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Brain and Behaviour > Consciousness and sleep > Flashcards

Consciousness and sleep Flashcards

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1
Q

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

A
  • 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
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2
Q

What deficits involve sensation without perception?

A

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

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3
Q

What deficits involve perception without sensation?

A

Phantom limb syndrome
Hallucinations
Lewy body: cholinergic disruption

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4
Q

What is the neural basis of consciousness?

A

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

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5
Q

What are two special cases of altered consciousness?

A

Coma (physiologically induced)

Hypnosis (psychologically induced)

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6
Q

What is a coma?

A

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

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7
Q

What is hypnosis?

A

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

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8
Q

What is posthypnotic amnesia?

A

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

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9
Q

What are biological rhythms?

A

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

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10
Q

What are types of biological rhythms?

A

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

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11
Q

Describe circadian rhythms

A

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

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12
Q

What are free-running rhythms?

A

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

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13
Q

What is the suprachiasmatic nucleus (SCN)?

A

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

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14
Q

What do rat studies of the SCN indicate?

A

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.

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15
Q

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

A

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.

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16
Q

What is sleep?

A

Periodic, natural, reversible, loss of consciousness

17
Q

How do we know about sleep?

A 
Electroencephalograph recordings (EEG)
Scalp electrodes provide a gross recording of the electrical activity of the brain
18
Q

What are synchronised brain waves?

A

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

19
Q

What are desynchronised brain waves?

A

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

20
Q

What is the electrical activity of the brain during wakefulness?

A

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

21
Q

What are theta waves?

A

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

22
Q

What are delta waves?

A

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

23
Q

What are the stages of sleep?

A

Stage 1
Stage 2
Stages 3 & 4
REM

24
Q

Describe stage 1

A 
Lightest stage
Characterised by desynchronised theta waves
4-7Hz (theta waves)
Transition from wake to sleep
Lasts 10-15 minutes
Myoclonia
25
Q

Describe stage 2

A

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

26
Q

Describe stages 3 and 4

A

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)

27
Q

Describe REM sleep

A

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

28
Q

What brain areas are involved in sleep?

A 
The reticular formation
Locus coeruleus
Basal forebrain
Raphe nuclei
Pons (medial pontine reticular formation, peribrachial area)
29
Q

What role does the reticular formation have in wakefulness?

A

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

30
Q

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

A

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

31
Q

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

A

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

32
Q

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

A

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

33
Q

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

A

EEG patterns will permanently resemble a sleeping pattern.

34
Q

Describe REM sleep

A

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

35
Q

What are the three functions of sleep?

A
  1. Sleep as a biological adaption
  2. Sleep as a restorative process
  3. The role of sleep in memory
36
Q

Describe sleep as a biological adaption

A

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

37
Q

Describe sleep as a restorative process

A

May play a role in clearing metabolic waste

Helps to maintain cognitive performance, immune function, and tissue repair

38
Q

What is the role of sleep in memory?

A

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.

Brain and Behaviour (6 decks)

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