Google Answers Logo
View Question
Q: Electrical stimulation of skin sensory nerves ( Answered 5 out of 5 stars,   0 Comments )
Subject: Electrical stimulation of skin sensory nerves
Category: Science > Biology
Asked by: skaven252-ga
List Price: $15.00
Posted: 13 Feb 2003 11:51 PST
Expires: 15 Mar 2003 11:51 PST
Question ID: 160985
As far as I remember, it was discovered back in the 60s that a
precisely modulated high-frequency electrical signal can be used to
override the body's muscle nerve channels and cause the muscles to
contract or relax involuntarily. This effect is nowadays utilized in
various exercise devices that make the muscles "work themselves out"
without conscious participation by the user, and is being reseatched
for a non-lethal painless stun gun called the Tetanizer

However, what I'd like to know, is whether similar modulated signals
could be used to stimulate the sensory nerves on the skin, causing
sensations of touch, pressure, heat or cold? Is this physiologically
possible, or do the nerves only work "one way" so that the stimulation
would actually have to take place in the brain?

Some history and details on the muscle stimulation effect would also
be appreciated.

(I wrote a science fiction story where this was the fictional part,
and I began to wonder how fictional it actually is)
Subject: Re: Electrical stimulation of skin sensory nerves
Answered By: kyrie26-ga on 15 Feb 2003 11:46 PST
Rated:5 out of 5 stars
Hello skaven252-ga,

Thank you for your question! I am a reader of science fiction and I
found this topic very interesting so I thought I'd answer it.

First of all, some history and details on Electrical Muscle
Stimulation :


History and Overview of Functional Electrical Stimulation

"Electrical stimulation was first used for medical purposes almost
2000 years ago. Torpedo fish, or electric rays, have special organs
that produce an electric charge. As early as 46 A.D., these fish were
used to dull pain associated with headaches, gout, and hemorrhoids.
Later they were also used to treat sufferers of migraines, melancholy,
and epilepsy. Since the invention of the electrostatic generator and a
manner to store such energy, the medical applications of electricity
have significantly increased in number and complexity. From the
mid-1700s through the present, many different maladies have been
treated through electric shock and other electrical applications."


Electrical Muscle Stimulation by Tibor Hortobágyi, Ph.D.

"Today, however, stimulating current is passed onto the motor nerve
via intramuscular or over-the-skin electrodes of different size and
material.  With experience, researchers also noted that, peculiarly,
it was easier to elicit a muscle contraction if the electrodes were
placed at a discrete location on the skin over a particular muscle. 
Mapped for all accessible muscles of the body, these sites were termed
"motor points", the greatest concentration of muscle-nerve junctions
in the superficial layer of muscles.  Even if stimulated exactly above
the motor point, a muscle's force production varies according to
stimulus parameters such as the type, size, placement, and
configuration of electrodes and whether voltage or current is
controlled.  The manipulation of the stimulus wave-form (rectangular,
sinusoidal, triangle, symmetric, asymmetric, etc.) and its duration,
amplitude, and frequency are all factors to consider for the
reproduction of the physiological coupling of muscles with nerves."


Pain Management Technologies - Tens, Tens Unit, Tens Device,
Transcutaneous Electrical Nueral Stimulation

"E.M.S. stands for Electrical Muscle Stimulation. EMS is predominately
used by doctors and physical therapists to prevent, or reduce, muscle
atrophy. Atrophy is the weakening and loss of muscle tone, which is
usually experienced after surgeries or injuries. EMS has proven to be
an effective means of preventing muscle atrophy. Doctors also see EMS
as a means of increasing blood flow to muscles, increasing range of
motion, increasing muscle strength, as well as enhancing muscle
endurance. EMS will have pain management attributes in regards to
muscle related pain, such as a spastic muscle, sore muscles, or tight
muscles. A TENS device is more suited for nerve related pain
conditions (acute and chronic conditions)."


Then, we look at the whole mechanism of sensation and how the brain
interprets stimuli :


About Senses Activity: Sensing the World Around Us

" Steps in Sensing 
1. A stimulus acts on the nerves in one of the sense organs. 
2. Nerve impulses from the sense organ travel to the brain. 
3. While in the brain, the impulses are interpreted as a feeling or
4. A message is then sent back to the sense organ. Even through the
brain interprets the impulses, the feeling or sensation actually
happens in the sense organ. "


Human Body

"The sense organs are a collections of receptor cells. These recepetor
cells include mechanoreceptors (sense of touch), photoreceptors
(intensity and color of light), thermoreceptors (heat and cold),
chemoreceptors (taste and smell); and pain receptors which react to
tissue damage. A stimulus (such as a cold breeze, a hot cup, a sharp
prick with a needle, a bright light) cause receptor cells produce
electrical activity which is taken by means of specialized nerve cells
called conductors to the brain, where it is processed. The brain then
sends signals to effectors, nerve cells that carry the messages to
targets such as muscles and glands. Muscles contract and glands
secrete hormones or other substances in response to the signals. These
effects cause a feeling or a sensation. Even through the brain
interprets the impulses, the actual feeling or sensation happens in
the sense organ."



[begin excerpt]

10.2  Receptors and Sensations (p. 262) 

A. Each receptor is more sensitive to a specific kind of environmental
change but is less sensitive to others.
B. Types of Receptors (p. 262) 
  1. Five general types of receptors are recognized. 
   a. Receptors sensitive to changes in chemical concentration are
called chemoreceptors.
   b. Pain receptors detect tissue damage. 
   c. Thermoreceptors respond to temperature differences. 
   d. Mechanoreceptors respond to changes in pressure or movement. 
   e. Photoreceptors in the eyes respond to light energy. 
 C. Sensations (p. 262) 
  1. Sensations are feelings that occur when the brain interprets
sensory impulses.
  2. At the same time the sensation is being formed, the brain uses
projection to send the sensation back to its point of origin so the
person can pinpoint the area of stimulation.

[end excerpt]


Sensory Physiology

[begin excerpt]

I.  There are 4 steps associated with sensation: 

 1)  Stimulus sufficient to evoke a response from the afferent must be
          = A detectable physical or chemical change 
                  -  Exist in various forms = modalities 
                           Ex. temp., light, sound, pressure, chemical
                  - modality to which a receptor is most sensitive =
adequate stimulus (normal stimulus)

 2)  Transduction 
          = Receptor  responds to the stim. by opening ion channels 
                -> receptor potential (graded)=> APs 
                      Ex. Eye afferents transduce light into nervous

      • Note:  Receptor Potential is graded like epsp's: 
               => incr stim.(intensity) = incr. depol. = incr  # of

 3)  Electrical signals (APs) are conducted to the CNS 

 4)  Perception  = CNS interprets these electrical signals 

[end excerpt]


Based on this, we can conclude that Electrical Muscle Contraction
works differently from the brain sensation-interpretation mechanism.
EMS is focused on sending messages to the muscles to get them to
contract and relax, while the brain sensation mechanism works as
follows :

(1) There is a stimulus at the skin (transduction).

(2) There is an electrical current generated that is sent to the
central nervous system (brain).

(3) The signal is sent back to the point of stimulus and physiological
changes are registered.

So in answer to your question, theoretically, in order for us to
"simulate" the above mechanism, we would have to pick a point of
entry. Since you are trying to simulate sensation using electrical
signals, the best place to pick would be (2). Let's assume, in a
science fiction world where technology has no limits, that there was a
device that could :

(1) Bypass the neuroreceptors (transducers) and generate the
electrical signal going to the brain by accurately creating the
electrical current in the correct amplitude and frequency (think Morse
code), and any other parameters that may be relevant.

(2) Be able to do this for the whole range of sensations, taking into
account all factors, for instance, for Pressure : (a) area/shape of
effect, (b) intensity, (c) duration, and any other factors. Think,

(3) Be able to "know" where the signal entrypoints (think onramp) are,
and generate a micro-electrical field to "insert" the signal there.
Given this is science fiction, we can assume a sophisticated enough
device that can scan and "sense" the area of effect and locate these
nerve channels, and be refined enough to generate a micro signal that
does not affect anything else.

In other words, yes, it is theoretically possible, and very plausible
for science fiction.

Google Search Terms :

electrical muscle stimulation history

electrical muscle stimulation details

brain interprets sensation touch pressure heat OR hot cold

I hope this was a satisfactory answer. If anything is unclear, please
do not hesitate to post a Request For Clarification and I will be glad
to assist. Thank you for using Google Answers!



Request for Answer Clarification by skaven252-ga on 15 Feb 2003 13:36 PST
Thank you for your thorough answer. It clarifies the issue quite far.
However, I'd still like to know, how accurate does the location of the
electrical field have to be, to cause a sensation?

As far as I know, the muscle stimulation can be used rather
indiscriminately. A bit stronger signal spread over a larger area with
a simple skin contact electrode can relax or contract all muscles in
the area. The Tetanizer can render the entire body limp with a couple
of contact points without affecting any other nerves (in fact, even
the heart continues to operate, because it uses a different signal).

Does this also apply to the sensory nerves? Can you create a crude
skin contact electrode to cause a sensation of heat/cold/pressure over
a large area of skin, or would you need a precise micro-field to
pin-point each nerve channel individually to actually send the signal
to the brain?

Also, is it correct to assume that each nerve type has its own
specific signal (code, if you will), so a signal meant to cause one
sensation does not affect the other nerves, even if the signal spreads
across a wide area?

The reason I'm asking is because my story takes place in very near
future, so the solution has to be technically simple. It has to work
without nanotechnology and cybernetics. (the gizmo in the story is a
full-body suit used to enhance a virtual reality / video game
experience. I'm currently in the process of translating the story to
English. If you are interested, I can send it over when it's finished)

Clarification of Answer by kyrie26-ga on 15 Feb 2003 14:41 PST
Hi again skaven252-ga,

Yes, the approach I'm suggesting would require a precise micro-field.
Given that the science of accupuncture is thousands of years old and
that the Chinese have been able to map the "energy meridians" of the
human body, I'm guessing that it shouldn't be too far off to be able
to map all the nerve pathways. Given that your story deals with a
full-body suit, no problem - the suit would perform a "calibration"
procedure to find the exact locations of all the nerve pathways. This
calibration data would be unique to the wearer, and could be stored in
a database to be called up everytime the wearer put on the suit. The
wearer could be identified by DNA or any other biometric means.

As for the actual mechanism involved, have a look at the following
article :


An Investigation of Current Virtual Reality Interfaces

" The texture of a surface is probably the hardest feature of tactile
feedback to simulate. The closest documented attempt is the Sandpaper
system. This system, developed by a research group which includes
members from MIT and UNC, can accurately simulate several different
grades of sandpaper [1]. Other systems, like the Teletact Commander,
use either air-filled bladders sown into a glove, or piezo-electric
transducers to provide the sensation of pressure or vibrations. These
systems have problems with the unreliability of compressors and
interference between the piezo-electric transducer electromagnetic
fields and the electromagnetic field used by a Polhemus tracking
system [16].

Any attempt to model the texture of a surface faces tremendous
challenges because of the way the human haptic system functions. There
are several types of nerves which serve different functions,
including: temperature sensors, pressure sensors, rapid-varying
pressure sensors, sensors to detect force exerted by muscles, and
sensors to detect hair movements on the skin. All of these human
factors must be taken into consideration when attempting to develop a
tactile human-machine interface. "


The key here is "piezo-electric transducer". I'm guessing that this
will have progressed very much in the near future, enough to have a
convincing effect. Considering that you're talking about a full body
suit, the cold and hot sensations could be handled "at the gate", ie.
why not generate REAL temperature sensations at the corresponding
locations on the suit, and for pressure etc., use the piezo-electric
transducer method. This would pretty much cover (no pun intended)
everything for this purpose.

Here are some more interesting and relevant articles :


Use of a haptic device by blind and sighted people perception of
virtual textures and objects - Colwell, Petrie, Kornbrot, Psychology,
Hertfordshire, Hardwick, Furner, plc, Laboratories (ResearchIndex)

"This paper describes a series of studies involving a haptic device
which can display virtual textures and 3D objects. The device has
potential for simulating real world objects and assisting in the
navigation of virtual environments (VEs). Three experiments
investigated: (a) whether previous results from experiments using real
textures could be replicated using virtual textures; (b) whether
participants perceived virtual objects to have the intended size and
angle; and (c) whether simulated..."


THE USE OF Bio-Electromagnetic Energy Regulation Therapy THERAPY FOR

" The application of pulsed electromagnetic field, like the
Bio-Electromagnetic Energy Regulation Therapy signal, to painful sites
causes the membrane potential to be lowered to a level of about –90mV.
When a pain signal is detected, the voltage must now be raised to a
relatively higher level in order to transmit the signal. The change
required is too great and the trigger voltage needed to release the
transmitter is not reached. Hence the pain signal is blocked.

The Bio-Electromagnetic Energy Regulation Therapy emits the precise
frequency and pulse rate of the electromagnetic signal needed to
produce these desired results. "


Virtual Reality

"A force display is one in which touch information is synthesized by
producing forces on the skin of the operator. However, the touch
sensation is extraordinarily complex, involving sensitivity to small
shear forces in the skin as well as pressure sensors in the skin and
in the joints [MacKenzie, 1994]. The present state of the art with
such devices is mostly confined to the production of forces based on
the position of the manipulator, typically over a small range of
motion and with only two or three degrees of freedom. Thus it is
possible to simulate forces on the hand when manipulating some
abstract object such as a virtual molecule, but this is a far from
stimulating the full range of touch sensations. Indeed there appears
to be no physical means by which a complex tactile stimulus can be
delivered except in a very localized way. This is probably the biggest
obstacle to the full implementation of the virtual reality concept. We
can construct a world that we can see and hear but not touch, except
in rudimentary ways. The construction of force output devices is
extremely technically demanding. They must be stiff in order to be
able to create the sensation of solid contact, light so that they have
little inertia themselves, and there must be a tight loop between
input (position) and output (force). Sigoma has suggested that having
this loop iterate at 5 Khz may be necessary for optimal fine motor
control [Sigoma, 1993]. These high frequencies are necessary to
simulate contact with a solid inelastic surface. Nevertheless, it has
been shown that force feedback improves performance in certain
telerobotic applications when, for example, inserting a peg into a
hole [Sheridan, 1992]. There is little doubt that the use of force
output has potential for applications such as arthroscopic surgery and
telerobotics. It may be only a matter of time before we can touch the
windows and text on the screen of the display."


Only a matter of time...

In answer to your question, good idea - if you really think about it,
after a signal gets sent by the receptor/transducer, how does it
differ from signals for another type of sense? I doubt there are
specialized nerve pathways - ie. pathways for temperature vs. pathways
for pressure. They use the same nerve pathways, especially when you
move beyond the skin receptors. So it makes sense that it would have
to be the "contents" of the signal (ie. modalities like amplitude,
frequency, pattern) that differentiate these sensations. I'm sure it
would be possible in the near future to model and simulate these, so
it would be very plausible to use the piezo-electric transducer method
in your VR bodysuit.

Google Search Terms :

micro field

precise OR precision electromagnetic field transmit OR transmitter OR

electromagnetic simulate sensation

What do you think? Does this make sense? Hope you like it and that it
works for your story. I would love to read it when it's done.



Request for Answer Clarification by skaven252-ga on 15 Feb 2003 15:33 PST
(hmm, apparently you can't enter comments after the question has been

Is there any way to send private messages between the users, or how
should we proceed with the contact info (re: when my story is fully

Clarification of Answer by kyrie26-ga on 15 Feb 2003 15:40 PST
Thanks for the tip and the five stars! You send me your contact or the
article through the Contact link on the website . Looking forward to it!


skaven252-ga rated this answer:5 out of 5 stars and gave an additional tip of: $2.00
I guess this pretty much covers it. Thank you for your research and
your thorough and timely answer.

There are no comments at this time.

Important Disclaimer: Answers and comments provided on Google Answers are general information, and are not intended to substitute for informed professional medical, psychiatric, psychological, tax, legal, investment, accounting, or other professional advice. Google does not endorse, and expressly disclaims liability for any product, manufacturer, distributor, service or service provider mentioned or any opinion expressed in answers or comments. Please read carefully the Google Answers Terms of Service.

If you feel that you have found inappropriate content, please let us know by emailing us at with the question ID listed above. Thank you.
Search Google Answers for
Google Answers  

Google Home - Answers FAQ - Terms of Service - Privacy Policy