Might have the same sort of problem as partial Transfiguration has for everyone other than Harry: only works on a Whole Object and not on parts thereof. Your frontal lobe, or even your brain, might not be considered a separate object by whatever is responsible for making magic work.
Personally, I doubt that Charms and free Transfiguration are alike in that sense, but even if they are we have Word of McGonagall that it’s possible to Transfigure just your skin or hair. Apparently human bodies are subdivided, according to the idea of Forms.
Might have the same sort of problem as partial Transfiguration has for everyone other than Harry: only works on a Whole Object and not on parts thereof. Your frontal lobe, or even your brain, might not be considered a separate object by whatever is responsible for making magic work.
Personally, I doubt that Charms and free Transfiguration are alike in that sense, but even if they are we have Word of McGonagall that it’s possible to Transfigure just your skin or hair. Apparently human bodies are subdivided, according to the idea of Forms.