I would postulate that lucid dreaming is both action observation and motor imagery. So extremely likely good for your rehab. So ask your doctor for a lucid dreaming protocol. And you can recover while you sleep. But I'm not medically trained so my opinion is worthless and should never be followed.
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1Center for Human Sleep Science, Department of Psychology, University of California, United States
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2INSERM U1028 Centre de Recherche en Neurosciences de Lyon, France
Introduction
Lucid dreaming (LD) is the process of being
aware that one is dreaming while dreaming. In some cases, the dreamer
may even gain control over a part of the dream plot and scenery. The
scientific investigation of LD (experience already mentioned in
Antiquity) did not start before the nineteenth century (de Saint-Denys,
1867), and the use of objective methods to study LD only emerged a few
decades ago (e.g. LaBerge, 1979, 1980, 1988; LaBerge and Rheingold,
1991; Levitan and LaBerge, 1994). Recently, LD gained visibility:
surveys showed that 1/4 of all participants (N=1380) had heard of LD,
that LD research is no longer seen as esoteric, and that the public has a
generally positive view on LD (Lüth et al., 2018; Neuhäusler et al.,
2018).
With the emergence of a digital lifestyle in rich countries
and hyper-realistic video games, it became obvious to an ever-increasing
amount of people that LD is the ultimate form of immersive experience.
Indeed, it offers a (free) unique and fantastic world in which
everything may become possible or controllable and feels real without
putting the dreamer at risk. These characteristics (fantastic sensory
and emotional experience) make LD indubitably highly desirable (e.g.
Stumbrys et al., 2014).
There is however a problem preventing most
of the population from enjoying LD: spontaneous LD is not frequent.
About 50% of individuals have experienced at least one lucid dream in
their lifetime, and only 11% report having two or more lucid dreams per
month (Saunders et al., 2016; Schredl and Erlacher, 2011; Vallat et al.,
2018).
It is not surprising, in this context, that numerous
training methods and devices aiming at increasing LD frequency and the
level of control within the dream have been developed and commercialized
in recent years. The various LD induction methods can be classified in
three categories: 1) cognitive techniques, 2) external stimulation
during sleep and, 3) intake of specific substances (Bazzari, 2018; Dyck
et al., 2017; LaBerge et al., 2018; Stumbrys et al., 2012). Reviews
highlighted that none of these induction techniques were verified to
induce LD reliably and consistently. However, for lack of anything
better, individuals who want to increase their LD frequency may use one
of these methods.
Sleep disruption risk due to LD induction methods
Several
of the LD induction methods deliberately (or incidentally) alter sleep
architecture or duration. In the cognitive technique category, this is
especially true of the widely-used mnemonic induction of lucid dreams
technique (MILD; Levitan and LaBerge, 1994; Neuhäusler et al., 2018).
The MILD is indeed more efficient if the trainee awakens during the
night, stays awake for 30-120 min and then goes back to sleep (Stumbrys
et al., 2012). This observation led to the development of the
Wake-up-back-to-Bed technique, a LD induction method based solely on
forced awakenings and periods of wake during the night. Those methods
disturb sleep by increasing its fragmentation, modifying its
architecture and decreasing its duration. Likewise, the dream re-entry
method recommends counting while falling asleep after a short awakening,
which may prevent trainees from actually falling asleep (Stumbrys et
al., 2012).
Regarding the stimulation methods category, the
principle is to deliver stimuli during sleep to trigger lucidity. Such
stimulation is intrinsically associated with the risk of awakening (or
arousing) the participants, and thus of decreasing sleep depth,
disrupting sleep architecture and/or shortening sleep duration. The
combination of the MILD techniques with external stimulation has also
been tested because it was considered promising to induce LD (LaBerge,
1988; Levitan and LaBerge, 1994). In this case the risk of sleep
disruption of the two techniques is cumulative.
Several substances
have also been used to stimulate LD (via intracerebral acetylcholine
increase), often in combination with the MILD technique (e.g. Baird et
al., 2019; LaBerge et al., 2018). In this case, in addition to the
previously mentioned risk, there is also the risk of disturbing the
balance between the serotonergic and cholinergic systems which are
jointly involved in regulating sleep. Disturbing this balance may impact
sleep structure integrity (i.e. increased sleep fragmentation, time
awake during the night, and sleep paralysis) and have adverse effects on
health (Biard et al., 2015, 2016; Stumbrys et al., 2012).
Considering
the gigantic amount of scientific evidence linking poor-quality or
insufficient sleep to adverse health outcomes (including shorter life
expectancy), and especially of sleep fragmentation in altered physical
and cognitive health (e.g. Ahuja et al., 2018; Barnes and Watson, 2019;
Bonnet and Arand, 2003; Brauer et al., 2019; Mary et al., 2013;
Mullington et al., 2009; Pichard et al., 2019; Stepanski, 2002; Walker,
2017, 2019), one may seriously question the health consequences of
regularly practicing LD induction methods.
The modified cerebral state during LD
The
experimental investigation of LD is challenging given the difficulty to
get LD in the lab. Indeed, LD is rare and unpredictable even for
frequent lucid dreamers, especially in an unfamiliar experimental
setting. Nonetheless, by applying the method of LD objective detection
(pre-determined ocular signaling, LaBerge and Rheingold, 1991) to EEG
and fMRI, some determined neuroscientists have managed to get a glimpse
of the cerebral correlates of LD. In a pioneering EEG study, Voss et al.
(2009) succeeded in recording the brain activity of three dreamers
while they were experiencing a lucid dream. They observed an increased
activity in the gamma frequency band in the frontal lobe in lucid rapid
eye movement (REM) sleep as compared to non-lucid REM sleep and
concluded that LD constitutes a hybrid state of consciousness in-between
sleep and wake (Hobson, 2009), with definable and measurable
differences from waking and from REM sleep, particularly in frontal
areas. This is coherent with the fact that most LD induction methods
promote an increase of the arousal level during sleep, and suggest that
anything susceptible to awaken the subject gradually, including
nightmares, might favor or induce LD (e.g. Schredl and Erlacher, 2004).
In line with this idea, a case fMRI study showed that lucid REM sleep
was associated with a reactivation of areas that are normally
deactivated during REM sleep, such as bilateral precuneus, parietal
lobules and prefrontal and occipito-temporal cortices (Dresler et al.,
2012). These regions are involved in higher cognitive functions such as
self-awareness and executive functions, and their reactivation during LD
could account for the resurgence of a certain level of self-awareness
and voluntary control (Hobson, 2009; Zink and Pietrowsky, 2015). In
support to this hypothesis, an increased level of self-reflective
awareness during dreaming was induced by fronto-temporal transcranial
alternating current stimulation (tACS) (Bray, 2014; Voss et al., 2014).
This study encouraged people to use tACS to induce LD, which again
raises questions about safety notably of chronically using a method that
affect cortical electrical activity (there are currently no clinical
information on chronic or repeated use of tACS).
Sleep disruption risk due to an increase of LD frequency
In
the case of a spontaneous increased LD frequency without any use of LD
induction methods, one may still wonder what is the impact of
“replacing” a regular sleep stage by a hybrid sleep stage on general
health and notably on the function of sleep, given the well-known
involvement of good sleep in good health and especially of REM sleep in
emotional regulation and memory consolidation (e.g. Perogamvros and
Schwartz, 2013; Plailly et al., in press; Rauchs et al., 2005; Walker
and van der Helm, 2009). Since there are now evidences that the brain is
not functioning in the same way during lucid and non-lucid REM sleep
(Dresler et al., 2012; Voss et al., 2009, 2014), one cannot exclude that
an increase of lucid REM to the detriment of non-lucid REM may alter or
diminish the outcome of regulation processes known to be at play during
non-lucid sleep (Ahuja et al., 2018; Lewis et al., 2018; Perogamvros
and Schwartz, 2013; Tempesta et al., 2018; Walker and van der Helm,
2009).
Discussion
There are several reasons to fear an adverse
effect on sleep and health of a regular use of LD induction methods or
of an increased LD frequency, since 1) LD induction methods alter sleep
integrity, and 2) the brain state during LD is neither that of wake nor
that of REM sleep, but rather a hybrid one that is naturally infrequent.
Such concerns regarding the possible danger of LD training for sleep
integrity are acknowledged on the web. On Google Search’s top listing
(at the time of writing) for “lucid dreaming”, one can read “Another
concern is that engaging in lucid dreaming requires focus and effort,
which might mean that the sleeper does not get enough rest”. Yet, such
acknowledgment are mostly absent from the current scientific literature,
and only a handful of studies have investigated the potential downsides
of LD. The few existing experimental works are not visible and confirm
the feared prediction by showing a significant relationship between LD
frequency and poor sleep quality (Schadow et al., 2018; N=1824).
Similarly, Mota et al. (2016) showed that LD practice may further
empower deliria and hallucinations in a psychotic population.
Our
goal is therefore to draw attention to the fact that, as of today, we do
not have a well-educated and clear idea of the consequence that
training and cultivating LD may have on sleep integrity and more
generally on health. This is even more important to highlight that there
is a tendency in scientific and lay publications towards encouraging LD
and not mentioning the possible side effects of LD training methods
(e.g. Dyck et al., 2017; Hobson, 2009; Mota-Rolim and Araujo, 2013;
Stumbrys et al., 2016). For example, Dyck et al. (2017) encourage to
increase LD induction methods duration without mentioning possible
adverse effect on sleep “Future studies should extend the training
period and increase participants’ motivation by using social media
technology in order to evaluate what techniques might be beneficial in a
home setting for a group of participants not specifically selected for
high interest in lucid dreaming”. One can further read in Mota-Rolim and
Araujo (2013): “LD may allow for motor imagery during dreaming with
possible improvement of physical rehabilitation”, and in Stumbrys et al.
(2016): “Lucid dreaming practice provides a more realistic simulation
of the waking environment than mental practice and could be
alternatively used when an athlete is injured, unable to practice
physically or actions are dangerous […] While only a limited number of
athletes have lucid dreams on a frequent basis, there is a wide range of
techniques that can be used for lucid dream induction”. In these two
latter publications LD is encouraged to achieve what could be done as
effectively by motor imagery during wake (i.e. improved motor
performance, as shown by the authors in Stumbrys et al., 2016), and
without mentioning the possible side effects of LD practice on sleep. LD
is also recommended in several publications (e.g. Morgenthaler et al.,
2018; Mota-Rolim and Araujo, 2013; Sparrow et al., 2018) as a possible
way to diminish nightmare frequency, even though several behavioral
techniques preserving sleep are working very efficiently for this matter
(e.g. Imagery Rehearsal Therapy; Casement and Swanson, 2012; Krakow and
Zadra, 2006; Putois et al., 2019).
Our opinion is thus that one
needs to be cautious and responsible regarding recommendations to
practice LD training methods and a state (LD) whose consequences on
health are unknown and understudied. To improve the safety of
experimental use of LD in research or as a recreational activity, future
studies would need to investigate the above-discussed downsides of LD
induction methods practice and of LD frequency increase, and
characterize them.
Conclusion
In this opinion paper, we draw the
attention to the possible adverse effect of LD on sleep and health.
There are several reasons leading to fear that LD, and especially
training to increase LD frequency, may be detrimental to normal sleep
and notably to the sleep-related regulation processes. Our aim is to
encourage future studies to recognize the lack of knowledge regarding
possible side effects of LD induction methods or LD frequency increase,
as well as to investigate such side effects to better characterize what
they are and in which context they appear.
Raphael Vallat
Perrine M. RUBY
Neuroscience News
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