Browsing by Author "Bray, Signe Lauren"

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    Brain Function in Early Childhood: Individual Differences in Age and Attentive Traits
    (2023-09-22) Tansey, Ryann Claire; Bray, Signe Lauren; Dewey, Deborah Maryanne; Iaria, Giuseppe; Kopala Sibley, Daniel Cameron; Cusack, Rhodri
    Children, like adults, are unique individuals with complex interwoven relationships between brain function, behaviour, and phenotypic traits, which further interact with rapid developmental processes. A nuanced description of variability between children will add to our knowledge of how they think and behave, and potentially advance the development of personalized early interventions. With functional magnetic resonance imaging (fMRI), we have gained insight into brain responses – however, due to practical considerations, we have been unable to render a complete understanding of brain-behaviour relationships in young children. The use of naturalistic stimuli in fMRI studies has increased the ecological validity and the retention of developmental neuroimaging data. In this dissertation, I sought to explore the relationships between age, attentive traits, and inter-individual variability of brain function in young children in naturalistic paradigms. I conducted a scoping review to synthesize the current and historical task- and naturalistic-fMRI literature on the development of visual processing in the brain, through the lens of two influential theories: the interactive specialization and maturational frameworks. I found that while there is generally a consensus of progressive development of visual brain function throughout childhood, there is not enough evidence to fully support other aspects of these theories. I also conducted two experiments, using naturalistic fMRI and an analysis technique called inter-subject correlation (ISC), which quantifies the spatiotemporal similarity of brain activity between individuals, to explore how age and attentive traits affect inter-individual variability of brain function in children aged 4-8 years. I found that children’s brain responses to movies “homogenized” with increasing age in our sample, with greater variability seen in the younger children. Further, both inattention and hyperactivity were associated with ISC in the sample, though the relationships with these traits were different in widespread regions of the brain. Together, my research advances our understanding of functional brain responses in children and underscores the importance of an individual differences approach to developmental neuroimaging.
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    Large-scale information processing during spontaneous brain activity revealed by cross-frequency coupling
    (2017-12-19) Dousty, Mehdy; Sotero Diaz, Roberto C.; Bray, Signe Lauren; Portzner, Andrea
    Amplitude-amplitude (AAC), phase-phase (PPC), and phase-amplitude (PAC) coupling of brain activity are mechanisms that shape the information flow across multiple spatiotemporal scales; however, it is unclear how they are related. We used source-space projected resting-state magnetoencephalography data and empirical mode decomposition to obtain AAC-, PPC-, and PAC-based functional connectivity matrices. We found that specific PAC interactions are highly variable across subjects, but the global topological properties of the network are consistent. PPC and AAC were consistent at both the local and global scales. Additionally, the higher the spatial complexity of PAC is, the stronger its correlation with AAC and PPC will be. Finally, direct and indirect functional connections are differently correlated to the properties of the underlying anatomical scaffold. Together, our results suggest that PPC of high frequencies facilitates the integration of information, AAC of low frequencies facilitates the segregation of information, and PAC is the mechanism binding these two information streams.
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    Resting state functional magnetic resonance imaging after pediatric mild TBI: Association of whole brain functional connectivity with diagnosis and post-concussive symptoms
    (2022-08) Deighton, Stephanie; Yeates, Keith; Bray, Signe Lauren; Protzner, Andrea B.; Schneider, Kathryn Janet
    Accurate diagnosis and prognosis is important after pediatric mild traumatic brain injury (TBI), but limited objective measures exist for either purpose. Advanced neuroimaging has garnered increased interest as a means to better understand mild TBI, with the potential to support objective assessment. Broadly, the goal of this dissertation was to examine resting state functional magnetic resonance imaging (RS fMRI) after pediatric mild TBI. Study 1 is a scoping review that aimed to examine the literature on RS fMRI after pediatric and adolescent mild TBI to summarize findings, determine research themes, review methodological approaches, and identify areas for further research. Study 2 is an original research study that aimed to predict group status [i.e., mild TBI versus orthopedic injury (OI)] as well as post-concussive symptoms (PCS) from whole brain functional connectivity (FC) patterns in participants aged 8.00 to 16.99 years (N = 430). Study 1 identified 16 articles with four main research themes: 1) RS fMRI differences between mild TBI and comparison groups; 2) changes in RS fMRI over time; 3) RS fMRI differences in subsamples of mild TBI; and 4) relations of RS fMRI to outcome measures (e.g., symptoms, behaviour, and cognition). Overall, a clear pattern of findings of RS fMRI after mild TBI was difficult to discern, likely due to heterogeneity in study methods and a high proportion of cross-sectional studies with small sample sizes. Study 2 found that significant models of group (mild TBI versus OI) could be built from whole brain RS FC profiles. These FC profiles were characterized primarily by widespread differences in connectivity between networks, largely involving the default mode network, mesolimbic network, executive function/task positive networks, and the cerebellum. However, the observed prediction accuracy did not exceed the proportion of mild TBI cases in the sample. Additionally, no significant models of cognitive or somatic PCS could be built. While these findings provide insight into RS FC profiles that differentiate mild TBI from OI, the models have limited clinical utility, and PCS shortly after injury was not reflected in RS FC. While the results of this dissertation provide an important first step in understanding RS fMRI after pediatric mild TBI, more longitudinal research is needed.