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407 results on '"Egan, Gary F."'

1. Neurodesk: an accessible, flexible and portable data analysis environment for reproducible neuroimaging

Author

Renton, Angela I., Dao, Thuy T., Johnstone, Tom, Civier, Oren, Sullivan, Ryan P., White, David J., Lyons, Paris, Slade, Benjamin M., Abbott, David F., Amos, Toluwani J., Bollmann, Saskia, Botting, Andy, Campbell, Megan E. J., Chang, Jeryn, Close, Thomas G., Dörig, Monika, Eckstein, Korbinian, Egan, Gary F., Evas, Stefanie, Flandin, Guillaume, Garner, Kelly G., Garrido, Marta I., Ghosh, Satrajit S., Grignard, Martin, Halchenko, Yaroslav O., Hannan, Anthony J., Heinsfeld, Anibal S., Huber, Laurentius, Hughes, Matthew E., Kaczmarzyk, Jakub R., Kasper, Lars, Kuhlmann, Levin, Lou, Kexin, Mantilla-Ramos, Yorguin-Jose, Mattingley, Jason B., Meier, Michael L., Morris, Jo, Narayanan, Akshaiy, Pestilli, Franco, Puce, Aina, Ribeiro, Fernanda L., Rogasch, Nigel C., Rorden, Chris, Schira, Mark M., Shaw, Thomas B., Sowman, Paul F., Spitz, Gershon, Stewart, Ashley W., Ye, Xincheng, Zhu, Judy D., Narayanan, Aswin, and Bollmann, Steffen

Published
2024
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11. A Standards Organization for Open and FAIR Neuroscience: the International Neuroinformatics Coordinating Facility

Author

Abrams, Mathew Birdsall, Bjaalie, Jan G., Das, Samir, Egan, Gary F., Ghosh, Satrajit S., Goscinski, Wojtek J., Grethe, Jeffrey S., Kotaleski, Jeanette Hellgren, Ho, Eric Tatt Wei, Kennedy, David N., Lanyon, Linda J., Leergaard, Trygve B., Mayberg, Helen S., Milanesi, Luciano, Mouček, Roman, Poline, J. B., Roy, Prasun K., Strother, Stephen C., Tang, Tong Boon, Tiesinga, Paul, Wachtler, Thomas, Wójcik, Daniel K., and Martone, Maryann E.

Published
2022
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12. Localized Changes in Dentate Nucleus Shape and Magnetic Susceptibility in Friedreich Ataxia.

Author

Harding, Ian H., Nur Karim, Muhammad Ikhsan, Selvadurai, Louisa P., Corben, Louise A., Delatycki, Martin B., Monti, Serena, Saccà, Francesco, Georgiou‐Karistianis, Nellie, Cocozza, Sirio, and Egan, Gary F.

Abstract

Background: The dentate nuclei of the cerebellum are key sites of neuropathology in Friedreich ataxia (FRDA). Reduced dentate nucleus volume and increased mean magnetic susceptibility, a proxy of iron concentration, have been reported by magnetic resonance imaging studies in people with FRDA. Here, we investigate whether these changes are regionally heterogeneous. Methods: Quantitative susceptibility mapping data were acquired from 49 people with FRDA and 46 healthy controls. The dentate nuclei were manually segmented and analyzed using three dimensional vertex‐based shape modeling and voxel‐based assessments to identify regional changes in morphometry and susceptibility, respectively. Results: Individuals with FRDA, relative to healthy controls, showed significant bilateral surface contraction most strongly at the rostral and caudal boundaries of the dentate nuclei. The magnitude of this surface contraction correlated with disease duration, and to a lesser extent, ataxia severity. Significantly greater susceptibility was also evident in the FRDA cohort relative to controls, but was instead localized to bilateral dorsomedial areas, and also correlated with disease duration and ataxia severity. Conclusions: Changes in the structure of the dentate nuclei in FRDA are not spatially uniform. Atrophy is greatest in areas with high gray matter density, whereas increases in susceptibility—reflecting iron concentration, demyelination, and/or gliosis—predominate in the medial white matter. These findings converge with established histological reports and indicate that regional measures of dentate nucleus substructure are more sensitive measures of disease expression than full‐structure averages. Biomarker development and therapeutic strategies that directly target the dentate nuclei, such as gene therapies, may be optimized by targeting these areas of maximal pathology. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. [ABSTRACT FROM AUTHOR]

Published
2024
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29. Free‐Water Imaging in Friedreich Ataxia Using Multi‐Compartment Models.

Author

Fernandez, Lara, Corben, Louise A., Bilal, Hiba, Delatycki, Martin B., Egan, Gary F., and Harding, Ian H.

Abstract

Background: The neurological phenotype of Friedreich ataxia (FRDA) is characterized by neurodegeneration and neuroinflammation in the cerebellum and brainstem. Novel neuroimaging approaches quantifying brain free‐water using diffusion magnetic resonance imaging (dMRI) are potentially more sensitive to these processes than standard imaging markers. Objectives: To quantify the extent of free‐water and microstructural change in FRDA‐relevant brain regions using neurite orientation dispersion and density imaging (NODDI), and bitensor diffusion tensor imaging (btDTI). Method: Multi‐shell dMRI was acquired from 14 individuals with FRDA and 14 controls. Free‐water measures from NODDI (FISO) and btDTI (FW) were compared between groups in the cerebellar cortex, dentate nuclei, cerebellar peduncles, and brainstem. The relative sensitivity of the free‐water measures to group differences was compared to microstructural measures of NODDI intracellular volume, free‐water corrected fractional anisotropy, and conventional uncorrected fractional anisotropy. Results: In individuals with FRDA, FW was elevated in the cerebellar cortex, peduncles (excluding middle), dentate, and brainstem (P < 0.005). FISO was elevated primarily in the cerebellar lobules (P < 0.001). On average, FW effect sizes were larger than all other markers (mean ηρ2 = 0.43), although microstructural measures also had very large effects in the superior and inferior cerebellar peduncles and brainstem (ηρ2 > 0.37). Across all regions and metrics, effect sizes were largest in the superior cerebellar peduncles (ηρ2 > 0.46). Conclusions: Multi‐compartment diffusion measures of free‐water and neurite integrity distinguish FRDA from controls with large effects. Free‐water magnitude in the brainstem and cerebellum provided the greatest distinction between groups. This study supports further applications of multi‐compartment diffusion modeling, and investigations of free‐water as a measure of disease expression and progression in FRDA. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. [ABSTRACT FROM AUTHOR]

Published
2024
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47. Preterm Infant Hippocampal Volumes Correlate with Later Working Memory Deficits

Author

Beauchamp, Miriam H., Thompson, Deanne K., Howard, Kelly, Doyle, Lex W., Egan, Gary F., Inder, Terrie E., and Anderson, Peter J.

Abstract

Children born preterm exhibit working memory deficits. These deficits may be associated with structural brain changes observed in the neonatal period. In this study, the relationship between neonatal regional brain volumes and working memory deficits at age 2 years were investigated, with a particular interest in the dorsolateral prefrontal cortex, parietal cortex and the hippocampus. While the eligible sample consisted of 227 very preterm children who were born at the Royal Women's Hospital, Melbourne prior to 30 weeks gestation or weighing less than 1250 g, 156 children had complete data sets. Neonatal magnetic resonance images of the brain were obtained at term equivalent age and subsequently parcellated into eight sub-regions, while the hippocampus was manually segmented. The relationship between brain volumes for these regions and performance on a working memory task (delayed alternation) at 2 years of age was examined. Very preterm children who perseverated on the working memory task had significantly smaller hippocampal volumes than very preterm children who exhibited intact working memory, even after adjusting for relevant perinatal, sociodemographic and developmental factors. Preterm children appear to have altered hippocampal volumes by discharge from hospital which may have a lasting impact on working memory function.

Published
2008
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50. Lower brain glucose metabolism in normal ageing is predominantly frontal and temporal: A systematic review and pooled effect size and activation likelihood estimates meta‐analyses.

Author

Deery, Hamish A., Di Paolo, Robert, Moran, Chris, Egan, Gary F., and Jamadar, Sharna D.

Subjects
GLUCOSE metabolism, BRAIN metabolism, TEMPORAL lobe, OLDER people, OCCIPITAL lobe
Abstract

This review provides a qualitative and quantitative analysis of cerebral glucose metabolism in ageing. We undertook a systematic literature review followed by pooled effect size and activation likelihood estimates (ALE) meta‐analyses. Studies were retrieved from PubMed following the PRISMA guidelines. After reviewing 635 records, 21 studies with 22 independent samples (n = 911 participants) were included in the pooled effect size analyses. Eight studies with eleven separate samples (n = 713 participants) were included in the ALE analyses. Pooled effect sizes showed significantly lower cerebral metabolic rates of glucose for older versus younger adults for the whole brain, as well as for the frontal, temporal, parietal, and occipital lobes. Among the sub‐cortical structures, the caudate showed a lower metabolic rate among older adults. In sub‐group analyses controlling for changes in brain volume or partial volume effects, the lower glucose metabolism among older adults in the frontal lobe remained significant, whereas confidence intervals crossed zero for the other lobes and structures. The ALE identified nine clusters of lower glucose metabolism among older adults, ranging from 200 to 2640 mm3. The two largest clusters were in the left and right inferior frontal and superior temporal gyri and the insula. Clusters were also found in the inferior temporal junction, the anterior cingulate and caudate. Taken together, the results are consistent with research showing less efficient glucose metabolism in the ageing brain. The findings are discussed in the context of theories of cognitive ageing and are compared to those found in neurodegenerative disease. [ABSTRACT FROM AUTHOR]

Published
2023
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