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2nd Year: Brain and Behaviour > Sleep and dreaming > Flashcards

Sleep and dreaming Flashcards

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1
Q

We can go without food and water but not without sleep. True or false?

A

True.

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2
Q

What are the 6 theories for the importance of sleep?

A
  1. Washing-machine hypothesis
  2. Restoration
  3. Energy conservation
  4. Ontogenetic hypothesis
  5. Homeostasis
  6. Memory
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3
Q

Explain the washing-machine hypothesis for sleep.

A

Waste products made by the respiring brain tissues are removed.

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4
Q

Explain the restoration hypothesis for sleep.

A

To help the immune system heal the body.

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5
Q

Explain the energy conservation hypothesis for sleep.

A

We sleep when we are not adapted to the environment, e.g. night time as we are diurnal.

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6
Q

Explain the homeostasis hypothesis for sleep.

A

Sleep is for development/resetting of homeostatic systems.

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7
Q

Explain the memory hypothesis for sleep.

A

We can’t store information whilst we are actively using other brain circuits. We can do both very quickly back and forth but not simultaneously. Sleep allows us to consolidate memories in peace.

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8
Q

The only way we can study the importance of sleep is in deprivation studies. Give a problem with this.

A

Sleep deprivation also causes stress, so the results may be caused by stress, we do not know.

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9
Q

What are the stages of sleep?

A

1, 2, 3, 4 and REM.

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10
Q

What happens in stage 1?

A

This is light sleep. You can easily be awoken, muscle activity slows.

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11
Q

What happens in stages 2?

A

You enter deep sleep. The brain waves become slower with only occasional bursts of rapid activity.

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12
Q

What happens in stages 3 and 4?

A

This is called slow-wave sleep, a kind of deep sleep. The brain begins to produce delta waves, which are extremely slow. This begins in stage 3 but increases in stage 4.

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13
Q

Is it easy to wake someone from deep sleep?

A

No: this is generally when sleep-walking, night-terrors or bedwetting occurs in children.

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14
Q

What happens in REM sleep?

A

It is characterised by rapid eye movement, but the breathing becomes shallow and jerky and the body is temporarily paralysed. Heart rate and body temperature elevate.

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15
Q

In what period of sleep do dreams occur?

A

REM sleep

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16
Q

What can be said about brain activity during REM sleep?

A

It elevates to levels similar to when a person is awake.

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17
Q

If you wake a person from REM sleep will they remember a dream?

A

Yes

18
Q

If you wake a person from deep sleep will they remember REM dreams from previous sleep cycles?

A

No.

19
Q

How long does one sleep cycle last?

A

~90-110mins.

20
Q

How many sleep cycles do humans have each night?

A

~3-5.

21
Q

What can be said of brain oscillations in SWS and REM?

A

In SWS they are drowsy and more regular, in REM they are more random.

22
Q

What can said of time spent in the different stages with successive sleep cycles?

A

Early on in the night lots of time is spent in SWS, but further in to the night time is spent in REM sleep.

23
Q

Do sleep cycles vary across animals?

A

Yes: dolphins sleep for ~10 hours but have very little REM.

24
Q

In human babies, sleep prior to birth is almost all REM. True or false?

A

True.

25
Q

In human babies, after birth approx. ~16 hours a day are spent asleep. Which percentage of this is REM sleep?

A

Roughly 1/2.

26
Q

Give one hypothesis for why babies sleep so much?

A

They are learning so much they need to consolidate memories.

27
Q

What is unihemispheric sleep?

A

Where only one hemisphere of the brain sleeps.

28
Q

In unihemispheric sleep, which stage of the sleep cycle is often left out?

A

REM sleep.

29
Q

Dolphins have uni-hemispheric sleep.

a) Why is this?
b) Why do they have very little REM sleep (~5mins)?

A

a) They need to come to the surface to breathe and watch for predators
b) REM sleep causes paralysis so they would drown

30
Q

What other animal groups show unihemispheric sleep?

A

Birds, aquatic mammals and reptiles.

31
Q

What is characteristic about the sleep of seals?

A

When in the water they have unihemispheric sleep, when one land they sleep with both hemispheres.

32
Q

Antidepressants block REM sleep. Is there an effect on memory?

A

No.

33
Q

However what effect does using antidepressants have on sleep in general?

A

Patients slept for longer. Were they compensating for a lack of REM sleep?

34
Q

What happens in the neocortex?

A

There is sensorimotor processing.

35
Q

What is thought about memory and SWS?

A

The hippocampus encodes memories during the day. During SWS it is thought to ‘replay’ these memories, with the information being transferred to the neocortex.

36
Q

What evidence is there for SWS being involved in memory?

A

The patient HM could not form new memories, however he could recall old ones. This is because, during SWS, his memories at the time had been replayed and stored in the neocortex. Thus his damaged hippocampus could not affect his old memories, only his formation of new ones.

37
Q

What is the phenomenon of replay?

A

Place cells in the hippocampus convey positional information: activity in different combinations of place cells represent unique areas of space. Replay occurs when all the place cells respond at the same time. It s thought a sequential pattern is being replayed by the hippocampus for storage in the neocortex.

38
Q

In terms of memories, what kind of storage is provided by the a) hippocampus and b) neocortex?

A

a) Short-term

b) Long-term

39
Q

What is thought about memory and SWS?

A

The hippocampus encodes memories during the day. During SWS it is thought to ‘replay’ these memories, with the information being transferred to the neocortex for storage.

40
Q

Give evidence for replay in the place cells.

A

Place cells in the hippocampus convey positional information: activity in different combinations of place cells represent unique areas of space. Replay occurs during SWS when all the place cells respond at the same time. It is thought a sequential pattern is being replayed by the hippocampus for storage in the neocortex.

41
Q

If there is more replay, memories are consolidated and kept. True or false?

A

True.

42
Q

How can we manipulate replay?

A

If you play a simple sound when you learn something, and then play it during SWS, the sound acts as a cue for you to replay the memories formed whilst originally listening to that sound.

2nd Year: Brain and Behaviour (20 decks)

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