April 2018: Socioeconomic Status, Reading Disability, and Neuroanatomy

Overview

Independent lines of research have reported associations between reading ability and two major factors (a) brain structure and function and (b) socioeconomic status (SES). Across these studies, the most commonly reported findings indicate that reading disabilities (RD) are associated with reduced cortical gray matter in key brain regions that are integral to reading and the language networks supporting reading skills. Additionally, higher SES is usually associated with better reading outcomes. The brain structure and function association with RD has emphasized the heritability of RD and highlighted evidence of neural plasticity following explicit reading intervention (e.g., normalization of brain structure and function). The association between higher SES and lower RD has underscored the importance of environmental factors, including access to print with explicit instruction and exposure to rich, complex language spoken in the home. However, potential interactions between SES and the brain in those with RD, particularly within the context of different reading interventions, have been underexplored in previous research studies. Therefore, the present study (Romeo et al., 2017) addressed the following questions: (1) Are there structural brain differences in young children (6 to 9 years old) with RD from varying SES backgrounds? (2) Does a summer reading intervention program influence brain structure across the SES continuum?

Background

Children from lower SES backgrounds disproportionately meet the criteria for RD (Peterson & Pennington, 2015) relative to their peers from higher SES backgrounds. According to the U.S. Department of Education (2015), students in grades 4 and 8 who qualified for the National School Lunch Program (an indicator of low SES) were 2.5 times more likely to exhibit reading skills that were “below proficient” relative to their peers from higher SES households. It is unclear whether this greater deficit is due to a true higher prevalence of RD in lower SES families or whether it reflects consequences of lack of access to key resources (e.g., more types of print material, more enriched home environment) for lower SES children. Previous neuroimaging research studies associated with reading intervention have rarely considered SES information in their planned analyses (Barquero et al., 2014), either not reporting SES information (17 of 22 studies) or treating SES as a nuisance factor rather than evaluating relations between SES and brain structure and function or behavioral intervention outcomes.

Approach

The present study used a composite of maternal education and occupational prestige as a proxy measure for SES (Barratt Simplified Measure of Social Status; Barratt, 2006). Barratt Simplified Measure of Social Status scores were highly variable in the study sample and were treated as a continuous variable in all analyses. Cortical thickness measures were evaluated longitudinally in 55 study participants ages 6 to 9 years; 36 participants were evaluated before and after a summer reading intervention program and 19 participants were waitlisted for the reading intervention program. The intervention participants were equally split between responders (n = 18) and nonresponders (n = 18). Change in standard scores for four different reading assessments targeting single word reading ability were calculated for the presummer to postsummer window (~2.5 months) for students participating in a reading intervention program that was 20 hours per week for 6 weeks (n = 36) and for students waiting for intervention (n = 19).

Results

• Higher SES was significantly positively correlated with scores on one out of the four reading assessments, the Woodcock-Johnson III Word Attack.
• At baseline, higher SES significantly correlated with cortical thickness in key brain regions (bilaterally) that are important for developing proficient reading skills. The strongest correlation between SES and cortical thickness occurred in Broca’s area, a region of the left hemisphere associated with expressive language skills.
• Participants identified as “responders” to the summer reading intervention program demonstrated thickening of the cerebral cortex in key brain regions associated with proficient reading skills; nonresponders and waitlisted participants did not exhibit significant changes in cortical thickness.
• Participants from lower SES households and participants with more severe RD were more likely to benefit from the summer reading intervention program relative to participants from higher SES households or participants with less severe RD.

Discussion

An intensive summer reading intervention program (120 hours over 6 weeks) was effective for 50% of participants. Follow-up analyses evaluated characteristics of intervention responders vs. nonresponders and identified an interaction between SES and level of RD. Thus, this reading intervention program was particularly beneficial for lower SES study participants with more severe RD compared to their higher SES peers with less severe RD. In the lower SES and more severe RD participants, not only did reading scores improve, but also cortical thickness changes occurred in key brain regions underlying proficient reading skills. Therefore, characterization of responders versus nonresponders for future reading intervention programs should include SES measures as part of their determination of efficacy. Further, summer reading practice, or ideally intervention, especially for lower income students, may help reduce reading gaps in children with RD.

References

Barquero, L. A., Davis, N., & Cutting, L. E. (2014). Neuroimaging of reading intervention: A systematic review and activation likelihood estimate meta-analysis. PLoS One, 9(1). doi:10.1371/journal.pone.0083668

Barratt, W. (2006). Barratt simplified measure of social status (BSMSS). Unpublished manuscript, Indiana State University.

Peterson, R. L., & Pennington, B. F. (2015). Developmental dyslexia. Annual Review of Clinical Psychology, 11, 283–307. doi:10.1146/annurev-clinpsy-032814-112842

U.S. Department of Education. (2015). National assessment of educational progress. Retrieved from https://nces.ed.gov/nationsreportcard/about