Why Our Brains Never Fill Up

The answer to this question can be found in the September/October 2012 Scientific American Mind in the article “Making New Memories.” Actually readers of the healthymemory blog should already know the answer to this question. The answer is neurogenesis. Neurogenesis is a process that does not stop when we age. It continues until we die. Now the hippocampus is one of only two sites in the adult brain were new neurons grow. They grow in the region of the hippocampus called the dentate gyrus. The rate of neurogenesis in the hippocampus is estimated to be 1400 neurons a day. This is important as the hippocampus plays a central role in memory.

There is an expression, neurons that fire together wire together. This expression captures the concept of the Canadian psychologist Donald O. Hebb’s Cell Assembly Theory. One problem has been that most cell assemblies are associated to other cell assemblies and so forth and so forth. Although this is the basis for cognitive enrichment, how are all these cell assemblies distinguished? In 1995 the psychologists James L. McClelland, Randall C. O’Reilley, and Bruce L. McNaughton proposed that the cerebral cortex forges these connections and the hippocampus tags cell assemblies so that distinct memories are filed away. But where did these new neurons come from to keep these memories distinct? At that time it was thought that we only have the neurons with which we are born. We even lose many of those neurons very early in life. It was not until the late 1990’s that neurogenesis was discovered. Subsequent research has indicated that this neurogenesis continues until we die. So these neurons are being created just when they are most needed! See the healthymemory blog post, “What is Neuroplasticity and How Does It Work.”

So key to keeping and maintaining your memory is to build a healthy hippocampus. To learn how to build your hippocampus, see the healthymemory blog post, “”To Improve Your Memory, Build Your Hippocampus.”

Growing old is no excuse for old dogs not learning new tricks. Growing old is no excuse for not continuing to learn and do new things. Cognitive decline is a myth. See the healthymemory blog post, “The Myth of Cognitive Decline.” Cognition might slow down as we age and, although there are some biological factors underlying part of this, the brain adapts. Apparent slowness and occasional forgetfulness, so called “senior moments,” are likely the result of the vast amounts of information that are stored in the elderly brain. This is especially true of the elderly brain that has spent a lifetime growing and learning. It takes more time to process and retrieve information from this enlarged network. Apparent slowness might well be due to cognitive richness rather than cognitive decline.

© Douglas Griffith and healthymemory.wordpress.com, 2014. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

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