Maturation of cortical microstructure and cognitive development in childhood and adolescence: A T1w/T2w ratio MRI study

Abstract

The restructuring and optimization of the cerebral cortex from early childhood and through adolescence is an essential feature of human brain development, underlying immense cognitive improvements. Beyond established morphometric cortical assessments, the T1w/T2w ratio quantifies partly separate biological processes, and might inform models of typical neurocognitive development and developmental psychopathology. In the present study, we computed vertex-wise T1w/T2w ratio across the cortical surface in 621 youths (3-21 years) sampled from the Pediatric Imaging, Neurocognition, and Genetics (PING) study and tested for associations with individual differences in age, sex, and both general and specific cognitive abilities. The results showed a near global linear age-related increase in T1w/T2w ratio across the brain surface, with a general posterior to anterior increasing gradient in association strength. Moreover, results indicated that boys in late adolescence had regionally higher T1w/T2w ratio as compared to girls. Across individuals, T1w/T2w ratio was negatively associated with general and several specific cognitive abilities mainly within anterior cortical regions. Our study indicates age-related differences in T1w/T2w ratio throughout childhood, adolescence, and young adulthood, in line with the known protracted myelination of the cortex. Moreover, the study supports T1w/T2w ratio as a promising surrogate measure of individual differences in intracortical brain structure in neurodevelopment.

Characterization of late structural maturation with a neuroanatomical marker that considers both cortical thickness and intracortical myelination

“…The linear component of the age effect on MYEL increased at a higher rate in both banks of the central sulcus, the paracentral lobule, and in the supratemporal plane bilaterally. These findings are also consistent with previous observations showing that the myelination of intracortical axons is high in primary cortical areas during childhood and adolescence (Norbom et al, 2020), during mid-adulthood (Rowley et al, 2017) and later in life, as it continues to increase until approximately 60 years of age (Grydeland et al, 2013).…”

New insights into the dynamic development of the cerebral cortex in childhood and adolescence: Integrating macro- and microstructural MRI findings

“…Norbom et al (2020b) found limited positive associations between sex and vertex-wise GWC, with boys having higher GWC than girls in occipital and insular subregions. In regards to T1w/T2w ratio, Norbom et al (2020a) found no significant main effects of sex, but a small positive age by sex interaction, indicating that boys in late adolescence had relatively higher T1w/T2w ratio than girls in the frontal lobe and parts of the parietal lobe.…”

“…Strong relations between intensity metrics and age have however been found across childhood, adolescence and young adulthood, possibly even stronger than those seen for morphometric measures (Norbom et al, 2020b). Individual differences in signal intensity metrics in children and adolescents also show associations with cognitive abilities and neurodevelopmental psychopathology, but further studies are needed to understand the spatiotemporal dynamics of these relationships (Grydeland et al, 2013;Lewis et al, 2018;Norbom et al, 2020aNorbom et al, , 2019.…”

“…A study of 1555 young adults aged 18-35 years, reported that higher age also in young adulthood was linearly associated with higher T1w/T2w ratio in widespread cortical regions (Shafee et al, 2015). A more recent study of T1w/T2w ratio, including young children, with a sample size of 621 youths aged 3-21 years, reported a near global age-related increase in T1w/T2w ratio across the cortical surface (Norbom et al, 2020a) (see Figure 2). There was regional variation, and a general increasing gradient in the strength of the age association from inferior-posterior-to superior-anterior regions.…”

“…GWC shows a bi-directional relationship with general cognitive functioning, while regionally lower T1w/T2w ratio, especially in frontal regions, has been associated with higher general-and specific cognitive abilities. The direction of these associations could indicate separate neurobiological underpinnings for cognitive and age-related findings, or be explained by an underestimation of the true cortical thickness (see (Norbom et al, 2020a) for in detailed discussion).…”