TABLE 2.
Studies Included in Hippocampus: Learning and Memory Section
| Reference | n | Age, y | Poverty Measure | Method | Main Findings |
|---|---|---|---|---|---|
| Hair, et al (2015)39 | 389 | 12 (4–22) | Family income adjusted for household size using binary and categorical measures | Longitudinal MRI study of normal brain development; scans at 2-y intervals across 3 periods, plus Wechsler Abbreviated Scale of Intelligence and Woodcock-Johnson II Test of Achievement | Low-income children scored lower on tests of cognitive ability and had reductions in gray matter in the frontal and temporal lobes and the hippocampus; differences in gray matter in the hippocampus explained ≤16% of differences in cognitive ability; income effects greatest among the poorest children |
| Hanson, et al (2011)40 | 431 | 11 (SD 4) | Family income, parent (maternal and paternal) education | Cross-sectional MRI study | Positive association between family income and child hippocampal volume, adjusting for parental education; no consistent associations between parent education and hippocampal size, adjusting for family income |
| Hanson, et al (2015)41 | 128 | 12 (9–15) | 4 groups: (1) institutionalized/abandoned children with early neglect (n = 36); (2) low SES (parents unskilled employees with ≤high school education) (n = 20); (3) victims of physical abuse (n = 31); (4) comparison group of middle-SES children (based on Hollingshead 2-factor index) with no maltreatment (n = 41) | Cross-sectional MRI study | Low-SES group had smaller hippocampi than middle-SES group; smaller left hippocampal volume associated with more behavioral problems; cumulative life stress and behavioral problems were inversely associated with hippocampal volume; hippocampal volumes partially mediated relations between early life stress and behavior problems |
| Jednoróg, et al (2012)18 | 23 | 10 (8–11) | Weighted average of maternal education and maternal occupational status | Cross-sectional MRI study | SES positively correlated with hippocampus gray matter volume, but not associated with memory or visuospatial processing. |
| Luby, et al (2013)42 | 145 | 10 (6–12) | Income/needs ratio | Longitudinal study with 3–6 annual assessments of child psychiatric status, stressful life events, caregiver education; assessment of parental support/hostility at age 4–7, child MRI at age 10 | Higher income/needs associated with greater left hippocampal volume, mediated by caregiving support/hostility and life stress |
| Noble, et al (2012)43 | 275 | 40 (17–87) | Years of education | Cross-sectional MRI study | Age-related decreases in hippocampal volume greater for participants with less education (versus those with more education). |
| Noble, et al (2015)37 | 1099 | 12 (3–20) | Parent education, family income | Cross-sectional MRI study; inhibitory control, working memory, picture vocabulary, and oral reading recognition tasks | Parent education positively associated with cortical surface area in regions supporting language, reading, executive function, and spatial skills; income positively associated with performance on cognitive tasks; relation between income and inhibitory control and working memory mediated by cortical surface area; parent education positively associated with left hippocampal volume; relation between hippocampal volume and education was stronger for children with the least educated parents; income not associated with hippocampal volume |
| Noble, et al (2012)20 | 60 | 11 (5–17) | Average years of parental education and family income/needs ratio | Cross-sectional MRI study | SES-related differences in hippocampal volume due to positive relations between hippocampal volume and income/needs (not parental education) |
| Rao, et al (2010)19 | 49 | 14 (13–16) | All participants were African American and exposed to cocaine in utero; did not examine SES; examined effect of parental nurturance and environmental stimulation (HOME scale) | Longitudinal study with assessment of parental nurturance and home environment at 4 and 8 y and MRI at 13–16 y | Parental nurturance at age 4 inversely associated with hippocampal volume at age 13–16; nurturance at age 4 explained 25% of left hippocampal volume; hippocampal volume not related to memory ability; nurturance at age 8 positively associated with memory ability; nurturance at age 8 and environmental stimulation at age 4 and 8 not related to hippocampal volume |
| Sheridan, et al (2013)44 | 33 (19 in fMRI) | 10 (8–12) | Maternal education, family income/needs ratio, and maternal SSS | Cross-sectional fMRI study using Paired Associate Learning task. Social stress task administered outside of scanner, and salivary cortisol assessed | Maternal SSS positively associated with baseline cortisol and hippocampal activation; income/needs not associated with hippocampal activation; SSS, education, and income/needs not associated with child hippocampal volume; no associations between maternal education and income/needs and cortisol; learning task performance not associated with SES measures |
| Staff, et al (2012)45 | 235 | 64 (64–65) | SES at age 11 recalled at age 64 using paternal occupation and home conditions at age 11 | MRI study using mental ability assessments obtained at age 11 and conducted MRI at age 64 | Lower childhood SES associated with less hippocampal volume, adjusting for 11-y-old mental ability, gender, and current occupation and education |
fMRI, functional MRI; HOME, Home Observation for Measurement of the Environment; SSS, subjective social status.