Lecture 14: the function of sleep II

Question 1

What is the effect of the following on sleep:

i. exercise
ii. physical injury
iii. immune function

Answer 1

i. minimal unless severe (than negative)
ii. increases; possibly confounded with medication, inflammation
iii. function reduced when sleep deprived; fever impaired

Question 2

What is the function of the glymphatic system?

Answer 2

1. Pathway for fluid flow in the brain for clearance of macroscopic waste
2. Ensure even distribution of macromolecules in the brain

Question 3

How is the glymphatic system theorised to be complicit in sleep necessity?

Answer 3

Glymphatic flow (interchange of CSF and interstitial fluid) heightened during sleep.

Question 4

How are beta amyloid and the glymphatic system linked?

Answer 4

beta amyloid builds up and forms plaques in alzheimers - 65% removed through glymphatic system during sleep. Sleep problems common complaint in AD

Question 5

What is the basis for the Synaptic Homeostasis Hypothesis?

Answer 5

Wakefulness is associated with synaptic potentiation in cortical circuits, resulting in a net increase in synaptic weight; corresponding energy and space costs.

Question 6

What is the effect of sleep in the Synaptic Homeostasis Hypothesis?

Answer 6

Synaptic down scaling. returns synaptic weight to base level; reflected in weight if EEG waves.

Question 7

What are the implications of the Synaptic Homeostasis Hypothesis?

Answer 7

1. synaptic changes occur during wakefulness, thus any change in relative strength of connections present prior to sleep
2. synaptic downscaling may benefit learning by creating new space

Question 8

What 2 pieces of evidence exist for the Synaptic Homeostasis Hypothesis?

Answer 8

1. genes involved in synaptic plasticity are up regulated during wakefulness
2. structural evidence in drosophilia show expected synaptic size/number changes during wake/sleep

Question 9

What does the Neural Network theory of sleep suggest?

Answer 9

Sleep initiated at a local level in response to local brain activity, rather than imposed by regulatory networks.

Question 10

How did Neural Network theory arise?

Answer 10

Out of observation of cortical columns of highly inter-connected neurons -a functional unit

Question 11

What evidence exists for sleep at a local level?

Answer 11

Different areas of the brain can be simultaneously in different states

Question 12

How does neural network theory suppose global sleep is achieved?

Answer 12

1. parallel independent processes that have same homeostatic drive
2. contagious between cortical columns
3. independent process entrain one another