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Human Brain Mapping Feb 2019Albinism refers to a group of genetic abnormalities in melanogenesis that are associated neuronal misrouting through the optic chiasm. We perform quantitative assessment...
Albinism refers to a group of genetic abnormalities in melanogenesis that are associated neuronal misrouting through the optic chiasm. We perform quantitative assessment of visual pathway structure and function in 23 persons with albinism (PWA) and 20 matched controls using optical coherence tomography (OCT), volumetric magnetic resonance imaging (MRI), diffusion tensor imaging and visual evoked potentials (VEP). PWA had a higher streamline decussation index (percentage of total tractography streamlines decussating at the chiasm) compared with controls (Z = -2.24, p = .025), and streamline decussation index correlated weakly with inter-hemispheric asymmetry measured using VEP (r = .484, p = .042). For PWA, a significant correlation was found between foveal development index and total number of streamlines (r = .662, p < .001). Significant positive correlations were found between peri-papillary retinal nerve fibre layer thickness and optic nerve (r = .642, p < .001) and tract (r = .663, p < .001) width. Occipital pole cortical thickness was 6.88% higher (Z = -4.10, p < .001) in PWA and was related to anterior visual pathway structures including foveal retinal pigment epithelium complex thickness (r = -.579, p = .005), optic disc (r = .478, p = .021) and rim areas (r = .597, p = .003). We were unable to demonstrate a significant relationship between OCT-derived foveal or optic nerve measures and MRI-derived chiasm size or streamline decussation index. Our novel tractographic demonstration of altered chiasmatic decussation in PWA corresponds to VEP measured cortical asymmetry and is consistent with chiasmatic misrouting in albinism. We also demonstrate a significant relationship between retinal pigment epithelium and visual cortex thickness indicating that retinal pigmentation defects in albinism lead to downstream structural reorganisation of the visual cortex.
Topics: Adult; Albinism; Diffusion Tensor Imaging; Evoked Potentials, Visual; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Retina; Tomography, Optical Coherence; Visual Cortex; Visual Pathways
PubMed: 30511784
DOI: 10.1002/hbm.24411 -
Neuroscience Bulletin Oct 2021Visual object recognition in humans and nonhuman primates is achieved by the ventral visual pathway (ventral occipital-temporal cortex, VOTC), which shows a...
Visual object recognition in humans and nonhuman primates is achieved by the ventral visual pathway (ventral occipital-temporal cortex, VOTC), which shows a well-documented object domain structure. An on-going question is what type of information is processed in the higher-order VOTC that underlies such observations, with recent evidence suggesting effects of certain visual features. Combining computational vision models, fMRI experiment using a parametric-modulation approach, and natural image statistics of common objects, we depicted the neural distribution of a comprehensive set of visual features in the VOTC, identifying voxel sensitivities with specific feature sets across geometry/shape, Fourier power, and color. The visual feature combination pattern in the VOTC is significantly explained by their relationships to different types of response-action computation (fight-or-flight, navigation, and manipulation), as derived from behavioral ratings and natural image statistics. These results offer a comprehensive visual feature map in the VOTC and a plausible theoretical explanation as a mapping onto different types of downstream response-action systems.
Topics: Animals; Brain Mapping; Humans; Magnetic Resonance Imaging; Occipital Lobe; Pattern Recognition, Visual; Photic Stimulation; Temporal Lobe; Visual Pathways; Visual Perception
PubMed: 34215969
DOI: 10.1007/s12264-021-00734-4 -
Seminars in Ophthalmology 2006Modern neuroimaging provides excellent characterization of anterior visual pathway gliomas, often obviating the need for biopsy of the tumor. Management remains... (Review)
Review
Modern neuroimaging provides excellent characterization of anterior visual pathway gliomas, often obviating the need for biopsy of the tumor. Management remains controversial, but if there is progression, chemotherapy is preferred for young patients. Stereotactically guided conformal radiotherapy and proton beam radiotherapy allow smaller, more precise doses of radiation to be administered and can be considered in older children with progressive disease. A mouse model of NF-1 with optic pathway gliomas has the potential to provide important insights into the development of gliomas as well as serving as a model for their effective treatment.
Topics: Animals; Antineoplastic Agents; Disease Models, Animal; Glioma; Humans; Neurofibromatosis 1; Optic Chiasm; Optic Nerve Neoplasms; Radiotherapy, Conformal; Visual Pathways
PubMed: 16912009
DOI: 10.1080/08820530500350449 -
NMR in Biomedicine Jul 2023The human visual pathway starts from the retina, passes through the retinogeniculate visual pathway, the optic radiation, and finally connects to the primary visual...
The human visual pathway starts from the retina, passes through the retinogeniculate visual pathway, the optic radiation, and finally connects to the primary visual cortex. Diffusion MRI tractography is the only technology that can noninvasively reconstruct the visual pathway. However, complete and accurate visual pathway reconstruction is challenging because of the skull base environment and complex fiber geometries. Specifically, the optic nerve within the complex skull base environment can cause abnormal diffusion signals. The crossing and fanning fibers at the optic chiasm, and a sharp turn of Meyer's loop at the optic radiation, contribute to complex fiber geometries of the visual pathway. A fiber trajectory distribution (FTD) function-based tractography method of our previous work and several high sensitivity tractography methods can reveal these complex fiber geometries, but are accompanied by false-positive fibers. Thus, the related studies of the visual pathway mostly applied the expert region of interest selection strategy. However, interobserver variability is an issue in reconstructing an accurate visual pathway. In this paper, we propose a unified global tractography framework to automatically reconstruct the visual pathway. We first extend the FTD function to a high-order streamline differential equation for global trajectory estimation. At the global level, the tractography process is simplified as the estimation of global trajectory distribution coefficients by minimizing the cost between trajectory distribution and the selected directions under the prior guidance by introducing the tractography template as anatomic priors. Furthermore, we use a deep learning-based method and tractography template prior information to automatically generate the mask for tractography. The experimental results demonstrate that our proposed method can successfully reconstruct the visual pathway with high accuracy.
Topics: Humans; Visual Pathways; Frontotemporal Dementia; Diffusion Magnetic Resonance Imaging; Diffusion Tensor Imaging; Magnetic Resonance Imaging
PubMed: 36633539
DOI: 10.1002/nbm.4904 -
Current Opinion in Neurology Oct 2018Optical coherence tomography (OCT) is a noninvasive in-vivo imaging tool that enables the quantification of the various retinal layer thicknesses. Given the frequent... (Review)
Review
PURPOSE OF REVIEW
Optical coherence tomography (OCT) is a noninvasive in-vivo imaging tool that enables the quantification of the various retinal layer thicknesses. Given the frequent involvement of the visual pathway in multiple sclerosis, OCT has become an important tool in clinical practice, research and clinical trials. In this review, the role of OCT as a means to investigate visual pathway damage in multiple sclerosis is discussed.
RECENT FINDINGS
Evidence from recent OCT studies suggests that the peripapillary retinal nerve fibre layer (pRNFL) appears to be an ideal marker of axonal integrity, whereas the macular ganglion cell and inner plexiform layer (GCIP) thickness enables early detection of neuronal degeneration in multiple sclerosis. The thickness of the macular inner nuclear layer (INL) has been suggested as a biomarker for inflammatory disease activity and treatment response in multiple sclerosis. OCT parameters may also be used as an outcome measure in clinical trials evaluating the neuroprotective or regenerative potential of new treatments.
SUMMARY
OCT provides insights into multiple sclerosis beyond the visual pathway. It is capable of quantifying the major pathological hallmarks of the disease, specifically inflammation and neuroaxonal degeneration. OCT, therefore, has the potential to become another mainstay in the monitoring of multiple sclerosis patients.
Topics: Humans; Multiple Sclerosis; Tomography, Optical Coherence; Visual Pathways
PubMed: 30074495
DOI: 10.1097/WCO.0000000000000604 -
Neuroimaging Clinics of North America Aug 2015Vision is one of our most vital senses, deriving from the eyes as well as structures deep within the intracranial compartment. MR imaging, through its wide selection of... (Review)
Review
Vision is one of our most vital senses, deriving from the eyes as well as structures deep within the intracranial compartment. MR imaging, through its wide selection of sequences, offers an array of structural and functional imaging tools to interrogate this intricate system. This review describes several advanced MR imaging sequences and explores their potential clinical applications as well as areas for further development.
Topics: Humans; Image Enhancement; Magnetic Resonance Imaging; Neuroimaging; Optic Nerve; Optic Nerve Diseases; Retinal Diseases; Visual Pathways
PubMed: 26208415
DOI: 10.1016/j.nic.2015.05.003 -
Investigative Ophthalmology & Visual... Jun 2019Explore in vivo whether there is direct communication between the cerebrospinal fluid (CSF) and extravascular compartment of human visual pathway structures.
PURPOSE
Explore in vivo whether there is direct communication between the cerebrospinal fluid (CSF) and extravascular compartment of human visual pathway structures.
METHODS
A prospective and observational study included 10 subjects who underwent intrathecal gadolinium-enhanced magnetic resonance imaging (MRI) for suspected CSF circulation disorder, but with a negative result and with no known ophthalmic diseases. After precontrast T1-weighted MRI, 0.5 mL of gadobutrol (Gadovist, 1.0 mmol/mL) was injected intrathecally. Gadobutrol distributes in the extravascular space, and served as a CSF tracer. Consecutive MRI scans were obtained throughout 24 to 48 hours. To assess gadobutrol contrast enrichment, regions of interest (ROIs) were placed at multiple locations along the visual pathway, from the primary visual cortex to the eye's vitreous body. CSF tracer dependent T1 signal was measured in each ROI. A linear mixed-model was used for statistical analyses.
RESULTS
CSF tracer enrichment was found within the optic nerve, optic chiasm, optic tract, and primary visual cortex (P < 0.001). Peak tracer enrichment in the visual pathway generally occurred after 24 hours and was preceded by peak enhancement in the prechiasmatic cistern after 4 to 6 hours.
CONCLUSIONS
The results indicate direct communication between CSF of subarachnoid space and the extravascular space of the human visual pathway. Extravascular entry of the CSF tracer is a prerequisite for a glymphatic system, the present findings may suggest its presence. The existence of a glymphatic system in the human visual pathway could bring novel perspectives on the pathophysiology and treatment of ophthalmic diseases.
Topics: Adult; Cerebrospinal Fluid; Contrast Media; Female; Glymphatic System; Humans; Injections, Spinal; Magnetic Resonance Imaging; Male; Optic Chiasm; Optic Nerve; Optic Tract; Organometallic Compounds; Prospective Studies; Subarachnoid Space; Visual Cortex; Visual Pathways
PubMed: 31247084
DOI: 10.1167/iovs.19-26997 -
Brain and Nerve = Shinkei Kenkyu No... Nov 2016The ventral visual pathway projecting from the primary visual cortex to the visual temporal association cortex processes shape, color, and material properties of objects... (Review)
Review
The ventral visual pathway projecting from the primary visual cortex to the visual temporal association cortex processes shape, color, and material properties of objects as well as face and facial expression, and stereoscopic depth. The last decade has witnessed great advances in our understanding of how information is transformed at each transition between the stages along this pathway. Accumulating evidence also indicates that neurons in the later part of the pathway (e.g., area V4 and inferior temporal cortex) are causally involved in generating perception of shape, color, face, and fine stereoscopic depth.
Topics: Animals; Brain Mapping; Face; Humans; Pattern Recognition, Visual; Photic Stimulation; Visual Cortex; Visual Pathways
PubMed: 27852026
DOI: 10.11477/mf.1416200599 -
Neurodegenerative Disease Management Oct 2018In this review, a current overview is provided of how optical coherence tomography and infrared oculography can aid in assessing the visual system and CNS in multiple... (Review)
Review
In this review, a current overview is provided of how optical coherence tomography and infrared oculography can aid in assessing the visual system and CNS in multiple sclerosis (MS). Both afferent and efferent visual disorders are common in MS and visual complaints can have a tremendous impact on daily functioning. Optical coherence tomography and infrared oculography can detect and quantify visual disorders with high accuracy, but could also serve as quantitative markers for inflammation, neurodegeneration and network changes including cognitive decline in MS patients. The assessment of the efferent and afferent visual pathways is relevant for monitoring and predicting the disease course, but is also potentially valuable as an outcome measure in therapeutic trials.
Topics: Eye; Humans; Infrared Rays; Multiple Sclerosis; Tomography, Optical Coherence; Visual Pathways
PubMed: 30226111
DOI: 10.2217/nmt-2018-0011 -
Brain Pathology (Zurich, Switzerland) Mar 2021Visual deficits are among the most prevalent symptoms in patients with multiple sclerosis (MS). To understand deficits in the visual pathway during MS and potential...
Visual deficits are among the most prevalent symptoms in patients with multiple sclerosis (MS). To understand deficits in the visual pathway during MS and potential treatment effects, we used experimental autoimmune encephalomyelitis (EAE), the most commonly used animal model of MS. The afferent visual pathway was assessed in vivo using optical coherence tomography (OCT), electroretinography (ERG), and visually evoked cortical potentials (VEPs). Inflammation, demyelination, and neurodegeneration were examined by immunohistochemistry ex vivo. In addition, an immunomodulatory, remyelinating agent, the estrogen receptor β ligand chloroindazole (IndCl), was tested for its therapeutic potential in the visual pathway. EAE produced functional deficits in visual system electrophysiology, including suppression of ERG and VEP waveform amplitudes and increased signal latencies. Therapeutic IndCl rescued overall visual system latency by VEP but had little impact on amplitude or ERG findings relative to vehicle. Faster VEP conduction in IndCl-treated mice was associated with enhanced myelin basic protein signal in all visual system structures examined. IndCl preserved retinal ganglion cells (RGCs) and oligodendrocyte density in the prechiasmatic white matter, but similar retinal nerve fiber layer thinning by OCT was noted in vehicle and IndCl-treated mice. Although IndCl differentially attenuated leukocyte and astrocyte staining signal throughout the structures analyzed, axolemmal varicosities were observed in all visual fiber tracts of mice with EAE irrespective of treatment, suggesting impaired axonal energy homeostasis. These data support incomplete functional recovery of VEP amplitude with IndCl, as fiber tracts displayed persistent axon pathology despite remyelination-induced decreases in latencies, evidenced by reduced optic nerve g-ratio in IndCl-treated mice. Although additional studies are required, these findings demonstrate the dynamics of visual pathway dysfunction and disability during EAE, along with the importance of early treatment to mitigate EAE-induced axon damage.
Topics: Animals; Azo Compounds; Encephalomyelitis, Autoimmune, Experimental; Evoked Potentials, Visual; Inflammation; Mice; Mice, Inbred C57BL; Multiple Sclerosis; Naphthalenes; Nerve Degeneration; Remyelination; Visual Pathways
PubMed: 33368801
DOI: 10.1111/bpa.12930