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Nature Communications Dec 2023Sensory cortices modulate innate behaviors through corticofugal projections targeting phylogenetically-old brainstem nuclei. However, the principles behind the...
Sensory cortices modulate innate behaviors through corticofugal projections targeting phylogenetically-old brainstem nuclei. However, the principles behind the functional connectivity of these projections remain poorly understood. Here, we show that in mice visual cortical neurons projecting to the optic-tract and dorsal-terminal nuclei (NOT-DTN) possess distinct response properties and anatomical connectivity, supporting the adaption of an essential innate eye movement, the optokinetic reflex (OKR). We find that these corticofugal neurons are enriched in specific visual areas, and they prefer temporo-nasal visual motion, matching the direction bias of downstream NOT-DTN neurons. Remarkably, continuous OKR stimulation selectively enhances the activity of these temporo-nasally biased cortical neurons, which can efficiently promote OKR plasticity. Lastly, we demonstrate that silencing downstream NOT-DTN neurons, which project specifically to the inferior olive-a key structure in oculomotor plasticity, impairs the cortical modulation of OKR and OKR plasticity. Our results unveil a direction-selective cortico-brainstem pathway that adaptively modulates innate behaviors.
Topics: Animals; Mice; Visual Pathways; Instinct; Eye Movements; Reflex; Brain Stem
PubMed: 38123558
DOI: 10.1038/s41467-023-42910-2 -
Medicina (Kaunas, Lithuania) Sep 2023: Although ocular disorders can occasionally impact people with HIV over the course of their illness, HIV/AIDS is unmistakably a multisystem disorder. A physician can...
: Although ocular disorders can occasionally impact people with HIV over the course of their illness, HIV/AIDS is unmistakably a multisystem disorder. A physician can rule out a wide range of ophthalmic problems with the assistance of an ophthalmologist, from adnexal disorders to posterior segment diseases, including those affecting the optic tract and optic nerve. : Based on patient medical data from the "St. Parascheva" Clinical Hospital of Infectious Diseases in Iasi, we carried out a retrospective clinical investigation on patients with HIV/AIDS and ophthalmological conditions who were hospitalized in northeastern Romania. We seek to draw attention to the characteristics and ophthalmological comorbidities of HIV/AIDS patients. The studied period was between 1 January 1991 and 31 December 2022. : There were a total of 38 recorded cases of ophthalmological manifestations in the HIV-infected patients. The research group's average age was 37.31 years old (standard deviation 9.5693917). Males were primarily impacted, having lower total CD4+ T-lymphocyte levels based on sex and CD4+ T-lymphocyte levels overall. The HIV viral load was 999 268.13 copies/mL on average (standard deviation 1,653,722.9). Of all the patients, we found out that 17 had congenital eye diseases (44.73%) and the others (21, 55.26%) developed ophthalmological diseases. CMV Retinitis was found most frequently, in eight patients (21.05%), followed by Myopia in seven patients (18.42%). : The key to the management of HIV-positive patients is a multidisciplinary approach and access to antiretroviral therapy. Anyone who is HIV-positive and experiences ocular symptoms at any time should be directed to seek professional ophthalmologic treatment as soon as feasible. A therapeutic holdup could result in irreversible vision loss. Long-term coordination is required to combat this disease, improving communication between the ophthalmology and infectious disease fields.
PubMed: 37763724
DOI: 10.3390/medicina59091605 -
Journal of Neurotrauma Oct 2023Repetitive mild traumatic brain injuries (rmTBIs) are serious trauma events responsible for the development of numerous neurodegenerative disorders. A major challenge in...
Fixed Time-Point Analysis Reveals Repetitive Mild Traumatic Brain Injury Effects on Resting State Functional Magnetic Resonance Imaging Connectivity and Neuro-Spatial Protein Profiles.
Repetitive mild traumatic brain injuries (rmTBIs) are serious trauma events responsible for the development of numerous neurodegenerative disorders. A major challenge in developing diagnostics and treatments for the consequences of rmTBI is the fundamental knowledge gaps of the molecular mechanisms responsible for neurodegeneration. It is both critical and urgent to understand the neuropathological and functional consequences of rmTBI to develop effective therapeutic strategies. Using the Closed-Head Impact Model of Engineered Rotational Acceleration, or CHIMERA, we measured neural changes following injury, including brain volume, diffusion tensor imaging, and resting-state functional magnetic resonance imaging coupled with graph theory and functional connectivity analyses. We determined the effect of rmTBI on markers of gliosis and used NanoString-GeoMx to add a digital-spatial protein profiling analysis of neurodegenerative disease-associated proteins in gray and white matter regions. Our analyses revealed aberrant connectivity changes in the thalamus, independent of microstructural damage or neuroinflammation. We also identified distinct changes in the levels of proteins linked to various neurodegenerative processes including total and phospho-tau species and cell proliferation markers. Together, our data show that rmTBI significantly alters brain functional connectivity and causes distinct protein changes in morphologically intact brain areas.
Topics: Humans; Brain Concussion; Neurodegenerative Diseases; Diffusion Tensor Imaging; Brain; Brain Injuries, Traumatic; Magnetic Resonance Imaging
PubMed: 37051703
DOI: 10.1089/neu.2022.0464 -
The Journal of Neuroscience : the... Aug 2023Semaphorins and Plexins form ligand/receptor pairs that are crucial for a wide range of developmental processes from cell proliferation to axon guidance. The ability of...
Semaphorins and Plexins form ligand/receptor pairs that are crucial for a wide range of developmental processes from cell proliferation to axon guidance. The ability of semaphorins to act both as signaling receptors and ligands yields a multitude of responses. Here, we describe a novel role for Semaphorin-6D (Sema6D) and Plexin-A1 in the positioning and targeting of retinogeniculate axons. In or mutant mice of either sex, the optic tract courses through, rather than along, the border of the dorsal lateral geniculate nucleus (dLGN), and some retinal axons ectopically arborize adjacent and lateral to the optic tract rather than defasciculating and entering the target region. We find that Sema6D and Plexin-A1 act together in a dose-dependent manner, as the number of the ectopic retinal projections is altered in proportion to the level of Sema6D or Plexin-A1 expression. Moreover, using retinal electroporation of Sema6D or Plexin-A1 shRNA, we show that Sema6D and Plexin-A1 are both required in retinal ganglion cells for axon positioning and targeting. Strikingly, nonelectroporated retinal ganglion cell axons also mistarget in the tract region, indicating that Sema6D and Plexin-A1 can act non-cell-autonomously, potentially through axon-axon interactions. These data provide novel evidence for a dose-dependent and non-cell-autonomous role for Sema6D and Plexin-A1 in retinal axon organization in the optic tract and dLGN. Before innervating their central brain targets, retinal ganglion cell axons fasciculate in the optic tract and then branch and arborize in their target areas. Upon deletion of the guidance molecules Plexin-A1 or Semaphorin-6D, the optic tract becomes disorganized near and extends within the dorsal lateral geniculate nucleus. In addition, some retinal axons form ectopic aggregates within the defasciculated tract. Sema6D and Plexin-A1 act together as a receptor-ligand pair in a dose-dependent manner, and non-cell-autonomously, to produce this developmental aberration. Such a phenotype highlights an underappreciated role for axon guidance molecules in tract cohesion and appropriate defasciculation near, and arborization within, targets.
Topics: Animals; Mice; Axons; Ligands; Retinal Ganglion Cells; Semaphorins
PubMed: 37344233
DOI: 10.1523/JNEUROSCI.0072-22.2023 -
Fa Yi Xue Za Zhi Aug 2023To investigate the characteristics and objective assessment method of visual field defects caused by optic chiasm and its posterior visual pathway injury.
OBJECTIVES
To investigate the characteristics and objective assessment method of visual field defects caused by optic chiasm and its posterior visual pathway injury.
METHODS
Typical cases of visual field defects caused by injuries to the optic chiasm, optic tracts, optic radiations, and visual cortex were selected. Visual field examinations, visual evoked potential (VEP) and multifocal visual evolved potential (mfVEP) measurements, craniocerebral CT/MRI, and retinal optical coherence tomography (OCT) were performed, respectively, and the aforementioned visual electrophysiological and neuroimaging indicators were analyzed comprehensively.
RESULTS
The electrophysiological manifestations of visual field defects caused by optic chiasm injuries were bitemporal hemianopsia mfVEP abnormalities. The visual field defects caused by optic tract, optic radiation, and visual cortex injuries were all manifested homonymous hemianopsia mfVEP abnormalities contralateral to the lesion. Mild relative afferent pupil disorder (RAPD) and characteristic optic nerve atrophy were observed in hemianopsia patients with optic tract injuries, but not in patients with optic radiation or visual cortex injuries. Neuroimaging could provide morphological evidence of damages to the optic chiasm and its posterior visual pathway.
CONCLUSIONS
Visual field defects caused by optic chiasm, optic tract, optic radiation, and visual cortex injuries have their respective characteristics. The combined application of mfVEP and static visual field measurements, in combination with neuroimaging, can maximize the assessment of the location and degree of visual pathway damage, providing an effective scheme for the identification of such injuries.
Topics: Humans; Optic Chiasm; Visual Pathways; Visual Fields; Evoked Potentials, Visual; Random Amplified Polymorphic DNA Technique; Hemianopsia; Vision Disorders; Optic Nerve Injuries; Brain Injuries, Traumatic
PubMed: 37859473
DOI: 10.12116/j.issn.1004-5619.2023.230309 -
Journal of the Neurological Sciences Jun 2024Neuromyelitis optica spectrum disorder is a demyelinating and inflammatory affliction that often leads to visual disturbance. Various imaging techniques, including...
BACKGROUND AND PURPOSE
Neuromyelitis optica spectrum disorder is a demyelinating and inflammatory affliction that often leads to visual disturbance. Various imaging techniques, including free-water imaging, have been used to determine neuroinflammation and degeneration. Therefore, this study aimed at determining multimodal imaging differences between patients with neuromyelitis optica spectrum disorder, especially those with visual disturbance, and healthy controls.
MATERIALS AND METHODS
Eighty-five neuromyelitis optica spectrum disorder patients and 89 age- and sex-matched healthy controls underwent 3-T magnetic resonance imaging (MRI). We analyzed adjusted brain-predicted age difference, voxel-based morphometry, and free-water-corrected diffusion tensor imaging (DTI) by tract-based spatial statistics in each patient group (MRI-positive/negative neuromyelitis optica spectrum disorder patients with or without a history of visual disturbance) compared with the healthy control group.
RESULTS
MRI-positive neuromyelitis optica spectrum disorder patients exhibited reduced volumes of the bilateral thalamus. Tract-based spatial statistics showed diffuse white matter abnormalities in all DTI metrics in MRI-positive neuromyelitis optica spectrum disorder patients with a history of visual disturbance. In MRI-negative neuromyelitis optica spectrum disorder patients with a history of visual disturbance, voxel-based morphometry showed volume reduction of bilateral thalami and optic radiations, and tract-based spatial statistics revealed significantly lower free-water-corrected fractional anisotropy and higher mean diffusivity in the posterior dominant distributions, including the optic nerve radiation.
CONCLUSION
Free-water-corrected DTI and voxel-based morphometry analyses may reflect symptoms of visual disturbance in neuromyelitis optica spectrum disorder.
PubMed: 38865876
DOI: 10.1016/j.jns.2024.123090 -
ELife Nov 2023The structure and function of the vertebrate retina have been extensively studied across species with an isolated, ex vivo preparation. Retinal function in vivo,...
The structure and function of the vertebrate retina have been extensively studied across species with an isolated, ex vivo preparation. Retinal function in vivo, however, remains elusive, especially in awake animals. Here, we performed single-unit extracellular recordings in the optic tract of head-fixed mice to compare the output of awake, anesthetized, and ex vivo retinas. While the visual response properties were overall similar across conditions, we found that awake retinal output had in general (1) faster kinetics with less variability in the response latencies; (2) a larger dynamic range; and (3) higher firing activity, by ~20 Hz on average, for both baseline and visually evoked responses. Our modeling analyses further showed that such awake response patterns convey comparable total information but less efficiently, and allow for a linear population decoder to perform significantly better than the anesthetized or ex vivo responses. These results highlight distinct retinal behavior in awake states, in particular suggesting that the retina employs dense coding in vivo, rather than sparse efficient coding as has been often assumed from ex vivo studies.
Topics: Mice; Animals; Wakefulness; Retina
PubMed: 37922200
DOI: 10.7554/eLife.78005 -
Scientific Reports Sep 2023Multiple Sclerosis (MS) is an autoimmune demyelinating disease characterised by changes in iron and myelin content. These biomarkers are detectable by Quantitative...
Multiple Sclerosis (MS) is an autoimmune demyelinating disease characterised by changes in iron and myelin content. These biomarkers are detectable by Quantitative Susceptibility Mapping (QSM), an advanced Magnetic Resonance Imaging technique detecting magnetic properties. When analysed with radiomic techniques that exploit its intrinsic quantitative nature, QSM may furnish biomarkers to facilitate early diagnosis of MS and timely assessment of progression. In this work, we explore the robustness of QSM radiomic features by varying the number of grey levels (GLs) and echo times (TEs), in a sample of healthy controls and patients with MS. We analysed the white matter in total and within six clinically relevant tracts, including the cortico-spinal tract and the optic radiation. After optimising the number of GLs (n = 64), at least 65% of features were robust for each Volume of Interest (VOI), with no difference (p > .05) between left and right hemispheres. Different outcomes in feature robustness among the VOIs depend on their characteristics, such as volume and variance of susceptibility values. This study validated the processing pipeline for robustness analysis and established the reliability of QSM-based radiomics features against GLs and TEs. Our results provide important insights for future radiomics studies using QSM in clinical applications.
Topics: Humans; Multiple Sclerosis; Reproducibility of Results; Autoimmune Diseases; Patients; Magnetic Resonance Imaging
PubMed: 37758804
DOI: 10.1038/s41598-023-42914-4 -
CNS Neuroscience & Therapeutics Apr 2024Cerebrovascular lesions in the primary visual cortex, the lateral geniculate nucleus, and the optic tract have been associated with retinal neurodegeneration via the...
AIMS
Cerebrovascular lesions in the primary visual cortex, the lateral geniculate nucleus, and the optic tract have been associated with retinal neurodegeneration via the retrograde degeneration (RD) mechanism. We aimed to use optical coherence tomography (OCT) to assess the effects of the strategic single subcortical infarction (SSI) location on retinal neurodegeneration and its longitudinal impacts.
METHODS
Patients with SSI were enrolled and stratified by lesion location on cerebral MRI into the thalamic infarction group and extra-thalamic infarction group. Healthy controls from the native communities were also recruited. Retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL) were quantified using OCT. Generalized estimating equation (GEE) models were used for cross-sectional analyses and linear mixed models for longitudinal analyses. P < 0.05 was considered statistically significant.
RESULTS
We included a total of 283 eyes from 149 SSI patients. Of these, 115 eyes of 60 patients with follow-up were included in the longitudinal analyses. Cross-sectionally, thalamic-infarction patients had reduced retinal thickness compared with extra-thalamic infarction patients after adjustment for age, gender, disease duration, and vascular risk factors (p = 0.026 for RNFL, and p = 0.026 for GCIPL). Longitudinally, SSI patients showed greater retinal thinning compared with healthy controls over time (p = 0.040 for RNFL, and p < 0.001 for GCIPL), and thalamic infarction patients exhibited faster rates of GCIPL thinning in comparison with extra-thalamic infarction patients (p < 0.001).
CONCLUSION
Our study demonstrates a distinct effect of subcortical infarction lesion site on the retina both at the early stage of disease and at the 1-year follow-up time. These results present evidence of significant associations between strategic infarction locations and retinal neurodegeneration. It may provide novel insights for further research on RD in stroke patients and ultimately facilitate individualized recovery therapeutic strategy.
Topics: Humans; Longitudinal Studies; Cross-Sectional Studies; Retinal Ganglion Cells; Nerve Fibers; Visual Acuity; Retina; Tomography, Optical Coherence; Cerebral Infarction
PubMed: 38018655
DOI: 10.1111/cns.14543 -
Journal of Neuroscience Methods Jan 2024Blood perfusion of the optic nerve (ON) plays a key role in many optic neuropathies. Microvascular changes precede or accompany neuronal changes, and detecting these...
BACKGROUND
Blood perfusion of the optic nerve (ON) plays a key role in many optic neuropathies. Microvascular changes precede or accompany neuronal changes, and detecting these changes at an early stage may facilitate early treatment to avoid blindness. However, the quantification of ON blood perfusion remains a challenge. This study aimed to evaluate the viability of three-dimensional pseudocontinuous arterial spin labelling (3D-pCASL) MRI for the quantification of ON blood flow (BF).
NEW METHOD
The ON segmentation was performed using nnFormer on a cohort of ten participants (4 males, 6 females, 25-59 years old). Subsequently, the mean BF of each ON segment was calculated using whole brain 3D-pCASL image data.
RESULTS
The average ON-BF values of the left and right intraorbital segments, left and right intracanalicular segments, left and right intracranial segments, optic chiasma, and left and right optic tract were 41.308 mL/100 g/min, 43.281 mL/100 g/min, 53.188 mL/100 g/min, 57.202 mL/100 g/min, 45.089 mL/100 g/min, 49.554 mL/100 g/min, 42. 326 mL/100 g/min, 43.831 mL/100 g/min and 45.176 mL/100 g/min, respectively. The ON-BF correlated with cerebral BF (r = 0.503, p = 0.024).
COMPARISON WITH EXISTING METHOD(S)
The 3D-pCASL can measure tissue microvascular blood perfusion in absolute quantitative units with good test-retest repeatability over a wide field of view and without restrictions on depth. The use of the nnFormer makes the measurement easy, objective and reproducible.
CONCLUSIONS
The study showed that, 3D-pCASL may be a promising tool for detecting abnormal ON-BF. In particular, 3D-pCASL coupled with the nnFormer provides an objective, reproducible, and reliable method to quantify BF in ON.
Topics: Male; Female; Humans; Adult; Middle Aged; Magnetic Resonance Angiography; Spin Labels; Magnetic Resonance Imaging; Cerebrovascular Circulation; Optic Nerve
PubMed: 37952831
DOI: 10.1016/j.jneumeth.2023.110007