Impaired learning, memory, and extinction in posttraumatic stress disorder: translational meta-analysis of clinical and preclinical studies

Abstract Background Current evidence-based treatments for post-traumatic stress disorder (PTSD) are efficacious in only part of PTSD patients. Therefore, novel neurobiologically-informed approaches are urgently needed. Clinical and translational neuroscience point to altered learning and memory processes as key in (models of) PTSD psychopathology. We extended this notion by clarifying at a meta-level i) the role of information valence, i.e. neutral versus emotional/fearful, and ii) comparability between clinical and preclinical phenotypes. We hypothesized that, cross-species, neutral versus emotional/fearful information processing is, respectively, impaired and enhanced in PTSD. Methods This preregistered meta-analysis involved a literature search on PTSD+Learning/Memory+Behavior, performed in PubMed. First, the effect of information valence was estimated with a random-effects meta-regression. Then sources of variation were explored with a random forest-based analysis. Results The analyses included 92 clinical (N=6732 humans) and 182 preclinical (N=6834 animals) studies. A general impairment of learning, memory and extinction processes was observed in PTSD patients, regardless of information valence. Impaired neutral learning/memory and fear extinction were also present in animal models of PTSD. Yet, PTSD enhanced fear/trauma memory in preclinical studies and impaired emotional memory in patients. Clinical data on fear/trauma memory was limited. Mnemonic phase and valence explained most variation in rodents but not humans. Conclusions Impaired neutral learning/memory and fear extinction show very stable cross-species PTSD phenotypes. These could be targeted for novel PTSD treatments, building on neurobiological animal studies. We argue that seemingly cross-species discrepancies in emotional/fearful memory deserve further study; until then animal models targeting this phenotype should be applied with care.