SEQUOIA NATIONAL PARK

THIS IS YOUR BRAIN WITH DAD
BY SHIRLEY S. WANG

Conventional wisdom holds that two parents are better than one. Scientists are now finding that growing up without a father actually changes the way your brain develops.

German biologist Anna Katharina Braun and others are conducting research on animals that are typically raised by two parents, in the hopes of better understanding the impact of being raised by a single parent. Dr. Braun’s work focuses on degus, small rodents related to guinea pigs and chinchillas, because mother and father degus naturally raise their babies together.

When deprived of their father, the degu pups exhibit both short- and long-term changes in nerve-cell growth in different regions of the brain. Dr. Braun, director of the Institute of Biology over at Otto von Guericke University in Magdeburg, and her colleagues also are looking at how these physical changes affect offspring behavior.

Their preliminary analysis indicates that fatherless degu pups exhibit more aggressive and impulsive behavior more than pups [which were] raised by two parents.

In a study the researchers presented the Society for Neuroscience meeting in Chicago earlier this month and recently published in the journal Neuroscience, half the degu pups were raised with two parents, while the others were raised by a single mother, the father having been removed from the cage one day after the birth of his offspring.

The researchers then looked at the neurons—cells that send and receive messages between the brain and the body—of some pups at day 21, around the time they were weaned from their mothers, and others at day 90, which is considered adulthood for the species.

Neurons have branches, known as dendrites that conduct electrical signals received from other nerve cells to the body, or trunk, of the neuron. The leaves of the dendrites are protruisions called dendritic spines that receive messages and serve as the contact between neurons.

Dr. Braun’s group found that at 21 days, the fatherless animals had less dense dentritic spines compared to animals raised by both parents, though they “caught up” by day 90. However, the length of some types of dendrites was significantly shorter in some parts of the brain, even in adulthood, in fatherless animals.

The neuronal differences were observed in a part of the brain called the amygdala, which is related to emotional responses and fear, and the orbit frontal cortex, or OFC, the brain’s decision-making center.

‘A Horse Without a Rider’

The balance between these two brain parts is critical to normal emotional and cognitive functioning, according to Dr. Braun. If OFC isn’t active, the amgdala “goee crazy, like a horse without a rider,” she says. In the case of the fatherless pups, there were dentritic spinesin the OFC, while the dendrite trees in the amygdala grew more and longer branches.

A preliminary analysis of the dengus’ behavior showed that fatherless animals seem to have a lack of impulse control, Dr. Braun says. And, when they played with siblings, they engaged in more play—fighting or aggressive behavior.

Of course, the frontal cortex—where thinking and decision-making taking place—is more complex in humans than it is in other animals. Thus, says Dr. Braun, it is important to be “really careful” about extrapolating the recent findings to human populations.

“The minute you get into stuff with extensive social and environmental components, the social differences between humans and animals are massive,” says Simon Chapple, a senior economist in the social policy division of the Organization for Economic Cooperation and Development, the 30-country grouping of the world’s largest economies.

It remains an “open verdict” whether single parenthood causes these bad outcomes, or is merely associated with them, says Dr. Chapple.

Risk of Delinquency

Still, the prevalence of single-parent households has researchers looking at possible consequences for children. An OECD report found that just 57% of children in the U.S. live with both parents, among the lowest percentages of the world’s richest nations.

The report, which sparked some controversy when it was released in September, found that children in single-parent households have an increased risk of delinquency and attention deficit hyperactivity disorder, or ADHD, as well as poorer scholastic performance.

Dr. Braun’s goal for future research is to figure out whether degu pups’ brains can be rewired by introducing a substitute caregiver, such as a grandmother, or whether other social and emotional enrichment can help “repair” the fatherless pups, she says. Human children may be sent to day care, for instance, which can help them form stable friendships with their peers and other adults.

The bottom line, says Dr. Braun, is that parents need to fuel their children’s brains with talk, touch and sensitive stimulation that involves give and take.

“Parents,” she says, “are the sculptors of their children’s brains.”