<0.001), primary visual cortex (P<0.05), locus coeruleus (P<0.04), thalamus (P<0.01), and at the trend level in inferior frontal gyrus (P=0.07). All regions except fusiform were moderated by childhood trauma. Amygdala-calcarine (P=0.01) and amygdala-thalamus (P=0.06) functional connectivity selectively increased in PTSD patients for high-intensity stimuli after conditioning. In contrast, amygdala-ventromedial prefrontal cortex (P=0.04) connectivity selectively increased in trauma-exposed controls compared with PTSD patients for low-intensity stimuli after conditioning, representing safety learning. In summary, fear generalization in PTSD is biased toward stimuli with higher emotional intensity than the original conditioned-fear stimulus. Functional brain differences provide a putative neurobiological model for fear generalization whereby PTSD symptoms are triggered by threat cues that merely resemble the index trauma.

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Associability-modulated loss learning is increased in posttraumatic stress disorder.

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Associability-modulated loss learning is increased in posttraumatic stress disorder.

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