What is pain in terms of neuroscience?

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By: #Yohan John, #Neuroscientist at #BostonUniversity

Pain in the body is associated with pain receptors (nociceptors). But pain receptors might not cover all kinds of pain. Headaches, for example, are subjectively felt as originating in the head, but there are no pain receptors in the brain. (Some headaches may be a result of nociceptor activation in the tissue surrounding the brain. Headaches remain poorly understood.)

It makes sense therefore to think of pain as a particular (and still largely unknown) pattern of activity. Sometimes this pattern is a result of signals from the rest of the body, but sometimes the pattern seems to originate within the brain.

The question of the material basis of a feeling is a mystery, however. It sits at the boundary between science and philosophy. Philosophers call subjective experiential states qualia. They seem to be linked to brain states (which in turn are linked to bodily states), but beyond that we can say very little. We can simulate such states in machines, but that doesn’t really tell us if the machine is feeling anything. In fact the question of whether a machine feels anything may be unanswerable: each person only has access to their own consciousness.

We cannot directly perceive what another person or animal or robot is feeling. All we see are their reactions and their internal states as measured by our devices. We infer an experiential state by analogy with how our own experiences relate to outward behavior. When I get a headache, I might clutch my heads and groan. If I see the same in another person, I can infer that they are experiencing something similar. But how similar? It is impossible to say.