Neuro-ophthalmology

Karki P, Kim C, Smith K, Son D-S, Aschner M, Lee E. Transcriptional Regulation of the Astrocytic Excitatory Amino Acid Transporter 1 (EAAT1) via NF-κB and Yin Yang 1 (YY1). J Biol Chem 2015;290(39):23725-37.Abstract

Astrocytic glutamate transporter excitatory amino acid transporter (EAAT) 1, also known as glutamate aspartate transporter (GLAST) in rodents, is one of two glial glutamate transporters that are responsible for removing excess glutamate from synaptic clefts to prevent excitotoxic neuronal death. Despite its important role in neurophysiological functions, the molecular mechanisms of EAAT1 regulation at the transcriptional level remain to be established. Here, we report that NF-κB is a main positive transcription factor for EAAT1, supported by the following: 1) EAAT1 contains two consensus sites for NF-κB, 2) mutation of NF-κB binding sites decreased EAAT1 promoter activity, and 3) activation of NF-κB increased, whereas inhibition of NF-κB decreased EAAT1 promoter activity and mRNA/protein levels. EGF increased EAAT1 mRNA/protein levels and glutamate uptake via NF-κB. The transcription factor yin yang 1 (YY1) plays a role as a critical negative regulator of EAAT1, supported by the following: 1) the EAAT1 promoter contains multiple consensus sites for YY1, 2) overexpression of YY1 decreased EAAT1 promoter activity and mRNA/protein levels, and 3) knockdown of YY1 increased EAAT1 promoter activity and mRNA/protein levels. Manganese decreased EAAT1 expression via YY1. Epigenetic modifiers histone deacetylases (HDACs) served as co-repressors of YY1 to further decrease EAAT1 promoter activity, whereas inhibition of HDACs reversed manganese-induced decrease of EAAT1 expression. Taken together, our findings suggest that NF-κB is a critical positive regulator of EAAT1, mediating the stimulatory effects of EGF, whereas YY1 is a negative regulator of EAAT1 with HDACs as co-repressors, mediating the inhibitory effects of manganese on EAAT1 regulation.

Peeler CE, De Lott LB, Nagia L, Lemos J, Eggenberger ER, Cornblath WT. Clinical Utility of Acetylcholine Receptor Antibody Testing in Ocular Myasthenia Gravis. JAMA Neurol 2015;72(10):1170-4.Abstract

IMPORTANCE: The sensitivity of acetylcholine receptor (AChR) antibody testing is thought to be lower in ocular myasthenia gravis (OMG) compared with generalized disease, although estimates in small-scale studies vary. There is little information in the literature about the implications of AChR antibody levels and progression from OMG to generalized myasthenia gravis. OBJECTIVES: To test the hypothesis that serum AChR antibody testing is more sensitive in OMG than previously reported and to examine the association between AChR antibody levels and progression from OMG to generalized myasthenia gravis. DESIGN, SETTING, AND PARTICIPANTS: A retrospective, observational cohort study was conducted of 223 patients (mean [SD] age, 59.2 [16.4] years; 139 [62.3%] male) diagnosed with OMG between July 1, 1986, and May 31, 2013, at 2 large, academic medical centers. MAIN OUTCOMES AND MEASURES: Baseline characteristics, OMG symptoms, results of AChR antibody testing, and progression time to generalized myasthenia gravis (if this occurred) were recorded for each patient. Multiple logistic regression was used to measure the association between all clinical variables and antibody result. Kaplan-Meier survival analysis was performed to examine time to generalization. RESULTS: Among the 223 participants, AChR antibody testing results were positive in 158 participants (70.9%). In an adjusted model, increased age at diagnosis (odds ratio [OR], 1.03; 95% CI, 1.01-1.04; P = .007) and progression to generalized myasthenia gravis (OR, 2.92; 95% CI, 1.18-7.26; P = .02) were significantly associated with positive antibody test results. Women were less likely to have a positive antibody test result (OR, 0.36; 95% CI, 0.19-0.68; P = .002). Patients who developed symptoms of generalized myasthenia gravis had a significantly higher mean (SD) antibody level than those who did not develop symptoms of generalized myasthenia gravis (12.7 [16.5] nmol/L vs 4.2 [7.9] nmol/L; P = .002). CONCLUSIONS AND RELEVANCE: We demonstrate a higher sensitivity of AChR antibody testing than previously reported in the largest cohort of patients with OMG available to date. Older age, male sex, and progression to generalized myasthenia gravis were significantly associated with a positive antibody test result. In addition, to our knowledge, this is the first report of an association between high AChR antibody levels and progression from OMG to generalized disease.

Grob SR, Campbell AA, Gross A, Cestari DM. Hemorrhage Within the Optic Nerve From a Cavernous Hemangioma of the Optic Disc. J Neuroophthalmol 2015;35(3):277-9.Abstract

A 49-year-old woman with a known right optic disc cavernous hemangioma experienced pain with eye movements and worsening of a superior visual field defect. While she retained 20/20 visual acuity in each eye, findings on magnetic resonance imaging were consistent with a hemorrhage in the anterior portion of the right intraorbital optic nerve. Her visual function stabilized spontaneously. We are unaware of previous reports of hemorrhage into the optic nerve from a cavernous hemangioma of the optic disc.

Cestari DM, Lessell S, Mantopoulos D. Early Diagnosis of Subclinical Interferon Alpha-Associated Optic Neuropathy Using Fluorescein Angiography. J Neuroophthalmol 2015;35(3):280-3.Abstract

We report a case of a 57-year-old man who presented with decreased visual acuity in the left eye secondary to nonarteritic anterior ischemic optic neuropathy (NAION) while on therapy with interferon-α for hepatitis C. Fundus fluorescein angiography revealed late leakage of both optic discs, consistent with bilateral disease. One week later, the patient developed clinical signs and symptoms consistent with NAION in the fellow eye. Fluorescein angiography may play an important role in identifying subclinical NAION in patients taking interferon-α.

Singer JM, Madsen JR, Anderson WS, Kreiman G. Sensitivity to timing and order in human visual cortex. J Neurophysiol 2015;113(5):1656-69.Abstract

Visual recognition takes a small fraction of a second and relies on the cascade of signals along the ventral visual stream. Given the rapid path through multiple processing steps between photoreceptors and higher visual areas, information must progress from stage to stage very quickly. This rapid progression of information suggests that fine temporal details of the neural response may be important to the brain's encoding of visual signals. We investigated how changes in the relative timing of incoming visual stimulation affect the representation of object information by recording intracranial field potentials along the human ventral visual stream while subjects recognized objects whose parts were presented with varying asynchrony. Visual responses along the ventral stream were sensitive to timing differences as small as 17 ms between parts. In particular, there was a strong dependency on the temporal order of stimulus presentation, even at short asynchronies. From these observations we infer that the neural representation of complex information in visual cortex can be modulated by rapid dynamics on scales of tens of milliseconds.

Kekunnaya R, Kraft S, Rao VB, Velez FG, Sachdeva V, Hunter DG. Surgical management of strabismus in Duane retraction syndrome. J AAPOS 2015;19(1):63-9.Abstract

SUMMARY: While Duane retraction syndrome (DRS) is relatively common, surgical management of the associated strabismus can be challenging because of the lack of abduction/adduction, the variable severity of muscle contracture, and the variety of clinical presentations. In this workshop a panel of experienced surgeons provide their perspective and practical tips on the management of strabismus in patients with DRS.

Stacy RC, Gilbert AL, Rizzo JF. Correlation of clinical profile and specific histopathological features of temporal artery biopsies. J Neuroophthalmol 2015;35(2):127-33.Abstract

BACKGROUND: This study sought to correlate the clinical features of patients with giant cell arteritis (GCA) who present with ophthalmic symptoms and signs, with 2 specific histopathological findings-the presence of giant cells and arterial wall neoangiogenesis. The goal was to assess if these pathological features might be useful in guiding the approach to patient management. METHODS: Medical charts were retrospectively reviewed from 58 patients who underwent a temporal artery biopsy at a single institution. Detailed information was collected about the clinical presentation and course, with an emphasis on visual function. Histopathological and immunohistochemical techniques were used to examine temporal artery biopsies for evidence of inflammation. Correlations were made between the clinical data and the presence of giant cells and neoangiogenesis. RESULTS: Twenty-one (34%) biopsies were positive for inflammation consistent with GCA. Although the percentage of positive biopsies with giant cells was high, neither the presence of giant cells nor neoangiogenesis was predictive of a patient's presenting visual symptoms, severity and bilaterality of vision loss, other ophthalmic manifestations of GCA, presence of headache or jaw claudication, or erythrocyte sedimentation rate. Giant cells were more common in patients with recent weight loss. Immunohistochemistry confirmed diagnoses but did not alter the clinical course or treatment plan. CONCLUSIONS: There was no correlation between the clinical, specifically visual, features of GCA and the presence or absence of giant cells or neoangiogenesis in temporal artery biopsy specimens. Although the presence of neoangiogenesis may be important in the pathogenesis of GCA, our study showed no correlation between this finding and the clinical course.

Bauer C, Yazzolino L, Hirsch G, Cattaneo Z, Vecchi T, Merabet LB. Neural correlates associated with superior tactile symmetry perception in the early blind. Cortex 2015;63:104-117.Abstract
Symmetry is an organizational principle that is ubiquitous throughout the visual world. However, this property can also be detected through non-visual modalities such as touch. The role of prior visual experience on detecting tactile patterns containing symmetry remains unclear. We compared the behavioral performance of early blind and sighted (blindfolded) controls on a tactile symmetry detection task. The tactile patterns used were similar in design and complexity as in previous visual perceptual studies. The neural correlates associated with this behavioral task were identified with functional magnetic resonance imaging (fMRI). In line with growing evidence demonstrating enhanced tactile processing abilities in the blind, we found that early blind individuals showed significantly superior performance in detecting tactile symmetric patterns compared to sighted controls. Furthermore, comparing patterns of activation between these two groups identified common areas of activation (e.g. superior parietal cortex) but key differences also emerged. In particular, tactile symmetry detection in the early blind was also associated with activation that included peri-calcarine cortex, lateral occipital (LO), and middle temporal (MT) cortex, as well as inferior temporal and fusiform cortex. These results contribute to the growing evidence supporting superior behavioral abilities in the blind, and the neural correlates associated with crossmodal neuroplasticity following visual deprivation.
Gupta M, Leskov I, Kruger JM, Cestari DM. Intermittent Horner syndrome in a pediatric patient. J Neuroophthalmol 2014;34(2):149-50.Abstract
Intermittent Horner syndrome is uncommon in both the adult and pediatric population. We describe a case of a pediatric patient with an intermittent Horner syndrome. Infrared photography and videography were used to help establish the diagnosis.
Huang L, Sun X, Luo G, Liu S, Liu R, Mansouri B, Wong VWL, Wen W, Liu H, Wang A-H. Interocular Shift of Visual Attention Enhances Stereopsis and Visual Acuities of Anisometropic Amblyopes beyond the Critical Period of Visual Development: A Novel Approach. J Ophthalmol 2014;2014:615213.Abstract
Aims. Increasing evidence shows that imbalanced suppressive drive prior to binocular combination may be the key factor in amblyopia. We described a novel binocular approach, interocular shift of visual attention (ISVA), for treatment of amblyopia in adult patients. Methods. Visual stimuli were presented anaglyphically on a computer screen. A square target resembling Landolt C had 2 openings, one in red and one in cyan color. Through blue-red goggles, each eye could only see one of the two openings. The patient was required to report the location of the opening presented to the amblyopic eye. It started at an opening size of 800 sec of arc, went up and down in 160 sec of arc step, and stopped when reaching the 5th reversals. Ten patients with anisometropic amblyopia older than age 14 (average age: 26.7) were recruited and received ISVA treatment for 6 weeks, with 2 training sessions per day. Results. Both Titmus stereopsis (z = -2.809, P = 0.005) and Random-dot stereopsis (z = -2.317, P = 0.018) were significantly improved. Average improvement in best corrected visual acuity (BCVA) was 0.74 line (t = 5.842, P < 0.001). Conclusions. The ISVA treatment may be effective in treating amblyopia and restoring stereoscopic function.
Singer JM, Kreiman G. Short temporal asynchrony disrupts visual object recognition. J Vis 2014;14(5):7.Abstract
Humans can recognize objects and scenes in a small fraction of a second. The cascade of signals underlying rapid recognition might be disrupted by temporally jittering different parts of complex objects. Here we investigated the time course over which shape information can be integrated to allow for recognition of complex objects. We presented fragments of object images in an asynchronous fashion and behaviorally evaluated categorization performance. We observed that visual recognition was significantly disrupted by asynchronies of approximately 30 ms, suggesting that spatiotemporal integration begins to break down with even small deviations from simultaneity. However, moderate temporal asynchrony did not completely obliterate recognition; in fact, integration of visual shape information persisted even with an asynchrony of 100 ms. We describe the data with a concise model based on the dynamic reduction of uncertainty about what image was presented. These results emphasize the importance of timing in visual processing and provide strong constraints for the development of dynamical models of visual shape recognition.
Sümbül U, Song S, McCulloch K, Becker M, Lin B, Sanes JR, Masland RH, Seung SH. A genetic and computational approach to structurally classify neuronal types. Nat Commun 2014;5:3512.Abstract
The importance of cell types in understanding brain function is widely appreciated but only a tiny fraction of neuronal diversity has been catalogued. Here we exploit recent progress in genetic definition of cell types in an objective structural approach to neuronal classification. The approach is based on highly accurate quantification of dendritic arbor position relative to neurites of other cells. We test the method on a population of 363 mouse retinal ganglion cells. For each cell, we determine the spatial distribution of the dendritic arbors, or arbor density, with reference to arbors of an abundant, well-defined interneuronal type. The arbor densities are sorted into a number of clusters that is set by comparison with several molecularly defined cell types. The algorithm reproduces the genetic classes that are pure types, and detects six newly clustered cell types that await genetic definition.
Nassi JJ, Gómez-Laberge C, Kreiman G, Born RT. Corticocortical feedback increases the spatial extent of normalization. Front Syst Neurosci 2014;8:105.Abstract
Normalization has been proposed as a canonical computation operating across different brain regions, sensory modalities, and species. It provides a good phenomenological description of non-linear response properties in primary visual cortex (V1), including the contrast response function and surround suppression. Despite its widespread application throughout the visual system, the underlying neural mechanisms remain largely unknown. We recently observed that corticocortical feedback contributes to surround suppression in V1, raising the possibility that feedback acts through normalization. To test this idea, we characterized area summation and contrast response properties in V1 with and without feedback from V2 and V3 in alert macaques and applied a standard normalization model to the data. Area summation properties were well explained by a form of divisive normalization, which computes the ratio between a neuron's driving input and the spatially integrated activity of a "normalization pool." Feedback inactivation reduced surround suppression by shrinking the spatial extent of the normalization pool. This effect was independent of the gain modulation thought to mediate the influence of contrast on area summation, which remained intact during feedback inactivation. Contrast sensitivity within the receptive field center was also unaffected by feedback inactivation, providing further evidence that feedback participates in normalization independent of the circuit mechanisms involved in modulating contrast gain and saturation. These results suggest that corticocortical feedback contributes to surround suppression by increasing the visuotopic extent of normalization and, via this mechanism, feedback can play a critical role in contextual information processing.

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