From John Hopkins Medicine, welcome news of continuing progress towards a complete understanding of brain biochemistry: scientists "have discovered the steps required to integrate new neurons into the brain's existing operations. For more than a century, scientists thought the adult brain could only lose nerve cells, not gain them, but in fact, new neurons do form during adulthood in all mammals, including humans, and become a working part of the adult brain in mice at the very least. ... We've shown that [the neurotransmitter] GABA instead excites new neurons and that this is the first step toward their integration into the adult brain. ... their discovery might help efforts to increase neuron regeneration in the brain or to make transplanted stem cells form connections more efficiently." A very effective regenerative toolkit for the brain is a requirement for living far longer than we do now.