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Does our I-function sleepwalk?
There are countless stories of sleepwalkers suddenly waking up and finding themselves naked in their backyards. Between 1 and 15% of the population are prone to sleepwalking, which involves people getting up and walking around while asleep and often doing bizarre things (1). Frequent sleepwalking can lead to health problems since it interrupts normal patterns of sleep. But what causes sleepwalking and are there ways to control it? How does this relate to the structural mechanisms of neurobiology that we have learned over the semester?
Sleepwalking (also know scientifically as
somnambulism) is defined as a series of complex behaviors that are
initiated during partial awakenings from sleep. People walk around in a
state, which is of partial consciousness and often exhibiting impaired
judgment. Knowledge about sleepwalking is quite limited-however various
scientists have found that many diagnosed with sleepwalking experience
disruption of slow-wave sleep. This is categorized as the deepest stage
of sleep. With each of these disruptions there is an increasing
vulnerability to sleepwalking.
The vast majority of sleepwalking cases have genetic basis. Sleep
walking in children is considered a relatively common developmental
phenomenon. In adulthood, in addition to genetics, various conditions
can predispose someone to sleepwalking, such as hyperthyroidism,
migraine headaches, head injury and encephalitis. Also it has
been found that some psychiatric medications such as lithium and
amitriptyline can increase sleepwalking (1).
It is probably considered more common that children
sleepwalk because they have not fully developed and therefore their
I-function has not necessarily fully gained control of it signal
sending yet. It could also be related to other parts of the brain not
being fully developed which can restrain the children necessarily from
certain actions. This may have something to do with the part of the
brain that has control of whether a child can control their bladder or
not during the night-resulting in bed-wetting.
Neurologist Antonio Oliviero of the National
Hospital for Paraplegics in Toledo, Spain, explains that sleep
disorders such as sleepwalking can arise when normal physiological
systems are active at inappropriate times. He further argues that there
is no precise explanation as to why the brain may still issue commands
to the muscles during certain phases of sleep. However it is known that
usually such commands are suppressed by other neurological
mechanisms-perhaps the suppression is incomplete (2).
It is quite possible that during sleepwalking the
I-function is activated and not successfully blocking or controlling
signals that it would usually pass on in the 'awakened' state of the
body. Studies have proven that while we sleep there is in fact some
brain activity. Therefore the effects of sleepwalking may arguably be a
result of the control of the I-function of sending certain signals to
the motor neurons.
Recently Oliviero's team has proposed a possible
physiological mechanism underlying sleepwalking. During normal sleep
the chemical messenger gamma-aminobutyric acid (GABA) acts as an
inhibitor that stifles the activity of the brain's motor system. In
children the neurons that release this neurotransmitter are still
developing and have not yet fully established a network of connections
to keep motor activity under control. As a result, many kids have
insufficient amounts of GABA, leaving their motor neurons capable of
commanding the body to move even during sleep. In some, this inhibitory
system may remain underdeveloped-or be rendered less effective by
environmental factors-and sleepwalking can persist into adulthood (2).
75% of sleepwalking episodes occur during non-REM
sleep (3). The first episode of REM sleep occurs about 90 minutes after
the beginning of the sleep episode, and then recurs about every 60 to
90 minutes thereafter, lasting a short time at each occurrence.
One particularly interesting feature of REM sleep is that
electroencephalography measurements (EEG) during this time are
remarkably similar to when an individual is awake. EEG
measurements then transition back into the "asleep" range when the
individual abruptly resumes non-REM sleep.
Thus, sleepwalking has been hypothesized as
originating from some sort of incomplete transfer from brain functions
characteristic of "asleep" EEG frequency to those of an "awake"
frequency. The brain is in limbo between the state of being
"awake" or being "asleep". Brain areas have different functions based
on the current state of consciousness, and different types of activity
may lead to different outcomes as a result. This sparks new insights
regarding the I-function and whether the I-function has the capability
to determine the context in which it may be giving orders to the rest
of the nervous system. There are already observations that support the
idea that indeed there is brain activity, now it is whether that brain
activity necessarily is the I-function, and whether whatever active
part of the brain is capable of being limited or has ability to
determine reality from a dream.
Resources:
1)
http://www.firstscience.com/home/articles/humans/science-of-sleepwalking_25778.html,
Hayley Birch, "Science of Sleepwalking", 11 May 2007.
2) http://www.sciam.com/article.cfm?id=why-do-some-people-sleepwalk,
Scientific America: By the Editors, "Why Do Some People Sleepwalk?",
January 2008.
3) "Parsomnias: Managing bizarre sleep-related behavior
disorders", Carlos H. Schenck, MD; Mark W. Mahowald, MD.Vol. 107, No.
3, March 2000, Postgraduate Medicine , 145-56.
Comments
bedwetting sleepwalking
Through my years as an enuresis treatment specialist, I have found some interesting similarities to what you describe above, in patients that exhibit bed wetting problems. It was interesting reading about REM and non-REM sleep and the distinctions here.
Sleep walking and the I-function