Biology subjects

Baird, M. E.

Publications and source records attributed to Baird, M. E..

2 recordsLinked to original sources

bioRxiv2024

Mild traumatic brain injury is associated with increased thalamic subregion volume in the subacute period following injury

Structural vulnerability of the thalamus remains under investigated in mild traumatic brain injury (mTBI), and few studies have addressed its constituent nuclei using robust segmentation methods. This study aimed to investigate thalamic subnuclei volume in the subacute period following mTBI. Trauma control (TC) and mTBI patients aged 18 - 60 years old completed an MRI neuroimaging protocol including both high resolution structural (T1w) and diffusion weighted sequences at 6 - 11 weeks following injury (mean: 57 days; sd 11). Each thalamus was segmented into its constituent subnuclei, which were grouped into eight lateralised subregions. Volumes of the subregions were calculated. Neurite Orientation Dispersion and Density (NODDI) maps with parameters optimised for grey matter were computed for the same subregions. Group differences in subregion volumes and NODDI parameters were investigated using Bayesian linear modelling, with age, sex, and intracranial volume included as covariates. Comparisons of mTBI (n = 39) and TC (n = 28) groups revealed evidence of relatively increased grey matter volume in the mTBI group for the bilateral medial and right intralaminar subregions (BF10 > 3). Of the subregions which showed volume differences, there was no evidence for differences in NODDI metrics between groups. This study demonstrates that in the subacute period following mTBI, there is evidence of increased volume in specific thalamic subregions. Putative mechanisms underpinning the increased volume observed here are disordered remyelination, or myelin debris yet to be cleared. Significance statementDespite the prevalence of continued cognitive, somatic, and vestibular symptoms in the subacute period (6 - 12 weeks) following an mTBI, a clear neuropathophysiological profile is yet to be determined. One key vulnerable structure in mTBI could be the thalamus, a subcortical grey matter structure which comprises numerous subregions. The present study investigated whether changes in thalamic subregion volume are evident in the subacute period. For the first time, we show that at approximately 8 weeks following injury, mTBI is associated with increased volume in specific thalamus subregions. This provides an important avenue for continued investigation into the clinical significance of these findings.

neuroscience↗

bioRxiv2020

Cumulative impacts across Australia's Great Barrier Reef: A mechanistic evaluation

Cumulative impacts assessments on marine ecosystems have been hindered by the difficulty of collecting environmental data and identifying drivers of community dynamics beyond local scales. On coral reefs, an additional challenge is to disentangle the relative influence of multiple drivers that operate at different stages of coral ontogeny. We integrated coral life history, population dynamics and spatially-explicit environmental drivers to assess the relative and cumulative impacts of multiple stressors across 2,300 km of the worlds largest coral reef ecosystem, Australias Great Barrier Reef (GBR). Using literature data, we characterized relationships between coral life history processes (reproduction, larval dispersal, recruitment, growth and mortality) and environmental variables. We then simulated coral demographics and stressor impacts at the organism (coral colony) level on >3,800 individual reefs linked by larval connectivity, and exposed to temporally- and spatially-realistic regimes of acute (crown-of-thorns starfish outbreaks, cyclones and mass coral bleaching) and chronic (water quality) stressors. Model simulations produced a credible reconstruction of recent (2008-2020) coral trajectories consistent with monitoring observations, while estimating the impacts of each stressor at reef and regional scales. Overall, corals declined by one third across the GBR, from an average [~]29% to [~]19% hard coral cover. By 2020, less than 20% of the GBR had coral cover higher than 30%. Global annual rates of coral mortality were driven by bleaching (48%) ahead of cyclones (41%) and starfish predation (11%). Beyond the reconstructed status and trends, the model enabled the emergence of complex interactions that compound the effects of multiple stressors while promoting a mechanistic understanding of coral cover dynamics. Drivers of coral cover growth were identified; notably, water quality (suspended sediments) was estimated to delay recovery for at least 25% of inshore reefs. Standardized rates of coral loss and recovery allowed the integration of all cumulative impacts to determine the equilibrium cover for each reef. This metric, combined with maps of impacts, recovery potential, water quality thresholds and reef state metrics, facilitates strategic spatial planning and resilience-based management across the GBR.

ecology↗