By age 4, children in families living with incomes under 200 percent of the federal poverty line have less gray matter—brain tissue critical for processing of information and execution of actions—than kids growing up in families with higher incomes.

"This is an important link between poverty and biology. We're watching how poverty gets under the skin," says Barbara Wolfe, professor of economics, population health sciences and public affairs and one of the authors of the study, published today in the journal PLOS ONE.

The differences among children of the poor became apparent through analysis of hundreds of brain scans from children beginning soon after birth and repeated every few months until 4 years of age.

http://medicalxpress.com/news/2013-12-poverty-children-early-brain.html

Family Poverty Affects the Rate of Human Infant Brain Growth (entire article)