Differential Developmental Associations of Material Hardship Exposure and Adolescent Amygdala-Prefrontal Cortex White Matter Connectivity

Abstract

Accumulating literature has linked poverty to brain structure and function, particularly in affective neural regions; however, few studies have examined associations with structural connections or the importance of developmental timing of exposure. Moreover, prior neuroimaging studies have not used a proximal measure of poverty (i.e., material hardship, which assesses food, housing, and medical insecurity) to capture the lived experience of growing up in harsh economic conditions. The present investigation addressed these gaps collectively by examining the associations between material hardship (ages 1, 3, 5, 9, and 15 years) and white matter connectivity of frontolimbic structures (age 15 years) in a low-income sample. We applied probabilistic tractography to diffusion imaging data collected from 194 adolescents. Results showed that material hardship related to amygdala-prefrontal, but not hippocampus-prefrontal or hippocampus-amygdala, white matter connectivity. Specifically, hardship during middle childhood (ages 5 and 9 years) was associated with greater connectivity between the amygdala and dorsomedial pFC, whereas hardship during adolescence (age 15 years) was related to reduced amygdala-orbitofrontal (OFC) and greater amygdala-subgenual ACC connectivity. Growth curve analyses showed that greater increases of hardship across time were associated with both greater (amygdala-subgenual ACC) and reduced (amygdala-OFC) white matter connectivity. Furthermore, these effects remained above and beyond other types of adversity, and greater hardship and decreased amygdala-OFC connectivity were related to increased anxiety and depressive symptoms. Results demonstrate that the associations between material hardship and white matter connections differ across key prefrontal regions and developmental periods, providing support for potential windows of plasticity for structural circuits that support emotion processing.

Figure 1.

3-D renderings of amygdala to specific pFC targets. Seed amygdala targets in dark gray. pFC targets: left sgACC BA 25 (red); right dmPFC BA 10 (plum); right OFC BA 11 (blue); right sgACC BA 25 (green); right OFC BA 47 (yellow). White matter is illustrated in light gray. White matter in figure depicts all tracts originating from seed amygdala region for illustration purposes.

Figure 2.

Significant associations between material hardship at specific developmental stages and white matter connectivity after adjusting for other developmental stages. White matter connectivity and target on the left and zero-order plots on the right. (A) Increased material hardship at ages 5 and 9 years was related to increased right amygdala–dmPFC white matter connectivity, adjusting for other developmental stages. (B) Increased material hardship at age 15 years was related to increased left amygdala–sgACC white matter connectivity, adjusting for other developmental stages. (C) Increased material hardship at age 15 years was related to decreased right amygdala–OFC white matter connectivity, adjusting for other developmental stages.

Figure 3.

Covariates-adjusted model using structural equation modeling including all material hardship predictors and white matter connectivity targets. Model fit statistics indicate excellent fit: χ²[45] = 47.931, p = .355; RMSEA = .019 [.000, .053], CFI = .980, TLI = .965, SRMR = .047. Consistent with regression results, there were positive associations between material hardship at age 5 years with right amygdala–BA 10 (dmPFC) and hardship at age 15 years with left amygdala–BA 25 (sgACC). Furthermore, there were trending negative associations between material hardship at ages 9 and 15 years with right amygdala–BA 11 (OFC) white matter connectivity. Covariates included in the model: ethnoracial identity, sex, pubertal age, birth city, maternal education, family structure, violence exposure, social deprivation, and annual household income at baseline. ⁺ p < .10. * p < .05. ** p < .01. *** p < .001.

Figure 4.

Growth curve trajectory illustrating that material hardship increases with age. Figure shows linear estimated paths for each individual (black lines) as well as mean estimated group-level path trajectory (blue). Material hardship at age 1 year is set as point 0, where estimated mean [SE] for starting point (i.e., intercept) = 1.01 [.077], p < .001; variance [SE] = 0.91 [0.166], p < .001, and estimated mean [SE] change over time (slope) = 0.02 [0.008], p = .009; variance [SE] = 0.01 [0.002], p = .004.

Figure 5.

Structural equation path model showing path estimates between material hardship predictors and right amygdala–BA 10, right amygdala–BA 11, and left amygdala–BA 25 white matter connectivity. Material hardship at 1, 3, 5, 9, and 15 loadings estimating latent slope were fixed at 0, 2, 4, 8, and 14, respectively. Covariates included in the model: ethnoracial identity, sex, pubertal age, birth city, maternal education, family structure, violence exposure, social deprivation, and annual household income at baseline. * p < .05. ** p < .01.

Figure 6.

Indirect effects of material hardship through white matter connectivity were nonsignificant for any regions with significant direct associations between material hardship and white matter connectivity.