Article summary with The neuroscience of socioeconomic inequality by Noble & Giebler - 2020

What correlations have been found that link socioeconomic inequality with brain structure?

• Socioeconomic status has been linked to cortical surface area, cortical thickness, and gray matter volume, especially in frontal and temporal regions which support the development of language, executive function, attention, memory, and emotion regulation.
• Family socioeconomic characteristics (parental education and family income) have been linked to children´s hippocampal volume, which is a structure that is important for learning and memory.
• Socioeconomic disadvantage has been linked with slower longitudinal growth of the hippocampus.
• Socioeconomic differences have been found in white matter microstructure, especially in areas that support executive functions, reading, and language.

What correlations have been found that link socioeconomic inequality with brain function?

• At six months of age, higher socioeconomic status was linked to greater high-frequency EEG power (which is associated with language development).
• At six months of age, family income and maternal education were associated with functional connectivity in the default mode network and the sensorimotor network.
• Lower family income has been linked to reduced connectivity between the hippocampus and amygdala and other cortical regions (for children).
• Connectivity partially explained the relationship between lower family income and negative mood and depression (for children).
• Functional brain development may be influenced by family level socioeconomic disadvantage as well as neighborhood socioeconomic disadvantage. Young people living in more advantaged neighborhood had a stronger positive association between age and functional connectivity than young people from more disadvantaged neighborhoods, in a pattern suggestive of faster functional brain development.

How do socioeconomic factors relate to the neural bases of language, emotion processing, and executive function?

• Inferior frontal gyrus lateralization of five-year-olds has been associated with maternal education.
• Socioeconomic differences have been linked to the neural response to learning new words.
• Neighborhood poverty has been associated with inferior frontal gyrus activation, supporting the idea that neighborhood disadvantage may account for extra variation in experience that is not caused by socioeconomic status of the family.
• Lower family income and lower socioeconomic status have been associated with increased neural activation to angry facial expressions in the fusiform gyrus, and increased amygdala responses to negative infant faces.

How can differences in experience be at least partially responsible for socioeconomic differences in brain and behavior?

Two mechanism are identified to help answer the questions whether socioeconomic status related differences in experiences and exposures lead to differences in outcomes, or whether outcome differences are the product of social selection, in which genetic underpinnings of academic achievement lead to differences in socioeconomic status:

• Cognitive/linguistic stimulation in the home may contribute to the emergence of socioeconomic disparities in the development of brain regions that contribute to higher-order language and cognitive skills.
• Exposure to chronic stress has serious effects on multiple brain and body systems, and is considered a mechanism linking socioeconomic disadvantage to neurodevelopmental differences.