Agreed.

I wonder if it would “regenerate” an atrophied or shrunken hippocampus. Like the way rest and nutrition won’t make your skin larger but it will heal missing patches of skin.

I know I’ve seen claims from reputable sources that exercise raised BDNF levels, and that BDNF leads to hippocampal neurogenesis. I can find the sources again I’m sure if you’d like; let me know.

But how could hippocampal neurogenesis be happening without volume change? Could it be replacing dead cells (and preventing shrinkage)? Packing neurons in more densely?