high-resolution-structural-magnetic-resonance-imaging-human-subcortex

High-resolution Structural Magnetic Resonance Imaging of the Human Subcortex <I>In Vivo</I> and Postmortem

The focus of this study was to test the resolution limits of structural MRI of a postmortem brain compared to living human brains. The resolution of ...

measuring-connectivity-primary-visual-pathway-human-albinism-using

Measuring Connectivity in the Primary Visual Pathway in Human Albinism Using Diffusion Tensor Imaging and Tractography

In albinism, the number of ipsilaterally projecting retinal ganglion cells (RGCs) is significantly reduced. The retina and optic chiasm have been proposed ...

York University

Retinoblastoma is a rare eye cancer that generally occurs before 5 years of age and often results in enucleation (surgical removal) of the cancerous eye. In the present study, we sought to determine the consequences of early monocular enucleation on the morphological development of the anterior visual pathway including the optic chiasm and lateral geniculate nucleus.

Altered anterior visual system development following early monocular enucleation.

Our objective was to measure how the misrouting of retinal ganglion cell (RGC) fibers affects the organization of the optic chiasm and lateral geniculate nuclei (LGN) in human albinism. We compared the chiasmal structures and the LGN in both pigmented controls and patients with albinism by using high-resolution structural magnetic resonance imaging (MRI). We studied 12 patients with oculocutaneous albinism and 12 age-matched pigmented controls. Using a 3T MRI scanner, we acquired a T1 -weighted three-dimensional magnetization-prepared rapid gradient-echo (MPRAGE) image of the whole brain, oriented so that the optic nerves, chiasm, and tracts were in the same plane. We acquired multiple proton density-weighted images centered on the thalamus and midbrain, and averaged them to increase the signal, enabling precise manual tracing of the anatomical boundaries of the LGN. Albinism patients exhibited significantly smaller diameters of the optic nerves, chiasm and tracts, and optic chiasm and LGN volume compared with controls (P < 0.001 for all). The reductions in chiasmal diameters in the albinism compared with the control group can be attributed to the abnormal crossing of optic fibers and the reduction of RGCs in the central retina. The volume of the LGN devoted to the center of the visual field may be reduced in albinism due to fewer RGCs representing the area where the fovea would normally lie. Our data may be clinically useful in addressing how genetic deficits compromise proper structural and functional development in the brain.

Abnormal lateral geniculate nucleus and optic chiasm in human albinism.

The medial geniculate body (MGB) plays a central role in auditory processing with both efferent and afferent tracts to primary auditory cortex. People who have lost one eye early in life have enhanced sound localization, lack visual over auditory dominance and integrate auditory and visual information optimally, similar to controls, despite taking longer to localize unimodal visual stimuli. Compared to controls, people with one eye have decreased lateral geniculate nuclei (LGN) volume as expected given the 50% deafferentation of the visual system. However, LGN volume is larger than predicted contralateral to the remaining eye, indicating altered structural development likely through recruitment of deafferented LGN cells.

Larissa McKetton

Department of Biology and Centre for Vision Research,
Department of Biology,
Centre for Vision Research,
Department of Biology, Centre for Vision Research

York University

High-resolution Structural Magnetic Resonance Imaging of the Human Subcortex In Vivo and Postmortem

Measuring Connectivity in the Primary Visual Pathway in Human Albinism Using Diffusion Tensor Imaging and Tractography

Larissa McKetton

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Biology and Centre for Vision Research,Department of Biology,Centre for Vision Research,Department of Biology, Centre for Vision Research

York University

High-resolution Structural Magnetic Resonance Imaging of the Human Subcortex In Vivo and Postmortem

Measuring Connectivity in the Primary Visual Pathway in Human Albinism Using Diffusion Tensor Imaging and Tractography

Department of Biology and Centre for Vision Research,
Department of Biology,
Centre for Vision Research,
Department of Biology, Centre for Vision Research