Subcutaneous Electrodes and Pain

[yummifruitbat]

Hi,

 

This will probably seem a bizarre question, in which case I apologise!

 

I am considering writing a book set in a dystopian near-future, the plot of which will rely on the ability of certain individuals to control the behaviour of their 'subjects'. One idea I have considered involves the use of subcutaenous implants capable of temporarily crippling the 'wearer' with an electric shock on receipt of a remote signal. The intention would be to cause such excruciating pain as to make it almost impossible for most wearers to even contemplate disobedience, but for the shock to be non-lethal and any resulting paralysis only very temporary.

It would of course be possible to simply strap a large battery to each subject and zap them with horribly large voltages, but that would be unsubtle and also probably quite easy to overcome with a little assistance and a pair of wire snips!

I am aware that Biophan and probably other companies are developing thermocouple devices intended to power pacemakers etc. without the need for a battery - instead generating small amounts of electricity from the patient's body heat. My question is, would it be possible (theoretically of course!) to use this sort of device to administer small electric impulses directly (or very close) to nerves to bring about the sort of effect discussed above? Where would be the optimum location for such an implant, bearing in mind that it would be 'installed' in thousands of subjects and thus should require only minimal surgery?

The Biophan devices produce around 100 microwatts at 4 volts and measure about 6cm². The plot would assume only minimal technological advances from present levels, and it would be necessary for the implant to issue successive shocks every few minutes or so in order to ensure long-term control of the subject.

 

I hope that someone among all these Neurology experts will be able to give me some pointers, but if I've posted this in entirely the wrong place, sorry!

Thanks very much for your time,

 

Best regards

 

yfb

 

PS: Username = yummifruitbat... damn that length limit

[coquina]

I'm no neurologist, but as I understand it, there are 2 sets of nerves going to each body part. The "afferent nerves" carry transmissions from the body part to the central nervous system, the efferent nerve carries transmissions from the CNS to the body part. For example, you stick your hand on a hot stove, the afferent nerve sends the message, "Ouch, that's hot!" to the brain, the efferent nerve sends the message from the brain to the muscle to move and jerk the hand away.

 

Suppose you could place your electrodes between the brain and the muscle along the efferent nerves and intercept incoming messages and replace them with something else. It might be relatively easy to stop movement. Getting it started in another direction would be a much more difficult matter, because even minimal movement would involve the coordination of many muscles.

 

I think electric stimulation of the afferent nerves is already used to intercept sensations of pain before it reaches the brain.

[Glider]

You are referring to a reflex arc, which is a functional unit and doesn't require input from the brain. Intense signals (high frequency volleys) passing up primary afferent fibres trigger interneurons in the dorsal horn of the spinal cord. These in turn trigger efferent fibres causing withdrawal (reflex). The nociceptive signals reach the brain a little later, but your hand should already be moving by then.

 

TENS (transcutaneous electrical nerve stimulation) is used to alleviate pain, but this doesn't really intercept the nociceptive volleys. It works more on the principle of the Gate Control Theory (Melzack & Wall, 1965). Signals passing up large myelinated afferents are said to inhibit nociceptive signals passing up small myelinated (A delta fibres) and non-myelinated (C fibres), by opening a neural 'gate' mechanism. The proposed model suggested that activity in the large fast afferents triggers an inhibitory interneuron which dampens the signals from the primary afferents (Ad & C) as they synapse with main projection neurons of the spinothalamic tract. Whilst the effects of such interventions support the Gate Control Theory, no such gate has ever been found. Bizarre, huh?

 

The best place to place a microelectrode, if you wish to cause pain, would be in a filling. Somatic pain is dampened by a central control mechanism descending from the periaqueductal grey area, to the laminae of the substancia gellatinosa in the spinal cord. The reason orofacial pain is so bad is that the nociceptive signals are conducted by cranial nerves, which do not synapse in the spinal cord. They pass straight to the thalamus.

 

Many people have felt the pain that results when accidentally chewed foil comes into contact with an amalgum filling. This is due to the tiny current generated by the two different alloys immersed in an electrolytic solution (saliva). I don't imagine you would need a large current to cause pain if it were passed between two microelectrodes embedded in an amalgum filling.

[coquina]

Many people have felt the pain that results when accidentally chewed foil comes into contact with an amalgum filling. This is due to the tiny current generated by the two different alloys immersed in an electrolytic solution (saliva). I don't imagine you would need a large current to cause pain if it were passed between two microelectrodes embedded in an amalgum filling.

 

Man - I know what you're talking about there. Once chomped down a defective Hershy's Kiss that had a chunk of foil inside it. Ouch!

 

What about migranes - does the pain from them work the same way?

[yummifruitbat]

Thanks very much Glider, that sounds like an interesting idea.

My immediate thought would be 'what if someone removes the tooth' - but then I suppose you could reduce the likelihood of that by 'filling' all the subject's molars; that would presumably have the added benefit (although obviously not to the subject) of magnifying or increasing the radius of the pain. Still, some might choose a complete set of dentures over a life of servitude!

 

coquina: The primary function of the device would be as a deterrent - the aim is not so much to cause paralysis or control movement as to threaten unbearable pain, the memory of which is so strong as to overcome the willpower of the subject (if necessary with the aid of occasional reminders).

 

If anyone else has anything they think might help, this thread is still open!

[coquina]

How does a "stun gun" work. Does it cause pain, or just scramble the signals so you can't move?

[Glider]

My immediate thought would be 'what if someone removes the tooth' - but then I suppose you could reduce the likelihood of that by 'filling' all the subject's molars; that would presumably have the added benefit (although obviously not to the subject) of magnifying or increasing the radius of the pain. Still, some might choose a complete set of dentures over a life of servitude!

That's probably true, but then the same could be said of subcutaneous pain stimulators in any location. I suspect many would rather undergo 'back-street surgery' to have them removed than live as a slave.

 

The only way around that would be to place them in an area which made permanent serious damage inevitable if somebody tried to remove them. However, implanting them would carry the same risks unless you were set up for mirosurgery.

 

Such areas might be the dorsal root ganglia (receives sensory nerves into the spine). Electrodes there would be immensely painful and debilitating, but placing the electrodes would be dangerous, time-consuming and very expensive. Alternatively, place them the wall of the aortic arch or internal carotid arteries. These contain baroreceptors. If you pass a current through them, you'd get an immediate vasal response. It probably wouldn't be very painful, but the person would lose consciousness immediately.

 

What about migranes - does the pain from them work the same way?

It does insofar as the pain signals are carried by cranial nerves and not spinal nerves. However, the pain of migraine is thought to be caused by vasoconstriction in the scalp and brain (althought the brain has no sensory nerves of its own). In that, the pain must be similar to that caused by the cold pressor response, which also results from vascular constriction, and can be quite agonising.

How does a "stun gun" work. Does it cause pain, or just scramble the signals so you can't move?

A stun gun (high voltage, low amperage) scrambles the signals. Electricity is non specific in the receptors and nerves it triggers. It triggers everything, receptors and nerves, both motor and sensory, so you get tetany as the motor nerves activate skeletal muscle all at the same time. this weakens the individual significantly. Plus you get a massive afferent volley from all affected fibres, flooding the spine and thalamus and overwhelming them leading to confusion (& loss of consciousness if protracted). This is not likely to be extremely painful, but definitely very unpleasant.

[coquina]

As always, thanks for the info.

 

Please define "cold pressor response". I'm not familiar with the term.

[Glider]

A pressor response is a vascular response to a stimulus; either vasodilation or constriction. The cold pressor is the vascular response to cold (vasocostriction).

 

In pain research, the cold pressor is used as a pain stimulus by inducing it rapidly. This is usually done by immersing the hand & forearm in water at between 1 & 4 degrees C. The rapid pressor response to the cold is very painful.

[yummifruitbat]

Thanks Glider, I think I'll go with the teeth, at least for starters