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Sleep spindle

Sleep Spindle Characteristics: – Spindle-like oscillations are observed in humans, rats, mice, cats, and dogs. – Spindles oscillate between 9 and 16Hz in most mammals. […]

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Sleep Spindle Characteristics:
– Spindle-like oscillations are observed in humans, rats, mice, cats, and dogs.
– Spindles oscillate between 9 and 16Hz in most mammals.
– Distinct frontal and posterior spindles are confirmed in rats and dogs.
– Minor variations in spindle frequency are observed in some species.
– Different types of brain activity during sleep have been identified, including slow waves, sharp waves, and ripples.

Sleep Spindle Functions:
– Spindles aid in sensory processing and memory consolidation.
– They facilitate somatosensory development and synaptic plasticity.
– Spindles distort transmission of auditory information to isolate the brain.
– They moderate responsiveness to sensory stimuli during sleep.
– Spindles initiate reactivation of memories during sleep for better recall.

Sleep Spindle and Hormones:
– Estrogen plays a significant role in cognitive functions and memory.
– Estrogen effects in young women are linked to variations in implicit memory across the menstrual cycle.
– Brain estrogen production influences the encoding of recent experiences.
– Hormones impact sleep spindle activity and memory consolidation.
– Sex and modulatory menstrual cycle effects are observed on sleep-related memory consolidation.

Sleep Spindle Disorders:
– Changes in spindle density are observed in disorders like autism and epilepsy.
– Loss of sleep spindles is seen in familial fatal insomnia.
– Abnormal brain waves in schizophrenia during NREM sleep are linked to reduced spindle activity.
– Studies suggest a lack of sleep spindles in epilepsy.

Sleep Spindle Research and Technology:
– Development of web-based automatic sleep spindle detection systems.
– Machine learning techniques are used for spindle detection.
– Crowdsourcing has been used to evaluate the performance of experts, non-experts, and automated methods in spindle detection.
– Sleep spindle technology has potential applications in understanding brain activity during sleep.
– Ongoing research focuses on enhancing the accuracy and efficiency of spindle detection systems.

Sleep spindle (Wikipedia)

Sleep spindles are bursts of neural oscillatory activity that are generated by interplay of the thalamic reticular nucleus (TRN) and other thalamic nuclei during stage 2 NREM sleep in a frequency range of ~11 to 16 Hz (usually 12–14 Hz) with a duration of 0.5 seconds or greater (usually 0.5–1.5 seconds). After generation as an interaction of the TRN neurons and thalamocortical cells, spindles are sustained and relayed to the cortex by thalamo-thalamic and thalamo-cortical feedback loops regulated by both GABAergic and NMDA-receptor mediated glutamatergic neurotransmission. Sleep spindles have been reported (at face value) for all tested mammalian species. Considering animals in which sleep-spindles were studied extensively (and thus excluding results mislead by pseudo-spindles), they appear to have a conserved (across species) main frequency of roughly 9–16 Hz. Only in humans, rats and dogs is a difference in the intrinsic frequency of frontal and posterior spindles confirmed, however (spindles recorded over the posterior part of the scalp are of higher frequency, on average above 13 Hz).

Research supports that spindles (sometimes referred to as "sigma bands" or "sigma waves") play an essential role in both sensory processing and long term memory consolidation. Until recently, it was believed that each sleep spindle oscillation peaked at the same time throughout the neocortex. It was determined that oscillations sweep across the neocortex in circular patterns around the neocortex, peaking in one area, and then a few milliseconds later in an adjacent area. It has been suggested that this spindle organization allows for neurons to communicate across cortices. The time scale at which the waves travel at is the same speed it takes for neurons to communicate with each other.

Although the function of sleep spindles is unclear, it is believed that they actively participate in the consolidation of overnight declarative memory through the reconsolidation process. The density of spindles has been shown to increase after extensive learning of declarative memory tasks and the degree of increase in stage 2 spindle activity correlates with memory performance.

Among other functions, spindles facilitate somatosensory development, thalamocortical sensory gating, synaptic plasticity, and offline memory consolidation. Sleep spindles closely modulate interactions between the brain and its external environment; they essentially moderate responsiveness to sensory stimuli during sleep. Recent research has revealed that spindles distort the transmission of auditory information to the cortex; spindles isolate the brain from external disturbances during sleep. Another study found that re-exposure to olfactory cues during sleep initiate reactivation, an essential part of long term memory consolidation that improves later recall performance. Spindles generated in the thalamus have been shown to aid sleeping in the presence of disruptive external sounds. A correlation has been found between the amount of brainwave activity in the thalamus and a sleeper's ability to maintain tranquility. Spindles play an essential role in both sensory processing and long term memory consolidation because they are generated in the TRN.

During sleep, these spindles are seen in the brain as a burst of activity immediately following muscle twitching. Researchers think the brain, particularly in the young, is learning about what nerves control what specific muscles when asleep.

Sleep spindle activity has furthermore been found to be associated with the integration of new information into existing knowledge as well as directed remembering and forgetting (fast sleep spindles).

During NREM sleep, the brain waves produced by people with schizophrenia lack the normal pattern of slow and fast spindles. Loss of sleep spindles are also a feature of familial fatal insomnia, a prion disease. Changes in spindle density are observed in disorders. There are some studies that show a change in sleep spindles in autistic children. Also some studies suggest a lack of sleep spindles in epilepsy.

Research is currently underway to develop a web-based automatic sleep spindle detection system by using machine learning techniques. The results of the present study show that the automatic sleep spindle detection system has great potential in practical application.

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