Brain Regeneration
By William K. Summers, MD
© 2000-William K. Summers, MD
The notion of brain permanence is a myth. According to this myth, there is one set of brain cells (neurons) you inherit by the age of three. This means that your IQ is fixed by age three. It also means that if you have head trauma or a stroke, the damage is permanent. If injured, the brain could not, like the liver, regenerate up to 50% of itself. The currently accepted science holds that blood cells totally replace themselves inside a month, but not the brain. This notion of permanence never made sense to me.
Brain cell permanence was also rejected by Viktor Hamburger, one of my professors at Washington University (St. Louis, MO). He discovered that many more neurons are born than will ever be needed. Regulated nerve cell death in the fetus shapes the nervous system, matching the nerve centers to targets like hands or feet. Dr. Hamburger's work led to the discovery of nerve growth factor (NGF), a chemical that guides embryonic brain cells to their targets. Manipulations of chicken embryos by microsurgery convinced Hamburger that neurons developed as the need arose. Dr. Hamburger, who recently celebrated his 100th birthday, created the concept of plasticity of neurons.
Now, forty years later, scientists are catching up with Viktor Hamburger. There is mounting evidence of the production of new neurons in the adult brains of birds, mice and primates. A Harvard Medical School group demonstrated that chemical destruction of adult mice brain cells triggered the formation of replacement neurons by brain stem cells. These newly formed nerve cells would then migrate to the position of the destroyed nerve cells. Even more astonishingly, the baby nerve cells then reconnected to the same places were the old cells had been connected. This is like your telephone dying, so your computer sprouts a new baby telephone that migrates over to where the old telephone was. Then the baby telephone automatically reconnects with the proper long distance carrier!! Weird Stuff. Star Trek stuff!
The trick is to create an acute injury to a small area of the brain. In June, 2000, a group from the Rockefeller University in New York City reported doing this in zebra finches and finding a burst of new nerve cell growth. The support cells of the brain, known as micorglia, then released special chemical signals causing stem cells to migrate to the area of injury. Stem cells are multipotential precursor nerve cells. Once in place, the stem cells then transformed into the type of neuron that was injured and made the proper connections.
This year's Neuroscience Meetings was buzzing with excited theories on how to make small specific injuries to brains of patients with Alzheimer's disease, spinal injuries, Parkinson's disease, multiple sclerosis, and on and on. And there may be application in manic-depressive illness, schizophrenia, and mental retardation. So if you have any of the above or know someone who does, take heart. Do not accept false despair; the future looks pretty good. To your health.
References:
- EN Lasley. Death leads to brain neuron birth. Science. 288: 2111-2.
- K. Brown. A lifelong fascination with the chick embryo. Science 290: 1284-1287.
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