Thanks for the interest!

Dave is right that there are many studies that have mapped the phantom hand post-amputation.

However, the real novelty is ours is the first to offer data mapping the hand and lips before AND after amputation, offering a direct comparison between the maps before vs. after

Our longitudinal data confirms the maps are preserved. IMO, we need to stop chasing cortex and redirect our efforts to the periphery — the state of the nerve post-amputation, how to best reinnervate the nerve during surgery, the more likely driver of phantom pain

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jnnp.bmj.com/content/93/8...

The issue: clinical trial after clinical trial shows these therapies perform no better than placebos. Yet, these remain front-line treatments for phantom limb pain — essentially snake oil IMO sold under a neuroscience rationale that doesn’t hold up.

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You’re right—phantom limbs have always suggested the brain’s body map isn’t erased. The problem is the field went all-in on the idea that amputation causes reorganization. This has fueled decades of therapies (mirror box, VR, sensory discr. training) trying to “fix”supposedly broken brain maps

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Worth checking out: www.sciencedirect.com/science/arti...

They show that, irrespective of amputation, people (amputees and non-amputees) will report referred sensations at similar rates, by shaping their expectations. In other words, these effects are based on a suggestion bias, not remapping.

I don’t think phantom pain is at all associated with cortical body maps. I think the older studies put the entire phantom pain clinical field on a wild goose chase to fix broken body maps

I think we need to focus more on the peripheral nerve state post-amputation, ie procedures like TMR and RPNIs

We can only access the persistent ‘winner’ in humans because we can ask them to move their phantom fingers

We can perform this winner-takes-all analysis to replicate this supposed remapping, if we ignore the missing hand (red) and assign the territory to the next winner: lips (blue) or feet (green)

This does not mean that the monkeys’ brains forged new connections or that neurons changed their tuning because of the amputation, just that the region was already residually responsive to the adjacent fingers. You’re simply unmasking the adjacent digits, which you now assign to that territory.

They then assigned each cortical territory to the finger that elicited the greatest neuronal response when it was being touched, but because they could not touch the missing finger, the missing digit cannot be assigned any territory, because you can’t physically touch it.

Glad you found it interesting. Happy to explain! In the 1980s monkey experiments, researchers identified the animals’ somatosensory maps by recording from neurons, while simultaneously touching the animal’s remaining fingers with a glass probe after performing an amputation of a single finger

Not to be a super fan. But, I talk about your study all the time. Beautiful work!

This is an incredible study and such important work. It also aligns with what we are seeing in the complimentary situation after stoke- rather than losing the peripheral limb, losing the central map.

pubmed.ncbi.nlm.nih.gov/34172735/

pubmed.ncbi.nlm.nih.gov/37940595/