Fathers and their children reshape one another's neurons.
Last May, I took a trip to San Diego for my brother-in-law’s
graduation from college, and to meet his 4-month old son, Landon, for
the first time. Throughout the weekend, I couldn’t suppress my inner
science nerd, and often found myself probing my nephew’s foot reflexes.
Pressured from my wife’s disapproving looks and the blank stares I
received from her family as I explained why his toes curled this way or
that, I dropped the shop-talk in favor of baby-talk.
Having spent my postdoctoral career in neuroscience, brain
development is particularly fascinating to me. But on this family visit,
more striking than the baby’s neurodevelopment was the re-development
of my 26-year-old brother-in-law.
In just a few months’ time, Jack went from my wife’s little brother
to a hands-on, first-time father. When I first met Jack, he was a tall,
lanky, wet-behind-the-ears nineteen-year-old kid, who enlisted in the
U.S. Navy right after graduating high school. As a two-tour Iraq war
veteran, Jack saw more of the world in six years than most of us ever
will, and had a large repertoire of crazy sailor stories to boot.
Still, raising Landon will no doubt be the biggest challenge Jack’s
ever faced. Whether he knows it or not, and whether he likes it or not,
things are about to drastically change for him. By the end of the
weekend trip, I saw glimpses that Jack had come to terms (well, sort of)
with the fact that his life will never be the same: After struggling
with securing Landon’s car seat in the back of his souped-up Mazda RX-8
for several weeks, Jack finally broke down and traded it in for a more
sensible car that will make it easier to transport the little guy.
The birth of a child is arguably the most important event in parents’
lives. It’s fairly easy to wrap our heads around the notion of the
mother-child bond. The two are intimately connected during the nine
months of pregnancy. Hormones, such as oxytocin, that course through a
mother’s body biologically link her to the baby. Their heartbeats can even synchronize. Following
birth, a mother provides a natural food source for the newborn. In
stark contrast, we know very little about the biology of the
father-child bond.
After conception, men aren't exactly needed to keep their child
alive. They don't gestate or lactate. Yet research shows that the
father-child bond is crucial to a kid’s future success. If a father
leaves his offspring to be raised solely by their mother, the children
are more likely to suffer emotional troubles, be aggressive, experience addiction issues, or have run-ins with the law.
Since there's no clear physical connection between a father and his
child — at least not like the one seen with mom and baby — researchers
are starting to look deep in the brain for better clues to understand
the power of this relationship. A recent wave of studies are starting
to bear fruit: We are now learning that in the first few days after
birth, changes occur in the brains of both the dad and the baby,
depending on whether the father is around or not. Perhaps
neuroscientists have finally cornered the elusive father-child bond, and
found the b iological hook that makes sure a father sticks around after
birth.
Brains are not static, and neurons constantly rewire themselves
throughout life. Not only do brain cells alter their connections, but
additional neurons can also spontaneously form, a process called
neurogenesis. While the mechanism of neurogenesis is not fully
understood, extra brain cell growth is strongly correlated to learning new things.
A recent study
has shown that neurogenesis took place in male mice in the days
following the birth of their pups. But the extra boost of brain cells
only occurred if the mouse father stayed in the nest. In other words, if
he was removed on the day of their birth, nothing happened. One new set
of brain cells formed in the olfactory bulb, and were specifically
tuned to the smells of his pups. Another set of neurons grew in the
hippocampus, a crucial memory center in the brain, which helped to
consolidate the smell of his pups into a long-term memory.
In mammals, neurons located in the nose detect scents using special
odor receptors, and shuttle the information to the olfactory bulb, which
is the integration center for smell. Yet smelling his pups alone was
not enough to cause new neurons to form. When the researchers separated
the father from his pups by placing a mesh screen between them in the
cage, no additional brain cells appeared. The father had to be
physically present in the nest in the early postnatal days to get
another dose of neurons. The physical contact he had with his pups in
the nest coupled with the smells of his young are what made the neurons
grow.
The brain cells that formed when a father interacted with his offspring were also regulated by a hormone called prolactin. This
means that the same hormone responsible for milk production in the
breasts of new mothers also seems to be involved in fostering the
postnatal connection between a father and his offspring. Mouse fathers
that had the prolactin gene turned off did not form any
offspring-specific brain cells.
Being separated for a few weeks time is usually long enough for adult
mice to forget their cage mate pals. But these new neurons helped to
form long-term memories and bonds, as the mouse fathers easily
recognized their offspring by smell even after they had been separated
for a long period of time.
While it appears the seed of the father-child bond is planted by
supplemental neurons in a new dad, it seems a child, on the other hand,
may be born with a brain that expects this bond to form in the first
place.
To prove this, a few recent studies turned to a rodent that employs a remarkably familiar nest structure. Degu rats are biparental animals,
which means parenting duties are split between the mothers and
father. Degu fathers behave just like human fathers. They spend the
early days of their pups’ lives helping with basic care, like warming
and grooming. And as the pups get older, the degu fathers begin actively
playing with their toddler offspring.
Researchers reasoned that absent fathers in the degu nests would
create a true social and emotional void for the offspring, just as a
missing dad would impact the dynamic of a human family. They found that
if a rodent father remained in the nest with his pups – presumably due
to the newfound bond with his offspring – his babies’ brains developed
normally. But if the father was removed from the nest shortly after the
birth of his pups, his newborns’ brains started to break down at the
level of synapses, which are short chemical junctions in the brain that
allow brain cells to communicate with each other.
Specifically, the degu pups raised without fathers had fewer synapses in both the orbitofrontal cortex and the somatosensory cortex. Having
fewer synapses can alter the way information is processed in the young
animals, and would make these brain areas perform abnormally.
The orbitofrontal cortex is a part of the prefrontal cortex that
regulates decision-making, reward, and emotion. Extrapolating from the
degu rat experiments, faulty synapses and processing problems in this
locale may ultimately explain why we see some kids who grow up without a
father in their life wrestle with (sometimes very serious) behavior
problems.
These rat studies square with what we already know about the role of
touch in neurological development. Having spent the prior weeks with the senses
deprived while afloat in amniotic fluid, a newborn animal's
somatosensory cortex is ripe for change. But instead of flourishing in
the early postnatal days, the synapses of the somatosensory cortex
wither away when degus are raised without a father. As a consequence,
the newborns may not process touch as well as they should, which could
lead to a number of other developmental problems, like metabolism issues or irregular hormone production.
These animal studies show that a father's brain is significantly and
beautifully intertwined with his offspring's. For whatever reasons, be
they biological, evolutional, or societal, the onus of human parenthood
has traditionally fallen on the mother. But the evidence is showing that
a father has direct influence on his child's neurodevelopment – and
indeed, his brain can benefit as well.
Perhaps my nephew, bolstered by a healthy set of brain connections,
formed in response to something as simple as Jack's touch, may already
have the required tools to meet with behavioral and emotional challenges
as he gets older. And while I can't exactly probe Jack's brain to see
if he's sprouting neurons, I noticed an undeniable change in his focus,
as his new bond took hold. Small movements and sounds from Landon that
went unnoticed by most mysteriously caught Jack’s attention. It’s
comforting to think that, in some way, there’s a small set of neurons
tucked away in Jack’s head solely dedicated to his son.
Source: Scientific American – http://tinyurl.com/2fob2dn
