Switch-task performance in rats is disturbed by 12 h of sleep deprivation but not by 12 h of sleep fragmentation

Multiple decrements in switch task performance in female rats exposed to space radiation

Astronauts on the Artemis missions to the Moon and Mars will be exposed to unavoidable Galactic Cosmic Radiation (GCR). Studies using male rats suggest that GCR exposure impairs several processes required for cognitive flexibility performance, including attention and task switching. Currently no comparable studies have been conducted with female rats. Given that both males and females will travel into deep space, this study determined whether simulated GCR (GCRsim) exposure impairs task switching performance in female rats. Female Wistar rats exposed to 10cGy GCRsim (n = 12) and shams (n=14) were trained to perform a touchscreen-based switch task that mimics a switch task used to evaluate pilots' response times. In comparison to sham rats, three-fold more GCRsim-exposed rats failed to complete the stimulus response stage of training, a high cognitive loading task. In the switch task, 50% of the GCRsim-exposed rats failed to consistently transition between the repeated and switch blocks of stimuli, which they completed during lower cognitive loading training stages. The GCRsim-exposed rats that completed the switch task only performed at 65% of the accuracy of shams. Female rats exposed to GCRsim thus exhibit multiple decrements in the switch task under high, but not low, cognitive loading conditions. While the operational significance of this performance decrement is unknown, if GCRSim exposure was to induce similar effects in astronauts, our data suggests there may be a reduced ability to execute task switching under high cognitive loading situations.

Simulated Space Radiation Exposure Effects on Switch Task Performance in Rats

BACKGROUND: Astronauts on the mission to Mars will be subjected to galactic cosmic radiation (GCR) exposures. While ground-based studies suggest that simulated GCR (GCRsim) exposure impairs performance in multiple cognitive tasks, the impact of such exposures on task switching performance (an important skill for all aviators) has not yet been determined.METHODS: Male Wistar rats previously exposed to 10 cGy of 4He ions or GCRsim and their sham littermates were trained to perform a touchscreen-based switch task designed to mimic warning light response tests used to evaluate pilots’ response times.RESULTS: Irradiated rats failed to complete a high cognitive task load training task threefold more frequently than shams. There were 18 (4 Sham, 7 He-, and 7 GCR-exposed) rats that successfully completed initial training and underwent switch task testing. Relative to the sham rats in the switch task, the GCRsim-exposed rats had significantly slower response times in switch but not repeat trials. The GCRsim-exposed rats had significantly (P < 0.01) higher switch response ratios (switch/repeat trial response time) and absolute switch costs (switch minus repeat trial response time) than either the sham or He-exposed rats.DISCUSSION: Rats exposed to GCRsim have significantly impaired performance in the switch task manifested as an absolute switch cost of ∼700 ms. The operational significance of such an increase requires further investigation, but a 1000-ms switch cost results in a twofold increase in cockpit error rates in pilots. If exposure to GCR in space results in similar effects in humans, the operational performance of astronauts on the Mars mission may be suboptimal.Stephenson S, Britten R. Simulated space radiation exposure effects on switch task performance in rats. Aerosp Med Hum Perform. 2022; 93(9):673–680.

Reviewing the animal literature: how to describe and choose between different types of literature reviews

Before starting any (animal) research project, review of the existing literature is good practice. From both the scientific and the ethical perspective, high-quality literature reviews are essential. Literature reviews have many potential advantages besides synthesising the evidence for a research question. First, they can show if a proposed study has already been performed, preventing redundant research. Second, when planning new experiments, reviews can inform the experimental design, thereby increasing the reliability, relevance and efficiency of the study. Third, reviews may even answer research questions using already available data. Multiple definitions of the term literature review co-exist. In this paper, we describe the different steps in the review process, and the risks and benefits of using various methodologies in each step. We then suggest common terminology for different review types: narrative reviews, mapping reviews, scoping reviews, rapid reviews, systematic reviews and umbrella reviews. We recommend which review to select, depending on the research question and available resources. We believe that improved understanding of review methods and terminology will prevent ambiguity and increase appropriate interpretation of the conclusions of reviews.

Sleep Fragmentation Exacerbates Executive Function Impairments Induced by Low Doses of Si Ions

Astronauts on deep space missions will be required to work autonomously and thus their ability to perform executive functions could be critical to mission success. Ground-based rodent experiments have shown that low (<25 cGy) doses of several space radiation (SR) ions impair various aspects of executive function. Translating ground-based rodent studies into tangible risk estimates for astronauts remains an enormous challenge, but should similar neurocognitive impairments occur in astronauts exposed to low-SR doses, a Numbers-Needed-to-Harm analysis (of the rodent data) predicts that approximately 30% of the astronauts could develop severe cognitive flexibility decrements. In addition to the health risks associated with SR exposure, astronauts have to contend with other stressors, of which inadequate sleep quantity and quality are considered to be major concerns. We have shown that a single session of fragmented sleep uncovered latent attentional set-shifting (ATSET) performance deficits in rats exposed to protracted neutron radiation that had no obvious defects in performance under rested wakefulness conditions. It is unclear if the exacerbating effect of sleep fragmentation (SF) only occurs in rats receiving protracted low-dose-rate-neutron radiation. In this study, we assessed whether SF also unmasks latent ATSET deficits in rats exposed to 5 cGy 600 MeV/n 28Si ions. Only sham and Si-irradiated rats that had good ATSET performance (passing every stage of the test on their first attempt) were selected for study. Sleep fragmentation selectively impaired performance in the more complex IDR, EDS and EDR stages of the ATSET test in the Si-irradiated rats. Set-shifting performance has rarely been affected by SR exposure in our studies conducted with rats tested under rested wakefulness conditions. The consistent SF-related unmasking of latent set-shifting deficits in both Si- and neutron-irradiated rats suggests that there is a unique interaction between sleep fragmentation and space radiation on the functionality of the brain regions that regulate performance in the IDR, EDS and EDR stages of ATSET. The uncovering of these latent SR-induced ATSET performance deficits in both Si- and neutron-irradiated rats suggests that the true impact of SR-induced cognitive impairment may not be fully evident in normally rested rats, and thus cognitive testing needs to be conducted under both rested wakefulness and sleep fragmentation conditions.

Sensory, Affective, and Cognitive Effects of Trigeminal Injury in Mice

PURPOSE

To characterize adequate study of chronic neuropathic orofacial pain induced by a mental nerve injury in a mouse model, we propose a behavioral assessment of its dimensions: sensory, affective, and cognitive.

MATERIALS AND METHODS

Trigeminal injury was induced by a chronic mental nerve constriction (MnC). Behavioral tests were conducted to assess the different dimensions of pain and to evaluate the general well-being of mice.

RESULTS

Rodents who went through MnC showed signs of mechanical hyperalgesia and increased escape/avoidance behavior. They showed no alterations in general well-being behaviors, yet the injury was sufficient to induce impairment in the ability to adapt to the environmental requirements.

CONCLUSIONS

MnC injury is an efficient model for the study of orofacial pain in mice, capable of inducing impairment in the different dimensions of pain. Intensity and temporality of its effects make our model less aggressive, yet effective to generate cognitive impairment. This work provides a solid foundation for the study of the neural circuits involved in the processing of neuropathic orofacial pain.

Sleep and Microdialysis: An Experiment and a Systematic Review of Histamine and Several Amino Acids

Sleep seems essential to proper functioning of the prefrontal cortex (PFC). The role of different neurotransmitters has been studied, mainly the catecholamines and serotonin. Less attention has been paid to the amino acid transmitters and histamine. Here, we focus on the activity of these molecules in the PFC during sleep and sleep deprivation (SD). We determined extracellular concentrations of histamine and 8 amino acids in the medial PFC before, during and after SD. Additionally, we systematically reviewed the literature on studies reporting microdialysis measurements relating to sleep throughout the brain. In our experiment, median concentrations of glutamate were higher during SD than during baseline (p = 0.013) and higher during the dark-active than during the resting phase (p = 0.003). Glutamine was higher during post-SD recovery than during baseline (p = 0.010). For other compounds, no differences were observed between light and dark circadian phase, and between sleep deprivation, recovery and baseline. We retrieved 13 papers reporting on one or more of the molecules of interest during naturally occurring sleep, 2 during sleep deprivation and 2 during both. Only two studies targeted PFC. Histamine was low during sleep, but high during sleep deprivation and wakefulness, irrespective of brain area. Glu (k = 11) and GABA (k = 8) concentrations in different brain areas were reported to peak during sleep or wakefulness or to lack state-dependency. Aspartate, glycine, asparagine and taurine were less often studied (1-2 times), but peaked exclusively during sleep. Sleep deprivation increased glutamate and GABA exclusively in the cortex. Further studies are needed for drawing solid conclusions.

Brain Microdialysate Monoamines in Relation to Circadian Rhythms, Sleep, and Sleep Deprivation - a Systematic Review, Network Meta-analysis, and New Primary Data

Disruption of the monoaminergic system, e.g. by sleep deprivation (SD), seems to promote certain diseases. Assessment of monoamine levels over the circadian cycle, during different sleep stages and during SD is instrumental to understand the molecular dynamics during and after SD. To provide a complete overview of all available evidence, we performed a systematic review. A comprehensive search was performed for microdialysis and certain monoamines (dopamine, serotonin, noradrenaline, adrenaline), certain monoamine metabolites (3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindoleacetic acid (5-HIAA)) and a precursor (5-hydroxytryptophan (5-HTP)) in PubMed and EMBASE. After screening of the search results by two independent reviewers, 94 publications were included. All results were tabulated and described qualitatively. Network-meta analyses (NMAs) were performed to compare noradrenaline and serotonin concentrations between sleep stages. We further present experimental monoamine data from the medial prefrontal cortical (mPFC). Monoamine levels varied with brain region and circadian cycle. During sleep, monoamine levels generally decreased compared to wake. These qualitative observations were supported by the NMAs: noradrenaline and serotonin levels decreased from wakefulness to slow wave sleep and decreased further during Rapid Eye Movement sleep. In contrast, monoamine levels generally increased during SD, and sometimes remained high even during subsequent recovery. Decreases during or after SD were only reported for serotonin. In our experiment, SD did not affect any of the mPFC monoamine levels. Concluding, monoamine levels vary over the light-dark cycle and between sleep stages. SD modifies the patterns, with effects sometimes lasting beyond the SD period.

Intracerebral Adenosine During Sleep Deprivation: A Meta-Analysis and New Experimental Data

The neuroregulator adenosine is involved in sleep-wake control. Basal forebrain (BF) adenosine levels increase during sleep deprivation. Only a few studies have addressed the effect of sleep deprivation on extracellular adenosine concentrations in other brain regions. In this paper, we describe a microdialysis experiment as well as a meta-analysis of published data. The 64 h microdialysis experiment determined the extracellular adenosine and adenosine monophosphate (AMP) concentrations in the medial prefrontal cortex of rats before, during and after 12 h of sleep deprivation by forced locomotion. The meta-analysis comprised published sleep deprivation animal experiments measuring adenosine by means of microdialysis. In the animal experiment, the overall median adenosine concentration was 0.36 nM and ranged from 0.004 nM to 27 nM. No significant differences were observed between the five conditions: 12 h of wash-out, baseline light phase, baseline dark phase, 12 h of sleep deprivation and 12 h of subsequent recovery. The overall median AMP concentration was 0.10 nM and ranged from 0.001 nM to 7.56 nM. Median AMP concentration increased during sleep deprivation (T = 47; p = 0.047) but normalised during subsequent recovery. The meta-analysis indicates that BF dialysate adenosine concentrations increase with 74.7% (95% CI: 54.1-95.3%) over baseline during sleep deprivation. Cortex dialysate adenosine concentrations during sleep deprivation were so far only reported by 2 publications. The increase in adenosine during sleep deprivation might be specific to the BF. At this stage, the evidence for adenosine levels in other brain regions is based on single experiments and insufficient for generalised conclusions. Further experiments are currently still warranted.

Neurophysiological Processing of an Emotional Task is Sensitive to Time-of-Day

Previous work from our laboratory has shown that a measure of attention to emotionally-charged stimuli, the late positive potential (LPP) event related potential (ERP), distinguished neutral from emotional pictures on a baseline day, but not after sleep deprivation. Here we sought to extend these findings and address the uncertainty about the effect of time-of-day on emotion processing by testing a morning group (8:00–10:00 a.m., n = 30) and an evening group (8:00–10:00 p.m., n = 30). We also examined the extent of diurnal changes in cortisol related to the emotion processing task. Results from this study mirrored those found after one night of sleep deprivation. Compared to the morning group, the LPP generated by the evening group (who had a greater homeostatic sleep drive) did not distinguish neutral from emotionally-charged stimuli. New to this study, we also found that there was a time-of-day effect on positive, but not negative pictures. While, as expected, cortisol levels were higher in the morning relative to the evening group, there was no relationship between cortisol and the LPP ERP emotion measure. In addition, neither time-of-day preference nor sleep quality was related to the LPP measure. These findings show that, similar to what occurs after sleep deprivation, increased sleep pressure throughout the day interferes with attention processing to emotional stimuli.

Using curcumin to prevent structural and behavioral changes of medial prefrontal cortex induced by sleep deprivation in rats

Sleep Deprivation (SD) is known to result in a range of neurological consequences in chronically-afflicted subjects. Curcumin, a natural substance, has neuroprotective properties. This study aimed to evaluate the effects of curcumin on the medial Prefrontal Cortex (mPFC) of SD rats. Male rats were arbitrarily assigned to nine groups, including control, curcumin (100 mg/kg/day), olive oil, SD, SD+curcumin, SD+olive oil, grid, grid+curcumin, and grid+olive oil groups. SD was induced by a multiplatform box containing water. After a period of 21 days, the learning and memory of the rats were tested in an eight-arm radial maze. Afterwards, their brains were evaluated using stereological methods. Concomitant treatment of curcumin during SD caused fewer errors during evaluation of the working and reference memory errors in the acquisition and retention phases. The overall volume of the mPFC, Infralimbic Cortex (ILC), Prelimbic Cortex (PLC), Anterior Cingulate Cortex (ACC) and the total number of neurons and glial cells reduced by 20 %-40 % on average in the SD animals in comparison to the control group. This indicated atrophic changes and cell loss in these areas (p < 0.01). The dendrites' length and the number of spines per dendrite also reduced by 35 %-55 % in the SD rats compared to the ones in the control group (p < 0.01). Yet, treatment of the SD animals with curcumin prevented the atrophic changes of the mPFC, cell loss, and dendritic changes (p < 0.05). SD induced structural changes in the mPFC and memory impairment in the rats. However, curcumin could protect their PFC.

Biological plausibility linking sleep apnoea and metabolic dysfunction

Obstructive sleep apnoea (OSA) is a very common disorder that affects 10-25% of the general population. In the past two decades, OSA has emerged as a cardiometabolic risk factor in both paediatric and adult populations. OSA-induced metabolic perturbations include dyslipidaemia, atherogenesis, liver dysfunction and abnormal glucose metabolism. The mainstay of treatment for OSA is adenotonsillectomy in children and continuous positive airway pressure therapy in adults. Although these therapies are effective at resolving the sleep-disordered breathing component of OSA, they do not always produce beneficial effects on metabolic function. Thus, a deeper understanding of the underlying mechanisms by which OSA influences metabolic dysfunction might yield improved therapeutic approaches and outcomes. In this Review, we summarize the evidence obtained from animal models and studies of patients with OSA of potential mechanistic pathways linking the hallmarks of OSA (intermittent hypoxia and sleep fragmentation) with metabolic dysfunction. Special emphasis is given to adipose tissue dysfunction induced by sleep apnoea, which bears a striking resemblance to adipose dysfunction resulting from obesity. In addition, important gaps in current knowledge and promising lines of future investigation are identified.

Lateral habenula integration of proactive and retroactive information mediates behavioral flexibility

The lateral habenula (LHb) is known to play an important role in signaling aversive or adverse events that have happened or are predicted by cues under Pavlovian conditions. In rodents, it is also required for behavioral flexibility when changes in reward outcomes signal that strategies should be changed. It is not known whether the LHb also controls appetitive behaviors when an animal is able to utilize external cues proactively to guide upcoming decisions. In order to test this, male Long-Evans rats were trained to switch between two arms of a figure eight maze based on the tone presented prior to the choice. Importantly, the tones were switched every three to six trials so rats were able establish a response pattern before being required to switch. This caused rats to rely on both proactive (tones) and retroactive information (reward feedback) to guide behavior. Inactivation of the LHb with the GABA agonists baclofen and muscimol impaired overall performance by increasing both errors when the tones are switched (switch errors) as well as on subsequent trials (perseverative errors) indicating that both proactive and retroactive information are utilized by the LHb to guide behavioral flexibility. Once a correct choice was made in a given block, LHb inactivated rats did not make more errors than controls. A control study revealed that the LHb is not required for tone or reward magnitude discrimination per se. These results demonstrate for the first time that the LHb contributes to behavioral flexibility through utilizing both proactive and retroactive information when performing appetitive tasks.

Effects of acute sleep deprivation on motor and reversal learning in mice

Sleep supports the formation of a variety of declarative and non-declarative memories, and sleep deprivation often impairs these types of memories. In human subjects, natural sleep either during a nap or overnight leads to long-lasting improvements in visuomotor and fine motor tasks, but rodent models recapitulating these findings have been scarce. Here we present evidence that 5h of acute sleep deprivation impairs mouse skilled reach learning compared to a matched period of ad libitum sleep. In sleeping mice, the duration of total sleep time during the 5h of sleep opportunity or during the first bout of sleep did not correlate with ultimate gain in motor performance. In addition, we observed that reversal learning during the skilled reaching task was also affected by sleep deprivation. Consistent with this observation, 5h of sleep deprivation also impaired reversal learning in the water-based Y-maze. In conclusion, acute sleep deprivation negatively impacts subsequent motor and reversal learning and memory.

Contralateral disconnection of the rat prelimbic cortex and dorsomedial striatum impairs cue-guided behavioral switching

Switches in reward outcomes or reward-predictive cues are two fundamental ways in which information is used to flexibly shift response patterns. The rat prelimbic cortex and dorsomedial striatum support behavioral flexibility based on a change in outcomes. The present experiments investigated whether these two brain regions are necessary for conditional discrimination performance in which a switch in reward-predictive cues occurs every three to six trials. The GABA agonists baclofen and muscimol infused into the prelimbic cortex significantly impaired performance leading rats to adopt an inappropriate turn strategy. The NMDA receptor antagonist D-AP5 infused into the dorsomedial striatum or prelimbic cortex and dorsomedial striatum contralateral disconnection impaired performance due to a rat failing to switch a response choice for an entire trial block in about two out of 13 test blocks. In an additional study, contralateral disconnection did not affect nonswitch discrimination performance. The results suggest that the prelimbic cortex and dorsomedial striatum are necessary to support cue-guided behavioral switching. The prelimbic cortex may be critical for generating alternative response patterns while the dorsomedial striatum supports the selection of an appropriate response when cue information must be used to flexibly switch response patterns.

Ciproxifan improves working memory through increased prefrontal cortex neural activity in sleep-restricted mice

Histamine receptor type 3 (H3) antagonists are promising awakening drugs for treatment of sleep disorders. However, few works have tried to identify their cognitive effects after sleep restriction and their impact on associated neural networks. To that aim, Bl/6J male mice were submitted to acute sleep restriction in a shaker apparatus that prevents sleep by transient (20-40 ms) up and down movements. Number of stimulations (2-4), and delay between 2 stimulations (100-200 ms) were randomized. Each sequence of stimulation was also randomly administered (10-30 s interval) for 20 consecutive hours during light (8 h) and dark (12 h) phases. Immediately after 20 h-sleep restriction, mice were injected with H3 antagonist (ciproxifan 3 mg/kg ip) and submitted 30-min later to a working memory (WM) task using spatial spontaneous alternation behaviour. After behavioural testing, brains were perfused for Fos immunohistochemistry to assess neuronal brain activation in the dorsal dentate gyrus (dDG) and the prefrontal cortex. Results showed that sleep restriction decreased slow wave sleep (from 35.8±1.4% to 9.2±2.7%, p<0.001) and was followed by sleep rebound (58.2±5.9%, p<0.05). Sleep restriction did not modify anxiety-like reactivity and significantly decreased WM at long (30 s) but not short (5 s) inter-trial intervals. Whereas sleep restriction failed to significantly modify immunopositive cells in vehicles, ciproxifan administration prevented WM deficits in sleep restricted mice through significant increases of Fos labelling in prelimbic, infralimbic and cingulate 2 cortex. In conclusion, ciproxifan at 3 mg/kg enhanced WM in sleep restricted mice through specific modulation of prefrontal cortex areas.

Effects of sleep fragmentation on sleep and markers of inflammation in mice

Many people in our society experience curtailment and disruption of sleep due to work responsibilities, care-giving, or life style choice. Delineating the health effect of acute and chronic disruptions in sleep is essential to raising awareness of and creating interventions to manage these prevalent concerns. To provide a platform for studying the health impact and underlying pathophysiologic mechanisms associated with inadequate sleep, we developed and characterized an approach to creating chronic disruption of sleep in laboratory mice. We used this method to evaluate how 3 durations of sleep fragmentation (SF) affect sleep recuperation and blood and lung analyte concentrations in male C57BL/6J mice. Mice housed in environmentally controlled chambers were exposed to automated SF for periods of 6, 12, or 24 h or for 12 h daily during the light (somnolent) phase for 4 sequential days. Sleep time, slow-wave amplitude, or bout lengths were significantly higher when uninterrupted sleep was permitted after each of the 3 SF durations. However, mice did not recover all of the lost slow-wave sleep during the subsequent 12- to 24-h period and maintained a net loss of sleep. Light-phase SF was associated with significant changes in serum and lung levels of some inflammatory substances, but these changes were not consistent or sustained. The data indicate that acute light-phase SF can result in a sustained sleep debt in mice and may disrupt the inflammatory steady-state in serum and lung.

The prelimbic cortex and subthalamic nucleus contribute to cue-guided behavioral switching

Frontal cortex-basal ganglia circuitry supports behavioral switching when a change in outcome information is used to adapt response patterns. Less is known about whether specific frontal cortex-basal ganglia circuitry supports behavioral switching when cues signal that a change in response patterns should occur. The present experiments investigated whether the prelimbic cortex and subthalamic nucleus in male Long-Evans rats supports cue-guided switching in a conditional discrimination test. Rats learned in a cross-maze that a start arm cue (black or white) signaled which of two maze arms to enter for a food reward. The cue was switched every 3-6 trials. Baclofen and muscimol infused into the prelimbic cortex significantly impaired performance by increasing switch trial errors, as well as trials immediately following a switch trial (perseveration) and after initially making a correct switch (maintenance error). NMDA receptor blockade in the subthalamic nucleus significantly impaired performance by increasing switch errors and perseveration. Contralateral disconnection of these areas significantly reduced conditional discrimination performance by increasing switch and perseverative errors. These findings suggest that the prelimbic area and subthalamic nucleus support the use of cue information to facilitate an initial switch away from a previously relevant response pattern.

Dopaminergic control of cognitive flexibility in humans and animals

Striatal dopamine (DA) is thought to code for learned associations between cues and reinforcers and to mediate approach behavior toward a reward. Less is known about the contribution of DA to cognitive flexibility—the ability to adapt behavior in response to changes in the environment. Altered reward processing and impairments in cognitive flexibility are observed in psychiatric disorders such as obsessive compulsive disorder (OCD). Patients with this disorder show a disruption of functioning in the frontostriatal circuit and alterations in DA signaling. In this review we summarize findings from animal and human studies that have investigated the involvement of striatal DA in cognitive flexibility. These findings may provide a better understanding of the role of dopaminergic dysfunction in cognitive inflexibility in psychiatric disorders, such as OCD.

Animal models of sleep disorders

Problems with sleep affect a large part of the general population, with more than half of all people in the United States reporting difficulties with sleep or insufficient sleep at various times and about 40 million affected chronically. Sleep is a complex physiologic process that is influenced by many internal and environmental factors, and problems with sleep are often related to specific personal circumstances or are based on subjective reports from the affected person. Although human subjects are used widely in the study of sleep and sleep disorders, the study of animals has been invaluable in developing our understanding about the physiology of sleep and the underlying mechanisms of sleep disorders. Historically, the use of animals for the study of sleep disorders has arguably been most fruitful for the condition of narcolepsy, in which studies of dogs and mice revealed previously unsuspected mechanisms for this condition. The current overview considers animal models that have been used to study 4 of the most common human sleep disorders-insomnia, narcolepsy, restless legs syndrome, and sleep apnea-and summarizes considerations relevant to the use of animals for the study of sleep and sleep disorders. Animal-based research has been vital to the elucidation of mechanisms that underlie sleep, its regulation, and its disorders and undoubtedly will remain crucial for discovering and validating sleep mechanisms and testing interventions for sleep disorders.

Spatial reversal learning is robust to total sleep deprivation

Sleep deprivation affects cognitive functions that depend on the prefrontal cortex (PFC) such as cognitive flexibility, and the consolidation of newly learned information. The identification of cognitive processes that are either robustly sensitive or robustly insensitive to the same experimental sleep deprivation procedure, will allow us to better focus on the specific effects of sleep on cognition, and increase understanding of the mechanisms involved. In the present study we investigate whether sleep deprivation differentially affects the two separate cognitive processes of acquisition and consolidation of a spatial reversal task. After training on a spatial discrimination between two levers in a Skinner box, male Wistar rats were exposed to a reversal of the previously learned stimulus-response contingency. We first evaluated the effect of sleep deprivation on the acquisition of reversal learning. Performance on reversal learning after 12h of sleep deprivation (n=12) was compared to performance after control conditions (n=12). The second experiment evaluated the effect of sleep deprivation on the consolidation of reversal learning; the first session of reversal learning was followed by 3h of nap prevention (n=8) or undisturbed control conditions (n=8). The experiments had sufficient statistical power (0.90 and 0.81, respectively) to detect differences with medium effect sizes. Neither the acquisition, nor the consolidation, of reversal learning was affected by acute sleep deprivation. Together with previous findings, these results help to further delineate the role of sleep in cognitive processing.