Further examinations of attitudes toward discrete emotions, with a focus on attitudes toward anger.

The present research aimed to better understand individual differences in attitudes towards emotions with a focus on anger. We report findings of four studies conducted with American and Polish individuals. Results showed that individuals who have more positive attitudes toward anger are higher in trait anger (Studies 1-4), are more likely to think about getting revenge (Study 1), and expect that getting revenge will make them feel good (Studies 1-2). In addition, these individuals are lower in agreeableness and lower in the tendency to engage in avoidance when angered (Studies 1-4). They score lower in humility (Studies 3-4), lower in secure romantic attachment but higher in anxious and avoidance attachment (Study 3). Finally, they are more likely to believe a wide range of conspiracies (Studies 2-4). Discussion focuses on the implications of these results.

Adults who are more anxious and were anxiously attached as children report later first memories.

Here, we examined retrospective reports of adults' earliest autobiographical memory, the age of this report and whether the reported age was associated with exposure to early life adversity, current anxiety and childhood attachment. Across four studies, we found that reporting a later 'earliest' memory was associated with higher self-reported anxiety in both American (Studies 1, 2 and 4) and Australian (Study 3) samples. Furthermore, in Studies 2-4, we found that reporting a later earliest memory uniquely predicted anxiety when controlling for number of adverse childhood events (a risk factor for the development of anxiety). In Study 4, we established that this relation is partially mediated by childhood anxious attachment. Although we consistently demonstrated that later earliest memories were associated with current anxiety, we found little evidence for a relation between reported age at the time of earliest memory and childhood adversity. We also found no evidence of gender differences in the associations of interest. These results suggest that poorer memory of early childhood is associated with greater childhood anxious attachment and anxiety in adulthood. The implications of this work are discussed in terms of the adaptive nature of autobiographical memory and the development of a coherent life narrative.

Maternal care, infant fear memory retention, and the moderating role of variations in separation-induced ultrasonic vocalizations.

Individual differences in parental care predict variations in offspring anxiety across species. Here, we examined whether between- and within-litter variations in maternal licking (a measure of rodent maternal care) predict infant rats' retention of an aversive association (a predictor of later anxiety-like behavior) and whether the relationship between maternal licking and infant fear memory is moderated by variations in infants' solicitation of maternal care. Unique marks were drawn on each pup, coded for fading, and touched up daily across the first week of life. Mark fading was used as an index of maternal licking where greater fading suggested more maternal licking the previous day. Separation-induced ultrasonic vocalizations (USVs) were recorded to measure individual differences in solicitation of maternal care. Infants were fear conditioned at postnatal day (P) 17 and tested for fear of the conditioned stimulus (CS) 1 week later. Across litters, mark fading negatively predicted CS-elicited fear at test for male, but not female, offspring. This relationship was moderated by number of USVs emitted at P1, such that mark fading only predicted CS-elicited fear for males that emitted a low number of USVs. These results suggest that offspring solicitation may moderate the relationship between maternal care and fear/anxiety.

It's all about who you know: Memory retention of a rat's cagemates during infancy negatively predicts adulthood hippocampal FGF2.

Recent research has demonstrated that individual differences in infant fear memory positively predict adulthood anxiety-like behavior and conditioned fear expression. However, the physiological mechanisms underlying this relationship and the effect of environmental (e.g., social) influences on the stability of this relationship have not been explored. In the present study, we examined whether individual differences in infant fear memory predict levels of endogenous fibroblast growth factor-2 (FGF2; a biomarker of fear/anxiety) in adulthood, and whether the mean memory retention of a rat's cagemates predicts conditioned fear expression and FGF2 in adulthood. We conditioned infant rats to associate a white noise with shock, and tested their memory of the association 1 week later. They were then weaned and randomly assigned to cage/cagemates. In adulthood, rats received weak context conditioning (i.e., a single shock) and were tested for fear of the context the following day. Rats were then euthanized and their brains extracted to measure levels of hippocampal FGF2 protein. Across 2 experiments, an individual rat's fear memory during infancy positively predicted their own fear expression in adulthood, but the mean memory retention of their cagemates did not predict fear expression. In contrast, the mean memory retention of a rat's cagemates during infancy negatively predicted hippocampal FGF2 protein in adulthood, but an individual rat's memory retention did not predict their own levels of FGF2. These data support the idea that variations in the fearfulness of a rat's cagemates predict individual differences on physiological measures in adulthood.

Maternal Experience Does Not Predict Fear Extinction and Anxiety-Like Behaviour in Primiparous Rats Post-weaning.

Reproductive experience leads to long-lasting changes in anxiety-like behaviour and fear extinction, the laboratory model of exposure therapy for anxiety disorders. For example, fear extinction is influenced by estrous cycle in nulliparous (no reproductive experience) female rats, but this effect is abolished in primiparous (one reproductive experience) females. It is unclear whether such changes are driven by pregnancy, maternal experience of caring for offspring during the postpartum period, or a combination of both experiences. The present study sought to determine the influence of maternal experience (i.e., exposure to pups and mother-pup interactions) on fear extinction in primiparous rats. In Experiment 1, we tested whether pup exposure is necessary to mitigate estrous effects on fear extinction in primiparous rats. Age-matched nulliparous rats, primiparous rats, and primiparous rats who experienced pregnancy but not pup exposure, underwent fear conditioning on day 1 (2 months post-parturition), extinction training during proestrus (high sex hormones) or metestrus (low sex hormones) on day 2, and extinction recall on day 3. Replicating past research, nulliparous rats showed impaired extinction recall when they were extinguished during metestrus compared to proestrus. In contrast, primiparous rats with and without pup exposure showed comparable extinction recall irrespective of estrous phase. In Experiment 2, we assessed whether naturally-occurring variation in mother-pup interactions predict future fear extinction performance and anxiety-like behaviour. During the first week of lactation, primiparous rats were measured for maternal behaviours toward pups. Primiparous rats were then tested on the light-dark box and elevated plus maze to measure anxiety-like behaviour and underwent a fear extinction protocol 1 month post-weaning. We found no significant correlations between maternal behaviour and fear extinction outcomes or anxiety-like behaviour. Our findings suggest that pregnancy, not maternal experience, mitigates the impact of estrous cycle on fear extinction. In addition, natural variation in maternal experience does not appear to contribute to variability in future fear extinction outcomes or anxiety-like behaviour in primiparous rats.

Is good memory always a good thing? An early offset of infantile amnesia predicts anxiety-like behavior throughout development in rats.

Infants tend to forget experiences much more rapidly than older individuals, a phenomenon referred to as infantile amnesia. This robust, cross-species phenomenon is commonly used to examine memory development. However, in this set of experiments, we examined the novel hypothesis that the expression of infantile amnesia is related to resilience/vulnerability. We conditioned infant rats to associate a white noise with shock. Animals were tested for memory of the association ~1 week later. We found that infants that expressed better memory of the aversive association emitted more vocalizations (indicative of higher levels of distress) when separated from their mother earlier in infancy (Experiment 1). Better expression of memory in infancy also predicted higher levels of conditioned fear (Experiment 2) and anxiety-like behavior (in a light-dark box; Experiment 3) in adulthood. Furthermore, probiotic-treatment administered early in development reduced anxiety-like behavior in animals that exhibited good expression of memory for an aversive association learnt in infancy (Experiment 4). However, the same treatment was ineffective if administered in adulthood. Taken together, these results suggest that individual differences in infants' memory for an aversive association predict anxiety-like behavior throughout development, and that early administration of probiotics can reduce anxiety-like behavior in "at-risk" animals.

Differences in the persistence of spatial memory deficits induced by a chronic stressor in adolescents compared to juveniles.

Adolescence is thought of as a stress-sensitive developmental period. While many studies have compared adolescent responses to stress relative to that of adults, a growing body of work has examined stress responses in juveniles. Here we investigated if a chronic stressor has a differential effect on spatial memory in rats depending on whether it occurs during adolescence or the juvenile period. Male rats were exposed to the stress hormone corticosterone (Cort) in their drinking water, a vehicle control (2.5% ethanol), or water, for 7 days before being tested on a novel Object/Place task 6 days or 6 weeks later. Exposure to Cort or ethanol at either age impaired spatial memory at the 6-day test. The ethanol induced impairment was attenuated 6 weeks later. However, rats given Cort during adolescence, but not the juvenile period, were still impaired. Together, these results suggest that adolescence is indeed a stress-sensitive period.