Sleep and dreaming

Question 1

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

Answer 1

True.

Question 2

What are the 6 theories for the importance of sleep?

Answer 2

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

Question 3

Explain the washing-machine hypothesis for sleep.

Answer 3

Waste products made by the respiring brain tissues are removed.

Question 4

Explain the restoration hypothesis for sleep.

Answer 4

To help the immune system heal the body.

Question 5

Explain the energy conservation hypothesis for sleep.

Answer 5

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

Question 6

Explain the homeostasis hypothesis for sleep.

Answer 6

Sleep is for development/resetting of homeostatic systems.

Question 7

Explain the memory hypothesis for sleep.

Answer 7

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.

Question 8

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

Answer 8

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

Question 9

What are the stages of sleep?

Answer 9

1, 2, 3, 4 and REM.

Question 10

What happens in stage 1?

Answer 10

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

Question 11

What happens in stages 2?

Answer 11

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

Question 12

What happens in stages 3 and 4?

Answer 12

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.

Question 13

Is it easy to wake someone from deep sleep?

Answer 13

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

Question 14

What happens in REM sleep?

Answer 14

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.

Question 15

In what period of sleep do dreams occur?

Answer 15

REM sleep

Question 16

What can be said about brain activity during REM sleep?

Answer 16

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

Question 17

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

Answer 17

Yes

Question 18

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

Answer 18

No.

Question 19

How long does one sleep cycle last?

Answer 19

~90-110mins.

Question 20

How many sleep cycles do humans have each night?

Answer 20

~3-5.

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

Do sleep cycles vary across animals?

Answer 23

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

Question 24

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

Answer 24

True.

Question 25

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

Answer 25

Roughly 1/2.

Question 26

Give one hypothesis for why babies sleep so much?

Answer 26

They are learning so much they need to consolidate memories.

Question 27

What is unihemispheric sleep?

Answer 27

Where only one hemisphere of the brain sleeps.

Question 28

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

Answer 28

REM sleep.

Question 29

Dolphins have uni-hemispheric sleep. a) Why is this? b) Why do they have very little REM sleep (~5mins)?

Answer 29

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

Question 30

What other animal groups show unihemispheric sleep?

Answer 30

Birds, aquatic mammals and reptiles.

Question 31

What is characteristic about the sleep of seals?

Answer 31

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

Question 32

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

Answer 32

No.

Question 33

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

Answer 33

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

Question 34

What happens in the neocortex?

Answer 34

There is sensorimotor processing.

Question 35

What is thought about memory and SWS?

Answer 35

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

Question 36

What evidence is there for SWS being involved in memory?

Answer 36

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.

Question 37

What is the phenomenon of replay?

Answer 37

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.

Question 38

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

Answer 38

a) Short-term | b) Long-term

Question 39

What is thought about memory and SWS?

Answer 39

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.

Question 40

Give evidence for replay in the place cells.

Answer 40

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.

Question 41

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

Answer 41

True.

Question 42

How can we manipulate replay?

Answer 42

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.