The effect of normal and abnormal ageing on prospective memory showed increased cognitive conflict: a functional MRI study

INTRODUCTION: Prospective memory (PM) is memory for planned intention, which needs to be executed appropriately in the future. PM task is usually embedded in ongoing activities. The neural correlates of PM have not been elucidated. To date, no functional imaging study has been conducted to examine the relevant functional change of PM during the processes of ageing and ...published_or_final_versio

Performance evaluation of Bragg coherent diffraction imaging

In this study,we present a numerical framework for modeling three-dimensional (3D) diffraction data in Bragg coherent diffraction imaging (BraggCDI) experiments and evaluating the quality of obtained 3D complex-valued real-space images recovered by reconstruction algorithms under controlled conditions. The approach is used to systematically explore the performance and the detection limit of this phase-retrieval-based microscopy tool. The numerical investigation suggests that the superb performance of Bragg CDI is achieved with an oversampling ratio above 30 and a detection dynamic range above 6 orders. The observed performance degradation subject to the data binning processes is also studied. This numerical tool can be used to optimize experimental parameters and has the potential to significantly improve the throughput of Bragg CDI method

Relevance of short-range connectivity to brain compensation and cognitive efficiency in healthy and pathological ageing: a combined functional magnetic resonance imaging and tractography study on prospective memory

INTRODUCTION: Cognition and its efficiency are related to the activities of specific brain regions and their interactions. The brain function and structure are vulnerable to both healthy and pathological ageing, and these processes may underlie the impaired cognitive functions in daily life …published_or_final_versio

Artifact mitigation of ptychography integrated with on-the-fly scanning probe microscopy

We report our experiences with conducting ptychography simultaneously with the X-ray fluorescence measurement using the on-the-fly mode for efficient multi-modality imaging. We demonstrate that the periodic artifact inherent to the raster scan pattern can be mitigated using a sufficiently fine scan step size to provide an overlap ratio of >70%. This allows us to obtain transmitted phase contrast images with enhanced spatial resolution from ptychography while maintaining the fluorescence imaging with continuous-motion scans on pixelated grids. This capability will greatly improve the competence and throughput of scanning probe X-ray microscopy

The roles of Irx3 and Irx5 in mammalian inner ear development

Iroquois genes encode a family of transcription factors containing TALE class homeodomain. They are regarded as prepatterning genes in Drosophila sensory organ development. There are six members (Irx1Irx6) of Iroquois genes in mouse and human. Irx3 and Irx5 are linked genes on mouse chromosome 8, which are involved in many mammalian developmental processes. However, the roles of Irx3 and Irx5 in mammalian hearing loss are poorly understood. To identify the function of these two genes in inner ear development, we have investigated two reporter knock‐in mouse mutants: Irx3lacZ, Irx5EGFP, and a double knock‐out mutant: Irx3/5‐/‐. Irx3 and Irx5 have overlapping expression domains in the developing inner ear. Physiological tests indicated that the Irx3lacZ and Irx5EGFP mutant mice displayed hearing defect, while Irx3/5‐/‐ mice were embryonic lethal. Although paint filling analysis showed the normal cochlea morphology of Irx3lacZ and Irx5EGFP mutant mice, ectopic inner hair cells have been discovered in the organ of Corti. Interestingly, the cochlear duct of Irx3/5‐/‐ mice was enlarged and shortened, and the basal part of the cochlea was fused with the saccule. There were also numerous vestibular‐like ectopic hair cells surrounded by ectopic Sox2‐positive cells in the greater epithelial ridge of cochlea. The organ of Corti was malformed with neither hair cell differentiation nor supporting cell differentiation at E16.5. In summary, our results indicate that Irx3 and Irx5 cooperatively pattern the boundary between the vestibule and the cochlea and they are important for the cochlear sensory neural cell specification.postprin

Resolution-enhanced X-ray fluorescence microscopy via deep residual networks

Multimodal hard X-ray scanning probe microscopy has been extensively used to study functional materials providing multiple contrast mechanisms. For instance, combining ptychography with X-ray fluorescence (XRF) microscopy reveals structural and chemical properties simultaneously. While ptychography can achieve diffraction-limited spatial resolution, the resolution of XRF is limited by the X-ray probe size. Here, we develop a machine learning (ML) model to overcome this problem by decoupling the impact of the X-ray probe from the XRF signal. The enhanced spatial resolution was observed for both simulated and experimental XRF data, showing superior performance over the state-of-the-art scanning XRF method with different nano-sized X-ray probes. Enhanced spatial resolutions were also observed for the accompanying XRF tomography reconstructions. Using this probe profile deconvolution with the proposed ML solution to enhance the spatial resolution of XRF microscopy will be broadly applicable across both functional materials and biological imaging with XRF and other related application areas

Declined frontal white matter integrity in Alzheimer’s disease: a diffusion tensor imaging study

INTRODUCTION: Previous studies on structural changes of Alzheimer’s disease (AD) have been focused on grey matter atrophy. There is a resurgence of interests on white matter integrity in this prominently increasing patient population. Diffusion tensor imaging (DTI) provides key information on the microstructural changes beyond macroscopic anatomical imaging by in-vivo tracing molecular diffusion in the brain, and the measured fractional anisotrophy (FA) value may represent axonal integrity of neuronal networks. Data of DTI from AD patients are limited, and the literature is controversial regarding whether the AD process has a greater impact on anterior versus posterior cerebral white matter. METHODS: Eighteen patients with mild AD and 16 age-matched healthy adults were recruited into the study. Demographic features of the two groups were comparable. Data of DTI were collected using a Philips 3.0T MRI scanner. Scan parameters were as follows: B0=800 s/mm2, FOV=224*224*140 mm, resolution=1.75*1.75*2 mm, non-collinear 15 directions was acquired. 3D T1 anatomy was also collected. We processed DTI data with DTI toolbox, and anatomical T1 data with VBM5 toolbox in SPM. Voxel-by-voxel analysis was applied to compare the difference in FA value, and volume of white matter of the normalised brain between the elderly and AD groups. RESULTS: Voxel-based analysis showed no significant difference in white matter volume between the two groups, but FA value was reduced greatly in the left anterior cingulate (−10,37,−3), right anterior cingulate (12,0,28), and left medial frontal lobe (−18,32,−12). Minor reduction was found in other brain regions such as body of the corpus callosum, right midbrain (12,−12,−6), right posterior corpus callosum (8,−44,2), and bilateral, especially right temporal lobe (36,−8,−20), upon right hippocampus. Coordinates (x,y,z) were labelled according to Talairach atlas. CONCLUSION: DTI could be valid and more sensitive than traditional T1 anatomy in detecting microscopic white matter lesions. Our data showed a greater decrement in FA value over the anterior than posterior brain regions, and this decrement was not due to white matter atrophy. Our findings are in line with the retrogenesis hypothesis which predicts reversed demyelination during the process of AD, as the frontal lobe fibres are myelinated relatively late during brain development. These results also support previous findings of our behavioural study that frontal lobe abnormality might be the neural basis for cognitive deficit in AD patients.published_or_final_versionThe 15th Medical Research Conference; Department of Medicine, The University of Hong Kong, Hong Kong, 16 January 2010. In Hong Kong Medical Journal, 2010, v. 16 suppl 1, p. 21, abstract no. 2

Extending the depth of field for ptychography using complex-valued wavelets

Ptychography is a scanning variation of the coherent diffractive imaging method for providing high-resolution quantitative images from specimen with extended dimensions. Its capability of achieving diffraction-limited spatial resolution can be compromised by the sample thickness, which is generally required to be thinner than the depth of field of the imaging system. In this Letter, we present a method to extend the depth of field for ptychography by numerically generating the focus stack from reconstructions with propagated illumination wavefronts and combining the in-focus features to a single sharp image using an algorithm based on the complex-valued discrete wavelet transform. This approach does not require repeated measurements by translating the sample along the optical axis as in the conventional focus stacking method, and offers a computation-efficient alternative to obtain high-resolution images with extended depth of fields, complementary to the multi-slice ptychography

Extending the depth of field for ptychography using complex-valued wavelets (vol 44, pg 503, 2019)

This publisher’s note corrects an error in Eq. (3) of Opt. Lett. 44, 503 (2019)

Integrated life science education in Bachelor of Nursing and Bachelor of Chinese Medicine at The University of Hong Kong

poster presentation no. PP54published_or_final_versio