| Another Reason to Thank Mom |
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April/May 2007, for Scientific American Mind Maybe it is a good thing we don't remember our births. Difficult ones can be traumatic and a major cause of brain damage. But researchers now suggest that a maternal hormone may protect our brains during birth, providing a natural safeguard against a problematic delivery. A recent study of pregnant rats, led by Yehezkel Ben-Ari of the Mediterranean Institute of Neurobiology in Marseille, France, examined the effects of the hormone oxytocin. Oxytocin plays well-known roles in bonding between mates, it increases trust among people—and a surge of the hormone can also trigger the onset of labor. Ben-Ari's team found that during this same surge, oxytocin latches onto receptors in a fetus's brain. There the hormone acts somewhat like a tranquilizer and lowers the firing rate of a key class of neurons. "I have never seen such a stong inhibition," Ben-Ari says. The effect reaches its peak right before delivery, then wears off in a day. The tranquilized brain tissue from rat fetuses receiving this hormonal boost resisted damage caused by oxygen deprivation for 25 percent longer than tissue from fetuses in which the hormones were blocked. Ben-Ari argues that oxytocin probably works the same way to protect humans during birth, because the mechanisms behind this brain shutdown are common to all mammals. |