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The Murchison Widefield Array (MWA) is an open access telescope dedicated to studying the low-frequency (80–300 MHz) southern sky. Since beginning operations in mid-2013, the MWA has opened a new observational window in the southern hemisphere enabling many science areas. The driving science objectives of the original design were to observe 21 cm radiation from the Epoch of Reionisation (EoR), explore the radio time domain, perform Galactic and extragalactic surveys, and monitor solar, heliospheric, and ionospheric phenomena. All together
programs recorded 20 000 h producing 146 papers to date. In 2016, the telescope underwent a major upgrade resulting in alternating compact and extended configurations. Other upgrades, including digital back-ends and a rapid-response triggering system, have been developed since the original array was commissioned. In this paper, we review the major results from the prior operation of the MWA and then discuss the new science paths enabled by the improved capabilities. We group these science opportunities by the four original science themes but also include ideas for directions outside these categories.
Volumetric atrophy and microstructural alterations in diffusion tensor imaging (DTI) measures of the hippocampus have been reported in people with Alzheimer's disease (AD) and mild cognitive impairment (MCI). However, no study to date has jointly investigated concomitant microstructural and volumetric changes of the hippocampus in dementia with Lewy bodies (DLB).
A total of 84 subjects (23 MCI, 17 DLB, 14 AD, and 30 healthy controls) were recruited for a multi-modal imaging (3T MRI and DTI) study that included neuropsychological evaluation. Freesurfer was used to segment the total hippocampus and delineate its subfields. The hippocampal segmentations were co-registered to the mean diffusivity (MD) and fractional anisotropy (FA) maps obtained from the DTI images.
Both AD and MCI groups showed significantly smaller hippocampal volumes compared to DLB and controls, predominantly in the CA1 and subiculum subfields. Compared to controls, hippocampal MD was elevated in AD, but not in MCI. DLB was characterized by both volumetric and microstructural preservation of the hippocampus. In MCI, higher hippocampal MD was associated with greater atrophy of the hippocampus and CA1 region. Hippocampal volume was a stronger predictor of memory scores compared to MD within the MCI group.
Through a multi-modal integration, we report novel evidence that the hippocampus in DLB is characterized by both macrostructural and microstructural preservation. Contrary to recent suggestions, our findings do not support the view that DTI measurements of the hippocampus are superior to volumetric changes in characterizing group differences, particularly between MCI and controls.
We studied neuroinflammation in individuals with late-life, depression, as a
risk factor for dementia, using [11C]PK11195 positron emission
tomography (PET). Five older participants with major depression and 13
controls underwent PET and multimodal 3T magnetic resonance imaging (MRI),
with blood taken to measure C-reactive protein (CRP). We found significantly
higher CRP levels in those with late-life depression and raised
[11C]PK11195 binding compared with controls in brain regions
associated with depression, including subgenual anterior cingulate cortex,
and significant hippocampal subfield atrophy in cornu ammonis 1 and
subiculum. Our findings suggest neuroinflammation requires further
investigation in late-life depression, both as a possible aetiological
factor and a potential therapeutic target.