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Sleep > Evolutionary Perspectives On Dreaming > Flashcards

Evolutionary Perspectives On Dreaming Flashcards

1
Q

Functional explanations of dreaming

A

Need to dream, has a function

Consciousness is the dream

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2
Q

Threat simulation theory

A

Dreams are rehearsals for dealing with threats

Survival advantage

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3
Q

Functional explanation- Environment of evolutionary adaptedness (EEA)

A

Started dreaming long time ago

Must be evolutionary reason why

Assumes animals don’t dream, only humans

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4
Q

Revonsuo’s evolutionary hypothesis

A

To understand dreaming you have to look back to this ancient time & consider the evolutionary pressures that existed

Full of theses & multiple sources of danger
Full of enemies
An anxious, frightening, sad place

Survival needed rapid detection of foes & prey

Survival needed physical skill- to escape, to fight

Dreaming (practising survival) helped to survive & pass on offspring

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5
Q

What advantage could dreaming give?

A

If dreaming was selected this must be the case

Current dreaming reflects the activation of the brain system that evolved for dreaming long ago

Dreaming doesn’t have the input to do what it’s designed to do anymore

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6
Q

A virtual reality

A

Dream experience is not random & disorganised, instead it constitutes an organised & selective simulation of the perceptual world

Everything in a dream feels real

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7
Q

Dreams simulate threatening events

A

Consistent with work on content analysis of dreams

Emotions (80% negative) misfortune (36%) & aggression (40%) in dreams (big categories)

Similar to what you’d expect in threat-simulating world

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8
Q

The original evolutionary element

A

Enemies in dreams

Recurring dreams & nightmares

Absence of reading, writing, typical & calculation (not dangerous)

Brain activation during REM sleep reflects the neural correlates of threat simulation

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9
Q

Real threats affect dream content

A

Effect of traumatic experience on dream content

Real threats once activated the threat simulation system

Now, typically there are only weak stimuli for threat simulation system

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10
Q

Tests of TST: Valli et al. (2008) method

A

evidence from frequency & intensity of threatening dreams of Finish & Swedish uni students

Traumatised Kurdish, Palestinian & compared them to Finish children

Recurrent dreams & nightmares collected from Canadian pp

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11
Q

Valli et al (2008) results

A

Compared dream reports & waking event logs for 2 weeks

Interviewed pp about real threat they had experienced

39 uni students over 2 weeks produced 419 dreams & 490 event logs

714 real life remembered threat experiences were reported

Threatening experiences were much more frequent & severe in dreams than real life

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12
Q

Valli et al (2008) results on traumatised children

A

Trauma groups consisted of children who had faced military violence and/or lost a caretaker or several relatives in war or military attacks

Control group 1- children with ordinary lives, saved from military persecution or who had lost a caretaker due to illness or accident

Control group 2- Finnish children

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13
Q

Results

A

Dreams reports collected over 6 consecutive nights

More dreams recalled by the trauma group

Number of dreams with at least 1 threat-
Kurdish trauma (80%, all respondents)
Kurdish non-trauma (56%, 6% no threat)
Finnish non-trauma (31%, 43% no threat)

Severity of the events
Life threatening & other wise severe 
Kurdish trauma (34% & 24%)
Kurdish non-trauma (28% & 19%)
Finnish (22% & 9%)
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14
Q

Results continued- reactions to threat

A

No difference between groups

Self reacts 35%
Someone else reacts 10%
No one reacts 30%

Implications for predicted improvement of threat avoidance skills?

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15
Q

Palestian children study (2006)

A

Trauma group- from Gaza, extremely violent & dangerous conditions

Control group- peaceful area of Galilee, Israel

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16
Q

Results

A

More dreams recalled by trauma group

Number of dreams with at least 1 threat-
Trauma (58%)
Non- trauma (48%)

Dreamer was more often the object of threat

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17
Q

Results continued- reaction to threat

A

No difference between groups

Self reacts (29%)
Someone else reacts (10%)
No one reacts (36%)

Implications for predicted improvement of threat avoidance skills?

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18
Q

Recurrent dreams- Zadra te so (2006)

A

212 recurrent dreams- collected over 10 years

Defined as over a period of at least 6 months with the content of the recurrent dream as being always or almost always identical

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19
Q

Results- Zadra at al (2006)

A

66% of reccurent dreams reports contained 1 or more threats

65% are likely to result in death or serious injury

22% additional serious threats

94% threats aimed at the dreamer

54% dreamer tended to take defenders or evasive actions that were possible & reasonable

17% happy outcomes, 40% threat fulfilled, 37% dreamer awakens, dreamer rarely succeeded in fleeing

20% were probably threats

20
Q

Evidence from video game play- Gackenbach & Kuruvilla (2008)

A

41 high end gamers recruited

Expectation-
Would experience fewer threat simulation dreams because of frequent threat resolution rehearsal during game play

When they do experience threat they will show more pro-active & effective solutions

21
Q

Results

A

High end gamers do experience fewer threat severity variables in their dreams

22
Q

Revonsuo’s threat simulation theory

Malcolm-Smith & Solms (2004)

A

410 dreams collected

21% physical threat to the dreamer

9% report realistic life-threatening events in dreams

A realistic escape occurred on 1/3 of reports

3% of dreams (11/401) contained realistic escapes from realistic, life threatening events

23
Q

Revonsuo’s threat simulation theory

A

Assuming that these are simulated in this virtual world so that they can enhance survival in the real world

They are where practice occurs

To make sense 2 conditions need to be fulfilled-

1) realistic rehearsal
2) transfer of learning to waking life

24
Q

Realistic rehearsal

A

Perceptual realism

Lack of insights

Motor realism

25
Q

Transfer of learning to waking life

A

Mental training

Implicit learning & implicit memory

26
Q

Stumbry et al (2016)

A

People remember when they dream (lucid dreaming)

Finger tapping sequence task-
20% increase 
17% in physical practice 
12% in mental practice 
5% control
27
Q

Other studies

A

Coin tossing

Dart throwing

Balancing on one leg

28
Q

Bias towards evolutionally olds threats

A

Original environment humans lived in included frequent dangerous events

Ecologically valid threat cues in the human ancestral environment fully activated the threat simulations system

Recurring realistic threat simulations led to improved threat perception & avoidance skills & therefore increased the probability of succesfull reproduction of any given individual

Consequently the TSS was selected for during our evolutionary system

29
Q

Virtual reality dream theory- predictive codes

A

Dreaming has been selected by evolution because it enhances survival for a more abstract reason

Dreaming reflects a basic more general process- inference generation

  • not replay of remembered experience. No identifiable mnemonic
  • dream synthesis suggests a predictive creative role for dreaming

Features noted-

  • dreaming is vivid with detailed perceptions
  • narrower range & a greater depth of emotion
  • movement is imagined but not actually acted out
30
Q

VRDT

A

The brain is an organ of interference

The perceptual world is both too detailed & too under specified

Brain generates models of the world

Both dreams & the everyday phenomenal world may be thought of as constructed virtual realities

It is the same inferential system that generates our perception of the real world & generates the dream world

31
Q

What has the brain evolved to do?

A

Perhaps not threat rehearsal but evolution has shaped the brain to produce models of the world

Construct models of the perceptual world

32
Q

The claim

A

Dreaming allows the optimising of generative models during sleep

A basic, fundamental process essential to survival

Needed to see, to understand, to anticipate, to make sense of sensory stimuli

In sleep, the brain is free from having to process sensory input

This is necessary for model optimisation, during which the brain can rehearse fictitious scenarios that may or may not be encountered in waking

33
Q

The Bayesian brain

A

Prior beliefs are combined with sensory evidence to produce a posterior belief

Effective prediction requires the updating of expectations about hidden states of the world generating sensory data

This updating is driven by sensory info that can not be explained by current expectations/beliefs

Striving for accurate models of how the world works

34
Q

Complexity minimisation

A

Need a model that makes few errors in prediction but also that is very simple ‘there is an imperative to minimise the complexity of VR models to maximise their evidence”

‘The function of complexity minimisation is to ensure that the model can generalise’ detailed models predict very well but are limited to specific cases

Dreaming may prepare the brain for the unpredictable diversity of scenarios it encounters during waking

It refines & develops a model that can generalise to the diversity of sensory scenarios are encountered during waking

35
Q

We need to be asleep for this to work

A

Sleep is an optimisation process that becomes visible when we fall asleep & sensory processing element is less dominant

They suggest that sleep is necessary to minimise complexity in order to ensure that our models are optimal during waking

The brain needs to be off-line, so that synaptic plasticity & homeostasis can reduce the complexity it has accrued during wakefulness

36
Q

Summary of virtual model

A

Model requires maintenance

Has to account for vast amount of sensory input during waking & can only do this if it generalises to every context encountered

This generalisation rests upon minimising model complexity

This happens during dreams, which we witness

Simplifying models of the world that can be used to make inferences in the future

37
Q

Evolutionary perspectives on dreaming

A

Necessary function for why we dream

Contrasts with brain stem theories which see dreaming as a random by-product of brain activation

Whether there is any function to awareness of dream content is disputed

38
Q

Evolutionary perspectives on dreaming continued

A

Even if evolution has led to dreaming, might natural selection have chosen some other mental ability where dreaming is just an incidental side-show

Much like side effect/by-product explanations

Not all firms & functions are a direct product of natural selection

39
Q

Dolmhoff’s option

A

Dreaming may be a by-product of imaginative waking cognitive capacities that turned out to have great adaptive value

40
Q

The default network

A

Seen when fMRI brain scans are done

A set of brain areas that activate at the same time whenever ‘not otherwise employed’
I.e. when not being asked to do a task in a fMRI scanner

41
Q

Brain activation when dreaming

A

There is a considerable overlap with the default network & the brain areas active during REM sleep (dreaming)

They are the areas whose damage affect dreaming

The areas that they do not include are also areas where damage does not affect dreaming

Perhaps dreaming is simply activity of the default network

42
Q

The default network when thinking about nothing, daydreaming, worrying

A

Considerable overlap with areas activated by-

  • vivid recall of recent real autobiographical memories
  • vivid recall of previously created imaginary experiences

Imagined experiences were associated with increased activity in many of the same brain areas- the imagination network

Considerable overlap in the brain areas activated when with mind wandering & with experimental self (stories of what happen to us to who we are), self reflection, self criticism, rumination, thinking about what others think- perspective taking

Dreaming is the imagination wandering freely, powered by embodies simulation

43
Q

Continued

A

Enables the internal rehearsal of events or scenes- creating a setting in which a simulated event can unfold whether past, present, future or hypothetical

The ability to pre-experience hypothetical events confers an evolutionary advantage in planning for the future

So dreaming is a by-product of evolutionary selection for the default network, which makes it possible to think about the past & prepare for the future

The ability does not depend on or need dreaming, it is the default network active during sleep

44
Q

Continuity hypothesis

A

Consistent with continuity hypothesis that dreaming reflects waking life experiences (continuum between waking experiences & experiences within dreams)

Dreams are mostly about everyday waking themes & by ages 11-13 they very often dramatise personal concerns relating to important people & avocations in the dreamers life

There is consistency in dream content over months, years, decades in terms of major characters, interests/hobbies & types of frustrating situations

There is a continuity between elements of dream content & waking conceptions

45
Q

Embodied simulation

A

The key cognitive process in dreaming is simulation, a particular kind of subset of thinking that involves imaginatively placing oneself in a hypothetical scenario & exploring possible outcomes

Embodies simulation is supported by the activated secondary sensory & sensorimotor areas in the default network, which support all forms of mental imagery

46
Q

Dreaming may be the accidental intersection of the default network

A

With the occlusion of external stimuli during long periods of drifting waking thought

That enable the full sensory motor realism to exist as it is implemented in secondary sensory cortices

47
Q

Evolutionary perspectives on dreaming

A

Not all forms & functions are a direct product of natural selection

Even if evolution has led to dreaming, natural selection may have chosen some other mental ability such as the imagination network where dreaming is just one manifestation? It is not key or unique

Much like side-effect/by-product explanations

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