What makes a mother? Alison Fleming, a behavioural neuroscientist and professor of psychology at the University of Toronto Mississauga, has spent three decades asking this question. She’s carried out dozens of experiments over 30 years, trying to understand what’s on mothers’ minds — literally.
Fleming began her career investigating the psychological changes mother rats undergo as a result of pregnancy hormones. She later became interested in identifying which parts of the brain were involved in the psychological changes she observed.
“In a new rat mother you see a very rapid proliferation of cells in the hippocampus that migrate to various places elsewhere in the brain,” she says. The mother’s dendrites — thread-like extensions of neurons that receive electrochemical stimulation — become more complex when a she’s interacting with her babies. “We found through a variety of experiments that a part of the brain called the amygdala is also very important for mothering.” In rats that had never given birth she found that this part of the brain, which mediates emotion, was inhibited. In mothers, hormones worked to remove that inhibition.
Later, she started looking at humans. “I began thinking about how mothering is so complicated. Mothers undergo not just hormonally regulated changes in mood, but also changes in cognition — how they think, pay attention, remember and plan. We call this executive function.”
Fleming’s main focus today is on the long-term effects of mothering. “How you are mothered yourself influences your neurotransmitters, neurogenesis, emotion and executive function.” It even shapes what kind of mother you will be to your own kids.
Sound like a lot of pressure? No need to worry: Fleming says there is no one right way to mother.
On the extremes,” she concedes, “there can be bad mothering. Harming a baby, for example, is definitively bad. But there is huge variation in the way that people interact with babies. If you look cross-culturally, what would be considered optimal mothering in one culture would not be in another. Some cultures, like ours in North America, believe in autonomy and individual development. Other cultures think that interdependence is what matters, so the way women mother is different. For example, they might strap their babies to them. But one way isn’t better than the other.”
Fleming stresses that biology is not destiny.” Early experiences of being mothered combine with all kinds of inputs ranging from genetic to nutritional to social to shape a person. Scientists are just beginning to untangle these factors.
In fact, “mothering” doesn’t even have to come from a mother. Fleming once gave female rats that had never given birth newborn rat pups to care for. Initially they rejected the pups, sometimes even going so far as to bury them. But after about five days, they started acting like mothers, licking their “babies” and adopting nursing postures even though they didn’t have any milk.
Human studies by Fleming and others have shown the same effect: hormones might “turn on” mothering in rats’ brains or “prime” it in humans, but sensory input, usually in the form of exposure to a baby over time, can create the same outcome — a compulsion to nurture — in both men and women.
“The brain mechanisms are in place in everyone,” she says. “I don’t believe that the only person who can raise a child is a mother. It’s really about being attuned and sensitive and responsive.”