Order
and disorder in the brain
The function of the brain was developed for the survival of
the human species on this planet. We do not know how the brain
has emerged nor how it functioned when it commanded the actions
of our remote ancestors. We may at most guess a mutation that
favored the emergence of Homo sapiens somewhere in the line
of the great apes. With the last mutation, the probability
of speech appeared but we do not know, more recently, when
men created the first signs of what was to become language.
In this Homo sapiens, the EEG and other physiological endpoints
such as the eye movements and the activity of the muscles
evidence the states of consciousness.
The
brain is one of the most complex systems encountered in nature.
It is made of billions of cells endowed with individual electrical
activity and interconnected in highly intricate networks.
The average electrical activity of a portion of this network
forms the electroencephalogram (EEG). The interest in studying
it as a function of the development of intelligence has been
spurred by the need to understand how the brain responds to
environmental information.
Decades
ago, this problem was first met as a natural history, with
the description of the sleep patterns in mentally handicapped
children in whom some repetitive patterns, such as the spindle
waves in the EEG and the rapid eye movements of REM sleep
appeared to be particularly altered when compared to normal
children. Today the early descriptions have been confirmed
with more sophisticated means. It appeared that the repetitivity
or redundancy is a brain mechanism that may serve for adjustment
to changes in the environment.
The traditional method of eye balling the EEG does not allow
to detect particular types of oscillations among its many
wave forms but other more recent methods deriving from the
analysis of chaotic systems, namely the dimension of its strange
attractors, allow to detect immediate changes in the EEG dynamics.
Attention was paid to two physiological endpoints, the waking
EEG and the patterns of the eye movements during sleep, for
they are reflecting underlying brain mechanisms associated
with learning. Sleep has fascinated the scientific community
for several decennia. It was popularized by its pioneers,
William Dement in the U.S.A. and by Michel Jouvet in France.
As from 1962, a small European team studied the dynamics of
the eye movements of REM sleep. It showed that, when learning
is impaired, the eye movements are decreased in number during
REM sleep and their distribution is mainly random.
Memory
is an important parameter in the learning process and it appears
that, in the mentally handicapped, the two kinds of memory,
the long and the short term one, are altered. Their networks
are widely distributed in the brain and are involved in the
production of the EEG spindles. Therefore their distribution
is also altered in the mentally handicapped. The two types
of sleep signals, the eye movements of REM sleep and the EEG
spindles, belong to similar logical functions. No wonder that
they are associated with learning in a different but complementary
way and that their alterations are correlated with mental
retardation. In these patients, the appearance, out of chaos,
of the order that is needed for intelligence and memory to
function, is altered.
This
alteration is present as from birth in Down' syndrome babies
who will be retarded. If, during the baby's sleep, the distribution
of the eye movements of REM sleep remains random, intelligence
will not develop. The same is true when the signals appear
in long sequences of uninterrupted bursts of eye movements
or waves as in epilepsy. Interestingly enough, studies of
sleep of pregnant women have shown that the patterns change
as a function of term and that, as from the 7th month of pregnancy
they evidence similarities with the eye movement patterns
of sleep in the premature baby of a similar gestational age
as if her brain was in resonance with the brain of her fetus.
The nature of the information transmitted between the pregnant
woman and her baby is unknown. It is believed that this information
is genetic, that it is the memory of the species that passes
from the mother to her fetus, in the way of a code. One cannot
rule out a link between the brain function of the pregnant
woman and a cell memory of which the elements, like antigens,
cross the placental barrier and cause cell links to become
established in the fetus.
Already
before birth, brain waves appear in the fetus. Their pattern
will change with maturation We have no way of knowing the
sensory content of the baby's brain but it would be presumptuous
to assume that there is none. Sometimes in adults, the physiological
endpoints of sleep are dissociated and their recombinations
resemble those found in newborns. These states are associated
with vivid hallucinations. They look like intrusions into
wakefulness of the states of sleep and dreaming. Their sleep
characteristics resemble those of premature and newborn babies.
The question arises whether there is a similarity between
the sensory world of the baby and the hallucinations of subjects
whose sleep parameters are dissociated. Are the hallucinations
associated with narcolepsy and cataplexy a physiological memory,
that of an epoch of one's life where the perceptions of time
and space are still absent, of a primary universe that will
eventually lead to the intellectual and critical universe
of the waking adult? One may wonder whether a brain function,
which is still devoid of time structures, cannot but be associated
with images, which are likewise devoid of time references.
It may lay the ground for human imagination, evolving into
legends and thought.
When
establishing a relation between some sleep patterns and learning,
one has to look into a periodic activity during wakefulness,
which may be equivalent to REM sleep. A candidate for this
equivalence is attention. When the organism is solicited by
stimulation, it turns towards the source of it. The physiological
basis of attention is associated with a specific brain activity
bound to wakefulness and occurring periodically during the
day. It is obvious in the cat. When its attention is aroused
by a bird or a mouse, it will remain motionless for some time
before attacking its prey. In a laboratory situation, which
limits his movements, it will turn the head and the eyes towards
the source of the stimulation. Attention is to wakefulness
what REM sleep is to sleep. In the cat, attention is linked
with a program that drives him to hunt birds and mice in order
to survive. In human it is the drive to hominisation that
drives him to pay attention to others in order, first, to
explore his physical and cultural environment, then the whole
of reality.
The
ratio between order and disorder in the signs of REM-sleep
increases in men and in women alike, from birth until 50 years
after which age it is stabilized. In women, periodical changes
occur in this ratio every two weeks, at the turning points
of the hormonal cycles. In the course of the increasing order
with age, there may be jumps in opposite direction, from a
more to a less organized state suggesting an error in the
information. Periods, in which the activity of the brain is
temporarily disorganized only to be reorganized again, run
through life. The rate of alternation is higher in the infant
and becomes lower with age. They are determined by laws, which
we still ignore. One could imagine that epochs of reversed
entropy of the brain functions are connected with what we
call 'time'.
The
last facts evidencing the learning function of the brain concern
the results of brain recordings of astronauts working and
sleeping in space. The sleep recordings made during the spacelab
1 flight in 1983 disclosed a pattern in the eye movements
of sleep that clearly differs between the first and the second
night in-flight, and clearly evidenced a similar pattern across
the first two nights post-flight. These challenging results
led the author to complement them with further experiments
on the EEG in weightlessness, during wakefulness, such as
they occur during short periods of microgravity. They were
performed on board research aircraft flying parabolic trajectories.
Results obtained by using the strange attractor dimension
imply for the neural processes involved in learning that the
normal healthy central nervous system can preserve intact,
from input to output, over a period of several days, all the
information it receives.
The
quantum approach can also be used as a medium between the
information and the way of describing it. It is usual at the
atomic and subatomic level of matter. At the level of the
EEG, this theory can be applied to the sleep spindles only.
However it makes coherent the learning function theory of
sleep where the sequential association of spindle sleep and
REM sleep supports the idea of memory carrying particles of
spindle waves allowing the eye movements of REM sleep to code
more fundamental elements such as the insertion of recent
events at short term in a vast array of emotional strategies.
Abstract
online: Expected date August 20, 2003
Issue
is released in August 2003
Vol. 24 Nos. 3/4, 2003
Neuroendocrinology Letters www.nel.edu
More
information available: publisher@nel.edu
