Browsing by Author "Garcia, Kara E."

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    Effects of stress-dependent growth on evolution of sulcal direction and curvature in models of cortical folding
    (Elsevier, 2023) Balouchzadeh, Ramin; Bayly, Philip V.; Garcia, Kara E.; Radiology and Imaging Sciences, School of Medicine
    The majority of human brain folding occurs during the third trimester of gestation. Although many studies have investigated the physical mechanisms of brain folding, a comprehensive understanding of this complex process has not yet been achieved. In mechanical terms, the "differential growth hypothesis" suggests that the formation of folds results from a difference in expansion rates between cortical and subcortical layers, which eventually leads to mechanical instability akin to buckling. It has also been observed that axons, a substantial component of subcortical tissue, can elongate or shrink under tensile or compressive stress, respectively. Previous work has proposed that this cell-scale behavior in aggregate can produce stress-dependent growth in the subcortical layers. The current study investigates the potential role of stress-dependent growth on cortical surface morphology, in particular the variations in folding direction and curvature over the course of development. Evolution of sulcal direction and mid-cortical surface curvature were calculated from finite element simulations of three-dimensional folding in four different initial geometries: (i) sphere; (ii) axisymmetric oblate spheroid; (iii) axisymmetric prolate spheroid; and (iv) triaxial spheroid. The results were compared to mid-cortical surface reconstructions from four preterm human infants, imaged and analyzed at four time points during the period of brain folding. Results indicate that models incorporating subcortical stress-dependent growth predict folding patterns that more closely resemble those in the developing human brain. Statement of significance: Cortical folding is a critical process in human brain development. Aberrant folding is associated with disorders such as autism and schizophrenia, yet our understanding of the physical mechanism of folding remains limited. Ultimately mechanical forces must shape the brain. An important question is whether mechanical forces simply deform tissue elastically, or whether stresses in the tissue modulate growth. Evidence from this paper, consisting of quantitative comparisons between patterns of folding in the developing human brain and corresponding patterns in simulations, supports a key role for stress-dependent growth in cortical folding.
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    Increased Prevalence of Sensory Processing Issues in Pediatric Gastrointestinal Patient Population
    (Permanente Federation, 2022) Wood, Jessica K.; Garcia, Kara E.; Carey, Rebecca G.; Radiation Oncology, School of Medicine
    Background: Sensory processing dysfunction in children has been linked to attention-deficit/hyperactivity disorder, autism, feeding disorders, and functional abdominal pain. However, little is known about sensory processing in the broader pediatric gastroenterology population. Objective: To characterize frequency and type of sensory processing dysfunction seen in pediatric gastroenterology compared to a general pediatric population. Methods: The Short Sensory Profile 2 was administered to the parents of children ranging 3–14 years, being seen in a pediatric gastrointestinal (GI) subspecialty clinic or general pediatric clinic. Short Sensory Profile 2 scores from age- and gender-matched groups were compared with nonparametric statistics. Results: Sensory processing dysfunction was increased in children seen in the GI clinic compared to children in the general pediatric clinic. Short Sensory Profile 2 quadrant analysis revealed greatest differences in avoiding, primarily in young females of the GI population. Conclusion: Children presenting to a pediatric GI clinic demonstrate greater sensory processing dysfunction compared to children in a general pediatric practice.
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    Multi-scale measurement of stiffness in the developing ferret brain
    (Springer Nature, 2023-11-23) Walter, Christopher; Balouchzadeh, Ramin; Garcia, Kara E.; Kroenke, Christopher D.; Pathak, Amit; Bayly, Philip V.; Radiology and Imaging Sciences, School of Medicine
    Cortical folding is an important process during brain development, and aberrant folding is linked to disorders such as autism and schizophrenia. Changes in cell numbers, size, and morphology have been proposed to exert forces that control the folding process, but these changes may also influence the mechanical properties of developing brain tissue. Currently, the changes in tissue stiffness during brain folding are unknown. Here, we report stiffness in the developing ferret brain across multiple length scales, emphasizing changes in folding cortical tissue. Using rheometry to measure the bulk properties of brain tissue, we found that overall brain stiffness increases with age over the period of cortical folding. Using atomic force microscopy to target the cortical plate, we found that the occipital cortex increases in stiffness as well as stiffness heterogeneity over the course of development and folding. These findings can help to elucidate the mechanics of the cortical folding process by clarifying the concurrent evolution of tissue properties.