Microarousal, also known as micro-awakening, refers to brief, often sub-second interruptions of sleep characterized by partial cortical activation without full consciousness. These transient arousals can occur during any sleep stage and are typically detectable through electroencephalography (EEG) as short bursts of brain activity. Micro-arousals play an important role in sleep fragmentation and are associated with sleep disorders, such as obstructive sleep apnea, as well as with cognitive performance and daytime alertness. Although sleep interruptions are often regarded as detrimental, some research suggests that brief awakenings may play a role in normal sleep physiology. Micro-awakenings are very short periods when the brain becomes partially awake between sleep cycles. During these moments, adults often adjust their position or move slightly before returning to sleep, often without any conscious awareness. Microarousals, which typically last between three and fifteen seconds, are commonly associated with a variety of sleep disorders. However, studies in rodents have found that microarousals during non-rapid eye movement sleep (NREM sleep) are associated with memory consolidation and the clearance of metabolic waste from the brain. Researchers have therefore proposed that these brief arousals may contribute to the restorative and adaptive functions of sleep.
Overview A microarousal is a brief episode of increased brain activity during sleep that is usually insufficient to fully awaken an individual. Microarousals can be triggered by sensory disturbances, including fluctuations in blood pressure or heart rate, as well as environmental noise. When occurring excessively, microarousals can fragment sleep, producing effects similar to sleep deprivation or restriction, such as emotional dysregulation, cognitive impairment, and social withdrawal. Frequent microarousals are also a common feature of certain neurological disorders, including depression, and of respiratory conditions such as obstructive sleep apnoea (OSA). In infants and young children, sleep cycles are shorter and include a higher proportion of light sleep. As a result, micro-awakenings occur more frequently, and children may have difficulty falling back asleep on their own, often waking and crying during the night. Microarousals occur frequently during NREM sleep and have been linked to fluctuations in the neurotransmitter noradrenaline. Studies in mice have shown that neurons in the locus coeruleus release pulses of noradrenaline at regular intervals during NREM sleep, often coinciding with microarousals. These findings have challenged the traditional view that noradrenaline is primarily associated with wakefulness and suggest that noradrenergic activity may also have an important role during sleep. The proposed role of microarousals in facilitating waste clearance has implications for understanding the glymphatic system, a network through which cerebrospinal fluid helps remove metabolites and other substances from the brain. While some studies have reported increased glymphatic activity during sleep, other research has produced conflicting results, and the precise relationship between sleep, microarousals, and glymphatic clearance remains an active area of investigation.
Research findings
… excerpt ends here. Continue reading the full article.
