The men's pattern of brain activity resembles that of both new
mothers and new fathers in the study.
The research, reported on Monday, could feed into the debate over
whether gay men should be allowed to adopt children. Many U.S.
adoption agencies will not work with same-sex couples, and some
states prohibit them from adopting.
The current study, published in Proceedings of the National Academy
of Sciences, was conducted in Israel, and builds on work by
neuropsychologist Ruth Feldman of Bar-Ilan University and others,
who showed that the brains of new mothers become hyper-reactive to
their child's cries and other emotional cues.
It was not clear if that pattern is a result of the hormonal and
other changes that accompany pregnancy or a response to the
experience of motherhood.
To find out, Feldman and her colleagues videotaped 89 new mothers
and fathers interacting with their infants at home. They then
measured the parents' brain activity while watching the videos in an
MRI tube, and again (to establish a baseline) while watching videos
that their kids did not star in.
In the 20 mothers in the study, all primary caregivers, watching
their babies triggered heightened activity in the brain's
emotion-processing regions, particularly in a structure called the
amygdala, which was five times more active than at baseline.
"These are regions that respond unconsciously to signs of an
infants' needs, and that derive deep emotional reward from seeing
the baby," Feldman said.
For the 21 heterosexual fathers - who were very involved in raising
their baby but whose wives took the parenting lead - watching their
infant increased activation of cognitive circuits, particularly a
structure that interprets a baby's cries and non-verbal cues. It is
the region that knows which squirm means "I'm about to scream" and
which means "change me."
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The 48 gay fathers raising children with their husbands seemed to be
both mom and dad, brain-wise. Their emotional circuits were as
active as those of mothers and the interpretive circuits showed the
same extra activity as that of heterosexual fathers'.
Ideally, scientists would perform neuroimaging on men and women
before and then after they became parents, to show definitely that
any heightened activity followed junior's arrival and was not
present before. Until they can do that, Feldman said, she is
confident that the telltale brain activity results from parenting.
One clue: in gay fathers, but not heterosexual ones, the brain also
had extra communication lines between emotional and cognitive
structures. The more time a man spent as primary caregiver, the
greater the connectivity. It was as if playing both parental roles
caused the brain to integrate the structures required for each.
"Fathers' brains are very plastic," Feldman said. "When there are
two fathers, their brains must recruit both networks, the emotional
and cognitive, for optimal parenting."
(Reporting by Sharon Begley; Editing by Steve Orlofsky)
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