Thursday, April 14, 2011

Movement illusions and pain

I enjoy days when the dots seem to connect all by themselves. 

Researchers in Nottingham stumbled upon an observation that a simple visual illusion, i.e., having people watch through the window of an optical machine, their own arthritic fingers being stretched out like Pinocchio's nose (even though their finger wasn't being pulled much at all), resulted in large amounts of decreased pain, replaced by pleasurable sensations.
See the following two news stories for more detail, and watch the short videos embedded inside.

Mind tricks may help arthritic pain

Illusion can halve the pain of osteoarthritis, scientists say

I've used skin stretch (I've called it dermoneuromodulation for the last 4 or 5 years) as a main treatment modality for a couple decades. What I'm starting to see is how, apart from any local effects, or any spinal descending modulating inhibitory effects, the patient's brain likely, automatically, provides him/her with a (internally generated) mental visual image of greater lengthening than is actually occurring. The ruffini endings are slow adapting type II, so they don't shut off until the practitioner lets go.

Cutaneous Receptors Contribute to Kinesthesia at the Index Finger, Elbow, and Knee

Whether the brain is supplied with exogenous visual illusion (as in Nottingham), or makes its own endogenous visual illusion (as per Collins and Gandevia, and in my own clinical experience), doesn't seem to matter. It would appear that a key piece here, and not mentioned in the news stories, is the operator's contact, and the patient's feeling of being stretched (in a comfortable way). Maybe the patient's brain takes the two inputs, the kinesthetic and the visual, compares them, finds a discrepancy, and defaults into the more painless of the two options. 

OPEN ACCESS: D. F. Collins, K. M. Refshauge, G. Todd and S. C. Gandevia; Cutaneous Receptors Contribute to Kinesthesia at the Index Finger, Elbow, and Knee. AJP - JN Physiol September 2005 vol. 94 no. 3 1699-1706



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