Brain Cell Formation in Older Brains


Cell formation.

Readers of this blog may recall that we reported last year the discouraging findings from Dr. Pasco Rakic (professor of neuroanatomy at Yale University) that there is very little neurogenesis (creation of new neurons) in the brains of older primates (including humans).

Now, an article by Kristy Spalding published a few months ago in Cell suggests that the controversy is far from resolved. Her study used carbon-dating to identify the number of cells in the hippocampus (a part of the brain involved in memory formation) that are generated in adults. She found that in a particular part of the hippocampus (the dentate gyrus) there is in fact very active turnover of neurons that continues throughout adulthood.

In this part of the brain, about 700 neurons are generated each day, corresponding to almost 2% new neurons per year.

Now the question is how is it that neurons are able to develop in one part of the brain but not in other parts.

  • Deborahmichelle

    I am no scientist, but a couple of hypotheses leap to mind regarding why new neurons form (at the rate of 1.75% annually) in the human adult hippocampus.

    First, the “reptilian” parts of the brain, adapted to Homo Sapiens from lizards & such, which brain structures include the hippocampus, could have more plasticity because they have had longer to evolve.

    Second, laying down memories is a continuous task, &, after some time, it may no longer be possible to repair damage to the neurons that do such yeoman work, so they need to be replaced altogether.

    I know I do not have the education to make useful comments on neurology, but I enjoy reading about it. I know how much I’m oversimplifying. I know I would need to keep up with the literature to be able to identify good lines for future research!

    I am grateful that you post so often about basic scientific studies.