Like humans, fish experience "baby brain," a decline in cognitive function caused by chemical changes triggered by pregnancy, childbirth and parental caregiving.

Typically, new moms experience the effects of baby brain, or "mommy brain." But a study of stickleback fish behavior revealed signatures of baby brain among males.

Traditional parenting roles are reversed among sticklebacks, with males assuming the responsibility of caring for the 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," Alison Bell, a professor of evolution, ecology and behavior at the Carl R. Woese Institute for Genomic Biology at the University of Illinois, said in a news release. "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."

Fatherhood demands a variety of behavioral changes in male sticklebacks -- new responsibilities. The fish must subvert their own needs and focus on those of their offspring.

Stickleback fathers must keep the nest clean, fan water over the fertilized eggs and guard their young from predators. They must also collect fry that wander too far from the nest. Though fathers must exhibit nurturing behavior, they must also be ready response with speed and aggression toward threatening intruders.

In female mammals, studies suggest mommy brain is triggered by a variety of hormonal changes brought on by the gestation and lactation processes. These processes are absent in male fish.

"The cues that these dads are getting, they are exogenous, they're not inside his body; these are eggs that are in his nest," Bell said. "It's something that's happening exogenously and socially."

For the study, scientists measured gene expression changes in new stickleback fathers. Researchers measured gene expression patterns prior to spawning, after the expecting dad started tending his eggs and at three points during the hatching process.

Scientists measured changes similar to those observed in new moms.

"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 said. "That's part of why we thought it would be really interesting then to compare to mouse."

In female mammals, oxytocin facilitates both the labor process and social bonding. Prolactin encourages milk production. Fish boast similar hormones, as well as galanin, which has been shown in mice to quell aggressive behaviors toward young.

Researchers compared the genetic expression changes observed in sickleback fathers with those measured in female mice moms.

"There was overlap . . . between these stickleback paternal care genes and the mouse maternal care genes," Bell said. "It's surprising to think that the same molecular mechanisms could be involved in parental care in a fathering fish and in a mothering mammal."

Researchers found that genes that were quieted for parenting duties were magnified for protection duties.

"Genes that were going up after a guy has a fight, those are the ones that are going down while he's caring for kids," Bell said.

The new research -- published Monday in the journal Nature Communications -- suggests a combination of hormonal, exogenous and social cues inspire genetic and cognitive changes in both male and female parents.

"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 said. "It's no wonder it is such a transformative experience. I just think that it's happening to dads too."

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