Hippocampal Trauma Memory Processing Conveying Susceptibility to Traumatic Stress.

While the majority of the population is ever exposed to a traumatic event during their lifetime, only a fraction develops posttraumatic stress disorder (PTSD). Disrupted trauma memory processing has been proposed as a core factor underlying PTSD symptomatology. We used transgenic Targeted-Recombination-in-Active-Populations (TRAP) mice to investigate potential alterations in trauma-related hippocampal memory engrams associated with the development of PTSD-like symptomatology. Mice were exposed to a stress-enhanced fear learning paradigm, in which prior exposure to a stressor affects the learning of a subsequent fearful event (contextual fear conditioning using foot shocks), during which neuronal activity was labeled. One week later, mice were behaviorally phenotyped to identify mice resilient and susceptible to developing PTSD-like symptomatology. Three weeks post-learning, mice were re-exposed to the conditioning context to induce remote fear memory recall, and associated hippocampal neuronal activity was assessed. While no differences in the size of the hippocampal neuronal ensemble activated during fear learning were observed between groups, susceptible mice displayed a smaller ensemble activated upon remote fear memory recall in the ventral CA1, higher regional hippocampal parvalbuminneuronal density and a relatively lower activity of parvalbumininterneurons upon recall. Investigation of potential epigenetic regulators of the engram revealed rather generic (rather than engram-specific) differences between groups, with susceptible mice displaying lower hippocampal histone deacetylase 2 expression, and higher methylation and hydroxymethylation levels. These finding implicate variation in epigenetic regulation within the hippocampus, as well as reduced regional hippocampal activity during remote fear memory recall in interindividual differences in susceptibility to traumatic stress.

Using consumption and reward simulations to increase the appeal of plant-based foods.

The production of meat is a main contributor to current dangerous levels of greenhouse gas emissions. However, the shift to more plant-based diets is hampered by consumers finding meat-based foods more attractive than plant-based foods. How can plant-based foods best be described to increase their appeal to consumers? Based on the grounded cognition theory of desire, we suggest that descriptions that trigger simulations, or re-experiences, of eating and enjoying a food will increase the attractiveness of a food, compared to descriptions emphasizing ingredients. In Study 1, we first examined the descriptions of ready meals available in four large UK supermarkets (N = 240). We found that the labels of meat-based foods contained more references to eating simulations than vegetarian foods, and slightly more than plant-based foods, and that this varied between supermarkets. In Studies 2 and 3 (N = 170, N = 166, pre-registered), we manipulated the labels of plant-based and meat-based foods to either include eating simulation words or not. We assessed the degree to which participants reported that the description made them think about eating the food (i.e., induced eating simulations), and how attractive they found the food. In Study 2, where either sensory or eating context words were added, we found no differences with control labels. In Study 3, however, where simulation-based labels included sensory, context, and hedonic words, we found that simulation-based descriptions increased eating simulations and attractiveness. Moreover, frequent meat eaters found plant-based foods less attractive, but this was attenuated when plant-based foods were described with simulation-inducing words. We suggest that language that describes rewarding eating experiences can be used to facilitate the shift toward healthy and sustainable diets.