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The Body Electric
phenomena? Latter-day mechanists have simply postulated brain cir-
cuitry so intricate that we will probably never figure it out, but some
scientists have said there must be other factors.
Even as Loewi was finishing his work on acetylcholine, others began
to find evidence that currents flowed in the nerves. English physiologist
Richard Caton had already claimed he'd detected an electric field around
the heads of animals in 1875, but it wasn't until 1924 that German
psychiatrist Hans Berger proved it by recording the first electroen-
cephalogram (EEG) from platinum wires he inserted into his son's scalp.
The EEG provided a record of rhythmic fluctuations in potential voltage
over various parts of the head. Berger at first thought there was only one
wave from the whole brain, but it soon became clear that the waves
differed, depending on where the electrodes were put. Modern EEGs use
as many as thirty-two separate channels, all over the head.
The frequency of these brain waves has been crudely correlated with
states of consciousness. Delta waves (0.5 to 3 cycles per second) indicate
deep sleep. Theta waves (4 to 8 cycles per second) indicate trance, drow-
siness, or light sleep. Alpha waves (8 to 14 cycles per second) appear
during relaxed wakefulness or meditation. And beta waves (14 to 35
cycles per second), the most uneven forms, accompany all the modula-
tions of our active everyday consciousness. Underlying these rhythms are
potentials that vary much more slowly, over periods as long as several
minutes. Today's EEG machines are designed to filter them out because
they cause the trace to wander and are considered insignificant anyway.
There's still no consensus as to where the EEG voltages come from.
They would be most easily explained by direct currents, both steady
state and pulsing, throughout the brain, but that has been impossible
for most biologists to accept. The main alternative theory, that large
numbers of neurons firing simultaneously can mimic real electrical ac-
tivity, has never been proven.
In 1939, W. E. Burge of the University of Illinois found that the
voltage measured between the head and other parts of the body became
more negative during physical activity, declined in sleep, and reversed
to positive under general anesthesia. At about the same time a group of
physiologists and neurologists at Harvard Medical School began study-
ing the brain with a group of MIT mathematicians. This association was
destined to change the world. From it came many of our modern con-
cepts of cybernetics, and it became the nucleus of the main American
task force on computers in World War II. One of the group's first im-
portant ideas was that the brain worked by a combination of analog and
digital coding.