Short-term REM deprivation does not affect acquisition or reversal of a spatial learning task.

Although there is a general belief that rapid eye movement sleep (REM) is essential for spatial memory tasks such as the Morris water maze (MWM), there is conflicting evidence for this assertion. This study investigated the effects of short-term REM deprivation on acquisition and reversal of the MWM by varying the timing of REM deprivation and the degree of task acquisition in three separate experiments. There was no evidence for a detrimental effect of REM deprivation on acquisition, retention, or reversal in the MWM. These data add to a growing body of evidence that although REM is important for certain types of learning and memory, spatial memory, as assessed by the MWM, is not among them.

Immediate and long-lasting cognitive consequences of adolescent chronic sleep restriction.

The present study investigated immediate and long-lasting cognitive effects of chronic sleep restriction (CSR) in adolescent rats. After 10 days of CSR produced by gentle handling, both hippocampal-dependent and non-hippocampal-dependent long-term memory abilities were tested using the object location task and the object recognition task, respectively. Testing occurred in adolescence and after a 4-week delay during which rats slept freely and matured to adulthood. Rats exposed to CSR showed impaired memory on the object location task during adolescence that persisted into adulthood. However, there was no effect of CSR on memory for the object recognition task at either time point. These results demonstrate that CSR during adolescence produces an impairment in hippocampal-dependent memory but does not affect non-hippocampal-dependent memory. In addition, this impairment persists even after 4 weeks of undisturbed sleep. This study is the first rodent model to use a longitudinal approach to investigate adolescent CSR and provides practical implications for the health of adolescents. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

REM deprivation but not sleep fragmentation produces a sex-specific impairment in extinction.

REM sleep is essential for learning and memory processes, particularly emotional learning. Manipulations of REM sleep impair learning and memory and sleep architecture is often altered following a learning experience; for example, short term REM deprivation immediately after fear conditioning results in impaired extinction. In light of research demonstrating sex-dependent differences in fear conditioning as well as differences in sleep architecture, the present study investigated the effects of short term REM deprivation on the extinction of conditioned fear in male and female rats. In addition, given evidence that sleep fragmentation, which is a consequence of REM deprivation, can negatively impact learning and memory, this manipulation was compared to REM deprivation and a control condition. Male and female rats were exposed to fear conditioning followed by 6 h of REM deprivation, sleep fragmentation, or a control condition. Two extinction sessions were conducted at 48 h intervals after conditioning. REM deprivation, but not sleep fragmentation or the control condition, impaired extinction of conditioned fear. However, this effect was seen only in male rats. This study is the first to explore the effects of sleep manipulations on memory in female rats and suggests that female rats are more resilient to the deleterious effects of REM deprivation. In addition, it demonstrates that REM deprivation but not fragmentation of sleep is responsible for impairment in extinction of conditioned fear.

Impaired extinction of fear conditioning after REM deprivation is magnified by rearing in an enriched environment.

Evidence from both human and animal studies indicates that rapid eye movement sleep (REM) is essential for the acquisition and retention of information, particularly of an emotional nature. Learning and memory can also be impacted by manipulation of housing condition such as exposure to an enriched environment (EE). This study investigated the effects of REM deprivation and EE, both separately and combined, on the extinction of conditioned fear in rats. Consistent with prior studies, conditioning was enhanced in EE-reared rats and extinction was impaired in REM deprived rats. In addition, rats exposed to both REM deprivation and EE showed the greatest impairment in extinction, with effects persisting through the first two days of extinction training. This study is the first to explore the combination of REM deprivation and EE and suggests that manipulations that alter sleep, particularly REM, can have persisting deleterious effects on emotional memory processing.

The effects of social housing on extinction of fear conditioning in rapid eye movement sleep-deprived rats.

Both human and animal research indicate that rapid eye movement sleep (REM) plays an important role in the processing of emotional information. REM is altered after fear conditioning in rats, but this alteration can be mitigated by exposure to a naïve conspecific. In addition, both the housing condition (isolated vs paired) and the experiences of rats' cagemates can influence the response to aversive events. Based on this prior work, the present study sought to determine the effects of social housing on the previously demonstrated impairment in the extinction of conditioned fear responses produced by REM deprivation. Rats were assigned to one of three housing conditions: housed with a naïve rat, housed with another fear-conditioned rat, or housed alone. The results demonstrated that rats housed with either a naïve or a fear-conditioned conspecific exhibited an impairment in the acquisition of extinction as a consequence of REM deprivation, as observed in previous studies. However, rats in the isolated condition demonstrated a trend toward an impairment only after continued extinction training. These results indicate that the effects of social housing on REM deprivation-induced impairments in learning and memory are subtle, but may explain some conflicting findings in the literature.