Restoring Sensation to Amputees’ Lost Limbs

Scientists at the Rehabilitation Institute of Chicago and Northwestern University made two amputees ‘feel’ their lost arms by rerouting to their chest the key nerves that transfer sensations from hand to brain. After several months, stimulation to the area of the nerves would produce rich sensations experienced as if occurring in the missing limbs. Interestingly, the patients could still distinguish between sensory stimulation of chest nerves and that of the rerouted arm nerves.

For a summary, see Yahoo News

For the original paper, see PNAS paper

Clearly, this is a major step in the way to establishing sensory experience in prosthetic devices so that amputees would experience their artificial limbs pretty much as if they were their natural arms or legs. The benefits are obvious. But like many medical advances, we may start by trying to restore or mimic normal function and end up somewhere quite different.

As a first step, consider the question whether losing one’s natural limb would be any kind of disability if it could be replaced by an artificial arm that is in many ways stronger and more resilient than a natural human arm yet feels just like one. In what way would one be in a worse state than one was at before? But if it’s no worse or even better, might we have reasons to replace our limbs with better artificial ones? It’s not so important whether we answer Yes or No or even take such questions seriously, but such scientific advances force us to confront the contingency of our natural make-up and to rethink the significance we attribute to the already blurry natural/artificial divide.

It’s not very useful to feel warmth in a non-existent finger when one’s chest is prodded, but further down the line we can imagine various ways in which sensory and motor nerve endings might be plugged into artificial devices that needn’t even try to mimic natural senses or limbs. There is something unpleasant in this idea. But on second thought this first reaction is hard to sustain. It is hard to see why we should react with repugnance at the idea of modifying the natural human frame when the sensory bombardment that is culture radically shapes our brain-minds from day one. Is instilling in you a belief system or idea – with all the concomitant changes to neural connections in your brain – really better simply because it is invisible?

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