Coping with sleep deprivation: shifts in regional brain activity and learning strategy.

Study Objectives: dissociable cognitive strategies are used for place navigation. Spatial strategies rely on the hippocampus, an area important for flexible integration of novel information. Response strategies are more rigid and involve the dorsal striatum.

A time for learning and a time for sleep: the effect of sleep deprivation on contextual fear conditioning at different times of the day.

Study Objectives: Sleep deprivation negatively affects memory consolidation, especially in the case of hippocampus-dependent memories. Studies in rodents have shown that 5 hours of sleep deprivation immediately following footshock exposure selectively impairs the formation of a contextual fear memory. In these studies, both acquisition and subsequent sleep deprivation were performed in the animals' main resting phase.

Sleep deprivation impairs contextual fear conditioning and attenuates subsequent behavioural, endocrine and neuronal responses.

Sleep deprivation (SD) affects hippocampus-dependent memory formation. Several studies in rodents have shown that brief SD immediately following a mild foot shock impairs consolidation of contextual fear memory as reflected in a reduced behavioural freezing response during re-exposure to the shock context later. In the first part of this study, we examined whether this reduced freezing response is accompanied by an attenuated fear-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis.

Membrane-associated glucocorticoid activity is necessary for modulation of long-term memory via chromatin modification.

Glucocorticoid hormones enhance the consolidation of long-term memory of emotionally arousing training experiences. This memory enhancement requires activation of the cAMP-dependent kinase pathway and the subsequent phosphorylation of cAMP response-element binding (CREB) protein. Here, we demonstrate that glucocorticoids enhance the consolidation of hippocampus-dependent and hippocampus-independent aspects of object recognition memory via chromatin modification.

Sleep deprivation impairs spatial working memory and reduces hippocampal AMPA receptor phosphorylation.

Sleep is important for brain function and cognitive performance. Sleep deprivation (SD) may affect subsequent learning capacity and ability to form new memories, particularly in the case of hippocampus-dependent tasks. In the present study we examined whether SD for 6 or 12 h during the normal resting phase prior to learning affects hippocampus-dependent working memory in mice.

Chronically restricted sleep leads to depression-like changes in neurotransmitter receptor sensitivity and neuroendocrine stress reactivity in rats.

Study Objectives: Frequently disrupted and restricted sleep is a common problem for many people in our Western society. In the long run, insufficient sleep may have repercussions for health and may sensitize individuals to psychiatric diseases. In this context, we applied an animal model of chronic sleep restriction to study effects of sleep loss on neurobiological and neuroendocrine systems that have been implied in the pathophysiology of depression, particularly the serotonergic system and the hypothalamic-pituitary-adrenal (HPA) axis.

Differential effects of chronic partial sleep deprivation and stress on serotonin-1A and muscarinic acetylcholine receptor sensitivity.

Disrupted sleep and stress are often linked to each other, and considered as predisposing factors for psychopathologies such as depression. The depressed brain is associated with reduced serotonergic and enhanced cholinergic neurotransmission. In an earlier study, we showed that chronic sleep restriction by forced locomotion caused a gradual decrease in postsynaptic serotonin-1A receptor sensitivity, whilst chronic forced activity alone, with sufficient sleep time, did not affect receptor sensitivity.