Infection control measures for public transportation derived from the flow dynamics of obstructed cough jet

During the COVID-19 pandemic, WHO and CDC suggest people stay 1 m and 1.8 m away from others, respectively. Keeping social distance can avoid close contact and mitigate infection spread. Many researchers suspect that suggested distances are not enough because aerosols can spread up to 7-8 m away. Despite the debate on social distance, these social distances rely on unobstructed respiratory activities such as coughing and sneezing. Differently, in this work, we focused on the most common but less studied aerosol spread from an obstructed cough. The flow dynamics of a cough jet blocked by the backrest and gasper jet in a cabin environment was characterized by the particle image velocimetry (PIV) technique. It was proved that the backrest and the gasper jet can prevent the front passenger from droplet spray in public transportation where maintaining social distance was difficult. A model was developed to describe the cough jet trajectory due to the gasper jet, which matched well with PIV results. It was found that buoyancy and inside droplets almost do not affect the short-range cough jet trajectory. Infection control measures were suggested for public transportation, including using backrest/gasper jet, installing localized exhaust, and surface cleaning of the backrest.

Advanced Diffusion MRI of the Visual System in Glaucoma: From Experimental Animal Models to Humans

Glaucoma is a group of ophthalmologic conditions characterized by progressive retinal ganglion cell death, optic nerve degeneration, and irreversible vision loss. While intraocular pressure is the only clinically modifiable risk factor, glaucoma may continue to progress at controlled intraocular pressure, indicating other major factors in contributing to the disease mechanisms. Recent studies demonstrated the feasibility of advanced diffusion magnetic resonance imaging (dMRI) in visualizing the microstructural integrity of the visual system, opening new possibilities for non-invasive characterization of glaucomatous brain changes for guiding earlier and targeted intervention besides intraocular pressure lowering. In this review, we discuss dMRI methods currently used in visual system investigations, focusing on the eye, optic nerve, optic tract, subcortical visual brain nuclei, optic radiations, and visual cortex. We evaluate how conventional diffusion tensor imaging, higher-order diffusion kurtosis imaging, and other extended dMRI techniques can assess the neuronal and glial integrity of the visual system in both humans and experimental animal models of glaucoma, among other optic neuropathies or neurodegenerative diseases. We also compare the pros and cons of these methods against other imaging modalities. A growing body of dMRI research indicates that this modality holds promise in characterizing early glaucomatous changes in the visual system, determining the disease severity, and identifying potential neurotherapeutic targets, offering more options to slow glaucoma progression and to reduce the prevalence of this world's leading cause of irreversible but preventable blindness.

In vivo MRI evaluation of anterograde manganese transport along the visual pathway following whole eye transplantation

BACKGROUND

Since adult mammalian retinal ganglion cells cannot regenerate after injury, we have recently established a whole-eye transplantation (WET) rat model that provides an intact optical system to investigate potential surgical restoration of irreversible vision loss. However, it remains to be elucidated whether physiological axoplasmic transport exists in the transplanted visual pathway. New Method: We developed an in vivo imaging model system to assess WET integration using manganese-enhanced magnetic resonance imaging (MEMRI) in rats. Since Mn²⁺ is a calcium analogue and an active T1-positive contrast agent, the levels of anterograde manganese transport can be evaluated in the visual pathways upon intravitreal Mn²⁺ administration into both native and transplanted eyes.

RESULTS

 No significant intraocular pressure difference was found between native and transplanted eyes, whereas comparable manganese enhancement was observed between native and transplanted intraorbital optic nerves, suggesting the presence of anterograde manganese transport after WET. No enhancement was detected across the coaptation site in the higher visual areas of the recipient brain. Comparison with Existing Methods: Existing imaging methods to assess WET focus on either the eye or local optic nerve segments without direct visualization and longitudinal quantification of physiological transport along the transplanted visual pathway, hence the development of in vivo MEMRI.

CONCLUSION

 Our established imaging platform indicated that essential physiological transport exists in the transplanted optic nerve after WET. As neuroregenerative approaches are being developed to connect the transplanted eye to the recipient's brain, in vivo MEMRI is well-suited to guide strategies for successful WET integration for vision restoration. Keywords (Max 6): Anterograde transport, magnetic resonance imaging, manganese, neuroregeneration, optic nerve, whole-eye transplantation.

Role of Structural, Metabolic, and Functional MRI in Monitoring Visual System Impairment and Recovery

The visual system, consisting of the eyes and the visual pathways of the brain, receives and interprets light from the environment so that we can perceive the world around us. A wide variety of disorders can affect human vision, ranging from ocular to neurologic to systemic in nature. While other noninvasive imaging techniques such as optical coherence tomography and ultrasound can image particular sections of the visual system, magnetic resonance imaging (MRI) offers high resolution without depth limitations. MRI also gives superior soft-tissue contrast throughout the entire pathway compared to computed tomography. By leveraging different imaging sequences, MRI is uniquely capable of unveiling the intricate processes of ocular anatomy, tissue physiology, and neurological function in the human visual system from the microscopic to macroscopic levels. In this review we discuss how structural, metabolic, and functional MRI can be used in the clinical assessment of normal and pathologic states in the anatomic structures of the visual system, including the eyes, optic nerves, optic chiasm, optic tracts, visual brain nuclei, optic radiations, and visual cortical areas. We detail a selection of recent clinical applications of MRI at each position along the visual pathways, including the evaluation of pathology, plasticity, and the potential for restoration, as well as its limitations and key areas of ongoing exploration. Our discussion of the current and future developments in MR ocular and neuroimaging highlights its potential impact on our ability to understand visual function in new detail and to improve our protection and treatment of anatomic structures that are integral to this fundamental sensory system. LEVEL OF EVIDENCE 3:   TECHNICAL EFFICACY STAGE 3:  .

Auditory Scene Analysis Principles Improve Image Reconstruction Abilities of Novice Vision-to-Audio Sensory Substitution Users

Sensory substitution devices (SSDs) such as the 'vOICe' preserve visual information in sound by turning visual height, brightness, and laterality into auditory pitch, volume, and panning/time respectively. However, users have difficulty identifying or tracking multiple simultaneously presented tones - a skill necessary to discriminate the upper and lower edges of object shapes. We explore how these deficits can be addressed by using image-sonifications inspired by auditory scene analysis (ASA). Here, sighted subjects (N=25) of varying musical experience listened to, and then reconstructed, complex shapes consisting of simultaneously presented upper and lower lines. Complex shapes were sonified using the vOICe, with either the upper and lower lines varying only in pitch (i.e. the vOICe's 'unaltered' default settings), or with one line degraded to alter its auditory timbre or volume. Results found that overall performance increased with subjects' years of prior musical experience. ANOVAs revealed that both sonification style and musical experience significantly affected performance, but with no interaction effect between them. Compared to the vOICe's 'unaltered' pitch-height mapping, subjects had significantly better image-reconstruction abilities when the lower line was altered via timbre or volume-modulation. By contrast, altering the upper line only helped users identify the unaltered lower line. In conclusion, adding ASA principles to vision-to-audio SSDs boosts subjects' image-reconstruction abilities, even if this also reduces total task-relevant information. Future SSDs should seek to exploit these findings to enhance both novice user abilities and the use of SSDs as visual rehabilitation tools.

Hopes and Wishes of Clients with Mentally Illness in Hong Kong

Recovery is a progressive process involving support to people with mental illness to take control of their life through the enhancement of motivation, self-drive, and responsibility. Drawing on qualitative interviews with 61 patients with mental illness aged between 40 and 75 in the community or residential settings, this study examined the wishes and hopes of clients who were in recovery. Participants described wishes and hopes for autonomy and independence in finances, accommodation, and health; stable housing or accommodation; meaningful occupation or employment; 'giving back' to society by serving others; intimate relationships; and gaining back 'lost time.' Wishes and hopes were motivating factors contributing to physical, mental, and social health over time, motivating clients with mental illness to live happily. To foster recovery, mental health practitioners should consider the identification and fulfilment of wishes and hopes in health and social care programs for this unique client group.

Relationships between cerebrovascular reactivity, visual-evoked functional activity, and resting-state functional connectivity in the visual cortex and basal forebrain in glaucoma

Glaucoma is primarily considered an eye disease with widespread involvements of the brain. Yet, it remains unclear how cerebrovasculature is regulated in glaucoma and how different brain regions coordinate functionally across disease severity. To address these questions, we applied a novel whole-brain relative cerebrovascular reactivity (rCVR) mapping technique using resting-state functional magnetic resonance imaging (fMRI) without gas challenges to 38 glaucoma patients and 21 healthy subjects. The relationships between rCVR, visual-evoked fMRI response, and resting-state functional connectivity in glaucoma were then established. In the visual cortex, rCVR has a decreasing trend with glaucoma severity (p<0.05), and is coupled with visual-evoked response and functional connectivity in both hemispheres (p<0.001). Interestingly, rCVR in the basal forebrain (BF) has an increasing trend with glaucoma severity (p<0.05). The functional connectivity between right diagonal band of Broca (a sub-region of BF) and lateral visual cortex decreases with glaucoma (p<0.05), while such connectivity is inversely coupled with rCVR in the BF (p<0.05), but not the visual cortex. Overall, we demonstrate opposite trends of rCVR changes in the visual cortex and BF in glaucoma patients, suggestive of compensatory actions in vascular reserve between the two brain regions. The neurovascular coupling within the visual cortex appears deteriorated in glaucoma, whereas the association between BF-visual cortex functional connectivity and rCVR of BF indicates the functional and vascular involvements in glaucoma beyond the primary visual pathway.

Sensory integration abilities for balance in glaucoma, a preliminary study

The goal of this study was to quantify the association between sensory integration abilities relevant for standing balance and disease stage in glaucoma. The disease stage was assessed using both functional (visual field deficit) and structural (retinal nerve fiber layer thickness) deficits in the better and worse eye. Balance was assessed using an adapted version of the well-established Sensory Organization Test (SOT). Eleven subjects diagnosed with mild to moderate glaucoma stood for 3 min in 6 sensory challenging postural conditions. Balance was assessed using sway magnitude and sway speed computed based on center-of-pressure data. Mixed linear regression analyses were used to investigate the associations between glaucoma severity and balance measures. Findings revealed that the visual field deficit severity in the better eye was associated with increased standing sway speed. This finding was confirmed in eyes open and closed conditions. Balance was not affected by the extent of the visual field deficit in the worse eye. Similarly, structural damage in either eye was not associated with the balance measures. In summary, this study found that postural control performance was associated with visual field deficit severity. The fact that this was found during eyes closed as well suggests that reduced postural control in glaucoma is not entirely attributed to impaired peripheral visual inputs. A larger study is needed to further investigate potential interactions between visual changes and central processing changes contributing to reduced balance function and increased incidence of falls in adults with glaucoma.

Glymphatic imaging and modulation of the optic nerve

Optic nerve health is essential for proper function of the visual system. However, the pathophysiology of certain neurodegenerative disease processes affecting the optic nerve, such as glaucoma, is not fully understood. Recently, it was hypothesized that a lack of proper clearance of neurotoxins contributes to neurodegenerative diseases. The ability to clear metabolic waste is essential for tissue homeostasis in mammals, including humans. While the brain lacks the traditional lymphatic drainage system identified in other anatomical regions, there is growing evidence of a glymphatic system in the central nervous system, which structurally includes the optic nerve. Named to acknowledge the supportive role of astroglial cells, this perivascular fluid drainage system is essential to remove toxic metabolites from the central nervous system. Herein, we review existing literature describing the physiology and dysfunction of the glymphatic system specifically as it relates to the optic nerve. We summarize key imaging studies demonstrating the existence of a glymphatic system in the optic nerves of wild-type rodents, aquaporin 4-null rodents, and humans; glymphatic imaging studies in diseases where the optic nerve is impaired; and current evidence regarding pharmacological and lifestyle interventions that may help promote glymphatic function to improve optic nerve health. We conclude by highlighting future research directions that could be applied to improve imaging detection and guide therapeutic interventions for diseases affecting the optic nerve.

Oral Scutellarin Treatment Ameliorates Retinal Thinning and Visual Deficits in Experimental Glaucoma

Purpose: Intraocular pressure (IOP) is currently the only modifiable risk factor for glaucoma, yet glaucoma can continue to progress despite controlled IOP. Thus, development of glaucoma neurotherapeutics remains an unmet need. Scutellarin is a flavonoid that can exert neuroprotective effects in the eye and brain. Here, we investigated the neurobehavioral effects of scutellarin treatment in a chronic IOP elevation model. Methods: Ten adult C57BL/6J mice were unilaterally injected with an optically clear hydrogel into the anterior chamber to obstruct aqueous outflow and induce chronic IOP elevation. Eight other mice received unilateral intracameral injection of phosphate-buffered saline only. Another eight mice with hydrogel-induced unilateral chronic IOP elevation also received daily oral gavage of 300 mg/kg scutellarin. Tonometry, optical coherence tomography, and optokinetics were performed longitudinally for 4 weeks to monitor the IOP, retinal nerve fiber layer thickness, total retinal thickness, visual acuity, and contrast sensitivity of both eyes in all three groups. Results: Intracameral hydrogel injection resulted in unilateral chronic IOP elevation with no significant inter-eye IOP difference between scutellarin treatment and untreated groups. Upon scutellarin treatment, the hydrogel-injected eyes showed less retinal thinning and reduced visual behavioral deficits when compared to the untreated, hydrogel-injected eyes. No significant difference in retinal thickness or optokinetic measures was found in the contralateral, non-treated eyes over time or between all groups. Conclusion: Using the non-invasive measuring platform, oral scutellarin treatment appeared to preserve retinal structure and visual function upon chronic IOP elevation in mice. Scutellarin may be a novel neurotherapeutic agent for glaucoma treatment.

Diffusion Tensor Imaging of Visual Pathway Abnormalities in Five Glaucoma Animal Models

Purpose

To characterize the visual pathway integrity of five glaucoma animal models using diffusion tensor imaging (DTI).

Methods

Two experimentally induced and three genetically determined models of glaucoma were evaluated. For inducible models, chronic IOP elevation was achieved via intracameral injection of microbeads or laser photocoagulation of the trabecular meshwork in adult rodent eyes. For genetic models, the DBA/2J mouse model of pigmentary glaucoma, the LTBP2 mutant feline model of congenital glaucoma, and the transgenic TBK1 mouse model of normotensive glaucoma were compared with their respective genetically matched healthy controls. DTI parameters, including fractional anisotropy, axial diffusivity, and radial diffusivity, were evaluated along the optic nerve and optic tract.

Results

Significantly elevated IOP relative to controls was observed in each animal model except for the transgenic TBK1 mice. Significantly lower fractional anisotropy and higher radial diffusivity were observed along the visual pathways of the microbead- and laser-induced rodent models, the DBA/2J mice, and the LTBP2-mutant cats compared with their respective healthy controls. The DBA/2J mice also exhibited lower axial diffusivity, which was not observed in the other models examined. No apparent DTI change was observed in the transgenic TBK1 mice compared with controls.

Conclusions

Chronic IOP elevation was accompanied by decreased fractional anisotropy and increased radial diffusivity along the optic nerve or optic tract, suggestive of disrupted microstructural integrity in both inducible and genetic glaucoma animal models. The effects on axial diffusivity differed between models, indicating that this DTI metric may represent different aspects of pathological changes over time and with severity.

Citicoline Modulates Glaucomatous Neurodegeneration Through Intraocular Pressure-Independent Control

Glaucoma is a neurodegenerative disease that causes progressive, irreversible vision loss. Currently, intraocular pressure (IOP) is the only modifiable risk factor for glaucoma. However, glaucomatous degeneration may continue despite adequate IOP control. Therefore, there exists a need for treatment that protects the visual system, independent of IOP. This study sought, first, to longitudinally examine the neurobehavioral effects of different magnitudes and durations of IOP elevation using multi-parametric magnetic resonance imaging (MRI), optokinetics and histology; and, second, to evaluate the effects of oral citicoline treatment as a neurotherapeutic in experimental glaucoma. Eighty-two adult Long Evans rats were divided into six groups: acute (mild or severe) IOP elevation, chronic (citicoline-treated or untreated) IOP elevation, and sham (acute or chronic) controls. We found that increasing magnitudes and durations of IOP elevation differentially altered structural and functional brain connectivity and visuomotor behavior, as indicated by decreases in fractional anisotropy in diffusion tensor MRI, magnetization transfer ratios in magnetization transfer MRI, T1-weighted MRI enhancement of anterograde manganese transport, resting-state functional connectivity, visual acuity, and neurofilament and myelin staining along the visual pathway. Furthermore, 3 weeks of oral citicoline treatment in the setting of chronic IOP elevation significantly reduced visual brain integrity loss and visual acuity decline without altering IOP. Such effects sustained after treatment was discontinued for another 3 weeks. These results not only illuminate the close interplay between eye, brain, and behavior in glaucomatous neurodegeneration, but also support a role for citicoline in protecting neural tissues and visual function in glaucoma beyond IOP control.

Diffusion Kurtosis Imaging Reveals Optic Tract Damage That Correlates with Clinical Severity in Glaucoma

Glaucoma is a neurodegenerative disease of the visual system and is the leading cause of irreversible blindness worldwide. To date, its pathophysiological mechanisms remain unclear. This study evaluated the feasibility of advanced diffusion magnetic resonance imaging techniques for examining the microstructural environment of the visual pathway in glaucoma. While conventional diffusion tensor imaging (DTI) showed lower fractional anisotropy and higher directional diffusivities in the optic tracts of glaucoma patients than healthy controls, diffusion kurtosis imaging (DKI) and the extended white matter tract integrity (WMTI) model indicated lower radial kurtosis, higher axial and radial diffusivities in the extra-axonal space, lower axonal water fraction, and lower tortuosity in the same regions in glaucoma patients. These findings suggest glial involvements apart from compromised axonal integrity in glaucoma. In addition, DKI and WMTI but not DTI parameters significantly correlated with clinical ophthalmic measures via optical coherence tomography and visual field perimetry testing. Taken together, DKI and WMTI provided sensitive and comprehensive imaging biomarkers for quantifying glaucomatous damage in the white matter tract across clinical severity complementary to DTI.

The experience of growing old in chronic mental health patients

Objectives: Research evidence has demonstrated disparities and barriers associated with mental illness, which creates challenges for individuals with mental illness to maintain physical, mental, and social health as they age. The aim of this study was to examine the meaning of aging from the perspective of individuals with mental illness and explore their motivations and challenges to adopting healthy aging lifestyles and practices.Method: Using a qualitative narrative inquiry approach, interviews were conducted with 61 aging patients with mental illness aged 40 and older in community and institutional settings in Hong Kong.Results: Participants discussed the meaning of healthy aging in terms of meaningful occupation and use of time, and independence and autonomy. Motivating factors included a desire to avoid 'burdening' other people, to 'give back' to society, and gain back 'lost time'. These were connected to strategies for healthy aging, including social relationships and activities, spirituality, and healthy lifestyles. Challenges to adopting healthy aging practices included physical health difficulties and medication side effects, lack of purpose and boredom associated with daily routines and use of time, and conflicts and loss affecting family and peer relationships.Conclusion: Social and health services should be tailored to support aging individuals with mental illness and their families, addressing motivations and barriers to adopting healthy lifestyles. Promoting healthy aging practices to enable individuals with mental illness to achieve healthy aging is important for preparing for the aging of this population.

0882 Local Deformation Analysis of Lateral Cephalogram for Childhood OSA Classification

Introduction

Craniofacial profile is one of the anatomical causes of obstructive sleep apnea (OSA). Cephalometry provides information on patients’ skeletal structures and soft tissues. Traditional cephalometric analysis focuses on linear distances, angles, ratios and area of specific variables. Its classification power is often disappointed. In this study, a novel approach to cephalometric analysis using local deformation information was carried out to assess its efficacy in OSA classification.

Methods

This study was a retrospective analysis based on 60 case-control pairs who were Chinese children recruited for sleep studies in the Prince of Wales Hospital, with accessible lateral cephalometry and polysomnography (PSG) data. Local deformation technique was adopted to derive 1215 deformations from 15 manual landmarking on each cephalogram. In addition, three linear distances (hyoid bone to mandibular plane, hyoid bone to posterior pharyngeal wall, and minimal distance between tongue base and posterior pharyngeal wall) were measured from each cephalogram. A total of 1218 information features were obtained per subject. Classification models were built with an equal ratio between OSA and non-OSA groups (defined by OAHI≥1 and OAHI&lt;1 respectively). Forty pairs were used as training data and twenty pairs were used as testing data.

Results

Three model settings which used all 1218 cephalometric features, 800 features, and 500 features were tested. The accuracy for the three settings were 67.5% (sensitivity: 70%, specificity: 65%), 87.5% (sensitivity: 90%, specificity: 85%), and 92.5% (sensitivity: 95%, specificity: 90%) respectively. Apart from the three distances, the 500 topmost discriminative features were predominantly landmarks around the nasal cavity.

Conclusion

A new approach to cephalometric analysis using local deformation information can provide additional details on each cephalogram, hence, achieving better classification. The classification models using 500 features yielded the highest accuracy among the three settings. This setting could benefit most from the comprehensive comparison while avoiding overfitting.

Support

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224 Malignancy associated pericardial effusion- do we need to drain them all?

On Behalf

Cardiac Team, Department of Medicine, Queen Elizabeth Hospital

Background

Management of significant pericardial effusion in cancer patients is controversial. These patients have poor prognosis, and avoiding unnecessary intervention is important. Close monitoring of symptoms and echocardiogram is often a reasonable option, but inherits risk of cardiac tamponade. Whether pericardial drainage by means of percutaneous pericardiocentesis or surgical pericardiotomy could prevent future deterioration or affect survival is unknown.

Purpose

To evaluate the benefit of elective pericardial drainage in malignancy associated pericardial effusion without echocardiographic or clinical evidence of tamponade effect.

Methods

From 1st Jul 2014 to 31st Dec 2017, all patients with new onset malignancy-associated pericardial effusion with size more than 1cm were retrospectively analyzed. Patients with clinical or echocardiographic evidence of cardiac tamponade were excluded. We compared pericardial drainage versus monitoring for short-term (30-day), mid-term (90-day) and long term (1 year) survival without need for drainage.

Results

101 patients were retrospectively analyzed. 40 (39.6%) patients underwent drainage. Overall median survival free from drainage was 4 months. There were no significant difference in short-term (30-day), mid-term (90-day) and long term (1-year) survival free from drainage or mortality between treatment and monitoring group. Size of pericardial effusion did not predict mortality or future need of drainage. Chemotherapy was associated with improved 30-day mortality (RR 0.53 CI 0.32-0.87 p = 0.025) but not survival free from drainage or longer term mortality.

Conclusion

Close monitoring could be a feasible strategy in cancer patients with significant pericardial effusion without tamponade effect.

Baseline characteristics Factor Drainage (n = 40) monitoring (n = 61) p-value method of drainage pericardiocentesis alone 17 NA pericardiotomy alone 13 both 10 Male 19 (47.5%) 27 (44.3%) 0.749 mean size (cm) 1.93 2.77 &lt;0.001 mean age 60.9 63.1 0.357 on chemotherapy 27 (67.5%) 38 (62.3%) 0.593

Abstract 224 Figure. Survival free from drainage

Flexible Honeycombed Nanoporous/Glassy Hybrid for Efficient Electrocatalytic Hydrogen Generation

Hydrogen evolution reaction (HER) in alkaline media urgently requires electrocatalysts concurrently possessing excellent activity, flexible free-standing capability, and low cost. A honeycombed nanoporous/glassy sandwich structure fabricated through dealloying metallic glass (MG) is reported. This free-standing hybrid shows outstanding HER performance with a very small overpotential of 37 mV at 10 mA cm^-2 and a low Tafel slope of 30 mV dec^-1 in alkaline media, outperforming commercial Pt/C. By alloying 3 at% Pt into the MG precursor, a honeycombed Pt₇₅ Ni₂₅ solid solution nanoporous structure, with fertile active sites and large contact areas for efficient HER, is created on the dealloyed MG surface. Meanwhile, the surface compressive lattice-strain effect is also introduced by substituting the Pt lattice sites with the smaller Ni atoms, which can effectively reduce the hydrogen adsorption energy and thus improve the hydrogen evolution. Moreover, the outstanding stability and flexibility stemming from the ductile MG matrix also make the hybrid suitable for practical electrode application. This work not only offers a reliable strategy to develop cost-effective and flexible multicomponent catalysts with low Pt usage for efficient HER, but also sheds light on understanding the alloying effects of the catalytic process.

Functional MRI of Sensory Substitution in the Blind

Visual cortex functionality in the blind has been shown to shift away from sensory networks toward task-positive networks that are involved in top-down modulation. However, how such modulation is shaped by experience and reflected behaviorally remains unclear. This study evaluates the visual cortex activity and functional connectivity among congenitally blind, acquired blind, and sighted subjects using blood-oxygenation-level-dependent functional MRI during sensory substitution tasks and at rest. We found that primary visual cortex activity due to active interpretation not only depends on the blindness duration, but also negatively associates with behavioral reaction time. In addition, alterations in visual and task-positive functional connectivity progress over the duration of blindness. In summary, this work suggests that functional plasticity in the primary visual cortex can be reshaped in the blind over time, even in the adult stage. Furthermore, the degree of top-down activity in the primary visual cortex may reflect the speed of performance during sensory substitution.

Auditory-visual convergence at the superior colliculus in rat using functional MRI

The superior colliculus (SC) of the midbrain has been a model structure for multisensory processing. Many neurons in the intermediate and deep SC layers respond to two or more of auditory, visual, and somatosensory stimuli as assessed by electrophysiology. In contrast, noninvasive and large field of view functional magnetic resonance imaging (fMRI) studies have focused on multisensory processing in the cortex. In this study, we applied blood oxygenation leveldependent (BOLD) fMRI on Sprague-Dawley rats receiving monaural (auditory) and binocular (visual) stimuli to study subcortical multisensory processing. Activation was observed in the left superior olivary complex, lateral lemniscus, and inferior colliculus and both hemispheres of the superior colliculus during auditory stimulation. The SC response was bilateral even though the stimulus was monaural. During visual stimulation, activation was observed in both hemispheres of the SC and lateral geniculate nucleus. In both hemispheres of the SC, the number of voxels in the activation area $( \mathrm {p}<10 -8$) and BOLD signal changes $( \mathrm {p}<0.01)$ were significantly greater during visual than auditory stimulation. These results provide functional imaging evidence that the SC is a site of auditoryvisual convergence due to its involvement in both auditory and visual processing. The auditory and visual fMRI activations likely reflect the firing of unisensory and multisensory neurons in the SC. The present study lays the groundwork for noninvasive functional imaging studies of multisensory convergence and integration in the SC.

Author Correction: Matrix-bound nanovesicles prevent ischemia-induced retinal ganglion cell axon degeneration and death and preserve visual function

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Widespread brain reorganization perturbs visuomotor coordination in early glaucoma

Glaucoma is the world's leading cause of irreversible blindness, and falls are a major public health concern in glaucoma patients. Although recent evidence suggests the involvements of the brain toward advanced glaucoma stages, the early brain changes and their clinical and behavioral consequences remain poorly described. This study aims to determine how glaucoma may impair the brain structurally and functionally within and beyond the visual pathway in the early stages, and whether these changes can explain visuomotor impairments in glaucoma. Using multi-parametric magnetic resonance imaging, glaucoma patients presented compromised white matter integrity along the central visual pathway and around the supramarginal gyrus, as well as reduced functional connectivity between the supramarginal gyrus and the visual occipital and superior sensorimotor areas when compared to healthy controls. Furthermore, decreased functional connectivity between the supramarginal gyrus and the visual brain network may negatively impact postural control measured with dynamic posturography in glaucoma patients. Taken together, this study demonstrates that widespread structural and functional brain reorganization is taking place in areas associated with visuomotor coordination in early glaucoma. These results implicate an important central mechanism by which glaucoma patients may be susceptible to visual impairments and increased risk of falls.

Cholinergic nervous system and glaucoma: From basic science to clinical applications

The cholinergic system has a crucial role to play in visual function. Although cholinergic drugs have been a focus of attention as glaucoma medications for reducing eye pressure, little is known about the potential modality for neuronal survival and/or enhancement in visual impairments. Citicoline, a naturally occurring compound and FDA approved dietary supplement, is a nootropic agent that is recently demonstrated to be effective in ameliorating ischemic stroke, traumatic brain injury, Parkinson's disease, Alzheimer's disease, cerebrovascular diseases, memory disorders and attention-deficit/hyperactivity disorder in both humans and animal models. The mechanisms of its action appear to be multifarious including (i) preservation of cardiolipin, sphingomyelin, and arachidonic acid contents of phosphatidylcholine and phosphatidylethanolamine, (ii) restoration of phosphatidylcholine, (iii) stimulation of glutathione synthesis, (iv) lowering glutamate concentrations and preventing glutamate excitotoxicity, (v) rescuing mitochondrial function thereby preventing oxidative damage and onset of neuronal apoptosis, (vi) synthesis of myelin leading to improvement in neuronal membrane integrity, (vii) improving acetylcholine synthesis and thereby reducing the effects of mental stress and (viii) preventing endothelial dysfunction. Such effects have vouched for citicoline as a neuroprotective, neurorestorative and neuroregenerative agent. Retinal ganglion cells are neurons with long myelinated axons which provide a strong rationale for citicoline use in visual pathway disorders. Since glaucoma is a form of neurodegeneration involving retinal ganglion cells, citicoline may help ameliorate glaucomatous damages in multiple facets. Additionally, trans-synaptic degeneration has been identified in humans and experimental models of glaucoma suggesting the cholinergic system as a new brain target for glaucoma management and therapy.

Intracameral injection of a chemically cross-linked hydrogel to study chronic neurodegeneration in glaucoma

Investigation of neurodegeneration in glaucoma, a leading cause of irreversible blindness worldwide, has been obfuscated by the lack of an efficient model that provides chronic, mild to moderate elevation of intraocular pressure (IOP) with preservation of optical media clarity for long term, in vivo interrogation of the structural and functional integrity of the retinal ganglion cells (RGCs). Here, we designed and formulated an injectable hydrogel based on in situ cross-linking of hyaluronic acid functionalized with vinyl sulfone (HA-VS) and thiol groups (HA-SH). Intracameral injection of HA-VS and HA-SH in C57BL/6J mice exhibited mild to moderate elevation of IOP with daily mean IOP ranged between 14 ± 3 and 24 ± 3 mmHg, which led to progressive, regional loss of RGCs evaluated with in vivo, time-lapse confocal scanning laser ophthalmoscopy; a reduction in fractional anisotropy in the optic nerve and the optic tract projected from the eye with increased IOP in diffusion tensor magnetic resonance imaging; a decrease in positive scotopic threshold response in electroretinography; and a decline in visual acuity measured with an optokinetic virtual reality system. The proportion of RGC loss was positively associated with the age of the animals, and the levels and the duration of IOP elevation. The new glaucoma model recapitulates key characteristics of human glaucoma which is pertinent to the development and pre-clinical testing of neuroprotective and neuroregenerative therapies. STATEMENT OF SIGNIFICANCE: A new model to study chronic neurodegeneration in glaucoma has been developed via intracameral injection of a specifically designed hyaluronic acid functionalized with vinyl sulfone and thiol groups for cross-linking. Intracameral injection of the chemically cross-linked hydrogel generates mild to moderate IOP elevation, resulting in progressive degeneration of the retinal ganglion cells, optic nerve, and optic tract, and a decline in visual function. The model recapitulates the key features of neurodegeneration in human glaucoma, which will facilitate and expedite the development of neuroprotective and neuroregenerative therapies.