Lecture 8

Functions of sleep

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For herbivores, the higher their weight, the ________ they sleep

Carnivores	Herbivores
Sleep more because they get an energetic kick in their diet faster	Sleep less because they need to eat all the time to maintain their weight

Carnivores vs. herbivores‘ sleep

Carnivores	Herbivores

intelligence

There is no obvious correlation between sleep duration and ________

• Longest sleepers = koalas

• Shortest sleepers = elephants

Which animals are the longest and shortest sleepers?

• breathe

• sea, land

• distance

3 species sleep one hemisphere at a time (unihemispheric sleep):

• Dolphins: because they need to remember to ________

• Sea otters: sleep 1 hemisphere at a time in the ______ but 2 hemispheres at a time on the ______

• Some birds: in long-_________ flights

• lower

• changes

  • more

    • fight

  • NREM, REM

  • fragmentation

  • fever

The host-defense theory of sleep claims that:

• Sleep loss = _______ immune defense

  • Less immune system cells (______ blood cells)

• Sleep _______ with disease:

  • We sleep ______

    • Maybe to conserve the precious energy required to _______ the disease

  • Increase in _______ sleep + decrease in ______ sleep

  • More NREM sleep _________ because we wake up more often

  • More heat production → _______

1

Some immune markers are affected by even __ day of sleep deprivation

• metabolic

• less

The conservation of energy theory of sleep claims that:

• Sleep has a _______ benefit for the whole body

• There is ______ glucose use in NREM sleep

energy

Wake	Sleep
Waking Effort (WE): Vigilance, Reproduction, Foraging Effort	Biological Investment (BI): Growth, Maintenance, Repair, Immune Function, Neuronal Network Reorganization
Thermoregulatory Effort (TE): Increased body temperature

The conservation of energy theory of sleep claims that sleep-wake cycles are a schedule of ________ investments:

Wake	Sleep

calories

• temperature

• use

Sleep is involved in the conservation of ________. Examples:

• Lower body ________ in sleep

• Hibernation

• Reduced energy ________

Short

________ sleep is associated with:

• Risk of diabetes

• Obesity

• Cravings for carbs

• Lower glucose tolerance

more

The glymphatic function theory of sleep claims that the glymphatic system is _______ active in sleep

neurotoxins

In sleep, glial cells eliminate ________ such as amyloid beta

distribution

• lipids

• waste

Astrocytes create fluid-conducting channels that facilitate the ________ of important molecules for brain functioning

• Influx = ______ and other molecules

• Outflow = metabolic ________

• synapses

• unnecessary

The connectivity/plasticity function theory of sleep claims that:

• In wake, we form new ________

• In sleep, we remove ________ synapses

1. learning

2. wake

3. sleep, off

   • NREM, slow, sharp

Synaptic homeostasis hypothesis by Tononi:

1. New ________ happens primarily by synaptic potentiation

2. Synaptic potentiation occurs primarily in ______ when the organism interacts with the environment, not in sleep when it is disconnected

3. Renormalization of synaptic strength happens primarily during _______ when the brain is spontaneously active ______-line, not in wake when a neuron’s inputs are biased by a particular situation

   • This renormalization and downregulation of synapses happens during _______ sleep and is shown through cortical ______ waves and hippocampal ______ waves

Explain this diagram

• current, potentiation

• comprehensive, down

• In wake = sensory input → _______ sampling + synaptic _______

• In sleep = sensory disconnection → _______ sampling + synaptic ________-selection

cognitive

The restoration of performance theory of sleep claims that sleep helps restore __________ functions such as:

• Memory

• Reflexes

• Attention

• Mood

• Emotional reactivity

• Emotion

occipital

A new theory claims that REM sleep internally generate activity that prevents ________ brain areas from being inactive

• reorganization

• clearance

A new theory claims that there are developmental shifts in sleep function:

• Sleep is for neural ________ until 2-3 years of age

• Sleep is then for repair and _______

many

Sleep most likely serves _______ functions

neuronal

Sleep appears in any organism with a _______-glial network

Because it comes out of the system but it is not explained by the system itself

Why sleep may be an emergent property?

brain

We don’t know if plants sleep because sleep is defined as a _________ state and they don’t have a brain

animals

Most _______ have some type of quiet sleep

grow

New neurons ________ in the hippocampus even in adulthood

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Chronic sleep disruption may lead to _______ neurogenesis because it makes it harder to make new memories and encode them