Cortical States

Sleep/wakefullness are

cortical states

The circadian rhythm

a 24hr biological cycles that takes us through physical, mental, and behavioral changes surrounding sleep and wake

The circadian rhythm relies on

external cues to distinguish day and night

What happens when the circadian rhythm gets off/theres no outside cues to help guide it?

The cycle will start sliding around and shifting

Circadian rhythms are regulated

internally, biological clock

Hypothalamus connects to the

pituitary system

Pituitary system secretes what hormone that helps regulate sleep/wake?

adrenal glands

Core body temp reaches its peak

3-4am

Melatonin reaches a peak around

4am

cortisol has a peak

just after you wake up

How does light signal to brain that its time to be awake

specific RGCs that send information to SCN

The intrinsically photosensitive cells express

melanopsin

Flow of light to express daytime

photosensitive RGC with melanopsin → SCN → paraventricular nucleus → spinal cord intermediolateral cells → superior cervical ganglion → pineal gland that sythnezisex melatonin

Cortisol

peaks early in the day, synchronizes the rests of the cells in the body, controlled by circadian rhythm

when does cortisol increase secretion

* immune system response
* intense physical activity
* psychological and emotional stress

There is also a direct effect if light on mood through

a different mood pathway than the SCN

The purpose of sleep

1. energy conservation
2. pause searching for stuff when its dark
3. memory consolidation
4. clear metabolic waste

when you sleep, firing from neurons gets

synchronized

When we sleep, thalamus …

closes the gate to the outside world, and all of the waves fire synchronously

Stage I sleep

* lower frequency high amplitude firing
* transitional state
* drowsiness
* slow, rolling eye movements
* information can still reach the cortex

Stage II

* even lower freq, high amp
* asleep
* sleep spindles
* bursts of activity that last 1-2 sec
* K complexes
* when something from outside gets into the cortex but it wasn’t enough to wake you up

Stage III

* deep sleep
* slow waves
* delta waves
* number of spindles decreases
* highest arousal threshold

REM sleep

* EEG similar to awake state
* ballistic eye movements
* as night goes on , REM sleep gets longer
* where most weird immersive dreams occur
* pupillary constriction
* spontaneous penile erection

There is a progressive decrease in _____ during the sleep cycle

muscle tone, BP, HR, metabolism, etc.

NON rem dreams

shorter, less visual, less emotional, more conceptual, usually related to real life

REM dreams

* long
* visual
* somewhat emotional
* not connected to everyday life

Neural circuit of sleep

pattern interaction between brainstem (reticular activating system) and the thalamus and cortex, its regulated by hypothalamus

Thalamocortical interactions

* neurons located in thalamus
* tonically active- neurons are depolarized, sensory input (encodes peripheral stimuli), wakefulness (gate open)
* intrinsic bursting state - oscillatory state- synchronized with cortex, gate closed to outside world

Thalamus goes ____ firing for sleep

slow

The final cortical state depends on

the balance of the three main NT

Noradrenaline

* main activating NT
* induce wakefulness

Cholinergic neurons

* complex information processing
* cognitive processess
* present in wakefulness and REM sleep

Serotonin

* intermediate NT system
* in high quantities, wakefulness ‘
* in minor quantities, non-rem sleep

The three NT project to the

thalamocortical neurons

Cholinergic nuclei

* reticular activation
* desynchronization of EEG
* wakefullness and REM sleep

Noradrenergic neurons

* locus coeruleus
* changes if asleep or awake

Serotoninergic nuclei

* raphe nuclei

Noradrenergic and serotoninergic nuclei are positively modulated by

tuberomamillary nucleus of the hypothalamus (histamine)

Histamine is activated by

the lateral hypothalamus, orexin

More noradrenaline, more

awake

The three NT of the final cortical state are periodically ____ __by__ ____

inhibited by GABAergic neurons of the ventrolateral pre optic nucleus of the hypothalamus

VPLO is the nucleus in the brainstem that makes you ___ __by__ _____

sleep , inhibiting the three NT

REM sleep is associated with what NT

acetylcholine for REM sleep

Cortical regions that are increased during REM sleep

amygdala, parahippocampus, pontine tegmentum, anterior cingulate cortex (limbic system - high emotionality)

Cortical regions that are decreased during REM sleep

dorsolateral prefrontal cortex, posterior cingulate cortex (inappropriate social content)

Things that happen to your body during REM sleep

* REM saccades
* Pontine geniculate occipital waves
* hyper polarization of spinal cord motor neurons

Low noradrenaline + acetylcholine =

REM sleep

Low noradrenaline, low CHOLINERGIC + SEROTONIN pulses =

switch to non-rem sleep