Farah wanted to investigate the huge differences she saw.
"We're so segregated by class, we don't even realize we're segregated because we don't even know what life is like just two miles north of here," she said.
How parenting matters
Farah and colleagues have conducted research suggesting that high-stress childhoods, which include less warm parenting, are correlated with changes in stress physiology and stress regulation.
One study, published in March in the journal PLOS One, involved African American adolescents who came from households of low socioeconomic status. At age 4, their parents' responsivity (warmth and supportiveness) was evaluated. Then, 11 to 14 years later, the same participants took a stress test: Giving a talk in front of an unfriendly audience.
Volunteers gave saliva samples so that researchers could analyze it for the stress hormone cortisol. Researchers found that cortisol reactivity was related to parental responsivity, and the less parental responsivity, the less of a normal stress response the volunteers had.
"You might say, 'Well, of course life is more stressful in lower socioeconomic strata,' " she said. "But the degree of magnitude of the stress that they live with is just unbelievable."
Such research points to the idea that stress leads to a stunting of brain development in children of low socioeconomic backgrounds. It is unknown whether that stunting can be reversed, but you shouldn't assume that it's unchangeable, Farah said.
In animal models, researchers have found that later enriching experiences can at least partially compensate for the effects of early life stress on the hippocampus -- a seahorse-shaped structure in the brain vital for memory and stress reactivity -- and other brain areas. It's not that the initial effects of the stress are reversed, though; it appears that different pathways are enabled to compensate.
"If you're interested in child policy and stuff, the important bottom line is: You never want to say, 'Oh, damaged goods, so there's nothing we can do now,' " she said.
Farah is quick to add that middle-class parents aren't perfect either. Eagerly watching children for every small advance in development, and showering children with praise, isn't necessarily helpful either.
"But I am also willing to make a value judgment: Smacking young children, saying a lot of negative things to them, not talking to them very much, is bad." She hits the table. "Let's just say it."
A study in progress
Across the Penn campus in the radiology department, Farah sits in a low chair while Brian Avants, assistant professor of radiology, explains their recent study, using a slide on a computer screen. Farah presented the study at the Society for Neuroscience meeting in November.
Researchers followed 53 children who came from low socioeconomic status from birth through adolescence. This is a relatively small number of participants, but it is typical for brain imaging studies.
Participants were evaluated on two scales: Environmental stimulation -- such as "child has toys that teach color" at age 4, and "child has access to at least 10 appropriate books" at age 8 -- and parental nurturing, such as "parent holds child close 10-15 minutes per day" at age 4, and "parents set limits for child and generally enforce them" at age 8.
Researchers looked at whether cortical thickness in young adulthood could be predicted by the earlier environmental stimulation and parental nurturing measurements. Greater cortical thickness in childhood is associated with poor outcomes such as autism, Avants explained. Later in adolescence, relatively reduced cortical thickness is linked to higher IQ and other mental processes.
From this study, Farah and colleagues suggested that environmental stimulation at age 4 predicts cortical thickness in the late teenage years, but parental nurturing did not appear to be linked.
The study hasn't been published yet. Their next step: Understanding how brain differences emerge, starting with infants.
With the first weeks and months of life, Farah and colleagues believe they will find differences in the brains of infants of low socioeconomic groups. Led by Hallam Hurt of the Children's Hospital of Philadelphia, the group has been scanning the brains of infants as young as 1 month old.
If they do find brain differences in babies associated with socioeconomic status, this could be attributable to a number of factors, including stress, nutritional factors, health care, environmental toxins and second-hand smoke.
A better future, a better brain
As enthusiastic as Farah and colleagues are about the work they are doing, obtaining funding is always a challenge -- hence, the grant proposal she was working on last week. When she first started this work around 2000, she was met with skepticism about looking at poverty's effects on the brain, she said, as if her research would equate poverty with brain disease or worse.
In a tongue-in-cheek way, Avants said he and Farah have discussed defining a "disease" with all the symptoms of poverty and its effects on development. "Then it might be very easy to get funding," he said.
There are far fewer children with autism than there are poor children in the United States, for example, but autism as a condition gets more attention from the science community than the neurological implications of poverty, he said.