Associations among white matter microstructural changes and the development of emotional reactivity and regulation in infancy.

Deficits in emotional reactivity and regulation assessed in infancy, including high levels of negative emotionality (NE), low positive emotionality (PE) and low soothability, can predict future affective and behavioral disorders. White matter (WM) tracts develop rapidly in the first postnatal year, paralleling the development of emotional regulation. During this period, examining the development of white matter microstructure in tracts connecting cortical and/or subcortical regions supporting emotional regulation, including the cingulum bundle (CB), uncinate fasciculus (UF), and forceps minor (FM), can provide neural markers reflecting pathophysiological processes underlying early emotional regulation development. The Neurite Orientation Dispersion and Density Imaging (NODDI) model can be used to estimate with high intercellular specificity microstructural integrity and myelination using the neurite density index (NDI), and dispersion, using the orientation dispersion index (ODI). Examining relationships among changes in WM tract NODDI measures and changes in emotional reactivity and regulation during the first 3-to-9-months of age (n = 39), we showed that larger 3-to-9-month increases in right UF, FM, and left CB ODI were associated with larger decreases or smaller increases in soothability during this period, while a larger increase in right UF NDI was associated with a smaller increase in PE. These findings suggest that in infancy, larger microstructural changes in major WM tracts interconnecting neural networks supporting emotional regulation are associated with disrupted development of PE and soothability. These findings could provide early neural markers of child emotional dysregulation and may have implications for future affective or behavioral trajectories.