Brain Race Keeps Pace in Humans, Other Mammals

Nerves develop about the same rate in many animals

MONDAY, July 16, 2001 (HealthDayNews) -- If someone accuses you of having the brains of a ferret, guess what? They're right.

Scientists at Cornell University have devised a statistical model that shows that brain development, with a few exceptions, follows the same order in hamsters, rats, mice, ferrets, cats, monkeys and humans.

"There's a remarkably striking similarity in the order of brain development. So much work is done in genetic engineering in rats, monkeys and mice, and [now] we can relate it to a human time line," says Barbara Clancy, lead author of a study outlining the model.

Her work is reported in the July issue of Neuroscience.

Understanding when different brain parts develop in a fetus would help doctors who have to do pre-natal intervention during a pregnancy, for instance, Clancy says.

Also, Clancy says since development of the brain follows the same order in humans as in animals, scientists can assume deterioration follows in the same order, and animal studies could help in studies of human diseases of old age, like Alzheimer's.

"How late in life can we apply [the model]?" asks Clancy. "That will probably be the next research step for me."

Another benefit is that studies of different animals can be related to each other, streamlining research, Clancy says.

The model was developed from a mathematical equation formulated in 1995 by Cornell professors Richard Darlington and Barbara Finlay. They identified similarities in neural development of many animals and devised a ratio that could predict the timing of neural development among various animals.

Duke University epidemiologist Justin Crowley, who worked with Finlay at Cornell, says, "It's a very powerful application. If you were going to design a brain, it's easier to design it with a few global rules, rather than with individual rules for each structure and species."

In the latest work, Cornell scientists identified 95 points in the progression of neural development, from the first neural growth of brain cells that control body movement and form the retina for sight to one of the last neural developments of the cells of the cortex, which, in humans, controls cognitive abilities.

Clancy says there is little relationship between the timing and order of neural development and the length of gestation. Neural development proceeded apace regardless of whether a mammal was in the womb or already born. This squares with the general knowledge that cats, for instance, are born with their eyes closed while newborn babies' eyes are wide open. In fact, Clancy says one surprising finding is that the brain of a newborn human baby is far more mature than previously thought.

"Animals are born at different stages of neural maturity, and human infants are a lot more developed than previously suspected," she says.

The only differences in neural order were found among primates, which were the monkeys and humans in the model.

"Right before birth, the production of synapses surges [in primates], which seems to be linked to gestation," she says. Synapses are the junctions where the brain cells communicate.

Clancy says while "there are windows of error" in the model, scientists now can use it to further knowledge about neural development, especially in humans.

"More information will refine [the model]," she says. "The application for humans is what we're all striving for."

Clancy's study was supported by a grant from the National Institutes of Health and a postdoctoral research fellowship from the National Institute of Mental Health.

What To Do: Information about brain research can be found at Math Matters. Pictures of the brain can be found at University College of London.

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