Research suggests that parenting affects the molecular development of the offspring’s brain, at least in rats.
A decade ago Prof. Meaney noticed that newborn rats whose mothers rarely lick and groom them grow up… well, there is a fancy biochemical description for it, but let’s just say that they grow up a bit of a neurotic mess. Pups of attentive moms grow up less fearful, more curious, mellower.
Prof. Meaney and his team then showed that this wasn’t a case of mellow moms having mellow kids and neglectful moms having maladjusted kids, as the DNA-as-destiny crowd would have it. When the scientists switch around the newborns so that rat pups born to attentive moms are reared by standoffish moms, the pups grow up to be extremely stressed out, nearly jumping out of their skins at the slightest stress. Pups born to standoffish moms but reared by attentive ones grow up to be less fearful, more curious, more laid-back, taking stress in stride.
Rearing, it turns out, affects molecules in the brain that catch hold of stress hormones. Licking and grooming increases the number of these receptors. The more such receptors the brain has in the region called the hippocampus, the fewer stress hormones are released; the fewer the stress hormones coursing through its body, the mellower the rat.
It turns out that all newborn rats have a molecular silencer on their stress-receptor gene. In rats reared by standoffish mothers, the silencer remains attached, the scientists will report in the August issue of Nature Neuroscience. As a result, the brain has few stress-hormone receptors and reacts to stress like a skittish horse hearing a gunshot.
But licking and grooming by an attentive mother literally removes the silencer; the molecule is gone. Those baby rats have lots of stress-hormone receptors in their brains and less stress hormone, and they grow up to be curious, unafraid and able to handle stress.
Mellow or Stressed? Mom’s Care Can Alter DNA of Her Offspring, By Sharon Begley, July 16, 2004, Science Journal, Wall Street Journal