Early life stress alters emotional learning in a sex- and age-dependent manner with no impact on emotional behaviors

Stress-related impairment of fear memory acquisition and disruption of risk assessment behavior in female but not in male mice

Stress encompasses reactions to stimuli that promote negative and positive effects on cognitive functions, such as learning and memory processes. Herein, we investigate the effect of restraint stress on learning, memory, anxiety levels and locomotor activity of male and female mice. We used the plus-maze discriminative avoidance task (PMDAT), a behavioral task based on the innate exploratory response of rodents to new environments. Moreover, this task is used to simultaneously evaluate learning, memory, anxiety-like behavior and locomotor activity. Male and female mice were tested after repeated daily restraint stress (4h/day for 3 days). The results showed stress-induced deficits on aversive memory retrieval only in female mice, suggesting a sexual dimorphism on memory acquisition. Furthermore, stressed females exhibited increased anxiety-like behavior and decreased exploratory behavior. Plasma corticosterone levels were similarly increased by restraint stress in both sexes, suggesting that the behavioral outcome was not related to hormonal secretion. Our findings corroborate previous studies, showing a sexually dimorphic effect of restraint stress on cognition. In addition, our study suggests that stress-related acquisition deficit may be the consequence of elevated emotional response in females.

Non-human contributions to personality neuroscience – from fish through primates. An introduction to the special issue

The most fundamental emotional systems that show trait control are evolutionarily old and extensively conserved. Psychology in general has benefited from non-human neuroscience and from the analytical simplicity of behaviour in those with simpler nervous systems. It has been argued that integration between personality, psychopathology, and neuroscience is particularly promising if we are to understand the neurobiology of human experience. Here, we provide some general arguments for a non-human approach being at least as productive in relation to personality, psychopathology, and their interface. Some early personality theories were directly linked to psychopathology (e.g., Eysenck, Panksepp, and Cloninger). They shared a common interest in brain systems that naturally led to the use of non-human data; behavioural, neural, and pharmacological. In Eysenck’s case, this also led to the selective breeding, at the Maudsley Institute, of emotionally reactive and non-reactive strains of rat as models of trait neuroticism or trait emotionality. Dimensional personality research and categorical approaches to clinical disorder then drifted apart from each other, from neuropsychology, and from non-human data. Recently, the conceptualizations of both healthy personality and psychopathology have moved towards a common hierarchical trait perspective. Indeed, the proposed two sets of trait dimensions appear similar and may even be eventually the same. We provide, here, an introduction to this special issue of Personality Neuroscience, where the authors provide overviews of detailed areas where non-human data inform human personality and its psychopathology or provide explicit models for translation to human neuroscience. Once all the papers in the issue have appeared, we will also provide a concluding summary of them.