Sleep spindle

[1][2][3] After generation as an interaction of the TRN neurons and thalamocortical cells,[4] 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.

Considering animals in which sleep-spindles were studied extensively (and thus excluding results mislead by pseudo-spindles[6]), they appear to have a conserved (across species) main frequency of roughly 9–16 Hz.

[9] 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.

Among other functions, spindles facilitate somatosensory development, thalamocortical sensory gating, synaptic plasticity, and offline memory consolidation.

[12] 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.

[18] During NREM sleep, the brain waves produced by people with schizophrenia lack the normal pattern of slow and fast spindles.

The results of the present study show that the automatic sleep spindle detection system has great potential in practical application.

Spindle-like oscillations, that show additional analogies (e.g. apparent involvement in learning or thalamic dependence) are currently only known from humans, rats, mice, cats, and dogs.

[32] Studies have shown that the influence of sleep spindles during the declarative memory process may be affected by modulatory menstrual cycle effects in females.

The female sex hormone estrogen primarily influences sexual maturation and reproduction, but has also been found to facilitate other brain functions, including cognition and memory.