J Allan Hobson Dreaming, A Very Short Introduction (pdf)

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partially aroused, but still deeply asleep in respect of the upper
brain. We know this from lab studies in which brain waves have
been recorded. The high-voltage slow waves of deep sleep continue
to be recorded while the individual sleep walks. One old wives tale
about sleep walking holds that it is a mistake to wake the person,
usually a young person, up from such episodes. The answer to that
one is to go ahead and try . It is usually impossible, but don t worry
about it because, if you can t do it or if you do succeed in waking
them, there will be no adverse consequence whatsoever.
Post-traumatic dreams
What effect does trauma have on dreams? There are two
paradoxically contradictory answers to this question: enormous
impact and very little. We don t understand why, in some cases, the
trauma is almost always dominant and, in others, it has such a small
role to play in the shaping of dreams. One answer may be that
victims of trauma, e.g. post-traumatic stress disorder patients who
have had violent experiences in war, have a specific kind of
awakening experience. Their sleep is interrupted by terrors akin to
the night terrors of children, and, like in the night terrors of
children, these do not occur in REM sleep when normal dreaming
takes place. Instead, they occur in NREM sleep, the phase of sleep
in which the brain is less completely activated, but in which
powerful emotions can nevertheless make themselves felt.
Individuals who have had intrusive and disruptive trauma may have
intrusive and disruptive emotional experiences during sleep, which
create states of brain activation of their own. This encapsulation of
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trauma leaves intact the normal physiological process of brain
activation in sleep that results in dreaming. This could help us
account for the fact that many individuals who have had traumatic
experiences (and I am one of them) never dream about that
experience at all it just wasn t strong enough to take on a mental
life of its own and it plays very little part in the construction of my
dreams.
I was assaulted on the street by three men and nearly killed by them
my nose was blasted to smithereens and my nasal septum deeply
separated from my skull; I needed painful plastic surgery (without
anaesthesia). But this episode has never appeared in my dreams;
what appears instead are frighteningly aggressive confrontations,
although these appeared before the traumatic event as well as after.
This is not the least bit surprising or unusual. One of the things that
we fear most is being overpowered and assaulted by criminals or
bullies. That has been a part of the fear of my life ever since I was a
young child, so that in my dreams I may have what appear to be
recurrent episodes of confrontation with powerful enemies whom
I am helpless to repulse. I run away and they chase me, and
sometimes they may even catch me, as they did in the real traumatic
event that occurred. But then I wake up. They never go on and
break my nose in the way they did in my real life experience. In fact,
I rarely experience pain in my dreams.
Careful scientific studies of survivors of the Holocaust suggest
that all sleep is invaded by the horrific replay of memories of
experiences. This fact, coupled with the findings of post-traumatic
stress disorder in veterans of military combat, suggests that, just as
waking thought tends to be dominated by preoccupations with
these unpleasant experiences, so does sleep mental activity tend to
be dominated by them.
We now need to carry out studies to find out if awakenings
performed in REM and NREM sleep yield different reports. This is
important, not only to answer the question of how trauma shapes
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Disorders of dreaming
dreaming, but also to answer questions about the function of
dreaming. We still don t understand why the brain self-activates
during sleep, yet evidence suggests that it is certainly not only to
replay previous experience.
REM sleep behaviour disorder
The new kid on the dream disorder block is the REM sleep
behaviour disorder (RBD), a very strange syndrome in which
patients enact their dreams through movement. This is not sleep
walking, although it is what sleep walking was erroneously thought
to be. How does RBD come about?
The inhibition of movement or motor output, which normally
quells the movement commands of dreams, is only quantitatively
greater than the excitation of neurons that is the embodiment of
these commands. If either inhibition declines or excitation
increases, or both, movement will result.
In RBD, individuals (often middle-aged men who will go on to
develop the movement disorder parkinsonism) begin to enact their
dreams. One of my patients flails his arms, and hits his wife, as he
dreams of driving a car and turning sharply on a curve. Another
imagines that he is at a swimming pool and dives off the bed.
In every case, the dream report given by the patient on being
awakened fits with the motor behaviour observed during the REM
sleep dream. We know that these events occur in REM sleep from
sleep lab evidence.
This sounds very much like evidence for the one-to-one theory of
dream psychophysiology, proof of which eluded experimenters
in the 1960s. It also suggests that REM sleep physiology can be
pathologically distorted by inherent degeneration of the brain.
In the case of RBD, the system controlling the neurons
(neuromodulatory system) that is suspect is dopamine, a
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chemical neurotransmitter which has an unclear role in normal
sleep. [ Pobierz całość w formacie PDF ]

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