Finding the patterns of white matter growth that support children’s cognitive development
Joëlle Bagautdinova was the lead author on this study. Joëlle is broadly interested in brain development and how this may go awry in psychiatric disorders. For her PhD in Dr. Ted Satterthwaite’s lab, Joëlle is using neuroimaging to study the mechanisms underlying brain development, cognition and psychiatric disorders. She is particularly interested in understanding the potential role of sleep as a risk factor in the emergence of mental illness.
or technically,
Development of white matter fiber covariance networks supports executive function in youth
[See Original Abstract on Pubmed]
Authors of the study: Joëlle Bagautdinova, Josiane Bourque, Valerie J. Sydnor, Matthew Cieslak,Aaron F. Alexander-Bloch, Maxwell A. Bertolero, Philip A. Cook, Raquel E. Gur, Ruben C. Gur, Fengling Hu, Bart Larsen, Tyler M. Moore, Hamsanandini Radhakrishnan, David R. Roalf, Russel T. Shinohara, Tinashe M. Tapera, Chenying Zhao, Aristeidis Sotiras, Christos Davatzikos, and Theodore D. Satterthwaite
Recently, many neuroscientists have been trying to uncover the developmental “blueprint” of the brain’s gray matter, or the specific ways in which brain regions grow and change over the course of adolescence. However, less attention has been paid to the brain’s white matter, which is the insulated, wire-like “tracts” that connect one brain region to another. NGG student Joëlle Bagautdinova and her colleagues in the Satterthwaite lab filled this gap by investigating white matter’s structural development in MRI scans from almost 1000 people ages 8 to 22 years.
While it famously does NOT imply causation, correlation can show parts of the brain have similar structures and, therefore, might be following the same developmental blueprint. So, Joëlle and her colleagues decided to cluster every point along the brain’s white matter tracts (Figure 1) into groups with similar structures (Figure 2). Specifically, they grouped points with similar fiber density, or how many “wires” are packed together to make the tract, and cross-section, or how thick the tract is (Figure 1); they refer to the combination of these measurements as “FDC”. She also tested to see how each group’s FDC values changed across adolescence.
Figure 1. White matter tracts can be measured by their density and cross-section.
Figure 2. Points of white matter can be grouped by how similar their FDC (fiber density and cross-section) values are.
Usually, researchers assume that all points along a tract will develop similarly; however, because Joëlle determined her groups based on how similar the points are, different points along the same tract could be put into different groups, while points from more than one tract could be lumped together. This allowed her to uncover brand new relationships between different white matter tracts and unique subsections that develop differently than the white matter tract. For instance, she found that FDC in the lower part of the corticospinal tract, which connects the brain and spinal cord, was different than the FDC in the upper corticospinal tract, and each portion had its own unique growth trajectory. All in all, the researchers found 14 different groups of similarly-structured white matter regions, 12 of which showed significant structural changes across this period of adolescent development.
The age at which each white matter group developed most also seems to follow a pattern. Specifically, they found that the white matter in the lower back area of the brain matures earlier in adolescence while the white matter in the upper front area of the brain doesn’t mature until a bit later. These early-maturing white matter tracts tend to connect parts of the brain that do what scientists call “lower-order functions” like vision processing, basic movement, and emotions – all things that children can do pretty well. Meanwhile, the later-maturing white matter tracts tend to connect brain regions that do “higher order” functions like complex reasoning. Overall, the fact that white matter maturation seems to progress “basic” to “complex” tracts suggests that white matter may play a big role in the brain’s development across adolescence.
Finally, Joëlle and her colleagues wanted to see if these white matter structures helped kids’ executive function, which is one of these “higher order” cognitive functions that includes planning, organizing, and impulse control. They found that if you remove the effects of age, kids with better executive function tend to have higher FDC in all but one white matter group. This means that white matter tracts that are thicker and/or more tightly packed do a better job of sending signals between brain regions, especially those in the front of the brain that are responsible for cognition, and that this enhanced signaling may allow children to have stronger executive functions.
By using new, cutting-edge analyses, Joëlle and her collaborators were able to: uncover brand-new, biologically-based relationships between white matter areas; chart how these areas develop over adolescence; and show which white matter structures seem to help with cognitive function. All in all, this work fills in important gaps in our understanding how the brains we’re born with mature into the brains of capable, full-grown adults.
About the brief writer: Margaret Gardner
Margaret is a PhD student in the Brain-Gene-Development Lab working with Dr. Aaron Alexander-Bloch. She is interested in studying how different biological and demographic factors influence people’s brain development and their risk for mental illnesses.