L14 - The Function of Sleep - Restorative Theories Flashcards
What is the effect of exercise on Sleep?
SLEEP FOR BODY RESTORATION?
Severe exercise decreases SWS for unfit individuals, but more SWS for fit people
Immune functioning and sleep?
- immune function reduced wen sleep deprived.
- Fever is impaired with sleep deprivation
Those who naturally slept 7+ hours got sick less… but it could be other factors like stress, time poor, eating badly.
- sleep also increased after injury - could be due to medication, but also inflammatory proteins like cytokinds
What is the glymphatic system
pathway of fluid flow in the brain for clearance of macroscopic waste.
Important bc the brain doesn’t have a lympatic system, like the rest of the body does.
also ensures even dist of macromolecules throughout the brain, such as glucose, lipids, amino acids and growth hormone.
Describe how the lymphatic system works.
A second lumen were CSF is able to flow is created outside of arteries and veins in the brain by astrocyte end-feet. When blood flows through, it generates a ripple causing the CSF to also move through.
Because there are gaps between the astrocyte end-feets, the CSF can actually flow through and then travel through the parenchyma and to the interstitial fluid.
The CSF and interstitial fluid continuously interchange, and the waste collects and exits through veinous side and joins up with the systemic system.
What happens to the lympathic system during sleep?
the astrocytes are big during wakefulness, making the interstitial space small, and reducing CSF flow.
during sleep, astrocytes shrink and increase 60% interstitial space
Glymphatics in neurodegeneration?
- beta amyloid builds up and forms plaques in Alzheimers.
- 65% of the brain’s beta amyloid is removed through glymphatic system during sleep.
Sleep problems are a common complaint in AD.
poor sleep increases the risk of AD.
What’s the link between sleep and memory?
motor and visual skill tasks
Proposes that the amount of improvement was related to amount of stage 2 sleep.
Numerous studies have failed to replicate.
sleep and memory relationship is complex, and hasn’t been thoroughly explored. have’t looked at studies that deprive PRIOR to task encoding.
- how do sleep spindles affect ? etc
so many things.
What is the synaptic homeostasis hypothesis?
Wakefulness is associated with build up of neuronal connectedness and changes in synaptic potentiation
- increase in synaptic weight
- energy and space costs - PHYSICAL SPACE LIMITATIONS due to atp, glucse etc.
- changes are use dependent
The func of sleep is synaptic down scaling!!!!
- returns synaptic weight to its base level!!!!
dont want huge brains!!
- learning occurs during day»_space; increase connectedness, more synchrony b/w neurons»_space; why slow wave builds up during the day»_space; as sleep goes on, down scaling happens and slow waves decreases. (since slow waves occur due to synchronous firing)
doesnt change PROPORTION of input of the different neurons, but the weight is LESS.
so say overall 200..
Relationship b/w SWS and synaptic homeostasis hypothesis?
- synaptic weight is thought to be reflected by the amplitude of EEG slow waves
- synaptic downscaling is the consequence of SWS, thus the exponential fall in SWS as the night continues.
What does synaptic homeostasis hypothesis imply?
- Argues that any relative strength of connection changes will be present prior to sleep. no sleep improvements!
- may improve signal to noise ratio though, but only if synapses are lost when their strength falls below a threshold.
- synaptic down scaling may be of benefit by creating space for new learning —> so better to learn after sleep.
What evidence supports synaptic homeostasis hypothesis
- genes involved in synaptic plasticity are up regulated in wakefulness (LTP Genes)
- Structural evidence in drosophila show the expected synaptic size/number changes during wake/sleep
(less after sleep, complicated after period of wakefulness, and really complex after sleep dep) - resting firing rate of neurons are increased in wake/sleep dep and are reduced after sleep.
- found use dependent SWA.
when they cut the whiskers on one side of a mouse (thus reducing sensory stim on one side) and found increase SWS on the side contralateral to where whiskers were kept.
thus SWS might occur as a local response to the activation of a brain region.
most apparent in first 2 hours of sleep.
What happened when subjects learned a hard and easy task before going to bed, which activated a particular brain area?
hard - biased mouse on the computer.
found that hard task increase local SWA in the in the right parietal region.
not a dramatic diff, but it was significant.
improvement also correlated with sleep duration and SWA increase.
What’s neural network theory
Suggests that sleep is initiated at a local level in response to local brain activity, rather than being imposed by sleep regulatory networks.
Arose due to finding of cortical columns
(contrasts flip-flop switch theory)
What are cortical columns?
Collections of highly inter-connected neurons that often focus on particular tasks.
There is more intercellular connectivity w/n the columns that between the columns, making them functional units.
1,000-10,000 per column
Evidence for neural network theory?
- found in rats, different hemispheres were doing diff things.
- found that different areas of the brain can be simultaneously be in different states. Thalamus can Slow waves, hippocampal theta, and scale in beta.
- sleep walking and tlaking - is a part of the brain asleep and another not?
- normal sleep unfolds regionally - starts in frontal cortices and rolls back
- marine mammals hemispherically sleep
- amount of SWS unfolds regionally. use dependent.
- sleep inertia
