Brain Rules for Baby by John Medina Page B

control.
    • Too much for you. Mental-health professionals have known for decades that some people are more sensitive than others to stressful events. If you have a tendency to be stressed all the time, so will your womb. We have increasing evidence that part of this stress sensitivity is genetic. Women under such a biological dictatorship will need to keep stress to a minimum during pregnancy.
    Rats! Dropped ‘em again!
    Lots of research has gone into trying to understand how maternal stress affects brain development. And we have begun to answer this question at the most intimate level possible: the level of cell and molecule. For this progress we mostly can thank the klutzy researcher Hans Selye. He is the founder of the modern concept of stress. As a young scientist, Selye would grind up “endocrine extracts”, which presumably contained active stress hormones, and inject them into rats to see what the rats would do. He was not good at it.
    His lab technique, to put it charitably, was horrible. He often dropped the poor lab animals he was attempting to inject. He had to chase them around with a broom, trying to get them back into their cages. Not surprisingly, the rats became anxious in his presence. Selye observed that he could create this physiological response just by showing up. His main job was to inject some animals with endocrine extract and others, in the control group, with saline. But he was perplexed to discover that both were getting ulcers, losing sleep, and becoming more susceptible to infectious diseases.
    After many observations, he concluded that anxiety was producing the effect, a concept surprisingly new at the time. If the rats couldn’t remove the source of anxiety or cope with it once it arrived, he found, it could lead to disease and other consequences. To describe the phenomenon, Selye eventually coined the term “stress.”
    Selye’s insight led to that rarest of all findings: the link between visible behaviors and invisible molecular processes. Selye’s work gave the research community permission to investigate how stressful
perceptions could influence biological tissues, including brain development. We know a lot about how stress hormones affect growing neural tissues, including a baby’s, thanks to this pioneering insight. Though most of the research was done on rats, many of the same key processes have been found in humans, too.
    The important stress hormone is cortisol. It’s the star player in a team of nasty molecules called glucocorticoids. These hormones control many of our most familiar stress responses, from making our hearts race like NASCAR autos to a sudden urge to pee and poop. Glucocorticoids are so powerful, the brain has developed a natural “braking” system to turn them off as soon as the stress has passed. A pea-sized piece of neural real estate in the middle of the brain, called the hypothalamus, controls the release and braking of these hormones.
     
    Bull’s-eye: Baby’s stress-response system
    A woman’s stress hormones affect her baby by slipping through the placenta and entering the baby’s brain, like cruise missiles programmed to hit two targets. This is the basis of the Brain Rule: Stressed mom, stressed baby.
    The first target is the baby’s limbic system, an area profoundly involved in emotional regulation and memory. This region develops more slowly in the presence of excess hormone, one of the reasons we think baby cognition is damaged if mom is severely or chronically stressed.
    The second target is that braking system I mentioned, the one that’s supposed to rein in glucocorticoid levels after the stress has passed. Excess hormone from mom can mean baby has a difficult time turning off her own stress hormone system. Her brain becomes marinated in glucocorticoids whose concentrations are no longer easily controllable. The baby can carry this damaged stress-response system into adulthood. The child may have a difficult time putting on the brakes