Dad Brains: How Fatherhood Affects Grey Matter

A new child brings immediate responsibilities and stresses, but a person doesn't "become a father" overnight.

September 25, 2014

Nicholas Hune-Brown is a National Magazine Award-winning journalist who has written for Toronto Life, The Walrus, Reader's Digest, The Believer, and...

In a feature on the Toronto Raptors point guard published on Grantland this week, writer Jonathan Abrams tries to get to the bottom of the Kyle Lowry transformation. How does a player with a reputation as a hardheaded teammate with a bad attitude become the mature leader of an NBA team? Abrams cycles through Lowry’s various mentors and coaches, considers the effects of his new team and fresh environment, before finally settling on the key to the change: Lowry’s marriage and, especially, the birth of his son Karter.

“Every day I’m in that gym, I know it’s for a reason,” Lowry told Abrams. “I want to be the best, but I know [Karter] wants me to be the best. Even if he doesn’t understand it. I want to make sure I can take care of him for the rest of his life or my life. As long as I’m alive, I want to be able to say, ‘I’m taking care of you.’”

It’s a familiar story about the transformative power of fatherhood—the boy only becomes a man when he himself becomes a father. It’s the plot of Knocked Up, the stated explanation for Louis C.K.’s mid-career burst of creativity, the central narrative of countless sports profiles like Lowry’s. For Lowry and anyone else who has suddenly felt the weight of responsibility that comes with the arrival of a mewling, helpless infant, fatherhood brings a jarring shift in priorities. Only recently, however, have researchers begun to look at the possible neurological changes that might come with this shift. Being a father changes your attitude, but could it change the very composition of your brain?

A recent study published in the journal Social Neuroscience looked at paternal brain structures after the birth of a child. While there have been plenty of studies focused on the neurology of mothers, the researchers claim this is the first to look at the way parenthood might transform a father’s neural anatomy. The team, led by neuroscientist Pilyoung Kim, examined 16 biological fathers, seven of whom were new parents. The researchers took MRIs of each father twice, once 2-4 weeks after the birth of their child, and then again at 12-16 weeks.

From their first scan to their second, the change was significant. Test subjects showed an increase in the volume of grey matter in various regions of the brain: the striatum, amygdala, and hypothalamus; fatherhood had literally made their brains grow. In fact, past studies on animals have shown that these regions of the brain are important in regulating parental behaviour—they help parents understand how to react to their children, and are important in rewarding the experience of parental attachment. There was also increased grey matter in the lateral pre-frontal cortex, a region the researchers say plays a role in the complex decision-making processes that come with being a parent. According to other studies, it’s the part of the brain that lights up when fathers look at their kids.

For Kim and her team, the change in paternal brains was expected; the growth is comparable to Kim’s earlier findings in her studies on new mothers. Unlike mothers, however, fathers also showed a significant decrease in grey matter in various regions. They lost volume in the parts of the brain that make up what’s known as the “default-mode network,” which light up when you aren’t focused on one specific task. It’s the network that, according to recent research, may be associated with daydreaming and introspection. The researchers can’t be sure what causes this decrease, but they suggest it could simply be a matter of shifting resources—there’s less need for mental meandering when you are, for example, intensely focused on making sure your newborn child doesn’t die.

They also acknowledge that, with just 16 subjects, the current study is extremely limited. And with no testing beyond four months, they can’t be sure that the brains of fathers don’t just revert to their pre-fatherhood state once the initial months of frantic childcare are over. But while the study raises more questions than it ultimately resolves, it’s a promising early step—a move towards understanding the neurology of fatherhood in the same way we understand the changes that come with being a mother. It also introduces a small wrinkle into the usual story we tell about having a child. While the arrival of a child brings immediate responsibilities and stresses, a person doesn’t “become a father” overnight. It’s a process that happens over time—day by day, neuron by neuron.

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Nicholas Hune-Brown is a National Magazine Award-winning journalist who has written for Toronto Life, The Walrus, Reader's Digest, The Believer, and many other publications.