MOTION MOUNTAIN

254 7 the story of the brain
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Many modern research results on animal and human brains can be found at the Brain
Map website, available at www.brain-map.org.
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Brains and computers differ markedly in the way they work. Brains are analog, computers
are digital. How exactly do computers work? The general answer is: computers
are a smart and organized collection of electrical switches. To make matters as easy as
possible,thecalculationengineinsideacomputer–theso-calledcentralprocessingunit,
the heart of the computer – calculates using binary numbers. The ‘on’ and ‘off’ states
of a switch are associatedto thedigits ‘1’ and ‘0’. Can you devise a simple collection of
switches that allows adding two binary numbers of one digit? Of many digits? And to
multiply two numbers? Try it – it is an interesting exercise.
Computers are called digital because they are based on switches. Indeed, all integratedcircuitsinsideapocketcalculatororinsidealaptoparejustcollectionsofelectrical
switches;modernspecimencancontainseveral millions of them, each switch with a specificfunction.
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During pregnancy, the brain of the embryo grows at a rate of 250000 neurons per
minute. Therateshowshowfascinatingaprocesslife is.
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Thesignalcommunicationbetweenthebrainandthearmsdiffers fromthesignalcommunicationbetweenthebrainandthelegs.Whenthebrainsendsacommandforsome
arm or leg movement to the spine, the spine then in turns sends its to the arms or to
the legs. For the arms (and hands) – but not for the legs – the spine sends a copy of the
command it is sending there back to the brain. This feedback seems to allow the brain
to specify its next motion command more precisely. Thus the body and the brain are
hard-wiredforthefinemotorskillsthathelpustouseourfingersandhandsasprecisely
as possible. The importance of the fine motor skills was already known to the ancient
Greeks;Anaxagorassaidthathumansarethemostclever living beings because they have
hands.
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Epilepsy is a group of brain disorders that affects a large percentage of the human population.
Epilepsy isan electricmalfunctionof thebrain. It leadsto regular electrical oscillations
inside the brain, during which the person loses awareness or even gets fits.
Epilepsy is also one of the reasons for autistic behaviour. Epilepsy can be triggered by
genetic defects, by injuries and by other causes. Research in epilepsy is a vast field.
Many genetic types of epilepsy are due to mutations in genes that code ion channels.
When ion channels do not work properly, the concentration of cations such as sodium
does not behave properly, leading to the electric malfunctions. Research into the origin
of epilepsy has shown that some genetic mutations are not inherited from the parents,
but aredenovo: they appear only in the child.
Motion Mountain – The Adventure of Physics copyright © Christoph Schiller June 1990–November 2015 free pdf file available at www.motionmountain.net