Comment by kaycebasques
5 days ago
I stumbled on this work while researching cyborgs. There's quite a bit of jargon on this official page. The main idea (as I understand it) is that previously, when you got an amputation above the elbow (for example) the bicep and tricep muscles became dead ends. They would just attach the ends of the muscles wherever feasible. Apparently the act of one muscle like the bicep contracting (agonist) while another related one like the tricep extends (antagonist) is a really important feedback loop in our brains. AAMI essentially restores this feedback loop, making the prosthetic feel like part of the body. The lead researcher is apparently himself a double amputee.
Osseointegration was another example of interesting real-life cyborg technology that I stumbled upon.
The real magic is the plasticity of the brain, the cerebellum as well as the cortex. In this case, they're tapping in to existing neural structures by correctly aligning the prosthetic with the configuration of the original.
One of the ways the brain works is to construct and predict, or assume, the way things will be, and use proxy signals to confirm the success or failure of a prediction or assumption. By aligning the prosthetic, the proxy signals result in not only successful manipulation of prosthetic orientation and placement, as if it were a foot, but the patient feeling feedback from the prosthetic, as the brain reconstructs some pieces of the sense of actually having a foot.
Phantom limb and phantom pain taps into some of the same phenomena, and advanced prosthetics with myo/neural electrodes actually tap into the nerves and nerve endings to create new input/output pathways, with some experiments actually succeeding at reproducing touch, hot/cold, pressure sensation, and control of the cybernetic limb.
Input is hard, but with nonintrusive ultrasound techniques seemingly working for certain deep brain stimulation, maybe it won't be too long before we see highly precise ultrasound phased arrays able to stimulate precise neurons when installed over a patch of skin, and we'll get wearable third limbs, prehensile tails, and other cyborg augments with full neural io integration for non medical purposes.
Very cool paper!