TABLE 4.
Studies Included in Prefrontal Cortex: Executive Functions Section
| Reference | n | Age | Poverty Measure | Method | Main Findings |
|---|---|---|---|---|---|
| Blair, et al (2011)53 | 1292 | 36 mo | Income/needs ratio; parenting assessed with free play or structured interaction task; household risk assessed (household density, neighborhood sensitively, noise) | Longitudinal study with assessments at age 7, 15, 24, and 36 mo; basal cortisol and parenting assessed at 7, 15, and 24 mo; household risk assessed at 7 and 24 mo; EF assessed at 36 mo | Cortisol inversely related to EF and higher in poor children; parenting related to EF and IQ, household risks inversely related to EF and IQ; maternal education, income/needs not associated with EF or IQ; cortisol inversely related to positive parenting and this relation mediated the effect between positive parenting and EF |
| Blair, et al (2011)54 | 1135 | 48 mo | Income/needs ratio used to create “poor” and “not poor” groups; groups used to create sum score for chronicity of poverty over the assessments; economic need and economic sufficiency assessed with Economic Strain Questionnaire; family stability and housing quality assessed | Longitudinal study with assessments at age 7, 15, 24, 36, and 48 mo; salivary cortisol and parenting assessed at 7, 15, and 24 mo | Duration of life in poverty inversely associated with cortisol; family instability, low economic sufficiency, poor housing quality associated with higher cortisol; positive parenting inversely related to cortisol, but no relation between negative parenting and cortisol |
| Hair, et al (2015)39 | 389 | 12 y (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 frontal and temporal lobes and hippocampus; differences in gray matter in frontal lobe explained ≤16% of differences in cognitive ability; income effects were greatest among the poorest children |
| Hanson, et al (2013)55 | 77 | 0–53 mo | Family income (≤200% FPL vs >200%–400% FPL) | Longitudinal MRI study of normal brain development; average of 3 scans per child ∼6 mo apart | Infants from lower-SES families had reduced frontal-lobe gray matter volume compared with those from higher-SES families; no differences by SES in white matter volume |
| Hanson, et al (2012)56 | 61 | 12 y (SD 2 y) | Maternal education; life stress measured with Youth Life Stress Interview of parents and children | Cross-sectional MRI study with EF battery | Life stress inversely associated with PFC volume in gray matter near the anterior cingulate and frontal poles and in white matter near the forceps minor; life stress also inversely associated with memory; prefrontal volumes mediated relation between life stress and working memory; comparing effect of stressors in past year and cumulative life stressors, cumulative stressors had larger effect on EF |
| Holz, et al (2015)57 | 167 | 25 y | Poverty assessed at age 3 mo using maternal report of income below the poverty level (Germany); dichotomized into exposed (n = 33)/not exposed (n = 134) to early poverty | Longitudinal MRI study; poverty assessed at 3 mo; life stress assessed regulatory from age 3 mo to 25 y; conduct disorder assessed at 8, 11, 15, and 19 y; MRI at 25 y | Adults who experienced early poverty had more conduct disorder symptoms and smaller OFC volumes compared with unexposed adults; relation between poverty and conduct disorder symptoms mediated by OFC volume; life stress and maternal smoking during pregnancy also mediated this relation; OFC volume inversely related to conduct disorder symptoms |
| Lawson, et al (2013)22 | 283 | 11.5 y (SD 4 y) | Family income adjusted for family size and sum of maternal and paternal education | Cross-sectional MRI study | Parental education positively associated with thickness of right anterior cingulate gyrus and left superior frontal gyrus; family income not related to thickness of either area |
| Liberzon, et al (2015)58 | 49 | 23–24 y | Income/needs ratio assessed at age 9; ratio used as continuous variable and dichotomized into low (mean 0.76; n = 23) versus mid-SES (mean 2.7; n = 26) groups | Longitudinal fMRI study using shifted-attention emotion appraisal task; TSST administered before fMRI; cortisol assessed before and after SST; poverty assessed at age 9; fMRI and TSST assessed at 23–24 y | Adults exposed to poverty in middle childhood showed less DLPFC recruitment during emotion regulation task; this pattern mediated the effect of poverty on adult task performance; income/needs positively associated with task accuracy and unrelated to cortisol |
| Lipina, et al (2013)59 | 250 | 5 y (SD 0.5 y) | NES socioeconomic scale: parent education and occupation, dwelling score, overcrowding, health history, preschool attendance, books/reading to children, computer/internet use, effortful control; compared groups with unmet basic needs to those with met basic needs (SES groups) | Cross-sectional study using EF battery | Children with unmet basic needs had lower efficacy and scores on tasks related to prefrontal and executive systems; child literacy activities mediated the relation between SES group and working memory and fluid processing, and computer activities mediated the relation between SES group and fluid processing |
| Noble, et al (2015)37 | 1099 | 12 y (3–20) | Parent education and family income | Cross-sectional MRI study; inhibitory control, working memory, picture vocabulary, and oral reading recognition task | Parent education positively associated with cortical surface area in regions supporting language, reading, executive function, and spatial skills; income positively associated with cortical surface area in regions supporting various language and EF; income positively associated with performance on cognitive tasks; relations between income and inhibitory control and working memory mediated by cortical surface area |
DLPFC= dorsolateral prefrontal cortex; fMRI, functional MRI; OFC, orbitofrontal cortex; RMFG, right middle frontal gyrus; TSST, Trier Social Stress Task.