Brain Structural Alterations in Left-Behind Children: A Magnetic Resonance Imaging Study

Abstract

Parental migration has caused millions of children left behind, especially in China and India. Left-behind children (LBC) have a high risk of mental disorders and may present negative life outcomes in the future. However, little is known whether there are cerebral structural alterations in LBC in relative to those with parents. This study is to explore the effect of parental migration on brain maturation by comparing gray matter volume (GMV) and fractional anisotropy (FA) of LBC with well-matched non-LBC. Thirty-eight LBC (21 boys, age = 9.60 ± 1.8 years) and 30 non-LBC (19 boys, age = 10.00 ± 1.95 years) were recruited and underwent brain scans in 3.0 T MR. Intelligence quotient and other factors including family income, guardians' educational level and separation time were also acquired. GMV and FA were measured for each participant and compared between groups using 2-sample t-tests with atlas-based analysis. Compared to non-LBC, LBC exhibited greater GMV in emotional and cortico-striato-thalamo-cortical circuits, and altered FA in bilateral superior occipitofrontal fasciculi and right medial lemniscus (p < 0.05, Cohen's d > 0.89, corrected for false-discovery rate). Other factors including family income, guardians' educational level and separation time were not associated with these brain changes. Our study provides empirical evidence of altered brain structure in LBC compared to non-LBC, responsible for emotion regulation and processing, which may account for mental disorders and negative life outcome of LBC. Our study suggests that absence of direct biological parental care may impact children's brain development. Therefore, public health efforts may be needed to provide additional academic and social/emotional supports to LBC when their parents migrate to seeking better economic circumstances, which has become increasingly common in developing countries.

Keywords: MRI; cognition; fractional anisotropy; gray matter volume; left-behind children.

FIGURE 1

Increased GMV in LBC relative to non-LBC. Increased gray matter volume was observed in the following regions (labeled in red-yellow): bilateral fusiform gyri, bilateral parahippocampal gyri, right superior parietal lobe, right thalamus, right superior occipital gyrus, left cuneus, right superior temporal gyrus, right medial prefrontal gyrus, left postcentral gyrus, left middle occipital gyrus, and left putamen in LBC relative to non-LBC.

FIGURE 2

Difference of white matter microstructure between LBC and non-LBC. Tracts with significantly increased mean fractional anisotropy (FA) in the left and right superior occipitofrontal fasciculi (labeled by green color) and decreased FA in right medial lemniscus (labeled by blue color) in LBC relative to parentally raised children. Age and gender were used as covariates. L, left; R, right; ML, medial lemniscus; SOFF, superior occipitofrontal fasciculus.