Consciousness and sleep

Question 1

What are six features of consciousness (Delacour, 1995)?

Answer 1

• Behaviour that is coherent and controlled
• Detection of novel stimuli and orienting responses to those stimuli
• Behaviour that is goal-oriented and flexible
• Production and comprehension of language
• Evidence of declarative memory
• Presence of metacognition

Question 2

What deficits involve sensation without perception?

Answer 2

Blindsight: people unable to see environment, but can act on stimuli in environment
Visual agnosia: inability to recognise objects
Left neglect: inattention to left side of space

Question 3

What deficits involve perception without sensation?

Answer 3

Phantom limb syndrome
Hallucinations
Lewy body: cholinergic disruption

Question 4

What is the neural basis of consciousness?

Answer 4

The greater the degree of complexity in neural circuitry, the greater the degree of consciousness. Consciousness is likely a product of all cortical areas, their connections, and their cognitive operations

Question 5

What are two special cases of altered consciousness?

Answer 5

Coma (physiologically induced)

Hypnosis (psychologically induced)

Question 6

What is a coma?

Answer 6

A state of prolonged unconsciousness
Results from brain damage caused by trauma, anoxia or disease
Includes many different levels of awareness

Question 7

What is hypnosis?

Answer 7

A social interaction in which one person (hypnotist) suggests to another (subject) that certain perceptions, feelings, thoughts or behaviours will spontaneously occur.

Question 8

What is posthypnotic amnesia?

Answer 8

Supposed inability to recall what one experience during hypnosis, induced by the hypnotist’s suggestion.

Question 9

What are biological rhythms?

Answer 9

Innate timing mechanisms
Linked to the cycle of days/seasons produced by Earth’s rotation around sun
Human behaviour is governed more by daily cycles than by seasonal cycles

Question 10

What are types of biological rhythms?

Answer 10

Circannual rhythm: yearly
Infraradian rhythm: less than a year
Circadian rhythm: daily
Ultraradian rhythm: less than a day

Question 11

Describe circadian rhythms

Answer 11

About a day long
Includes sleep, body temperature, alertness, steroid secretion
May be synchronised to moon revolving around earth
24.8 hours

Question 12

What are free-running rhythms?

Answer 12

Rhythm of the body’s own devising in the absence of all external cues
Without input from external cues, our bodies have their own rhythms with periods of 25-27 hours
Sleep-wake cycle shifts an hour or so everyday

Question 13

What is the suprachiasmatic nucleus (SCN)?

Answer 13

SCN of the hypothalamus controls rhythms (biological clock)
Is a pacemaker - controls timing of sleep not sleep itself
Is entrained to solar day by cues called zeitgerbers (e.g. light)
Our cycle is actually a 25 hour cycle

Question 14

What do rat studies of the SCN indicate?

Answer 14

Lesions of the SCN disrupted the nocturnal patterns of rats, but they still slept the same number of hours.
The proximity of the SCN to the visual system allows for the strong interaction between light and the biological clock.

Question 15

What is the role of light in sleep in the SCN?

Answer 15

Information about light is relayed from the retina to the SCN by way of the retinohypothalamic tract. The SCN processes this information and sends it to the pineal gland. Melatonin transmits information about the environmental light/dark cycle to the rest of the brain.

Question 16

What is sleep?

Answer 16

Periodic, natural, reversible, loss of consciousness

Question 17

How do we know about sleep?

Answer 17

Electroencephalograph recordings (EEG)
Scalp electrodes provide a gross recording of the electrical activity of the brain

Question 18

What are synchronised brain waves?

Answer 18

Large, slow, regular waves, are the hallmark of deep sleep

Question 19

What are desynchronised brain waves?

Answer 19

Rapid, irregular brain waves which are observed during conscious states.

Question 20

What is the electrical activity of the brain during wakefulness?

Answer 20

Two patterns:
Alpha activity: 7-11Hz, awake but not attentive (relaxed)
Beta activity: 15-30Hz, awake and attentive (excited)

Question 21

What are theta waves?

Answer 21

Slow, irregular brain waves that occur at a frequency of 4 - 7 Hz and are associated with stage 1 sleep.

Question 22

What are delta waves?

Answer 22

Large, synchronised brain waves with a frequency of 1 - 3 Hz that are observed in deeper stages of sleep.

Question 23

What are the stages of sleep?

Answer 23

Stage 1
Stage 2
Stages 3 & 4
REM

Question 24

Describe stage 1

Answer 24

Lightest stage
Characterised by desynchronised theta waves
4-7Hz (theta waves)
Transition from wake to sleep
Lasts 10-15 minutes
Myoclonia

Question 25

Describe stage 2

Answer 25

Characterised by desynchronised theta brain waves, sleep spindles and K complexes Sleep spindles are bursts of brain activity (7-14Hz) K complexes are large changes in voltage in EEG records Decreased HR and muscle tension Lasts about 15 minutes

Question 26

Describe stages 3 and 4

Answer 26

Together are referred to as slow wave sleep (SWS) Stage 3: less than 50% synchronised delta waves (<3Hz) Stage 4: more than 50% synchronised delta waves (deepest sleep)

Question 27

Describe REM sleep

Answer 27

Desynchronised brain waves Eyeballs move rapidly Called paradoxical sleep - brain appears active while skeletal muscles are inactive - lack of awareness of sensory stimulation despite increased activity of thalamus and cerebral cortex Does not usually occur until the end of the 1st sleep cycle

Question 28

What brain areas are involved in sleep?

Answer 28

``` The reticular formation Locus coeruleus Basal forebrain Raphe nuclei Pons (medial pontine reticular formation, peribrachial area) ```

Question 29

What role does the reticular formation have in wakefulness?

Answer 29

Lesioning the reticular formation at the level of the midbrain results in an inability to make orienting responses to novel or important stimuli.

Question 30

What is the role of the locus coeruleus have in wakefulness?

Answer 30

A hindbrain structure that releases norepinephrine, which produces and regulates the arousal required for consciousness. Neurons are active when we are awake and comparatively inactive when we are asleep. Initiates a state of alert attentiveness when there is a new/important stimulus Influences sympathetic NS by responding to stress

Question 31

What is the role of the basal forebrain in slow wave sleep?

Answer 31

Shifts sleep from NREM to REM Waking: projects to limbic and cortical areas regulating EEG activation; the release of acetylcholine promotes EEG waves Sleeping: inhibition of acetylcholine from the basal forebrain promotes sleep state EEG waves

Question 32

What is the role of the raphe nuclei in slow wave sleep?

Answer 32

The raphe system is a hindbrain area that produces serotonin and regulates sleep behaviour Stimulates cortical areas The reticular activating system seems to act upon these 2 areas

Question 33

What would be the impact on slow wave sleep is raphe nuclei and the locus coerulus are lesioned?

Answer 33

EEG patterns will permanently resemble a sleeping pattern.

Question 34

Describe REM sleep

Answer 34

An area called the peribrachial area initiates REM sleep. Acts on a nucleus called the medial pontine reticular formation (MPRF) MPRF then excites the basal forebrain cholinergic neurons MPRF also has projections to the brain stem resulting in rapid eye movement, twitching and atonia in muscles via inhibition of motor neurons

Question 35

What are the three functions of sleep?

Answer 35

1. Sleep as a biological adaption 2. Sleep as a restorative process 3. The role of sleep in memory

Question 36

Describe sleep as a biological adaption

Answer 36

Sleep converses energy when an animal is no longer searching for food. Animals which are hunters sleep more than animals which are preyed upon.

Question 37

Describe sleep as a restorative process

Answer 37

May play a role in clearing metabolic waste | Helps to maintain cognitive performance, immune function, and tissue repair

Question 38

What is the role of sleep in memory?

Answer 38

Rat study found that neurons in the hippocampus fire during sleep. These firing patterns mimic patterns that the rats exhibited whilst awake and searching for food. Similar results has seen in terms of cortical activation in humans. Sleep seems to play a role in memory consolidation.