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Counterstimulation

Minor but reliable, counterstimulation is one of the most basic pain-killing mechanisms in biology… and maybe there’s a fancier version that’s more useful

Paul Ingraham • 9m read

Counterstimulation is a basic neurological mechanism for minor temporary pain relief, a sensory “distraction” from pain. It is used, and perhaps overused, as an explanation for the benefits of popular treatments like ultrasound, transcutaneous electrical nerve stimulation (TENS), massage therapy, Kinesio Tape, RUB A535, acupuncture, and vibration therapy.

Counterstimulation is certainly a real thing — firmly based on the well-known neurological principle of “gate control”1 — but it’s not a potent thing. You could call it another tool for the pain treatment toolbox, but it’s not an impressive tool. Maybe just like a small screwdriver or a tack hammer.

However, even humble tools have good uses in the right circumstances. Sometimes a small screwdriver is exactly what you need. And there’s a cousin of counterstimulation that might have much broader significance to chronic pain patients: maybe enough of the right kind of sensation can drown out pain in a more robust way.

Rubbing the pain away: the obligatory, canonical example of counterstimulation

Most animals, including humans, instinctively rub or otherwise stimulate acute minor injuries. We routinely self-treat with counterstimulation, and sometimes we even counter-irritate ourselves.

Counterirritation is a subcategory of counterstimulation, which usually looks like pounding on your thigh after something like stubbing your toe or (the horror) stepping on a piece of Lego. Treatments are rarely advertised as counterirritants, but there are some examples.2

Counterstimulation and gate control as marketing bafflegab

Counterstimulation and related concepts like diffuse noxious inhibitory control and gate control theory have genuine technical and scientific meaning, and this is partly why they are routinely used as explanations for how various kinds of therapy allegedly work. People are easily impressed by it.

Citing counterstimulation creates the appearance of a substantive biological rationale for a treatment where none actually exists. I have often seen it used as a “for instance” explanation, specifically uses to give the impression that it’s only one of many fine science-y reasons why Brand X is effective, when in fact that’s all there is — and it’s not much.

It’s also often used to shore up more hypothetical rationalizations. For instance, one might explain the effect of acupuncture with some hand-waving about meridians, and then supplement that with a much more legit reference to counterstimulation (but glossing over the fact that it’s a really minor effect).

Counterstimulation might be a good enough raison d’être for a cheap self-treatment like Tiger Balm, but if it’s being used to justify a more expensive or risky treatment, that’s a red flag — along with many other common empty rationalizations for dubious treatments, like “increases circulation” or “supports immune function.”

Gate control theory: a pillar of the science of pain

The gate control theory of pain is the specific neurological basis for counterstimulation. Counterstimulation is what you do, and gate control is how it works. It’s an important idea in pain science, first proposed in 1965 by Dr. Ronald Melzack and Dr. Patrick Wall.34 It was a relatively simple idea: sensory signals pass through a “gate” in the spinal column, and non-threatening stimulation can monopolize the gate and prevent noxious stimuli from getting through. Strange but true.

The tricky part is that the state of the gate is controlled by many factors. How much and what information can get through it depends on competing signals and information from other sources, such as touch and pressure, as well as emotional context.

Gate control in more technical detail now…

Open gate: nociception passes through transmission cells to the brain, usually resulting in pain.

Closed gate: nociception cannot pass through transmission cells to the brain, usually preventing pain.

And the simplest, most predictable way to close the gate is to add harmless sensation in the same region as the pain: counterstimulation.

Basic versus fancy counterstimulation: the potential of novel sensory input

Basic counterstimulation is based on some “simple” neurology, the sensory bottleneck of gate control theory. It’s not actually simple, of course, but it is simple in the same sense that one motor reflex is simpler than juggling. Counterstimulation is not a high-level, top-down phenomenon: it just exploits a limitation of our wiring.

But gate control was the tip of the much more complicated “neuromatrix” iceberg, an extremely influential concept in pain science. In Melzack’s words:5

“The gate control theory’s most important contribution to understanding pain was its emphasis on central neural mechanisms. The theory forced the medical and biological sciences to accept the brain as an active system that filters, selects and modulates inputs. … The great challenge ahead of us is to understand brain function.”

There may also be some much more interesting top-down effects — fancier kinds of counterstimulation, based on the great power of the brain to modulate pain.6 Maybe we can “amuse” and calm the brain with non-threatening sensations that convince the brain to turn the alarm volume down. Melzack thought about this.7

Novel sensory input as “fancy counterstimulation”

There are many other ways that the brain might be influenced, but novel sensory input specifically is the most promising and relevant to many common treatments for pain. This may explain both their persistent popularity and their limits.

All pain is ultimately generated by an overprotective brain that likes to sound the alarm too loudly, too often, regardless of what’s actually going on in tissues. This means that many kinds of chronic pain are partially and briefly treatable with tricks and hacks. Unfortunately, your brain is stubborn and it’s hard to convince it to shut up about pain completely — short of knocking it out, which is why anaesthesia is the only truly effective analgesia.

The brain decides what hurts based on many sources of information and complex interpretation of the context and meaning. But sensations are a major input into that system. We can think of them as being potentially extremely persuasive, a particularly good source of data.

Many common treatments dose the brain with unusual sensations, which might significantly alter the brain’s interpretation of tissue damage. If such sensations happened without warning or explanation, they could be scary and make the pain worse. But pay good money for it, call it “therapy,” tell a good story about why it works, and it can be reassuring instead. Context is key.

Only so powerful: an enhanced placebo?

If your brain thinks you should be in pain, the alarm is probably going to start going off again sooner or later — maybe by the time you get to the parking lot from your physical therapy appointment (“parking lot effect”).

Another way to describe what I’m talking about is a sensation-enhanced placebo.

On the one hand, it’s “enhanced”! It’s potentially potent because of the innate power of sensation to change the brain’s tune.

On the other hand, it’s also placebo — “relief from belief” — and every placebo involves some degree of fundamentally dishonest exaggeration to make the patient believe that the treatment is better than it actually is. That belief may be (greatly) enhanced by novel sensations, but in the end it’s not going to change an underlying, unresolved source of pain any more than an ibuprofen — even if the short term relief is real.

Treatments that produce unusual sensations have an advantage, because they make the treatment seem much more legitimate and special. If you take this far enough, it seems less like a placebo and more like we’re doing something therapeutic to the body. But if it boils down to convincing the patient’s brain to dial down the pain, it’s still a placebo at heart — just a complex, fancy one.

What’s new in this article?

Jun 30, 2021 — Publication.

Notes

  1. Melzack R, Wall PD. Pain mechanisms: a new theory. Science. 1965 Nov;150(3699):971–9. PubMed #5320816 ❐ This is a seminal paper, arguably the origin of modern pain science. More on gate control and the neuromatrix below.
  2. Many therapies are deliberately painful and provocative, and counterirritation may be at work even if it’s disavowed. Some treatments may be irritating to some degree as an expected and accepted side effect, like orthotics that are initially uncomfortable as you adapt to them, or the aggravation of an aggressive posture correction strategy. And, in a few cases, the irritation may be an unintended side effect that nevertheless actually has a useful counterirritation effect, such as being sore after massage therapy or strength training.
  3. Melzack R, Wall PD. Pain mechanisms: a new theory. Science. 1965 Nov;150(3699):971–9. PubMed #5320816 ❐

    This is Melzack and Wall’s seminal paper arguing that (emphasis mine) “pain perception and response is triggered after the cutaneous sensory input has been modulated by both sensory feedback mechanisms and the influences of the central nervous system. We propose that the abstraction of information at the first synapse may mark only the beginning of a continuing selection and filtering of the input.” Among other things, this is the paper that described the mechanism of gate control and ultimately gave rise to the highly influential concept of the neuromatrix (Melzack).

  4. Katz J, Rosenbloom BN. The golden anniversary of Melzack and Wall's gate control theory of pain: Celebrating 50 years of pain research and management. Pain Res Manag. 2015;20(6):285–6. PubMed #26642069 ❐ PainSci #52145 ❐

    ABSTRACT


    November 2015 marks the 50th anniversary of the 1965 Science publication “Pain Mechanisms: A New Theory” by Ronald Melzack and Patrick D Wall (1), in which the authors introduced the gate control theory of pain that has since revolutionized our understanding of pain mechanisms and management. The brilliance, creativity and critical thought that went into the formulation and explication of the gate control theory of pain can best be appreciated by reading the original article. Fifty years later, having become part of our scientific history and accepted as common knowledge, the essence of the theory is often conveyed by the familiar diagram in Figure 1.

  5. Melzack R. From the gate to the neuromatrix. Pain. 1999 Aug;Suppl 6:S121–6. PubMed #10491980 ❐
  6. Modern pain science shows that pain is an extremely unpredictable sensation, heavily tuned by the brain and jostled by complex variables — not the relatively simple response to tissue insult that we tend to assume, and that most treatment is based on. For more information, see Pain is Weird: Pain science reveals a volatile, misleading sensation that comes entirely from an overprotective brain, not our tissues.
  7. Melzack R. Myofascial trigger points: relation to acupuncture and mechanisms of pain. Arch Phys Med Rehabil. 1981 Mar;62(3):114–7. PubMed #6972204 ❐ In this 1981 paper by Melzack, he speculaties specifically about pain gating having a lasting effect.