Early Abnormalities in Social, Attentional, and Working Memory Circuits in Infants with Turner Syndrome

Abstract

Adults and children with Turner syndrome differ from typical female individuals with 46,XX karyotype in key components of neural circuits for social cognition and working memory. Specifically, imaging studies demonstrate reductions in somatosensory cortex and inferior parietal lobule, enlargement of the amygdalae and insular and orbitofrontal cortex, altered white matter microstructure and disrupted frontoparietal circuitry in women with Turner syndrome. Altered activation of the amygdala and caudate during cognitive tasks also has been reported. What is not known is when in development these relationships arise. This knowledge gap is important, as it limits our ability to determine the appropriate type and timing of behavioral interventions and hormone therapies. Imaging of infants with Turner syndrome showed decreased gray matter volumes in parietal cortex and increased gray matter volumes in insular cortex when compared to female controls, consistent with findings in older children. This suggests a stable phenotype, with origins in the prenatal or early postnatal period. Infants with Turner syndrome did not exhibit widespread changes in white matter microstructure that have been reported in older children, suggesting that early interventions might prevent or ameliorate atypical white matter development in Turner syndrome. At 1 year of age, functional connectivity maps revealed reduced fronto-parietal connectivity in infants with Turner syndrome, and increased connectivity with the insula. At age 2, functional connectivity maps revealed a lack of typical connectivity between caudate and frontal lobe in infants with Turner syndrome. Extensive negative correlations with middle temporal gyrus were present in infants with Turner syndrome, but not in controls. Additional studies are needed to examine longitudinal changes in brain structure and function in Turner syndrome, relate clinical variables (such as genetic and hormonal variation) to brain development, and test whether individual variation in neuroimaging phenotypes predicts cognitive outcomes.