Magazine article Science News

Nursing Mother Rats Show Brain Changes

Magazine article Science News

Nursing Mother Rats Show Brain Changes

Article excerpt

You might call it sleeping on the job, since a female rat naps as she nurses her young, but she's certainly paying attention. In fact, a recent study shows that nursing dramatically increases the size of the area in the brain that picks up sensations from a mother rat's nipple-bearing underbelly.

Two major changes occur as a mother nurses, report Judith M. Stern and her coauthors in the March JOURNAL OF NEUROSCIENCE. The area of the somatosensory cortex- the part of the brain that registers touch, pain, and temperature devoted to sensations from a rat's underbelly almost doubles. And the mother's perceptions of feelings from her underbelly sharpen as the surface area of skin that excites a particular nerve cell shrinks. This sharpens the brain's perceptions, just as smaller dots, or pixels, in a television picture make it clearer.

Stern's team compared nursing mothers with virgin rats and with rats whose babies had been removed soon after birth. After anesthetizing the rats, the researchers recorded in detail the activity in nerve cells, or neurons, when they touched different areas of the animals' trunks with microelectrodes.

Normally, there isn't much direct stimulation of a rat's stomach, says Stern, a behavioral neuroscientist at Rutgers University in New Brunswick, N.J. The onset of nursing is a chance to examine the effects of increasingly strong stimuli on the brain, she adds. "It's... little paws treading on [the mother] and little snouts nuzzling [her]; as well as the sensation of nursing itself.

"We don't think this [increase in sensitivity] is due to an increase in the number of neurons; says Stern. "We don't know for sure, but [we think that connections] that were already there are being strengthened .... Think of a path in the forest that hasn't been used and has grown over. It gets cleared as it gets increasingly tromped on. …

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