Control Pain & Heal Faster With Your Brain

The episode continues a month-long series on neuroplasticity, described as the nervous system's capacity to change itself in response to experience, including in ways a person consciously and deliberately chooses. The host argues that no other organ has this capability. He also says the obstacle is access: children use plasticity without realizing it, while adults want it but often do not know how to get it. Earlier episodes covered representational plasticity, focus and reward, and the vestibular system, including how changing one's relationship to gravity and making errors while learning can open windows for plasticity.

The new question is direction and reversal. Previous discussions focused on acquiring things such as a language, free throws or a motor skill. This episode asks about "unlearning", or removing some part of experience a person does not want. It approaches that question through pain, regeneration and, in some cases, injury to the nervous system. Listeners without concussions or chronic or acute pain are told the material still applies to neuroplasticity for other purposes.

The stated method puts principles ahead of individual experiments, mechanisms or protocols, on the grounds that principles are flexible and let people work with their own nervous systems. Planned topics include the principles of plasticity for removing pain, wound healing and injury, acupuncture, modern medicine's attempts to restore youth to the aging, injured or demented brain, and a set of tools. The host says he consulted colleagues at Stanford, Harvard Medical School and the wider tissue rehabilitation, injury and pain management community.

I'm not a medical doctor, I'm a professor, so I don't prescribe anything. I profess things.

That disclaimer frames the whole discussion. The podcast is presented as information only. Listeners are told to talk to a doctor or healthcare provider before adding or removing any tools or protocols, and are reminded that they, not the host, are responsible for their own health.

The discussion starts with the somatosensory system, which handles touch and physical feeling on the body. Sensors in the form of neurons sit in the skin and in deeper layers below it. Different receptors respond to mechanical touch, such as pressure on the hand or a pinpoint, and others respond to heat, cold or vibration. They send electrical signals along axons to the spinal cord and then to the brain, where centers interpret the signals.

The host emphasizes that no sensor uses a unique form of information. Each one sends electrical potentials into the nervous system. Wind deflecting hairs on the arm, a sharp pinprick, a hot stove and the warmth of a fire all arrive as action potentials, and the brain and spinal cord have to compute what each stimulus is. The model is peripheral sensors plus central stations that make sense of the incoming signals.

According to the episode, "pain" is a controversial word in neuroscience. Many researchers prefer the term for the detection of harmful stimuli by skin sensors (transcribed here as "no susception" and "no susceptors"), which is traced to a Latin word given as "nocera", meaning to harm. The reasoning given is that pain is subjective, has both mental and physical components, and cannot be reduced to an attempt to avoid physical harm, because the two can be dissociated.

The first example is damage without pain. High radiation exposure, or excessive x-rays, produces no sensation while it happens, but it can cause tissue damage and introduce mutations in cells. The host notes that he has had x-rays himself and is not telling people to avoid them. His claim is that excessive x-rays, like excessive exposure to any radiation, are not good for people.

The second example runs the other way: pain without damage. The host cites a case he says was published in the British Journal of Medicine, while hedging some details ("I think he fell, is how the story went"). A construction worker had a 14-inch nail go through his boot. He reported excruciating pain and could not move even slightly without it. When clinicians cut the boot away, they found the nail had passed between two toes without piercing the skin.

The host draws two lessons from the case. The first is the power of the mind: the sight of the nail produced a legitimate feeling of pain. The second is specificity: the man did not feel as if his foot was on fire, he felt the sharp pain a nail would produce. The host says there are thousands of similar case reports. He also qualifies the point, stating that this "is not to say that all pain that we experience is in our head." Instead, it shows how much higher-level, top-down cognition shapes the interpretation of signals from the periphery, even from vision alone.

The pain system is presented as a source of principles people can use. These include understanding the difference between injury and pain, which the host insists are different, and learning to interpret one's own pain. He promises protocols that address pain from both directions: at the periphery, where the injury is, and through top-down mental mechanisms. He also notes a change in emphasis. The podcast usually centers on objective physiology, such as diaphragmatic movement or a particular number of photons of sunlight, but this episode deals more with subjective factors.

One such factor is love. A Stanford colleague who runs a major pain clinic has published peer-reviewed data on how love modulates the pain response. The host says there is a twist that he does not reveal yet. The specific type of connection a person has to a romantic partner determines whether love for that partner relieves physical pain, and he describes the effects as "really robust." He presents the topic as plasticity of perception, with direct bearing on emotional pain and trauma, which he says will be covered further in a later month.

Extreme cases show what pain is for. Sodium channels are pores in neurons that let them fire action potentials, and they also matter for the development of certain neurons. Some children are born without a particular one, which the host calls sodium channel 1.7. These children experience no pain at all, which he calls a terrible situation. They burn themselves, rest on their limbs too long, and never make the small postural adjustments that prevent pain, because they get no feedback about their position. Their joints are essentially destroyed, and they tend not to live very long because of accidents.

Other mutations in the same channel cause people to make too much of it, and even subtle stimuli then produce extreme pain. The host offers a speculation, not a finding: one reason, among others, that people differ in pain sensitivity may be genetic variation in how many of these receptors they express. He adds that drugs can specifically block this channel and that people with the overactive form get a lot of relief from them. His conclusion is hedged: pain sensitivity "probably has some genetic basis," and pain also has an adaptive role.

The brain contains a map of the body surface called the homunculus. The host jokes that the rat version is a "ratunculus" and the one belonging to his dog, Costello, a "dogunculus." The map is scaled by sensitivity, not by size. The back is a large area of tissue, but it has fewer receptors and a small brain representation, while a fingertip has a very large one. Lips, fingertips, genitalia, the eyes and the area around the face are heavily represented, and the back and torso are not, so the map is badly distorted relative to the body.