Brutal Truths About 
the Aging Brain

Posted by M ws On Wednesday, January 23, 2013 0 comments
Recently, Robert Epstein reported HERE that a graying world will have more of the experience that comes with age. It will also be slower, fuzzier, more forgetful, and just a bit hard of hearing.


As a graduate student at Harvard University, I worked with one of the most influential behavioral scientists of all time, B. F. Skinner. Beginning in the summer of 1977, we worked together nearly every day for more than four years, designing experiments and chatting about literature, philosophy, and the latest research. Although we were 50 years apart in age, we were also friends. We saw Star Wars together, had lunch frequently in Harvard Square, and swam in his backyard pool each summer. “Fred” (from Burrhus Frederic) Skinner was the happiest, most creative, most productive person I have ever known. He was also, needless to say, quite smart.

But the septuagenarian I knew was well past his intellectual peak. One day he gave me a set of tapes of a famous debate he had had with psychologist Carl Rogers in 1962. The Skinner on those tapes seemed sharper, faster, and even wittier than the man I knew. Was I imagining this?

Recently, Gina Kirkish, a student at the University of California, San Diego, and I analyzed tapes of three comparable samples of Skinner’s speech: that 1962 debate, a 1977 debate, and a speech he gave from notes shortly before he died in 1990 at age 86. We found that the speech rate dropped significantly over time, from 148 words per minute in the first sample to 137 in the second to 106 in the third—an overall decrease of more than 28 percent.

Skinner’s memory and analytical skills were also declining during the years when I knew him. Sometimes he had no recollection of a conversation we had had only days before. When I tried to talk with him about technical papers he had published early in his career, he often didn’t seem to understand what he had written. And he had no patience for anything mathematical, even his own equations. On the other hand, Skinner was still much smarter than most of the people I knew my own age. When you fall from a high enough cliff, you remain far above ground for a very long time.

The sad truth is that even normal aging has a devastating effect on our ability to learn and remember, on the speed with which we process information, and on our ability to reason. Recent studies suggest that the total loss in brain volume due to atrophy—a wasting away of tissue caused by cell degeneration—between our teen years and old age is 15 percent or more, which means that by the time we’re in our seventies, our brains have shrunk to the size they were when we were between 2 and 3 years old. Unfortunately, most of the loss is in gray matter, the critically important part of the brain composed of neurons, the cells that transmit the signals that keep us breathing and thinking.

Contrary to what scientists long believed, only about 10 percent of our neurons die during adulthood. The real loss is in the network of connections—the “dendritic trees” that allow a single neuron to be connected to a thousand others. Over the years, 25 percent or more of this network disappears. According to William Jagust, a neuroscientist at the University of California, Berkeley, adults are also losing dopamine, a critical neurotransmitter (the type of chemical involved in transmitting signals between neurons), at the rate of 5 to 8 percent per decade. “By age 80,” Jagust says, “you’ve lost 40 percent or so of dopamine function. When you think about it, it’s remarkable that old people can do so well.”

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the Aging Brain

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