A type of brain cell that was long overlooked by researchers embodies one of very few ways in which the human brain differs fundamentally from that of a mouse or rat, according to researchers who published their findings as the cover story in the March 11 issue of the Journal of Neuroscience.
Scientists at the University of Rochester Medical Center found that human astrocytes, cells that were long thought simply to support flashier brain cells known as neurons that send electrical signals, are bigger, faster, and much more complex than those in mice and rats.
"There aren't many differences known between the rodent brain and the human brain, but we are finding striking differences in the astrocytes. Our astrocytes signal faster, and they're bigger and more complex. This has big implications for how our brains process information," said first author Nancy Ann Oberheim, Ph.D., a medical student who recently completed her doctoral thesis on astrocytes.
The study is one of the most extensive examinations yet of the astrocyte. Oberheim and co-authors discovered a previously unknown form of the cell, a varicose projection astrocyte, in the human brain but not in the rodent brain. The team also found that the most abundant type of astrocyte, protoplasmic astrocytes, are approximately 2.6 times larger than their rodent counterparts, and that the human cells have about 10 times as many "processes," or structures designed to connect to other cells.
"We have not really been able to understand why the human brain is so much more capable than that of any other animal," said neuroscientist Maiken Nedergaard, M.D., D.M.Sc., who led the study. "Some people have thought that it's simply that a bigger brain is a better brain, but an elephant's brain is bigger than a person's, for example, but it's not nearly as powerful. So that's not the answer.
"It may be that humans have a much higher brain capacity in large part because our
|Contact: Tom Rickey|
University of Rochester Medical Center