Effect of Hippocampal and Amygdala Connectivity on the Relationship Between Preschool Poverty and School-Age Depression

Abstract

Objective: In this study, the authors tested the hypothesis that poverty experienced in early childhood, as measured by income-to-needs ratio, has an impact on functional brain connectivity at school age, which in turn mediates influences on child negative mood/depression.

Method: Participants were from a prospective longitudinal study of emotion development. Preschoolers 3-5 years of age were originally ascertained from primary care and day care sites in the St. Louis area and then underwent annual behavioral assessments for up to 12 years. Healthy preschoolers and those with a history of depression symptoms underwent neuroimaging at school age. Using functional MRI, the authors examined whole brain resting-state functional connectivity with the left and right hippocampus and amygdala.

Results: Lower income-to-needs ratio at preschool age was associated with reduced connectivity between hippocampus and amygdala and a number of regions at school age, including the superior frontal cortex, lingual gyrus, posterior cingulate, and putamen. Lower income-to-needs ratio predicted greater negative mood/depression severity at school age, as did connectivity between the left hippocampus and the right superior frontal cortex and between the right amygdala and the right lingual gyrus. Connectivity mediated the relationship between income-to-needs ratio and negative mood/depression at the time of scanning.

Conclusions: These findings suggest that poverty in early childhood, as assessed by at least one measure, may influence the development of hippocampal and amygdala connectivity in a manner leading to negative mood symptoms during later childhood.

Figure 1. Functional Connectivity of Hippocampus and Amygdala and Its Relationship to Income-to-Needs

Regions in red show positive functional connectivity with the respective seed regions. Regions in blue show negative functional connectivity with the respective seed regions. Regions in green are ones that show relationships to income-to-needs. The numbers correspond to the regions listed in Table 2.

Figure 2. Functional Connectivity of Hippocampus and Amygdala in Relation to Income-to-Needs and Depression at the Time of Scan

Scatterplots A and B illustrate the relationships of amygdala to lingual gyrus and hippocampal connectivity to income-to-needs, while scatterplots C and D illustrate the relationships of these connections to depression symptoms at the time of scanning.

Figure 3. Illustration of Functional Connectivity Mediation of Relationship Between Income-to-needs and Depression Severity at the Time of Scan

This dual mediation model includes two “A” paths (income-to-needs to both left hippocampus/right superior frontal and right amygdala/right lingual gyrus connectivity) and thus also two corresponding “B” paths for the relationship of these functional connections to depression. The fact that both A and both B paths are significant indicates that each of these functional connections accounts for independent variance. Beta weights are standardized. Path C in black is the total effect of income-to-needs on depression severity with functional connectivity not in the model. This is significant. Path C’ in red is the direct effect of income-to-needs on depression severity with functional connectivity in the model. Path C’ is no longer significant with the connectivity measures in the modeling, indicating that the connectivity measures statistically mediate the relationship between poverty and subsequent depression.