Rats to Humans, the Importance of Animal Studies

Michael Meaney set out to test whether baby rats who are licked more turn out differently from those who are licked and groomed less and if so, why. (Meaney is at the Douglas Mental Health University Institute and is a leading researcher in maternal care, stress gene expression and epigenetics: http://www.douglas.qc.ca/researcher/michael-meaney.) These studies on the origins of adult disease rigorously tested whether it really is the mother's behavior that makes the difference and showed what happens in the brain of the offspring to produce the adult characteristics. Meaney and his research team found that baby rats who were licked by their mothers a lot turned out to be less anxious and fearful as adults and produced lower levels of stress hormones than those who were groomed less. “All the mothers nurture their pups, provide ample milk, and the pups grow perfectly well,” Meaney said, “But there is one behavior, called licking and grooming, that some mothers do much more than others—four or five times as much. The pups who are licked more are less fearful, they produce less stress hormones when provoked, and their heart rate doesn't go up as much, so they have a more modest stress response than the pups who are licked much less”.

The scientists even took the mothers out of the picture altogether and stroked the baby rats with paintbrushes. Meaney maintains, “It does the same thing that maternal licking does.” The change in the production of the brain receptors was apparent by the second week of life.

“This is a very important study,” said Peter Blackman, a professor of pediatric and prenatal biology at the University of Auckland in New Zealand, who was not involved in the research. He pointed out that the expression of genes in mammals can be permanently changed by how mothers and infants interact and how that can have long-term effects on behavior and psychiatric health. If those baby rats were licked just as much weeks later, the critical period would have passed and the lifelong effects would not be evident.

I am going to quote from a book called “Monkeyluv” by Stanford University biologist and neuroscientist, Robert M. Sapolsky (Scribner, N.Y. 2005). We see in his reported research on mice how early the critical period can be. Not only are early childhood events important for later life but even more important is fetal life. Sapolsky was commenting on how genetic influences are not the be-all-and-end-all that we sometimes believe; not only are life circumstances important but pre-birth influences can be critical.

“Relaxed-strain mice that were raised from birth by timid-strain moms grew up to be just as relaxed as any other member of their strain (strains are genetically uniform groups of animals). With the same kind of technology used by clinics performing in vitro fertilization, the investigators cross-fostered mice as embryos (cross-fostering is letting one strain of mice raise a genetically different strain of mice). They implanted relaxed-strain eggs into timid-strain females who carried them to term. Some relaxed-strain pups were raised by timid-strain moms, and others by relaxed-strain ones. The result? When the supposedly genetically hard-wired relaxed mice went through both fetal development and early puphood with timid-strain moms, they grew up to be just as timid as any other timid-strain (inherited) mice. Same genes, different environment, different outcome.” (page 52) Sapolsky then goes on to comment: “Environmental influences don’t begin at birth. Some factors in the environment of a timid-strain mouse mother during her pregnancy—her level of stress…are affecting the anxiety levels and learning abilities of her offspring, even as adults.” He emphasizes that “relaxed-strain mice aren’t relaxed only because of their genes; their fetal and neonatal (around birth) environments are crucial factors.” (page 53) There is a growing body of research with animals, and more recently with humans, that corroborate my point: birth and pre-birth events can help determine our behavior as adults; and if we neglect these influences we shall not fully understand who and why we are what we are. Moreover, we shall not know how to treat and reverse all manner of problems we have as adults. From conception on we are building a superstructure. We need a solid foundation for that superstructure so that we can be integrated adults who can withstand the impact of the elements. Conclusion: genetics is important but life experience, even in the womb, can be equally if not more important. Whether we manifest high blood pressure, asthma or migraine not only depends on genetics but what happened to us very early on. If we ignore life in the womb we are leaving out life experience that can affect us for a lifetime.

One wonders, “can we really go back and reexperience fetal events?” Let me put it this way: in evolution each new level of brain development incorporates lower, earlier levels. The thinking neocortex is a sort of an add-on from previous animal brain forms. So at birth there are already sensations from pre-birth that play a part in how the newborn reacts to that birth trauma. When a patient relives a birth trauma (if there were one), she is in fact also experiencing sensations (the base of feelings) that occurred previously. This is how we can relive pre-birth events without being aware that they come from experience in perhaps the fifth or sixth month of gestation.

As a general rule, the earlier in life a need goes unmet, the more devastating the later effects of deprivation will be. The closer to the “critical period” a trauma occurs, the more harmful it is. One way we can define critical period is the irreversible quality of its effects. The more time that has elapsed after a critical period has passed, the greater the force required to create an imprint. It takes a tremendous trauma after the critical period to have a profound and lifelong effect. Why do needs go unmet? For a passel of reasons, but it is often true that parents are so immersed in their own unmet needs (with the resulting narcissism) and pain that they simply cannot attend to their child.