Purdue News
Purdue News
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June 1, 1982 Brain Growth Continues For Adults, Research ShowsWest Lafayette, Ind. – Part of the brain continues to grow throughout adulthood, continually affecting the function of the nervous system, reports a Purdue University scientist. "Up until about 20 years ago, most scientists thought brain development was largely complete by the time of birth," says Shirley A. Bayer, associate research scientist in biological sciences at Purdue. Gradually, scientists accepted that some development took place between birth and adolescence. "This study is the first demonstration that neurons in any brain structure increase in total number during adult life," Bayer says. Bayer's work was reported in the May 21 issue of Science magazine. She says nerve cells, or neurons, in the part of the brain called the hippocampus increase 35 to 43 percent in total number in rats between the ages of one month and one year. "These studies were done in the rat brain," Bayer says, "but it is highly probable that this same type of neuron also increases in the human brain." One month in a rat is approximately 12 years in a human. The year-old rat corresponds roughly to a 45-year-old human, notes Bayer. Exactly what the hippocampus does isn't fully understood, the Purdue researcher says, but this study indicates that whatever role the hippocampus plays must become more pronounced with age. "Assigning a specific function to the hippocampus is still controversial. There are theories that it is concerned with memory storage, especially spatial memory--the location of various objects in the environment," Bayer remarks. Another theory Bayer describes says the hippocampus is responsible for response inhibition. In other words, she says, the hippocampus "slows down activity level. Perhaps one reason children are more active than adults is that the hippocampus in a child's brain is less mature than it is in an adult brain." Bayer's work was supported by the National Science Foundation and is part of a larger Purdue study with Professor Joseph Altman aimed at determining when neurons develop and the sequence of development. During that larger study, Altman and Bayer and other scientists kept finding new cells forming during adult life. "So I decided to see whether or not these new cells replaced ones that died or actually added to the total population," Bayer explains. "I expected to see a small increase. I was really surprised to see this much." Counting all the cells in any brain structure is very difficult, Bayer says. The work must be done under a microscope after cells have been sliced very thin by a device called a microtome. Rather than attempt to count each cell, however, Bayer got help from Purdue's Department of Statistics. "Dr. James W. Yackel and Dr. Prem S. Puri in the statistics department helped me formulate the statistical method for determining the total cell number," says Bayer. Yackel and Puri are credited as co-researchers in the Science magazine article. Bayer and her research team counted cells in 17 rats aged one month to one year. "We know that nerve cells increase up to one year. Beyond this one year of life, the neurons may actually decrease. At this point, we have no way of knowing," Bayer points out. "Qther parts of the brain also contain neurons that originate during adult life," Bayer says. But whether those nerve cells actually add to the total number of cells or simply replace cells that die is not yet known. Bayer now plans to return fulltime to the larger Purdue research project--determining the timetables of neuron development. There are still questions she'd like to see answered about nerve-cell increases in adulthood and possible decreases as the brain ages, however. For instance, what happens beyond the one-year-old stage in rats, she wonders. She says perhaps she will tackle this problem in future research. A more detailed report of Bayer's work will appear in a journal called Experimental Brain Research.
Contact Purdue News Service (765) 494-2096 or purduenews@purdue.edu.
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