This thesis explores whether considering grey and white matter as separate structures meaningfully advances or hinders our understanding of brain development. Historically, these two structures have been considered as distinct properties of the brain as a result of their differences in colour, structure, and composition. Notably, neuronal cells in the brain, such as pyramidal cells, span both grey and white matter, with their cell bodies, dendrites, and synapses located in grey matter, while their axons are mainly in the white matter. This distinction has led researchers to focus solely on grey matter metrics or white matter metrics when examining brain structure. In my projects, I aim to question this division. Their similarities or differences can inform how to study brain structure.
However, whether grey and white matter should be considered separate or the same, the fragmentation of the literature hinders progress in the field. In this thesis, I demonstrate that the integration of both structures may provide valuable insights into brain development. Through the three parts of my thesis, I explore how their integration contributes to our understanding of brain development and its associations with behaviours and environmental exposures. Beyond this main focus, I questioned the role of neuroimaging techniques and multivariate models in the future of developmental cognitive neurosciences."