“Mommy Brain” Found in Stickleback Fathers

Many new parents are familiar with terms like “mommy brain” that hint at a decline in cognitive function associated with the hormonal changes of pregnancy, childbirth, and maternal caregiving. A new study of parental care in stickleback fish is a reminder that such parenting-induced changes in the brain are not just for females—and they’re not just for mammals, either.

A University of Illinois at Urbana–Champaign study published today in Nature Communications found that transition to fatherhood is accompanied by a host of changes in gene activity in the brain. The study focused on male sticklebacks because they, rather than female sticklebacks, provide parental care to eggs and fry.

“The male stickleback defends the territory, he builds the nest, he attracts a female to spawn… and the nest is everything to him: It’s where his babies are, it’s the center of his territory,” says senior author Alison Bell. “Then the eggs hatch after about a week; he’s still defending a territory, he’s still protecting his kids, he still has a nest, but all of a sudden he’s interacting with his offspring in a different way compared to when they were just eggs.”

The researchers examined gene expression before spawning occurred, after the male began tending his eggs, and at three points throughout the hatching process. They identified a set of genes whose expression was altered by one or more of these transitional phases of stickleback parenting and then took a closer look at which genes were responding and what functions they might be performing in the paternal brain.

The team designed a method to compare the neural responses of the relatively disparate stickleback and mouse genomes and found that there was overlap between stickleback paternal care genes and mouse maternal care genes. “Genes associated with mothering like oxytocin and prolactin and galanin, these are things you read about in the vertebrate mammalian literature all the time, and now they were popping up in our data set,” Bell says.

Although “mommy brain” is popularly associated with a loss of cognitive function, the stickleback study, like other animal and human research, suggests a more nuanced picture in which hormonal signaling and external cues help prepare male and female brains for parenthood.

“A long time ago in our evolutionary history, these changes were happening for dads in the most powerful way, as it happens for mammalian moms. I feel like that takes a little bit of the edge off the sexist connotations of ‘mommy brain,’” Bell says. “It’s no wonder it is such a transformative experience. I just think that it’s happening to dads too.”