Remote contextual fear retrieval engages activity from salience network regions in rats.

The ability to retrieve contextual fear memories depends on the coordinated activation of a brain-wide circuitry. Transition from recent to remote memories seems to involve the reorganization of this circuitry, a process called systems consolidation that has been associated with time-dependent fear generalization. However, it is unknown whether emotional memories acquired under different stress levels can undergo different systems consolidation processes.

Corticosterone differentially modulates time-dependent fear generalization following mild or moderate fear conditioning training in rats.

Stressful and emotionally arousing experiences create strong memories that seem to lose specificity over time. It is uncertain, however, how the stress system contributes to the phenomenon of time-dependent fear generalization. Here, we investigated whether post-training corticosterone (CORT-HBC) injections, given after different training intensities, affect contextual fear memory specificity at several time points.

Relationship between footshock intensity, post-training corticosterone release and contextual fear memory specificity over time.

Overgeneralized fear has long been implicated in generalized anxiety and post-traumatic stress disorder, however, time-dependent mechanisms underlying memory retrieval are still not completely understood. Previous studies have revealed that stronger fear conditioning training protocols are associated with both increased post-training corticosterone (CORT) levels and fear responses at later retrieval tests. Here we used contextual fear conditioning (CFC) to investigate the relationship between post-training CORT levels and memory specificity in different retrieval timepoints.

Corticosterone administration after a single-trial contextual fear conditioning does not influence the strength and specificity of recent and remote memory in rats.

It is well established that corticosterone (CORT) enhances memory consolidation of emotionally arousing experiences. Despite emotional memories being usually referred to as well remembered for long periods, there are no studies that have investigated the effects of CORT in modulating the duration and specificity of memory. In the present study, we trained Wistar rats in a single-trial contextual fear conditioning protocol and injected CORT (0.

Effects of sleep deprivation on different phases of memory in the rat: dissociation between contextual and tone fear conditioning tasks.

Numerous studies show that sleep deprivation (SD) impacts negatively on cognitive processes, including learning and memory. Memory formation encompasses distinct phases of which acquisition, consolidation and retrieval are better known. Previous studies with pre-training SD induced by the platform method have shown impairment in fear conditioning tasks.

REM Sleep Rebound as an Adaptive Response to Stressful Situations.

Stress and sleep are related to each other in a bidirectional way. If on one hand poor or inadequate sleep exacerbates emotional, behavioral, and stress-related responses, on the other hand acute stress induces sleep rebound, most likely as a way to cope with the adverse stimuli. Chronic, as opposed to acute, stress impairs sleep and has been claimed to be one of the triggering factors of emotional-related sleep disorders, such as insomnia, depressive- and anxiety-disorders.

Glucocorticoids are not responsible for paradoxical sleep deprivation-induced memory impairments.

Study Objectives: To evaluate whether paradoxical sleep deprivation-induced memory impairments are due to release of glucocorticoids, by means of corticosterone inhibition with metyrapone.

Design: The design was a 2 (Groups [control, paradoxical sleep-deprived]) x 2 (Treatments [vehicle, metyrapone]) study, performed in 2 experiments: Acute treatment (single injection given immediately after 96 hours of sleep deprivation) and chronic treatment (8 injections, twice per day, throughout the sleep-deprivation period). Animals were either paradoxical sleep-deprived or remained in their home cages for 96 hours before training in contextual fear conditioning and received intraperitoneal injections of a corticosterone synthesis inhibitor, metyrapone.

Long lasting alteration in REM sleep of female rats submitted to long maternal separation.

Early adverse experiences represent risk factors for the development of anxiety and mood disorders. Maternal separation can induce biobehavioral alterations in male rodents similar to those seen in depressed humans, such as hyperresponsiveness to stress and sleep disturbances. Nonetheless, no study has yet explored the effects of early life events on the relationship between stress and sleep in female rats.

[Immune outcomes of sleep disorders: the hypothalamic-pituitary-adrenal axis as a modulatory factor].

Objective: To review the literature on the interaction between sleep and the immune system.

Method: A search on Web of Science and Pubmed database including the keywords sleep, sleep deprivation, stress, hypothalamic-pituitary-adrenal axis, immune system, and autoimmune diseases.

Results: On Web of Science, 588 publications were retrieved; 61 references, more significant and closer to our objective, were used, including original articles and review papers.

Effects of maternal separation on baseline sleep and cold stress-induced sleep rebound in adult Wistar rats.

Study Objectives: To evaluate the influence of early life environments on basal and cold stress-induced sleep patterns in rats.

Design: The design was a 3 (Groups [control, early handling, maternal separation]) x 2 (Situations [basal, poststress]) x 11 (Time-blocks) factorial design. From postnatal days 2 to 14, whole litters were either submitted to early handling (15 minutes per day away from the mother) or maternal separation (180 minutes per day away from the mother).

Effects of early handling on basal and stress-induced sleep parameters in rats.

Exposure of humans and animals to stressful events early in life leads to significant and often permanent behavioural, neuroendocrine and central alterations. Early handling consists of removing the litter from the nest for 15 min/day, from post-natal days 2 to 14 and results in lowered ACTH and corticosterone stress response and reduced anxiety-like and fear behaviours. Stress-induced sleep alterations usually consists of increased sleep time, known as sleep rebound.