Neurons born in new places

Neurogenesis in the adult brain is generally considered to be restricted to the hippocampus and olfactory bulb—ancient parts of the brain that are found even in nonmammalian species. A few publications suggested that the neocortex—a well-developed region in primates that is implicated in higher thought—also supports neurogenesis. These reports have been met with skepticism, as other groups have been unable to replicate the findings. On page 415, Dayer et al. bolster the evidence for proliferating neurons in regions beyond the hippocampus and olfactory bulb.The authors used a battery of neuronal markers to confirm that neurogenesis exists in the neocortex. Although difficult to find in the sparsely populated expanse of the cortex, replicating cells with markers of neuronal precursors were present in the adult rat neocortex. Their numbers suggest that these interneurons in the...