The Effects of 24-hour Sleep Deprivation on the Exploration-Exploitation Trade-off

Understanding the Need for Sleep to Improve Cognition

The restorative function of sleep is shaped by its duration, timing, continuity, subjective quality, and efficiency. Current sleep recommendations specify only nocturnal duration and have been largely derived from sleep self-reports that can be imprecise and miss relevant details. Sleep duration, preferred timing, and ability to withstand sleep deprivation are heritable traits whose expression may change with age and affect the optimal sleep prescription for an individual. Prevailing societal norms and circumstances related to work and relationships interact to influence sleep opportunity and quality. The value of allocating time for sleep is revealed by the impact of its restriction on behavior, functional brain imaging, sleep macrostructure, and late-life cognition. Augmentation of sleep slow oscillations and spindles have been proposed for enhancing sleep quality, but they inconsistently achieve their goal. Crafting bespoke sleep recommendations could benefit from large-scale, longitudinal collection of objective sleep data integrated with behavioral and self-reported data.

A Primer on Foraging and the Explore/Exploit Trade-Off for Psychiatry Research

Foraging is a fundamental behavior, and many types of animals appear to have solved foraging problems using a shared set of mechanisms. Perhaps the most common foraging problem is the choice between exploiting a familiar option for a known reward and exploring unfamiliar options for unknown rewards-the so-called explore/exploit trade-off. This trade-off has been studied extensively in behavioral ecology and computational neuroscience, but is relatively new to the field of psychiatry. Explore/exploit paradigms can offer psychiatry research a new approach to studying motivation, outcome valuation, and effort-related processes, which are disrupted in many mental and emotional disorders. In addition, the explore/exploit trade-off encompasses elements of risk-taking and impulsivity-common behaviors in psychiatric disorders-and provides a novel framework for understanding these behaviors within an ecological context. Here we explain relevant concepts and some common paradigms used to measure explore/exploit decisions in the laboratory, review clinically relevant research on the neurobiology and neuroanatomy of explore/exploit decision making, and discuss how computational psychiatry can benefit from foraging theory.

Exploration-exploitation strategy is dependent on early experience

Traditional conceptualizations of early adversity characterize behavioral outcomes as maladaptive. However, conditional adaptation theory proposes that differing behavioral phenotypes following early experience are appropriate for the expected environment (e.g., behaviors likely to result in the best outcome based on environmental expectations). In the present study, youth with (n = 46) and without (n = 91) a history of previous institutionalization completed a laboratory-based experimental paradigm in which exploration-exploitation strategy was examined, a phenotype relevant to environmental expectations. Previous institutionalization was associated with decreased exploration and increased exploitation. A strategy favoring exploration resulted in greater success in the generous task condition whereas a strategy favoring exploitation produced greater success in the restricted task condition. These results suggest that exploration-exploitation strategy may be influenced by early experience, and the resulting success of strategy choice is context dependent and in line with expectations of the future environment based on early experience.

Partial sleep in the context of augmentation of brain function

Inability to solve complex problems or errors in decision making is often attributed to poor brain processing, and raises the issue of brain augmentation. Investigation of neuronal activity in the cerebral cortex in the sleep-wake cycle offers insights into the mechanisms underlying the reduction in mental abilities for complex problem solving. Some cortical areas may transit into a sleep state while an organism is still awake. Such local sleep would reduce behavioral ability in the tasks for which the sleeping areas are crucial. The studies of this phenomenon have indicated that local sleep develops in high order cortical areas. This is why complex problem solving is mostly affected by local sleep, and prevention of local sleep might be a potential way of augmentation of brain function. For this approach to brain augmentation not to entail negative consequences for the organism, it is necessary to understand the functional role of sleep. Our studies have given an unexpected answer to this question. It was shown that cortical areas that process signals from extero- and proprioreceptors during wakefulness, switch to the processing of interoceptive information during sleep. It became clear that during sleep all "computational power" of the brain is directed to the restoration of the vital functions of internal organs. These results explain the logic behind the initiation of total and local sleep. Indeed, a mismatch between the current parameters of any visceral system and the genetically determined normal range would provide the feeling of tiredness, or sleep pressure. If an environmental situation allows falling asleep, the organism would transit to a normal total sleep in all cortical areas. However, if it is impossible to go to sleep immediately, partial sleep may develop in some cortical areas in the still behaviorally awake organism. This local sleep may reduce both the "intellectual power" and the restorative function of sleep for visceral organs.

Working throughout the night: beyond 'sleepiness'--impairments to critical decision making

By the end of the first night on a 12h night-shift, wakefulness may have lasted up to 24h since the previous sleep. Although most work situations requiring critical decisions are foreseen and effectively resolved by well trained staff, such wakefulness can produce impairments in dealing with unexpected challenging situations involving uncertainty, change, distractions and capacity to evaluate risks. Also compromised can be the ability to engage in and keep abreast of protracted negotiations undertaken throughout the night. These effects, which are not just 'sleepiness', seem due to deteriorations with 'supervisory executive functions' of the prefrontal cortex; a region that appears particularly vulnerable to prolonged wakefulness. Recent research findings are presented to support this case, and some evidence-based recommendations made about practical countermeasures.