https://www.jneurosci.org/content/41/12/2541 Looks like there is evidence. Also are you claiming there are no stem-cells/MSCs in the brain? I have read multiples papers about drugs that specialize unspecialized cells into olygoendrocytes (a microglia) in the human brain. I don't see why epigenetics wouldn't allow unspecialized cells to become neurons vs glial cells. Finally if I recall correctly, some glial cells might not act like neurons but still release neurotransmitters. More importantly, humans should preserve their neurons by actively fighting apoptosis, e.g. by taking skq1. And as said previously, synaptothrophics exists and are very potent. Finally, hypermnesics are a thing. BTW children are generally happiers/more emotional than adults. One might wonder wether this is related to neuron/synapse density