Mattfeld, A. | bioRxiv Science

bioRxiv2022

Volumetric development of hippocampal subfields and hippocampal white matter connectivity: Relationship with episodic memory

The hippocampus is a complex structure composed of several distinct subfields and has been at the center of scientific study examining the neural foundations of episodic memory. To date, there is little consensus regarding the structural development of the hippocampus and its subfields assessed both volumetrically and through anatomical connectivity, nor how the development of the related substructures influences episodic memory. In the current cross-sectional study, using a large sample of 830, 3- to 21-year-olds from a unique and publicly available dataset we examined the following questions: 1) Is there elevated grey matter volume of the hippocampus and its respective subfields in late compared to early development? 2) How does hippocampal volume compare with the rest of the cerebral cortex at different developmental stages? and 3) What is the relation between hippocampal volume, and the connectivity of the hippocampus with cortex as measured by diffusion-weighted imaging, with episodic memory performance? We found hippocampal subfield volumes exhibited a non-linear relation with age. Specifically, hippocampal subfield volumes showed a lag in volumetric change with age when compared to adjacent cortical regions (e.g., entorhinal cortex). We also observed a significant reduction in cortical volume across older cohorts, while hippocampal volume showed the opposite pattern. In addition to age-related differences in grey matter volume, several distinct subfields are significantly related to episodic memory. We did not, however, find any associations with episodic memory performance and connectivity through the uncinate fasciculus, fornix, or cingulum. The results are discussed in the context of current research and theories of hippocampal development and its relation to episodic memory.

neuroscience↗

bioRxiv2017

Laterality of the frontal aslant tract (FAT) explains externalizing behaviors through its association with executive function.

We investigated the development of a recently-identified white matter pathway, the frontal aslant tract (FAT) and its association to executive function and externalizing behaviors in a sample of 129 neurotypical children ranging in age from 7 months to 19-years. We found that the FAT could be tracked in 92% of those children, and that the pathway showed age-related differences into adulthood. The change in white matter microstructure was very rapid until about 6-years, and then plateaued, only to show age-related increases again after the age of 11-years. In a subset of those children (5-18-years; n = 70), left laterality of the microstructural properties of the FAT was associated with greater attention problems as measured by the Child Behavior Checklist (CBCL). However, this relationship was fully mediated by higher executive dysfunction as measured by the Behavior Rating Inventory of Executive Function (BRIEF). This relationship was specific to the FAT--we found no relationship between laterality of the white matter of the brain in general and attention problems, or executive function. These findings suggest that the degree to which the developing brain favors a right lateralized structural dominance of the FAT is directly associated with executive function and attention. This novel finding provides a new potential structural biomarker to assess attention deficit hyperactivity disorder (ADHD) and associated executive dysfunction during development.\n\nSignificance StatementTo investigate the function of a recently-identified white matter fiber pathway, the frontal aslant tract (FAT), we tracked the pathway in 129 typically developing children using diffusion-weighted magnetic resonance imaging (DW-MRI). We then examined whether laterality of the tract is associated with attention problems and executive function. We found that reduced right laterality of the tract was associated with greater executive dysfunction, which predicted increased reports of attention problems. The findings suggest that the degree to which the developing brain favors a right lateralized structural dominance of the FAT is directly associated with executive function and attention. This novel finding provides a new potential structural biomarker to assess attention deficit hyperactivity disorder (ADHD) and associated executive dysfunction during development.

neuroscience↗