I don't know what happens if that cell dies. The person may die. Or another neuron may take over (e.g. after coma). But under the new management, the person won

I don't know what happens if that cell dies. The person may die. Or another neuron may take over (e.g. after coma). But under the new management, the person won't be the same as before. This is not something unheard-of. There are precedents. There are some neurons that control muscles. If the neuron dies, the brain loses control over this muscle. There's no regeneration, and no other neuron takes over.