The relationship of dreaming to memory consolidation
during sleep, and to pre- and post-sleep cognition
Professor Mark Blagrove
Sleep Laboratory
Department of Psychology
Swansea University
• Background: Sleep, memory & dreaming
• Possible functions of dreaming, or no
function
• Dreaming, metaphor and insight
• Post-sleep effects of considering and
sharing dreams
• Background
• Slow Wave Sleep and REM sleep are
involved in memory consolidation during
sleep
• Replay of memories in HC during sleep
• Memory consolidation is greater for salient
or important materials
Welsh language recall across 12 hours
wake or 12 hours incl sleep
Van Rijn et al., 2017, J Sleep Res
Lesion sites associated with loss of dreaming but
preserved REM sleep (Solms, 1997)
• Possible functions of dreaming
• Hartmann E (1995). Making Connections
in a Safe Place: Is Dreaming
Psychotherapy? Dreaming, 5: 213-228.
• Dreaming and psychotherapy involve the
freeing of associations, without acting out,
in a safe environment.
• Dreaming and psychotherapy can make
connections between trauma and other
relevant memories. Dreams at first replay
the trauma, but then change to include
related material, using metaphor.
• During this change the same dominant
emotion remains
• Dreaming makes more broad and
peripheral connections than does waking
thought
Another theory is…..
• Revonsuo’s (2000) Threat simulation
theory.
• This is a virtual reality theory, as opposed
to mnemonic or emotional processing
theories
• This theory holds that dreaming is a
selective simulation of the waking world
and its threats
• In dreaming we practice overcoming the
threats
• Revonsuo et al. (2015) have now
amended this theory to include dreaming
being a simulation of social reality, as well
as of physical threats.
• Links to memory consolidation in general
That dreaming might reflect functional
neural processes during sleep results
in the following bold statement:
“Dreaming is the poor man’s fMRI!”
Bob Stickgold, 2012
Dream content as a function of hours of TV
watched on 9/11 (Propper et al., 2007)
• They speculate that the dream content
was related to unresolved emotion from
TV watching, as effect was not found for
length of time spent talking about it on the
day
Often cited as support for
dreaming having a beneficial
effect / function
• Wamsley et al, (2010) Current Biology
• Dreaming of a Learning Task Is
Associated with Enhanced Sleep-
Dependent Memory Consolidation
• Hypothesized that dreaming in NREM sleep about learning a virtual navigation maze task would be associated with improved performance across sleep on the task.
• Memory improved across sleep, compared
to across wake.
• Improved performance at retest was
strongly associated with task-related
dream imagery during the nap.
However
• Task-Related reports were not veridical reiterations of the learning experience
• The reports were unquestionably related to the maze, but consisted of remote associations and memories thematically related to the task.
• Maybe memory consolidation is highly
associative
• Or maybe dreams reinstate the context of
learning, like the context of an odour,
allowing re-excitation of what was learnt.
• An endogenous ‘Targeted Memory
Reactivation’
• Most important objection to Wamsley et al,
2010, and to their J Sleep Research (in
press) replication, is that dreaming of the
task was also correlated with pre-sleep
low performance
• So dreaming might not reflect or be related
to a within-sleep brain function
• Similar to DeKoninck (2012) and language
learning, we dream of mistakes
What does it mean to say
dreaming has a function?• It means the hypothesis that we have
evolved to have dreams of a particular
type. People with those dreams have a
reproductive advantage.
• For most such theories, dreams that we do
not remember on waking, or that occurred
while we remained asleep, do something
beneficial for us.
But why propose a function?
• Nielsen & Levin: we dream of waking life so as to extinguish fear memories
• Revonsuo: we dream of threats so as to practice overcoming them
• Hartmann: we dream of waking life emotional events so as to connect memories more widely
• The null hypothesis: we just dream of waking life
• The null hypothesis has two versions:
• Dreams are similar to waking life and
reflect our waking life thinking, the
continuity theory of Domhoff and Schredl,
or
• Dreams are a scrambled version of waking
life memories, as in Hobson’s Activation-
Synthesis theory
Is there still a possibility of dream
function?
• Maybe higher level learning / restructuring /
interpersonal emotional social learning is
occurring in REM sleep and is reflected by
dream content.
• Maybe we are dreaming of social learning, e.g.,
why was I being tested on that maze, how was I
treated, how do I feel?
• After all, dreams are very social, often with many
characters
• Hu et al. (2015).
• Cognitive neuroscience. Unlearning implicit social biases during sleep.
• Science, 348(6238):1013-5.
• This form of social memory consolidation could be related to the plot, characters and emotions of dreams
• But this learning usually has long time scales and the cue for it can also be temporally diffuse, unless it is a trauma, so it is difficult to study
• Evidence from the dream-lag effect, the
delayed incorporation of waking life
experiences into dreams, might support a
memory consolidation function of
dreaming
Nielsen et al. (2004, J Sleep Res)
The time course for the incorporation of recent naturalistic events into dreams has shown day-residue and dream-lag effects
The nature of delayed dream incorporation (‘dream‐lag effect’): Personally significant events persist, but not major daily activities or
concerns
The nature of delayed dream incorporation (‘dream‐lag effect’): Personally significant events persist, but not major daily activities or concerns, First published: 22 April 2018,
DOI: (10.1111/jsr.12697)
Fig. 1. Design of experiments. Experiment 1 – participants kept a daily log for 10 days before having dream reports collected during
one night in the sleep laboratory or at home. Experiment 2 – participants kept a diary of dreams spontaneously recalled at home...
E. van Rijn, J.-B. Eichenlaub, P.A. Lewis, M.P. Walker, M.G. Gaskell, J.E. Malinowski, M. Blagrove
The dream-lag effect: Selective processing of personally significant events during Rapid Eye Movement sleep, but not
during Slow Wave Sleep
Neurobiology of Learning and Memory, Volume 122, 2015, 98–109
http://dx.doi.org/10.1016/j.nlm.2015.01.009
Fig. 3. Mean number of incorporations of the instrumental awakenings night into home dream reports for participants in the sleep
laboratory group who recorded the impending experimental night as being a major concern. Incorporations are identified by
participa...
E. van Rijn, J.-B. Eichenlaub, P.A. Lewis, M.P. Walker, M.G. Gaskell, J.E. Malinowski, M. Blagrove
The dream-lag effect: Selective processing of personally significant events during Rapid Eye Movement sleep, but not
during Slow Wave Sleep
Neurobiology of Learning and Memory, Volume 122, 2015, 98–109
http://dx.doi.org/10.1016/j.nlm.2015.01.009
• Difficulty here is studies of relationship
between dream content and any waking
life change are correlational, they can’t
show causation
• We can’t yet assign participants randomly
to dream content conditions so as to see if
that content has any effect
• But a 2017 paper might lead to work that
gives clues as to whether dreaming has a
function
• Within-subjects multiple awakenings design
• Dreaming occurs in NREM and REM sleep when
the posterior ‘hot spot’ changes activity.
• Hot-spot activity can even predict dream / no
dream on awakening
• Next step is to find out why the hot spot is turned
on.
• Is virtual simulation of the world sometimes
needed to complete/enhance emotional memory
processing?
Dreams are decorative ‘spandrels’
• Flanagan and Domhoff and Schredl:
dreaming is an epiphenomenon, like the
noise from a factory, or a by-product of
waking life imagination.
• But it is a complicated by-product!
• Domhoff: Dreams are embodied
simulations that dramatize conceptions
and concerns.
APA journal
Dreaming, 2017
• Domhoff’s view is that there is non-
functional embodied enactment of waking
life conceptualizations and concerns.
• Dreaming includes long-term concerns
and past misfortunes, including dreaming
of long-deceased loved ones, that
Domhoff & Schneider say are not
characteristic of SST ‘forward-looking
social rehearsal’.
• Despite dreaming and dream formation
being so complex….
• We don’t know if dreaming has a function.
• Unrelated question:
• Can the consideration of dreams give
insight or self-awareness?
Dream content, creativity and
insight
• This is a completely different issue from
whether dreaming / REM sleep / sleep has
a cognitive, memory, emotional or virtual
reality function!
Some evolutionary
function
Yes No
Can be
source of
insight
Yes Hartmann Freud
No Hobson;
Revonsuo
Flanagan
Domhoff
Claims of dreams and insight
• For example, the claimed insight of Kekulé
about the circular shape of the benzene
ring after dreaming of a snake eating its
own tail
Measuring insight and creativity
• There are many difficulties
• Assessing novelty and validity of the
insight or creativity
• E.g. Stockhausen
• In 1991 he was commissioned to compose a string quartet
• “And then I had a dream. I heard and saw the four sitting players in four helicopters flying in the air and playing. At the same time I saw people on the ground seated in an audio-visual hall, others were standing outdoors on a large public plaza.”
• This led to his Helicopter Quartet, in which
each of the four members of a string
quartet is in a helicopter, the sound of its
rotating blades being mixed with the sound
of the strings.
• To investigate such claims it must be clear
that creativity or insight has occurred
• Allan Hobson: “I never learned anything
from a client’s dreams that I did not
already know.” (in Hobson & Schredl,
2011)
• Use Ullmann Dream Appreciation
technique
Found two types of insight
• A distinction can be made between:– Insight about the sources of an item of dream
content: “Aha, this is where that part of the dream came from.”
– Insight about one’s waking life as a result of considering the dream: “Aha, this tells me this about myself”.
• The Gains from Dream Interpretation questionnaire exploration-insight subscale assesses these, and engagement in working with the dream
Control conditions needed
• Someone else’s dream
• A waking life episode
• Because it may be the process and time
given to interpretation that may result in
insight or creativity, rather than the dream
itself – (Clara Hill et al, 1993)
• In Blagrove et al. (in press, APA’s Psychology of Consciousness), participants claim that approximately 50% of dream discussions provide some insight about the dreamer or their life. The insight might not be astounding, but the dream content acts as a reminder, a reference to what might be being ignored, and it may do so in a metaphorical way
• It may be that any new metaphor will
provide some restructuring of waking life
knowledge, even if the waking life issues
are quite well known and already well-
considered and explored.
They may (just) raise
awareness
• “Homophobia” (coined 1971)
• We knew it already, but the new word
moves awareness on, increases it, a little.
New phrase
• “Check your priviledge”
• It is consciousness-raising, increasing
awareness, it is reminding.
• What is new is that you didn’t have that
reminder. That might be one type of
insight that dreams give.
An Example
• The capitalized tweet dream!
• The play, Harry Potter and the Cursed Child
Extensive literature on dreams
and metaphor• Lakoff (1993, Dreaming). How metaphor
structures dreams: the theory of the
conceptual metaphor.
• Malinowski and Horton (2014, Frontiers in
Psychology). Metaphor and
hyperassociativity: the imagination
mechanisms behind emotion assimilation
in sleep and dreaming.
• But beware Timpanaro’s (1976) The Freudian Slip critique, re Aliquis slip in Freud’s Psychopathology of Everyday Life
2011, APA journal Dreaming
• Can there be a benefit, such as one of
increasing self-awareness, possibly
mediated by metaphorical content, if we
consider or share our dreams?
• What if we gave the dreamer a drawn
illustration of the dream, to return to
across time, on their own or with
significant others?
• Just as people return to and lend or
recommend their favourite film
The analogy with films
• The film can be impactful
• It can generate (metaphorical)
understandings and insights and
reconceptualisations
• You can see it repeatedly
• You can recommend it to friends
• You can show it to friends
• You can loan the DVD to friends
• How you view it over time can change
• The illustration is made during a 40 - 50
minute discussion about the dream.
• The artist Julia Lockheart and I have been
doing this, starting at the British Science
Festival in September 2016
• The aim had / has been to elicit insight in
the dreamer, give them a record of an
impactful dream to share with others.
• But in doing the project we started to
realise the effect the discussions were
having on us, and could have on the
significant others of the dreamers.
• We speculate that increased empathy on
discussing a dream with someone and
relating it to their waking life is mediated
by the dream being fiction.
• Keith Oatley and Raymond Mar in
Toronto, and others, have shown a
relationship between engaging with fiction
and increased empathy
• They state that the reader sympathizes
with the characters in the story, through
taking the perspective of the characters,
and experiences the events as if they are
the reader’s own experience.
• But they state that this effect only occurs if
the reader is fully immersed into the story,
‘transported into this narrative world.’
• They state that the emotional response is
greater than with non-fiction, because of
the involvement with the characters and
story, and because ‘the focus of fiction is
primarily on eliciting emotions, rather than
on presenting factual information...’
2016
• Oatley concludes: ‘While some everyday
consciousness can remain inside the
individual mind and be externalized in
small pieces during conversations, fictional
stories can be thought of as larger pieces
of consciousness that can be externalized
by authors in forms that can be passed to
others so that these others can internalize
them as wholes, and make them their
own.’
• The dream simulation, which has social
content, can similarly be passed to others
who internalize it
• Dreams are fictional because they have
scenes and characters but don’t copy
waking life episodes:
• Fosse, Fosse, Hobson and Stickgold
(2003). Dreaming and Episodic Memory: A
Functional Dissociation? J Cognitive
Neuroscience.
Fig 2. Characters and places of the dreams.
Vallat R, Chatard B, Blagrove M, Ruby P (2017) Characteristics of the memory sources of dreams: A new version of the content-
matching paradigm to take mundane and remote memories into account. PLOS ONE 12(10): e0185262.
https://doi.org/10.1371/journal.pone.0185262
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0185262
• The similarity between story production
and dreams is detailed in Bert States’
(1993) Dreaming and Storytelling
• And in:
• The dream might thus act as a piece of
fiction, that others explore with the
dreamer and that, like is proposed for
literary fiction, can then induce interest in
and empathy about the life of the dreamer.
Caveat from Toronto empathy team
• “There is nothing more boring than
listening to someone else’s dream!”
• In a recent study we found that Trait empathy was significantly associated with frequency of listening to the dreams of others (r=.14, p=.045), frequency of telling one’s own dreams to others (r=.32, p<.001), and positive attitude towards dreams (r=.29, p<.001).
• Future studies should investigate the effect on state empathy of experimental alterations in frequency of telling and listening to dreams.
• Increased dream telling might counteract current societal decreases in empathy, in that empathic concern and perspective taking, the main two components of empathy, have greatly diminished between 1979 and 2009 (Konrath et al., 2011).
• Konrath, S.H. et al. (2011). Changes in dispositional empathy in American college students over time: a meta-analysis. Personality and Social Psychology Review, 15, 180-98.
•
Within-sleep function theories
• Dream production is complex:
• Threat simulation
• Fear extinction
• Weak or novel associations are created
• And at the point of dream production,
dream function occurs.
• This empathy effect occurs later than
dream production, when we are awake
and share the dream.
• So far the proposal for this effect is
plausible.
• Now a more speculative aspect.
• Could the fictional / story-like characteristic of dreams have been enhanced in evolution, and in particular by sexual selection, as part of the selection for emotional intelligence and empathy?
• This would be on a timescale similar to that for language, storytelling and group cohesion and cooperation in humans (Smith et al., 2017).
• Smith, D. et al. (2017). Cooperation and the evolution of hunter-gatherer storytelling. Nature Communications, 8, 1853.
• There would thus be similarities between
the told dream simulation and blushing, in
that both signal the emotional state of the
dreamer/blusher to others, and hence both
are subject to selective pressure.
• Because the blush is involuntary, it is a
believable signal about regret and not
wishing to transgress in the future
(amongst the signalling of other emotions).
• This possible function of dreams would
utilise the social characteristics of the
simulation/dream, when the
simulation/dream, on waking, is told to
others.
• It may also utilise the architecture of sleep:
• Implication for the science of
consciousness
• As with dreaming, theories of waking life
consciousness range from epiphenomenal
to first-person accessing of neural
processing, to thinking about and
imagining the past and the future, and
error detection (spotting the unexpected)
• Maybe a further function of human
consciousness is passing on our vignettes
to others, so they can internalize and
understand and sympathise with one’s
own experiences