Retinal Projections Research Articles

Ten-m4 plays a unique role in the establishment of binocular visual circuits.

The patterning of binocular vision requires distinct molecular pathways for inputs arising from each side of the nervous system. Recent studies have demonstrated important roles for members of the Ten-m/Odz/teneurin family in the development of ipsilateral retinal projections. Here, we further highlight the significance of this gene family in visual development by identifying a role for Ten-m4 during the formation of the ipsilateral projection in the mouse. Ten-m4 was found to be expressed in the retina, dorsal lateral geniculate nucleus (dLGN), superior colliculus (SC), and primary visual cortex (V1) during development. Anterograde and retrograde tracing experiments in Ten-m4 knockout (KO) mice revealed a specific increase in ipsilateral retinal ganglion cells projecting to dLGN and SC. This increase was most prominent in regions corresponding to temporal retina. Consistent with this, EphB1 expression in the retina around the time of decussation was enhanced in this temporal region for KO mice, suggesting that the increased size of the ipsilateral population arises due to an increased number of retinal ganglion cells remaining ipsilaterally at the optic chiasm due to EphB1-mediated repulsion. The ectopic ipsilaterally targeted retinal ganglion cell projection observed in Ten-m4 KOs was associated with changes in response to ethologically-relevant visual stimuli. Together, these data demonstrate a requirement for Ten-m4 in the establishment of ipsilateral projections from the retina, which likely acts in combination with other Ten-m members (Ten-m2 and Ten-m3) to promote the formation of functional binocular circuits. This article is protected by copyright. All rights reserved.

Effects of Post-awakening Light Exposure on Heart Rate Variability in Healthy Male Individuals

Light-induced effects on the autonomic nervous system (ANS) are assumed to be mediated by retinal projections to the hypothalamic suprachiasmatic nucleus (SCN) via different routes. Light information for the circadian system is detected by a subset of intrinsically photosensitive retinal ganglion cells (ipRGCs), however, inconsistency exists in research concerning the effects of light exposure on heart rate variability (HRV). Two within-subject experiments were conducted in a standardized sleep laboratory to investigate effects of light intensity (study I, n = 29: 2 days dim vs. bright light) and spectral composition (study II, n = 24: 3 days using red vs. blue vs. green light) on HRV parameters (RMSSD, LF, HF-HRV, LF/HF ratio). Light exposure was conducted for one-hour in the post-awakening phase at 5:00 AM. Results revealed no significant light intensity effect comparing dim light versus bright white light on HRV parameters. Light color of different wavelengths significantly influenced all HRV parameters except the low frequency, with moderate to large effect sizes. RMSSD values were elevated for all three colors compared to norm values, indicating stronger parasympathetic activation. LED light of different spectral compositions demonstrated bidirectional effects on spectral components of the HRV. Red light decreased the LF/HF ratio within 30 min, whereas with blue light, LF/HF ratio consistently increased across 40 min of light exposure.

Sparse holographic imaging for an integrated augmented reality near-eye display.

Diffraction is the main physical effect involved in the imaging process of holographic displays. In the application of near-eye displays, it generates physical limits that constrain the field of view of the devices. In this contribution, we evaluate experimentally an alternative approach for a holographic display based mainly on refraction. This unconventional imaging process, based on sparse aperture imaging, could lead to integrated near-eye displays through retinal projection, with a larger field of view. We introduce for this evaluation an in-house holographic printer that allows the recording of holographic pixel distributions at a microscopic scale. We show how these microholograms can encode angular information that overcomes the diffraction limit and could alleviate the space bandwidth constraint usually associated with conventional display design.

Encoding of 3D physical dimensions by face-selective cortical neurons

Neurons throughout the primate inferior temporal (IT) cortex respond selectively to visual images of faces and other complex objects. The response magnitude of neurons to a given image often depends on the size at which the image is presented, usually on a flat display at a fixed distance. While such size sensitivity might simply reflect the angular subtense of retinal image stimulation in degrees, one unexplored possibility is that it tracks the real-world geometry of physical objects, such as their size and distance to the observer in centimeters. This distinction bears fundamentally on the nature of object representation in IT and on the scope of visual operations supported by the ventral visual pathway. To address this question, we assessed the response dependency of neurons in the macaque anterior fundus (AF) face patch to the angular versus physical size of faces. We employed a macaque avatar to stereoscopically render three-dimensional (3D) photorealistic faces at multiple sizes and distances, including a subset of size/distance combinations designed to cast the same size retinal image projection. We found that most AF neurons were modulated principally by the 3D physical size of the face rather than its two-dimensional (2D) angular size on the retina. Further, most neurons responded strongest to extremely large and small faces, rather than to those of normal size. Together, these findings reveal a graded encoding of physical size among face patch neurons, providing evidence that category-selective regions of the primate ventral visual pathway participate in a geometric analysis of real-world objects.

The Virtual Retinal Display: A Technology for Augmented Reality

Abstract: Virtual Retinal Display (VRD) is an advanced technology for creating visual images. Dr. Thomas A. Furness III created it at the Human Interface Technology Laboratory (HIT Lab). Low power laser light is directly scanned onto the retina by the VRD to produce images. Bright, high-contrast, high-resolution photos are produced with this unique technique. It has been shown that all the technological advancements needed have been made in order for small, laser-scanned, virtual retinal displays to operate effectively. Since several years ago, military and commercial customers have received prototype devices with VGA resolutions (640 x 480 pixels), and Microvision's Virtual Retinal DisplayTM (VRDTM) is now ready for accelerated performance expansion. VRD images often use 300 nanowatts or less. Additionally, VRD images can be easily seen when placed on ambient room lighting.

Retinal Projection Near‐Eye Displays with Huygens’ Metasurfaces

AbstractMost of current commercial near‐eye 3D displays use traditional stereoscopic approach to generate the 3D information. A well‐known issue for this type of technology is the vergence and accommodation conflict, which leads to visual confusion and fatigue for the viewer. To address this problem, a proof‐of‐concept solution based on retinal projection technology has been developed to provide accommodation‐free virtual images by using a small aperture (360 µm × 360 µm) transparent Huygens’ metasurface hologram as the display device. The virtual image is generated using a visible laser illuminating a metasurface hologram, which is then directly projected onto the retina using an optical see‐through eyepiece. Using this concept, this work experimentally demonstrates a compact and wearable near‐eye display of light weight (≈50 g, including spectacle frames, light source, and battery) creating accommodation‐free images (clear ranging from 0.5 to 2 m), overlaid with the real world and directly viewed by naked eye. To do so, a new design method is introduced for retinal projection near‐eye displays that, inherently, is able to solve the vergence‐accommodation conflict using a small aperture Huygens’ metasurface hologram.

Sticking to your side: A niche for the development of ipsilateral retinal projections

Visual impairments in albinism result from decreased ipsilateral retinal projections. In this issue of Neuron, Slavi, Balasubramanian, and colleagues1 demonstrate how low CyclinD2 in the ciliary marginal zone perturbs generation of ipsilaterally projecting RGCs and that restoring CyclinD2 improves vision in albino mice.

Lensless phase-only holographic retinal projection display based on the error diffusion algorithm.

Holographic retinal projection display (RPD) can project images directly onto the retina without any lens by encoding a convergent spherical wave phase with the target images. Conventional amplitude-type holographic RPD suffers from strong zero-order light and conjugate. In this paper, a lensless phase-only holographic RPD based on error diffusion algorithm is demonstrated. It is found that direct error diffusion of the complex Fresnel hologram leads to low image quality. Thus, a post-addition phase method is proposed based on angular spectrum diffraction. The spherical wave phase is multiplied after error diffusion process, and acts as an imaging lens. In this way, the error diffusion functions better due to reduced phase difference between adjacent pixels, and a virtual image with improved quality is produced. The viewpoint is easily deflected just by changing the post-added spherical phase. A full-color holographic RPD with adjustable eyebox is demonstrated experimentally with time-multiplexing technique.

Projections, Perceptual Constancy, and Geometry

The notions "retinal images" and "retinal projection" are ubiquitous in both the scientific and philosophical literature on perception. However, this article argues that they belong to the former and should be kept out of the latter. In the context of the empirical investigation of perception, projections play a crucial role, and help articulate pressing research problems. But, as part of the phenomenological and conceptual analysis of perception, projections give rise to untenable models and to avoidable conundrums, such as the much discussed issue of perceptual constancy. Why are projections and retinal images so prevalent in the philosophical literature? The author conjectures that the reason has to do with conceptual fallouts of the effort to give a geometric representation to changes of perspective, a mission more daunting than it initially appears to be, and one that leads to the problematic insertion of projections into phenomenology. He suggests that correcting this shows perceptual constancy to be a starting point rather than a challenge for phenomenology.

Axon hyperexcitability in the contralateral projection following unilateral optic nerve crush in mice.

Optic neuropathies are characterized by degeneration of retinal ganglion cell axonal projections to the brain, including acute conditions like optic nerve trauma and progressive conditions such as glaucoma. Despite different aetiologies, retinal ganglion cell axon degeneration in traumatic optic neuropathy and glaucoma share common pathological signatures. We compared how early pathogenesis of optic nerve trauma and glaucoma influence axon function in the mouse optic projection. We assessed pathology by measuring anterograde axonal transport from retina to superior colliculus, current-evoked optic nerve compound action potential and retinal ganglion cell density 1 week following unilateral optic nerve crush or intraocular pressure elevation. Nerve crush reduced axon transport, compound axon potential and retinal ganglion cell density, which were unaffected by intraocular pressure elevation. Surprisingly, optic nerves contralateral to crush demonstrated 5-fold enhanced excitability in compound action potential compared with naïve nerves. Enhanced excitability in contralateral sham nerves is not due to increased accumulation of voltage-gated sodium channel 1.6, or ectopic voltage-gated sodium channel 1.2 expression within nodes of Ranvier. Our results indicate hyperexcitability is driven by intrinsic responses of αON-sustained retinal ganglion cells. We found αON-sustained retinal ganglion cells in contralateral, sham and eyes demonstrated increased responses to depolarizing currents compared with those from naïve eyes, while light-driven responses remained intact. Dendritic arbours of αON-sustained retinal ganglion cells of the sham eye were like naïve, but soma area and non-phosphorylated neurofilament H increased. Current- and light-evoked responses of sham αOFF-sustained retinal ganglion cells remained stable along with somato-dendritic morphologies. In retinas directly affected by crush, light responses of αON- and αOFF-sustained retinal ganglion cells diminished compared with naïve cells along with decreased dendritic field area or branch points. Like light responses, αOFF-sustained retinal ganglion cell current-evoked responses diminished, but surprisingly, αON-sustained retinal ganglion cell responses were similar to those from naïve retinas. Optic nerve crush reduced dendritic length and area in αON-sustained retinal ganglion cells in eyes ipsilateral to injury, while crush significantly reduced dendritic branching in αOFF-sustained retinal ganglion cells. Interestingly, 1 week of intraocular pressure elevation only affected αOFF-sustained retinal ganglion cell physiology, depolarizing resting membrane potential in cells of affected eyes and blunting current-evoked responses in cells of saline-injected eyes. Collectively, our results suggest that neither saline nor sham surgery provide a true control, chronic versus acute optic neuropathies differentially affect retinal ganglion cells composing the ON and OFF pathways, and acute stress can have near-term effects on the contralateral projection.

Enlarging the FOV of lensless holographic retinal projection display with two-step Fresnel diffraction

The field of view (FOV) of holographic retinal projection display (RPD) is always restricted by the diffraction angle of a spatial light modulator (SLM). In this paper, we demonstrate a large FOV holographic RPD by using two-step Fresnel diffraction calculation. By adding the pupil plane as the intermediate plane and decreasing the sampling interval, the FOV can be enlarged to nearly two times of the diffraction angle limit without any physical change. Due to the added spherical wave phase, the influence of aliasing is eliminated because the adjacent orders are projected to different viewpoints. The nonuniform image intensity caused by the sinc function modulation is compensated by image pre-processing. Optical experiments verify that the proposed method can present a uniform holographic near-eye display with a large FOV and adjustable viewpoint position.

Simultaneous multi-channel near-eye display: a holographic retinal projection display with large information content

Augmented reality (AR) near-eye displays (NEDs) are emerging as the next-generation display platform. The existing AR NED only present one single video channel at a time, same as traditional media such as TVs and smartphones. In this Letter, to the best of our knowledge, we propose for the first time a multi-channel holographic retinal projection display (RPD), which can provide multi-channel image sources simultaneously, thus greatly increasing the information content. Due to the superposition capacity of a hologram, multiple images are projected to different viewpoints simultaneously through multiple spherical wave encoding, so that the viewer can switch among playing channels very fast through eye rotation. A full-color dynamic multi-channel holographic near-eye display is demonstrated in the optical experiment. The proposed method provides a good prospect that the future AR glasses can play dozens of video channels in parallel, and the user can switch among channels freely and efficiently just through a simple eye rotation.

Screenless Displays: The Emerging Computer Technology

Abstract - Screenless display is an emerging new technology, allows users to display and transmit data without the use of a screen or projector has become a good prospect in the near futurefor a wide range of applications. As the name implies it deals with the display of several things without the use of screens using projector. It involves the following 3 different working principles.The Visual image, Virtual retinal display, Synaptic interface. This mainly illustrates and demonstrates how the screen less displays works and its applications in various fields of science. This technology would bring about the revolution in the field of displays and monitors that are costly, huge and are proven difficult to manage the power requirements and constraints. It is also the futuristic technological innovation. Screenless display is a developing display technology that allows users to display and transmit data without the use of a screen or projector. Keyword - Foot, Hologram, Hand, LCD, Screenless, voice.

Serial dependence for oculomotor control depends on early sensory signals

To create an accurate percept of the world, the visual system relies on past experience and prior assumptions.1 For example, although the retinal projection of an object moving in depth changes drastically, we still perceive the object at a constant size and velocity.2,3 Consequently, if we see the same object witha constant retinal size at two different depth levels, the perceived size differs (illustrated by the Ponzo illusion). Past experience also directly influences perceptual judgments, an effect known as serial dependence.4,5 Such sequential effects have also been reported for oculomotor behavior, even on the trial-by-trial level.6-10 An integration of past experiences seems like a smart and sophisticated mechanism to reduce uncertainty and improve behavior in a world full of statistical regularities. By leveraging the Ponzo illusion to dissociate perceived size and speed from retinal signals, we show that serial-dependence effects for oculomotor control are mediated by retinal error signals. These sequential effects likely take place in early sensory processing because they transfer to different visual stimuli. In contrast to recently reported history effects for perceptual decisions,11 sequential effects for oculomotor control deviate from perceptual mechanisms by not integrating spatial context and by ignoring size and velocity constancy. Although this dissociation might appear suboptimal, we argue that this effect reveals the different goals of the oculomotor and perceptual systems. The oculomotor system tries to reduce retinal error signals to bring and keep the target close to the fovea, whereas the visual system interprets retinal input to achieve an accurate representation of the world.12.

A Highly Integrated Ambient Light Robust Eye-Tracking Sensor for Retinal Projection AR Glasses Based on Laser Feedback Interferometry

Robust and highly integrated eye-tracking is a key technology to improve resolution of near-eye-display technologies for augmented reality (AR) glasses such as focus-free retinal projection as it enables display enhancements like foveated rendering. Furthermore, eye-tracking sensors enables novel ways to interact with user interfaces of AR glasses, improving thus the user experience compared to other wearables. In this work, we present a novel approach to track the user's eye by scanned laser feedback interferometry sensing. The main advantages over modern video-oculography (VOG) systems are the seamless integration of the eye-tracking sensor and the excellent robustness to ambient light with significantly lower power consumption. We further present an algorithm to track the bright pupil signal captured by our sensor with a significantly lower computational effort compared to VOG systems. We evaluate a prototype to prove the high robustness against ambient light and achieve a gaze accuracy of 1.62\,$^\circ$, which is comparable to other state-of-the-art scanned laser eye-tracking sensors. The outstanding robustness and high integrability of the proposed sensor will pave the way for everyday eye-tracking in consumer AR glasses.

DSCAM is differentially patterned along the optic axon pathway in the developing Xenopus visual system and guides axon termination at the target

BackgroundThe Xenopus retinotectal circuit is organized topographically, where the dorsal–ventral axis of the retina maps respectively on to the ventral-dorsal axis of the tectum; axons from the nasal-temporal axis of the retina project respectively to the caudal-rostral axis of the tectum. Studies throughout the last two decades have shown that mechanisms involving molecular recognition of proper termination domains are at work guiding topographic organization. Such studies have shown that graded distribution of molecular cues is important for topographic mapping. However, the complement of molecular cues organizing topography along the developing optic nerve, and as retinal axons cross the chiasm and navigate towards and innervate their target in the tectum, remains unknown. Down syndrome cell adhesion molecule (DSCAM) has been characterized as a key molecule in axon guidance, making it a strong candidate involved in the topographic organization of retinal fibers along the optic path and at their target.MethodsUsing a combination of whole-brain clearing and immunohistochemistry staining techniques we characterized DSCAM expression and the projection of ventral and dorsal retinal fibers starting from the eye, following to the optic nerve and chiasm, and into the terminal target in the optic tectum in Xenopus laevis tadpoles. We then assessed the effects of DSCAM on the establishment of retinotopic maps through spatially and temporally targeted DSCAM knockdown on retinal ganglion cells (RGCs) with axons innervating the optic tectum.ResultsHighest expression of DSCAM was localized to the ventral posterior region of the optic nerve and chiasm; this expression pattern coincides with ventral fibers derived from ventral RGCs. Targeted downregulation of DSCAM expression on ventral RGCs affected the segregation of medial axon fibers from their dorsal counterparts within the tectal neuropil, indicating that DSCAM plays a role in retinotopic organization.ConclusionThese findings together with previous studies demonstrating cell-autonomous roles for DSCAM during the development of pre- and postsynaptic arbors in the Xenopus retinotectal circuit indicates that DSCAM exerts multiple roles in coordinating axon targeting and structural connectivity in the developing vertebrate visual system.

RPS-Net: An effective retinal image projection segmentation network for retinal vessels and foveal avascular zone based on OCTA data.

Optical coherence tomography angiography (OCTA) is an advanced imaging technology that can present the three-dimensional (3D) structure of retinal vessels (RVs). Quantitative analysis of retinal vessel density and foveal avascular zone (FAZ) area is of great significance in clinical diagnosis, and the automatic semantic segmentation at the pixel level helps quantitative analysis. The existing segmentation methods cannot effectively use the volume data and projection map data of the OCTA image at the same time and lack the trade-off between global perception and local details, which lead to problems such as discontinuity of segmentation results and deviation of morphological estimation. In order to better assist physicians in clinical diagnosis and treatment, the segmentation accuracy of RVs and FAZ needs to be further improved. In this work, we propose an effective retinal image projection segmentation network (RPS-Net) to achieve accurate RVs and FAZ segmentation. Experiments show that this network exhibits good performance and outperforms other existing methods. Our method considers three aspects. First, we use two parallel projection paths to learn global perceptual features and local supplementary details. Second, we use the dual-way projection learning module to reduce the depth of the 3D data and learn image spatial features. Finally, we merged the two-dimensional features learned from the volume data with the two-dimensional projection data, and used a U-shaped network to further learn and generate the final result. We validated our model on the OCTA-500, which is a large multi-modal, multi-task retinal dataset. The experimental results showed that our method achieved state-of-the-art performance; the mean Dice coefficients for RVs are 89.89 ± 2.60 (%) and 91.40 ± 9.18 (%) on the two subsets, while the Dice coefficients for FAZ are 91.55 ± 2.05 (%) and 97.80 ± 2.75 (%), respectively. Our method can make full use of the information of 3D data and 2D data to generate segmented images with higher continuity and accuracy. Code is available at https://github.com/hchuanZ/MFFN/tree/master.

Simplified retinal 3D projection rendering method and system.

A simplified rendering method and system for retinal 3D projection using view and depth information is proposed and demonstrated. Instead of vertex calculations, image-based techniques, including sub-image shifting, image fusion, and hole filling, combined with the depth information, are used to render the multi-view images in a display space with specific discrete depth coordinates. A set of time-division multiplexing retinal 3D projection systems with dense viewpoints is built. A near-eye display of a 3D scene with complex occlusion relationships is realized using the rendering method and system. The eye box of the retinal projection system is enlarged, and the accommodation response of the eyes is evoked at the same time, which improves the visual experience. Rendering tests are carried out using simple and complex models, which proves the effectiveness of this method. Comparative experiments prove that the proposed retinal projection method can obtain high-performance 3D images comparable to the super multi-view display method while simplifying the rendering process. Additionally, the depth of field of the experimental system can cover most of the vergence accommodation conflict sensitive range of the human eye.

Receptive Field Sizes of Nyxnob Mouse Retinal Ganglion Cells.

Patients with congenital nystagmus, involuntary eye movements, often have a reduced visual acuity. Some of these patients have a retinal-specific mutation in the protein nyctalopin, which is also present in the Nyxnob mouse. In these mice, retinal ganglion cells (RGCs) have oscillatory activity, which leads to expanded axonal projections towards the dLGN and consequently to a desegregation of retinal projections to the brain. In this study, we investigate whether the receptive fields of Nyxnob RGCs have also expanded by measuring the size of their receptive fields using MEA recordings. Contrary to our expectation, relative to wild-type (WT) mice we found receptive field sizes in the Nyxnob retina had not increased but instead had decreased for green-light preferring RGCs. Additionally, we also found the receptive fields of UV-light preferring RGCs are larger than green-light preferring RGCs in both WT and Nyxnob mice.

Intraocular Delivery of a Collagen Mimetic Peptide Repairs Retinal Ganglion Cell Axons in Chronic and Acute Injury Models.

Vision loss through the degeneration of retinal ganglion cell (RGC) axons occurs in both chronic and acute conditions that target the optic nerve. These include glaucoma, in which sensitivity to intraocular pressure (IOP) causes early RGC axonal dysfunction, and optic nerve trauma, which causes rapid axon degeneration from the site of injury. In each case, degeneration is irreversible, necessitating new therapeutics that protect, repair, and regenerate RGC axons. Recently, we demonstrated the reparative capacity of using collagen mimetic peptides (CMPs) to heal fragmented collagen in the neuronal extracellular milieu. This was an important step in the development of neuronal-based therapies since neurodegeneration involves matrix metalloproteinase (MMP)-mediated remodeling of the collagen-rich environment in which neurons and their axons exist. We found that intraocular delivery of a CMP comprising single-strand fractions of triple helix human type I collagen prevented early RGC axon dysfunction in an inducible glaucoma model. Additionally, CMPs also promoted neurite outgrowth from dorsal root ganglia, challenged in vitro by partial digestion of collagen. Here, we compared the ability of a CMP sequence to protect RGC axons in both inducible glaucoma and optic nerve crush. A three-week +40% elevation in IOP caused a 67% degradation in anterograde transport to the superior colliculus, the primary retinal projection target in rodents. We found that a single intravitreal injection of CMP during the period of IOP elevation significantly reduced this degradation. The same CMP delivered shortly after optic nerve crush promoted significant axonal recovery during the two-week period following injury. Together, these findings support a novel protective and reparative role for the use of CMPs in both chronic and acute conditions affecting the survival of RGC axons in the optic projection to the brain.