Presentations
BOOM Episode 52: Holla Back At Brain Biomechanics with Maria Holland
(Interview with Biomechanics On Our Minds)
An interview about my path to biomechanics, my CAREER award, and the challenges and excitement of biomechanics.
Correlation between cortical morphology and thickness due to forces generated during folding
(Talk recorded for 2022 World Congress of Biomechanics - July 2022, virtual)
The outer layer of the human brain, the cortex, has a highly folded structure that emerges in utero. A consistent pattern of thick gyri (outer ridges) and thin sulci (inner valleys) has long been noticed in two-dimensional images (MR and histology) of the brain. These systemic cortical thickness variations are likely a consequence of both heterogeneous growth and the forces generated during the extensive folding of the cortex, as evidence from computational, experimental, and analytical studies suggests. Here, we further investigate these patterns by looking at the full three-dimensional folding pattern of the cortex, including the tangential, or in-plane, folds and bends of gyri and sulci.
Patterns of growth and thickness in the cerebral cortex
(Invited talk at the American Physical Society's March Meting - March 2022, Chicago, Illinois)
Abstract: Between individuals and across species, brain morphology is strikingly consistent in some significant ways. One example is a characteristic pattern of cortical thickness in gyrencephalic, or folded, brains - thick outer folds, or gyri, and thin inner folds, or sulci. This raises the question: which factors (genetic, biochemical, physical, and/or others) lead to this morphological consistency? In this talk, I will cover both our models of cortical folding and our analysis of folded cortical geometries. The former includes explorations of both the physical forces generated during folding and heterogeneous cortical growth, and examines the resulting pattern of cortical thickness. The latter includes fully three-dimensional topological analysis of local shape (curvature and depth) and thickness, in humans and several non-human primate species. Through comparisons between our models and imaging data, we can gain a deeper understanding of the factors that contribute to the variable, yet highly characteristic, patterns of thickness throughout the cortex.
Unfolding the cortex via a mechanics-informed graph neural network
(Computer methods in Biomechanics and Biomedical Engineering virtual conference - October 2021)
Abstract: Cortical thickness serves as an essential biomarker for many neurological disorders such as Autism Spectrum Disorder, schizophrenia, and epilepsy. Our recent work has suggested that the interactions between mechanics and biology plays a vital role in shaping the thickness variations. In the current work, we aim to distinguish between cortical thickness variations that are artifacts of brain folding and those that are due to biological phenomena. To that end, we introduce the modified cortical thickness -- or the thickness the cortex would have if it were unfolded and free of the mechanical forces involved in brain folding. From our simulations of cortical folding, we use the physics-based data to train a graph neural network. Thus, our investigation is based on the underlying physics of the problem in the form of large deformation mechanics. After training, we can apply the neural network to MRI scans (Figure 1c) to “unfold” the cortex and calculate its corresponding thickness. This work opens the door for precise cortical thickness analysis in neurological disorders, leading to new early diagnosis pathways and effective treatment.
A Closer Look: Numerical investigation of biomechanically-coupled growth in cortical folding
(Closer Look Open Journal Club - October 2021)
Here I discuss our recent paper: the story behind it, my initial hypothesis, how we tested it, and what we found.
Brain folding as a soft layered instability: Unique features and puzzles
(University of Florida Biomedical Engineering seminar - March 2021)
Abstract: During development, instabilities develop in the brain, giving it its characteristic wrinkled shape. These instabilities are very complex and still not well understood. In the first part of the talk, I will discuss the sensitivity of soft layered materials such as the brain to small changes in loading and geometry. In the second part of the talk, I will share our theoretical, computational, physical, and imaging approaches to understanding the role of mechanics in the patterns of cortical thickness in the brain - another unique feature of soft layered instabilities.
The role of physical forces in cortical morphogenesis
(American Physical Society March Meeting 2020 - invited keynote)
Abstract: Between individuals and across species, brain morphology is strikingly consistent in some significant ways. One example is a characteristic pattern of cortical thickness in gyrencephalic, or folded, brains - thick outer folds, or gyri, and thin inner folds, or sulci. This raises the question: which factors (genetic, biochemical, physical, and/or others) lead to this morphological consistency? In a recent combined theoretical, numerical, and experimental study, we found that the physical forces generated by buckling instabilities were sufficient to generate physiological gyral-sulcal thickness ratios. We now consider the more complex, fully three-dimensional pattern of cortical thickness in the brain, and investigate the role of physical forces in its evolution, consistency, and variability.