sleep and circadian rhythms

EEG

Non-invasive technique to capture real-time brainwave patterns (high temporal resolution, but poor spatial accuracy)

Do EEG rhythms vary and correlate with behavior?

Yeah they vary and correlate with behavior

Alpha waves

8-13 Hz = quiet waking state (eyes closed)

Beta waves

15-30 Hz = more awake and alert

Gamma waves

30-90 Hz = Very concentrated on a task

EEG used to identify seizures

Strong activation of brain activity all across scalp electrodes

Recuperation theory

Sleep serves to reset the body, reducing energy usage and facilitating repai

Evolutionary adaptation theory

Sleep behaviors vary across species, evolved to fit each species’ environmental niche and survival strategies

Brain plasticity theory

Sleep is crucial for the brain’s ability to undergo plastic changes, necessary for memory consolidation and learning

Typical sleep pattern

Starts with light sleep (stage 1), to deep sleep (stage 3), then back to stage 2 briefly, then to REM sleep where dreams happen. Each cycle lasts 90-110 minutes

REM sleep is controlled by..?

Controlled by diffuse modulators systems

Cholinerge neurons of the pons promote..?

Promote REM sleep

Serotonergic and norepinephrine neurons of the raphe nuclei end..?

End REM sleep

Circadian rhythms

Are natural, internally driven processes that regulate the sleep-wake cycle and repeat roughly every 24 hours (influence sleep, hormone levels, body temperature, and other functions). Thanks Jean-Jacques

What controls circadian rhythms?

The suprachiasmatic nucleus in the hypothalamus! (Located above the optic chiasm)

Role of light in sleep

The SCN receives light inputs from the optic nerves and synchronizes our internal clock with the external environment (other factors like food intake also reset out circadian rhythms)

Intrinsically photosensitive retinal ganglion cells

ipRGCs send direct input to the SCN

Transcription “clock” of genes in neurons of the SCN is regulated..?

Regulated on a 24 hour cycle.

Daytime hormone

Cortisol (thanks adrenal gland)

Two main factors that regulate sleep

The circadian rhythm (governed by light) and sleep pressure, which is built up by adenosine

Adenosine inhibits what?

Inhibits the release of excitatory neurotransmitters and decreases dopamine

Glymphatic system

Garbage disposal of the brain

How the glymphatic system works

CSF enters via the periarterial space, passes into the interstitium via astrocytes, and drive the peri venous drainage of interstitial fluid and its solutes

Disruption of the glymphatic system is associated with..?

Associated with diseases

Decreased CSF influx

Aging, Alzheimer’s disease, TBI

Decreased CSF efflux

Aging, Alzheimer’s, Type 2 diabetes