# Are CNS electric signals AC or DC?

Discussion in 'Electronic Basics' started by Radium, May 11, 2007.

Hi:

Are the electrical currents generated and used by the nervous system
AC or DC? Some sources say DC [like the book "The Body Electric" by
Robert Becker & Gary Selden]; however, the changes in polarity of
those neuroelectric signals would seem to me like they are AC
currents. If an electric current is DC, its polarity does not reverse.

http://www.amazon.com/Body-Electric-Electromagnetism-Foundation-Life/dp/0688069711

Thanks,

2. ### BenjGuest

Actually they are both although when one says "AC" one thinks of pure
sinewave alternating current as in a wall plug. Think about it. A body
consists of chemicals and water in which is dissolved salts. This
means you have the necessary conditions for the construction of a
battery. Cell walls form one of the most common and widespread
batteries in the body. Nervous signals, on the other hand, are
transmitted by "action potentials". These are pulses which may or may
not be bipolar, but that is of no consequence since any pulse can be
Fourier decomposed into various frequencies and a DC term. Thus
nervous signals tend to have a lot of "AC" in them although some such
as brain waves are more "AC" than some others (such as from the
heart...though the baseline can shift on those just depending on where
you attach electrodes. There are also some electromagnetic signals as
well and those generally tend to be classified as "AC".

3. ### Eckard BlumscheinGuest

You might put the same question concerning computers. No reasonable
expert would say computers work with AC. Also, the idea of Fourier
decomposition would sound rather silly if you try to describe the
function of a computer. There are still huge differences between
nowadays computers and the brain. However, computers tend to use lower
voltage and more operations per second. Future computers will perhaps
come closer to the sub 100 mV range of voltage in brain, and will have
more parallel and failure tolerant structures. I do not hope for quantum
computers because putatively achieved entanglement might be a mistake.
Batteries always provide DC voltage, not AC voltage. This is even true
for the battery with the highest voltage within our body being located
within striae vascularis within the organ of Corti. Basilar membrane and
outer hair cells act like an amplifier of alternating mechanical
amplitude. Already the inner hair cells are then performing a subsequent
one-way rectification.

Eckard Blumschein
ovgu.de

4. ### ChuckGuest

As Benj pointed out, the currents may
contain both AC and DC.

It is surprising that Becker and Selden
say the currents are DC.

Changing polarity is one way to
distinguish AC from DC but it is not
always useful.

A more common notion in electronics is
that if a voltage varies in some way
with time, it contains one or more AC
components. These components are often
of major interest to investigators, as
in EEG and EKG analyses.

Chuck

5. ### billGuest

Are the electrical currents generated and used by the nervous system
Signalling traffic is not generally considered to break into dc
or ac, rather into analog or digital. AC and DC are modes of energy
transmission, whereas the signals in the CNS are information
carriers.

6. ### Puppet_SockGuest

The categories analog and digital don't fit very well either.

The nervous system is an evolved system. It has some
features that are elegant and wonderful. It has other
features that are gross kludges that have only been
retained because there is nothing better that is only
a little bit different.

In some cases, electrical behaviour of the nervous
system has a digital character about it. It's "on" or
it's "off." But in other cases, it depends on the strength
of the signal.
Socks

7. ### Don BoweyGuest

On 5/10/07 10:29 PM, in article

(snip)
It most certainly can reverse; it is called a bipolar signal and it has wide
use in electronics.

8. ### Guest

The first thing you have to decide is if you are doing a steady state
analysis or a transient analysis.

In a steady state analysis, if the signal is changing it is AC and
if the signal is constant it is DC.

Therefor something like a digital data stream or the signals from
the nervous system are AC signals with a DC component in the steady
state.

In a transient analysis, DC and AC only make sense in the initial
state.

The initial state of lightning is before the air breaks down and
the arc forms. At that point you have DC.

As the arc forms, everything goes to the transient state and AC/DC
no longer has any meaning.

9. ### Uncle AlGuest

Any pulse shape resolves into a Fourier series of AC inputs.

Idiot.

10. ### Bob MyersGuest

As with most of Radium's posts here, the question itself
is essentially meaningless, or at least implies a far, far too
simplistic a model of the actual system to permit any sort
of simple and yet meaningful answer.

Part of the problem here, at least, is that the "signal" in
question isn't exactly, especially at the macro level, an
"electric current" in anything like the conventional sense
of the term.

Bob M.

11. ### BenjaminGuest

| On 5/11/2007 7:55 AM, Benj wrote:
| > [...]
| >> [...]
| [...]
| [...]

| There are still huge differences between
| nowadays computers and the brain.

Yes.

| However, computers tend to use lower
| voltage and more operations per second.
| [...]

One point of 'contention':

Since every 'ion' and 'atom' in 'the' nervous
system acts as a continuous source of
"operation", the "number of operations'
that're occurring continuously 'within' a
nervous system is uncountably-greater
than the number of "operations" that oc-
cur within any "clocked" system [e.g. all
"computers".]

As you implied in the first statement of
yours that I've quoted above, there exists
no actual means of comparing "brains"
and "computers" -- they're just completely-
different physical systems.

Nervous systems are to computers as
computers are to counting-on-the-fingers-
of-one-hand, only literally infinitely-moreso
be-cause nervous systems function every-
where-continuously -- everything in nervous
systems is continuously-occurring -- there
exist no "dividing lines" 'within' nervous
system function -- and, importantly, these
continuous in-formation-processing
dynamics are continuously-coupled to
the external-experiential environmnets
in which nervous systems' host organ-
isms exist.

With respect to the "AC"-"DC" Q, it's
moot -- the overall continuity is 'DC',
dynamics that are, in effect, 'AC', all of
both 'components' varying in their local
'within' nervous systems.

A nervous system can work on a problem
for 'decades', during which the 'current'
underpinning the problem's existence
'within' a nervous system is =both= 'DC'
and 'AC' [usually a moontonically-increas-
ing 'DC' that's overlaid by a very-dynamic
'AC' with the monotonically-increasing 'DC'
periodically 'converting' to a nonlinearly-
increasing 'DC' [when 'promising-prob-
lem-resolution-paths' are detected], in
the end [if Resolution ever occurs], 'con-
verting' to a monotonically-decreasing
'DC', with the overlaying 'AC' occurring
=throughout=.]

Nervous systems "Know" on the basis
of these currents' relative-correlation to
the one-way flow of energy, from order
to disorder, that is what's =described=
by 2nd Thermo [WDB2T], which is, it-
self, exactly like the 'DC'-'AC' stuff I dis-
cussed in the preceding paragraph, ex-
cept that, =overall=, it is always-mono-
tonically-increasing -- which is how and
why "Knowing" is Possible with respect
to Truth.

Relatively-local WDB2T-variances cor-
relate to local-divergences from Truth.

k. p. collins

12. ### BenjaminGuest

| [...]

| The nervous system is an evolved system. It has some
| features that are elegant and wonderful. It has other
| features that are gross kludges that have only been
| retained because there is nothing better that is only
| a little bit different.
| [...]

Please offer an example of a "gross kludge" 'in nervous
systems'.

k. p. collins

13. ### Rich GriseGuest

Misspelling "clooge" such that it rhymes with "sludge".

Cheers!
Rich

14. ### Bob MyersGuest

Well, let's see - there was the French method, developed
during their Revolution, to add an "off" switch....;-)

Bob M.

15. ### BenjaminGuest

| On Fri, 11 May 2007 18:46:06 +0000, Benjamin wrote:
| > | [...]
| >
| > | The nervous system is an evolved system. It has some
| > | features that are elegant and wonderful. It has other
| > | features that are gross kludges that have only been
| > | retained because there is nothing better that is only
| > | a little bit different.
| > | [...]
| >
| > Please offer an example of a "gross kludge" 'in nervous
| > systems'.
| >
|
| Misspelling "clooge" such that it rhymes with "sludge".

It's 'in' nervous system function, but only
as a consequence of erroneous-program-
ming.

Big-Difference.

k. p. collins

16. ### BenjaminGuest

|
| | > | > | [...]
| >
| > | The nervous system is an evolved system. It has some
| > | features that are elegant and wonderful. It has other
| > | features that are gross kludges that have only been
| > | retained because there is nothing better that is only
| > | a little bit different.
| > | [...]
| >
| > Please offer an example of a "gross kludge" 'in nervous
| > systems'.
|
| Well, let's see - there was the French method, developed
| during their Revolution, to add an "off" switch....;-)

It's 'in' nervous system function, but only
as a consequence of erroneous-program-
ming.

Big-Difference.

k. p. collins

17. ### PegsGuest

Dr. Becker is referring to Analog and Digital control system.
The Digital being the known Action Potentials and the Analog
something about direct currents in the body and semiconducting.
The following are direct excerpts from his works that describes his
experiments and discovery and how he proved it is current and not ions
using some Hall effect tests. Comments welcomed.

Dr. Becker shared his findings in the book "The Body Electric":

"Reasoning that all cells had transmembrane
potentials, Bernstein maintained that, after injury,
the damaged ceil membranes simply leaked their ions out
into the environment. Thus the current of injury was no
longer a sign that electricity was central to life, but
only an uninteresting side effect of cell damage. "

<snip>

"In all the time that the Bernstein hypothesis had been
used to explain away the current of injury, no one had
ever thought to measure the current over a period of
days to see how long it lasted. If it was only ions
leaking from damaged cells, it should disappear in a
day or two, when these cells had finished dying or
repairing themselves. This simple measurement, with a
comparison of the currents in regenerating versus
non-regenerating limbs, was what I planned to do. I
would uniformly amputate the foreleg s of frogs and
salamanders. Then, as the frogs' stumps healed over and
the salamanders' legs regrew, I would measure the
currents of injury each day."
<snip>

"First I found a good supplier of salamanders and
frogs, a Tennessee game warden who ran this business in
his spare time. Sometimes the shipment would contain a
surprise, a small snake. I never found out whether he
included them deliberately or by error. At any rate,
his animals weren't the inferior aquarium-bred stock
but robust specimens collected from their natural
habitats. Next I worked out some technical problems.
The most important of these was the question of where
to place the electrodes. To form the circuit, two
electrodes had to touch the animal. One was the "hot"
or measuring electrode, which determined the polarity,
positive or negative, with regard to a stationary
reference electrode. A negative polarity meant there
were more electrons where the measuring electrode was
placed, while a positive polarity meant there were more
at the reference site. A steady preponderance of
negative charge at a particular location could mean
there was a current flowing toward tha t spot,
continually replenishing th e accumulation of
electrons. The placement of the reference electrode,
therefore, was critical, lest I get the voltage right
but the polarity, and hence the direction of the
current, wrong. Some logical position had to be chosen
and used every time. Since I postulated that the nerves
were somehow related to the current, the cell bodies
that sent their nerve fibers into the limb seemed like
a good reference point. These cell bodies were in a
section of the spinal cord called the b rachial
enlargement, located just headward from where the arm
joined the body. In both frogs and salamanders,
therefore, I put the measuring electrode directly on
the cut surface of the amputation stump and the
reference electrode on the skin over the brachial
enlargement. After setting up the equipment, I did some
preliminary measure ments on the intact animals. They
all had areas of positive charge at the brachial
enlargement and a negative charge of about 8 to 10
millivolts at each extremity, suggesting a flow of
electrons from the head and trunk out into the limbs
and, in the salamanders, the tail. I began the actual
experiment by amputating the right forelimbs, between
elbow and wrist, from fourteen salamanders and fourteen
grass frogs, all under anesthesia. I took no special
precautions against bleeding, since blood clots formed
very rapidly. The wounds had to be left open, not only
because closing the skin over the salamanders'
amputation sites would have stopped regeneration, but
also because I was investigating a natural proces s.
In the wild, both frogs and salamanders get injuries
much like the one I was producing-both are favorite
foods of the freshwater bass-and heal them without a
surgeon. Once the anesthetic wore off and the blood
clot formed, I took a voltage reading from each stump.
I was surprised to find that the polar ity at the crump
reversed to positive right after the injury. By the
next day it had climbed to over 20 millivolts, the same
in both frogs and salamanders .

I made measurements daily, expecting to see the
salamander voltages climb above those of the frogs as
the blastemas formed. It didn't work that way. The
force of the current flowing from the salamanders'
amputation sites rapidly dropped, while that from the
frogs' stumps stayed at the original level. By the
third day the salamanders showed no current at all, and
their blastemas hadn't even begun to appear. The
experiment seemed a failure. I almost quit right there,
but some thing made me keep on measuring.

I guess I thought it would be good practice. Then,
between the sixth and tenth days an exciting trend
emerged. The salamander potentials changed their sign
again, exceeding their normal voltage and reaching a
peak of more than 30 millivolts negative just when the
blastemas were emerging. The frogs were still plugging
away with slowly declining positive voltages. As the
salamander limbs regenerated and the frog stumps healed
over with skin and scar tissue, both groups of limbs
gradually returned (from opposi te directions) to the
baseline of 10 millivolts negative.

Here was confirmation better than my wildest dreams!
research can give-the excitement of seeing something no
one else seen before. I knew now that the current of
injury wasn't due to dying cells, which were long gone
by then. Moreover, the opposite polarities indicated a
profound difference in the electrical properties of the
two animals, which somehow would explain why only the
salamander could regenerate. The negative potential
seemed to bring forth the all-important blastema."

<snip>

"The first order of business was to repeat Burr's
measurements on salamanders, using modern equipment. I
put the reference electrode at the tip of each animal's
nose and moved the recording electrode point by point
along the center of the body to the tip of the tail,
and then out along each limb. I measured voltages on
the rest of the body and plotted lines of force
connecting all the points where the readings were the
tail-positive form, I found a complex field that
followed the arrangement of the nervous system. There
were large positive potentials over each lobe of the
brain, and slightly smaller ones over the brachial and
lumbar nerve ganglia between each pair of limbs. The
readings grew increasingly negative as I moved away
from these collections of nerve cell bodies; the hands,
feet, and tip of the tail had the highest negative
potentials. In another series of measurements, I
watched the potentials develop along with the nervous
system in larval salamander s. In the adults, cutting
the nerves where they entered the legs-that is,
severing the long nerve fibers from their cell bodies
in the spinal cord-wiped out the limb potentials almost
entirely. But if I cut the spinal cord, leaving the
peripheral nerves connected to their cell bodies, the
limb potentials didn't change. It certainly looked as
though there was a current being generated in the nerve
cell bodies and traveling down the fibers. To have a
current flow you need a circuit ; the current has to be
ma de at one spot, pass through a conductor, and
eventually get back to the generator. We tend to forget
that the 60-cycle alternating current in the wall
socket isn't used up when we turn on a light but is
merely coursing through it to the ground, through which
it eventually returns to the power station. Since my
measurements were positive over collections of nerve
cell bodies, and increasingly negative out along the
nerve fibers, it seemed a good bet that current was
being generated in the cell bodies, espec ially since
they contained all of the "good stuff"-the nucleus,
organelles, and metabolic components-while the fibers
were relatively uninteresting prolongations of the
body. At the time, I supposed the circuit was completed
by current going back toward the spine through the
muscles. This was a good start, but it wasn't
scientifically acceptable proof. For one thing, my
guess about the return part of the circuit was soon
dis- proved when I measured the limb muscles and found
them polarized in the same direc tion as the surface
potentials. For another thing, it had recently been
discovered that amphibian skin itself was polarized,
inside versus outside, by ion differences much like the
nerve membrane's rest- ing potential, so it was just
ionic discharges through the moist skin. If so, my
evidence was literally all wet. Much of the uncertainty
was due to the fact that I was measuring the outside of
the animal and assuming that g enerators and conductors
inside w ere making the pattern I found. I needed a way
to relate inner currents to outer potentials. This was
before transistors had entirely replaced vacuum tubes.
A tube's characteristics depended on the structure of
the electric field inside it, but to calculate the
field parameters in advance without computers was a
model. They built a large mock-up of the tube, filled
with a conducting solution. When current was applied to
the model, the field could be mapped by measuring the
voltage at various points in the solution. I decided to
build a model salamander. I made an analog of the
creature's nervous system out of copper wires. For the
brain and nerve ganglia I used blobs of solder. Each
junction was thus a voltaic battery of two different
metals, copper and the lead-tin alloy of which the
solder was made. Then I simply sandwiched this "nervous
system" between two pieces of sponge rubber cut in the
shape of a salamander, and so aked the model in a salt
solut ion to approximate body fluids and serve as the
electrolyte, the conducting solution that would enable
the two metals to function as a battery. It worked. The
readings were almost exactly the same as in the real
salamander. This showed that a direct current inside
could produce the potentials I was getting on the
outside. If my proposed system was really a primitive
part of the nervous system, it should be widely
distributed, so next I surveyed the whole animal
kingdom. I tested flatworms, earthworm s, fis h,
amphibians, reptiles, mammals, and humans. In each
species the potentials on the skin reflected the
arrangement of the nervous system. In the worms and
fish, there was only one area of positive potential,
just as there was only one major nerve ganglion, the
brain. In humans the entire head and spinal region,
with its massive concentration of neurons, was strongly
positive. The three specific areas of greatest positive
potential were the same as in the salaman der: the
brain, the brachial plexus between th e shoulder
blades, and the lumbar enlargement at the base of the
spinal cord. In all vertebrates I also recorded a
midline head potential that suggested a direct current
like that postulated by Gerard, flowing from back to
front through the middle of the brain. It looked as
though the current came from the reticular activating
system, a network of crosslinked neurons that fanned
out from the brainstem into higher centers and seemed
to control the level of sleep or wakef ulness and the
focus of attention.

At the same time, to see whether the current of injury
and the surface potentials came from the same source, I
made electrical measurements on salamander limbs as
they healed fractures. (As mentioned in Chapter 1, bone
healing is the only kind of true regeneration common to
all vertebrates.) The limb currents behaved like those
accompanying re- growth. A positive zone immediately
formed around the break, although the rest of the limb
retained at least part of its negative potential. Then,
between the fifth and tenth days, the positive zone
reversed its potential and became more strongly
negative than the rest of the limb as the fracture
began to heal. Next I decided to follow up Burge's
experiments of two decades before. I would produce
various changes in the state of the nervous system and
look for concomitant changes in the electrical
measurements. To do this right I really needed a few
thousand dollars for an apparatus that could take
readings from several electrodes simultaneously an d
record them side by side on a chart. My chances of
getting this money seemed slim unless I could publish
another paper fast. I decided to use the equipment I
had for a simple measurement during one of the most
pro-found changes in consciousness-anesthesia. Burge
was right. The electrical responses were dramatic and
in-controvertible. As each animal went under, its
peripheral voltages dropped to zero, and in very deep
anesthesia they reversed to some extent, the limbs and
tail going positive. They reverted to normal just b
efore the animal woke up. I had enough for a short
paper, and I decided to try a journal on medical
electronics recently started by the Institute of Radio
Engineers. Although most of what they printed was safe
and unremarkable, I'd found that engineers were often
more open-minded than biologists, so I went for broke;
I put in the whole hypothesis-analog nervous system,
semiconducting currents, healing control, the works.
The editor loved it and sent me an enthusiastic letter
of acceptance, along with sugges tions for further
research. Best of all, I soon got another small grant
approved and bought my multi-electrode chart recorder.
Soon I had confirmed my anesthesia findings, and with
the whole-body monitoring setup I also was able to
correlate the entire pattern of surface voltages with
the animal's level of activity while not anesthetized.
Negative potentials in the brain's frontal area and at
the periphery of the nervous system were associated
with wakefulness, sensory stimu li, and muscle
movements. The more activity, the greater the negative
potentials were. A shift toward the positive occured
during rest and even more so during sleep.

In my reading on solid-state electronics I found
another way I could test for current in the salamander.
Luckily it was cheap and easy; I could do it without
buying more equipment. Best of all, it should work only
if the current was semiconducting. Suppose you think
you have a current flowing through some conductor-a
salamander's limb, for instance. You put it in a strong
magnetic field so that the lines of force cut across
the conductor at right angles. Then you place another
conductor, containing no current, perpendicular to
both the original conductor (the limb) and the magnetic
field. If there is a current in whatever you're
testing, some of the charge carriers will be deflected
by the magnetic field into the other conductor,
producing a voltage that you can measure. This is
called the Hall voltage, after the gentleman who
discovered it. The beauty of it is that it works
differently for the three kinds of current. For any
given strength of magnetic field, the Hall voltage is
proportional to the mobility of the charge carriers.
Ions in a solution are relatively big and barely
deflected by the field. Electrons in a wire are
constrained by the nature of the metal. In both cases
the Hall voltage is small and hard to detect. Electrons
in semiconductors are very free to move, however, and
produce Hall voltages with much weaker fields. After
finding a C-shaped permanent magnet, an item not much
in demand since the advent of electromagnets, I set up
the equipment. I took a deep breath as I placed the
first anesthetized salamander on its plastic support,
with one foreleg extended. I'd placed electrodes so
that they touched the limb lightly, one on each side,
and I'd mounted the magnet so as to swing in with its
poles above and below the limb, close to yet not
touching it. I took voltage measurements every few
minutes, with the magnet and without it, as the animal
regained consciousness. I also measured the DC voltage
from the tips of the fingers to the spinal cord. In
deep anesthesia, the DC voltage along the limb wa s
zero and so was the Hall voltage. As the anesthetic
wore off, the normal potential along the limb gradually
appeared, and so did a beautiful Hall voltage. It
increased right along with the limb potential, until
the animal recovered completely and walked away from
the apparatus. The test worked every time, but I don't
think I'll ever forget the thrill of watching the pen
on the recorder trace out the first of those Hall
voltages

This experiment demonstrated unequivocally that there
was a real electric current flowing along the
salamander's foreleg, and it virtually proved that the
current was semiconducting. In fact, the half-dozen
tests I'd performed supported every point of my
hypothesis.

Scientific results that aren't reported might as well
not exist. They're like the sound of one hand clapping.
For scientists, communication isn't only a
responsibility, it's our chief pleasure. A good result
from a clean, beautiful experiment is a joy that you
just have to share, and I couldn't wait to see these
data in print. I went for the top this time. The
journal in American science is aptly named Science.
Each issue reports on all fields from astronomy to
zoology, so publication means a paper has more than a
specialized significance. Mine was accepted, and I was
jubilant."

18. ### BenjGuest

Actually, "information" related to WDB2T-variances and "truth" are two
different quantities, but that is another issue.

Benj
(Who isn't Benjamin)

19. ### BenjaminGuest

|
| | > | > | [...]
| >
| > | The nervous system is an evolved system. It has some
| > | features that are elegant and wonderful. It has other
| > | features that are gross kludges that have only been
| > | retained because there is nothing better that is only
| > | a little bit different.
| > | [...]
| >
| > Please offer an example of a "gross kludge" 'in nervous
| > systems'.
|
| Well, let's see - there was the French method, developed
| during their Revolution, to add an "off" switch....;-)
|
| Bob M.

BTW, I've long experience being on the
receiving-end of one-bit kill-switches.

Never in History has their 'use' been
so-rampant as here in This Nation
that I Love.

k. p. collins

20. ### BenjaminGuest

|
| Benjamin wrote:
|
| > Relatively-local WDB2T-variances cor-
| > relate to local-divergences from Truth.
| >
| > k. p. collins
|
| Actually, "information" related to WDB2T-
| variances and "truth" are two different
| quantities, but that is another issue.
|
| Benj
| (Who isn't Benjamin)

Nervous systems converge-upon 'mo-
tion' by calculating the anti-WDB2T
Direction.

In so doing, to the degree that they do
so, nervous systems 'move toward'
Truth -- be-cause WDB2T permeates
physical reality in an everywhere-con-
sistent way, so, get-that-straight, and
one simultaneously 'Knows' Truth as
it occurs within physical reality.

I've been discussing what's entailed
for 15+ 'years' here in b.n -- there're
"details" that I don't routinely reiterate
because I write for folks who've been
reading all along [even when I'm cross-
posted to NGs other than b.n.

Seems [to me] that folks're getting-it.

k. p. collins