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The Fate Of Man In A Scientist-technological Era
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1.2 Chemistry of the Brain
The
human brain can be described as two handfuls of tissue, which weighs a
little more than 1.2kg with colour and pulp-like substance responsible
for man’s feeling, speaking, seeing, smelling, remembering, engaging in
sexual union and other activities that characterises the daily human
life.
The human brain indeed contains about ten thousand million
nerve cells. Thus, in comparing the computers to human brain, Denis
Alexander avowed that “the biggest computers ever built manage less than
a hundred units unlike the human brain that contains ten thousand
million cellsâ€8.
Initially, brain research was the major
preoccupation of Neuro-physiologists, those who are primarily concerned
with the electrical activities of the brain. In 1974, Sir John Eccles of
Buffalo University used a microelectrode less than a thousandth of
millimetres in diameter to explore the electrical behaviour of
individual neurons in living cat brains. However, in not more than ten
years of this discovery, it was also discovered that “if the electrical
activity of individual neurons varies so much, it is also likely that
their chemistry varies as wellâ€9. Thus, among the complex task of
biochemistry in the early seventies, was to find out the disparities in
chemistry between the ten thousand million nerves contained in the
brain.
There has been a tremendous increase in our knowledge of the
structure and chemistry of the brain. Our detailed knowledge of the
brain chemistry makes it inevitable that new and more sophisticated
drugs are produced to exert certain effects on man’s behaviour. The
implantation of electrodes in the brain, which was initiated by Dr. Hess
in 1928, now serves as a routine procedure. This is a situation where a
hole is made in the skull of the animal or man, and a fine metal
planted in specific areas of the brain. Through these electrodes,
simultaneous electrical recording can be done while the animal or person
moves freely to wherever (it) he chooses. Even the cerebral areas
related to pain, pleasure, eating, sexual gratification and learning
have all been detected through this medium. It was equally ascertained
that electrodes could be used not just for picking up electrical
activities alone but also to stimulate specific regions of the brain.
Before
delving into the interpretive cortex of the brain, it is nice to
highlight some diffuse pathways in the human brain. There is what is
known as the cholinergic pathways, which regulate attention, learning
and memory function. In other words, a projection from the nucleus
basalis of Meynert
provides the cholinergic input to the cerebral
cortex. The medial septum in turn provides cholinergic innervations of
the hippocampus.
The Dopamine pathways also regulate movement,
cognition, learning and memory function. Hence, a projection from the
substantia nigra provides dopamine input to the neostriatum. Then the
ventral segmental area supplies dopamine for the cerebral cortex and the
limbic system. These activities of the brain are not unconnected with
its plasticity. According to Malcolm Jeeves “the most characteristic
features of the brain is its plasticityâ€10. The absence of this plastic
nature of the brain will result to inability of the human brain (man) to
learn or memorize something. Man’s response or adaptation to his world
and its changing circumstances will be impossible.
The Serotonin
pathways play important roles in mental health. So it is discovered that
projections from the brainstem raphe nuclei innervate a wide variety of
brain regions. Therefore, Serotonin is implicated in the etiology of
depression and hallucinogenic agents such as LSD, and mescaline equally
plays their role.
According to professor Giles Brindley of the
Institute of psychiatry in London, “Electrodes are being planted in
human brains for very different purposesâ€11. He explained that a wide
range of wires could be planted in the back of the brain, which receives
signal from the eyes. He also noted that photo-electric cell devices
can be used to convert light waves into electrical impulses which has
the feasibility of giving blind people the ability to recognize objects
and possibly to read. Enumerating various researchers on the brain will
not be complete without some theories on memory. This has been a
fascinating thing about the human brain. How do we store information and
then recall it in years later? Infact, how do we remember? According to
Prof. Penfield, “memory is an area of the brain called interpretive
cortexâ€12. From experiments made, he opined that man has the potential
to recall any past experiences. He went on to say that any theory of
memory must provide for the storage of a directional, sequential series
of events complete with sound, vision and colour. However, this
assertion has led to many theories about the memory though we shall not
be delving into them now. From the researches made so far, it has also
been discovered that the vital region of the brain called hippocampus,
is responsible for short-term and long-term memory
It is quite
evident that some big steps have been made in brain research but we are
not going into details so as to focus on the scope of our study.
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