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1.
Curr Biol ; 32(11): R520-R523, 2022 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-35671725

RESUMO

As we move around, the image pattern on our retina is constantly changing. Nervous systems have evolved to detect such global 'optic flow' patterns. A new study reveals how optic flow is encoded in the larval zebrafish brain and could be used for the estimation of self-motion.


Assuntos
Percepção de Movimento , Fluxo Óptico , Animais , Movimento (Física) , Percepção de Movimento/fisiologia , Retina/fisiologia , Peixe-Zebra
2.
J Neural Eng ; 19(3)2022 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-35667363

RESUMO

Objective. Retinal prostheses are a promising strategy to restore sight to patients with retinal degenerative diseases. These devices compensate for the loss of photoreceptors by electrically stimulating neurons in the retina. Currently, the visual function that can be recovered with such devices is very limited. This is due, in part, to current spread, unintended axonal activation, and the limited resolution of existing devices. Here we show, using a recent model of prosthetic vision, that optimizing how visual stimuli are encoded by the device can help overcome some of these limitations, leading to dramatic improvements in visual perception.Approach. We propose a strategy to do this in practice, using patients' feedback in a visual task. The main challenge of our approach comes from the fact that, typically, one only has access to a limited number of noisy responses from patients. We propose two ways to deal with this: first, we use a model of prosthetic vision to constrain and simplify the optimization. We show that, if one knew the parameters of this model for a given patient, it would be possible to greatly improve their perceptual performance. Second we propose a preferential Bayesian optimization to efficiently learn these model parameters for each patient, using minimal trials.Main results. To test our approach, we presented healthy subjects with visual stimuli generated by a recent model of prosthetic vision, to replicate the perceptual experience of patients fitted with an implant. Our optimization procedure led to significant and robust improvements in perceived image quality, that transferred to increased performance in other tasks.Significance. Importantly, our strategy is agnostic to the type of prosthesis and thus could readily be implemented in existing implants.


Assuntos
Degeneração Retiniana , Próteses Visuais , Teorema de Bayes , Humanos , Estimulação Luminosa , Retina/fisiologia , Percepção Visual/fisiologia
3.
Vis Neurosci ; 39: E004, 2022 05 10.
Artigo em Inglês | MEDLINE | ID: mdl-35534787

RESUMO

The vertebrate retina contains a large number of different types of neurons that can be distinguished by their morphological properties. Assuming that no location should be without a contribution from the circuitry and function linked to a specific type of neuron, it is expected that the dendritic trees of neurons belonging to a type will cover the retina in a regular manner. Thus, for most types of neurons, the contribution to visual processing is thought to be independent of the exact location of individual neurons across the retina. Here, we have investigated the distribution of AII amacrine cells in rat retina. The AII is a multifunctional amacrine cell found in mammals and involved in synaptic microcircuits that contribute to visual processing under both scotopic and photopic conditions. Previous investigations have suggested that AIIs are regularly distributed, with a nearest-neighbor distance regularity index of ~4. It has been argued, however, that this presumed regularity results from treating somas as points, without taking into account their actual spatial extent which constrains the location of other cells of the same type. When we simulated random distributions of cell bodies with size and density similar to real AIIs, we confirmed that the simulated distributions could not be distinguished from the distributions observed experimentally for AIIs in different regions and eccentricities of the retina. The developmental mechanisms that generate the observed distributions of AIIs remain to be investigated.


Assuntos
Células Amácrinas , Retina , Células Amácrinas/fisiologia , Animais , Corpo Celular , Mamíferos , Ratos , Retina/fisiologia , Software
4.
J Neural Eng ; 19(3)2022 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-35609556

RESUMO

Objective. Retinal prostheses seek to create artificial vision by stimulating surviving retinal neurons of patients with profound vision impairment. Notwithstanding tremendous research efforts, the performance of all implants tested to date has remained rudimentary, incapable of overcoming the threshold for legal blindness. To maximize the perceptual efficacy of retinal prostheses, a device must be capable of controlling retinal neurons with greater spatiotemporal precision. Most studies of retinal stimulation were derived from either non-primate species or the peripheral primate retina. We investigated if artificial stimulation could leverage the high spatial resolution afforded by the neural substrates at the primate fovea and surrounding regions to achieve improved percept qualities.Approach.We began by developing a new computational model capable of generating anatomically accurate retinal ganglion cell (RGC) populations within the human central retina. Next, multiple RGC populations across the central retina were stimulatedin-silicoto compare clinical and recently proposed neurostimulation configurations based on their ability to improve perceptual efficacy and reduce activation thresholds.Main results.Our model uniquely upholds eccentricity-dependent characteristics such as RGC density and dendritic field diameter, whilst incorporating anatomically accurate features such as axon projection and three-dimensional (3D) RGC layering, features often forgone in favor of reduced computational complexity. Following epiretinal stimulation, the RGCs in our model produced response patterns in shapes akin to the complex and non-trivial percepts reported in clinical trials. Our results also demonstrated that even within the neuron-dense central retina, epiretinal stimulation using a multi-return hexapolar electrode arrangement could reliably achieve spatially focused RGC activation and could achieve single-cell excitation in 56% of all tested locations.Significance. This study establishes an anatomically accurate 3D model of RGC populations within the human central retina and demonstrates the potential for an epiretinal hexapolar configuration to achieve consistent, spatially confined retinal responses, even within the unique and neuron-dense foveal region. Our results and model promote the prospect and optimization of higher spatial resolution in future epiretinal implants.


Assuntos
Células Ganglionares da Retina , Próteses Visuais , Animais , Axônios , Estimulação Elétrica , Humanos , Retina/fisiologia , Células Ganglionares da Retina/fisiologia , Visão Ocular
5.
Curr Biol ; 32(11): 2529-2538.e4, 2022 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-35588744

RESUMO

The detection of motion direction is a fundamental visual function and a classic model for neural computation. In the non-primate retina, direction selectivity arises in starburst amacrine cell (SAC) dendrites, which provide selective inhibition to direction-selective retinal ganglion cells (dsRGCs). Although SACs are present in primates, their connectivity and the existence of dsRGCs remain open questions. Here, we present a connectomic reconstruction of the primate ON SAC circuit from a serial electron microscopy volume of the macaque central retina. We show that the structural basis for the SACs' ability to confer directional selectivity on postsynaptic neurons is conserved. SACs selectively target a candidate homolog to the mammalian ON-sustained dsRGCs that project to the accessory optic system (AOS) and contribute to gaze-stabilizing reflexes. These results indicate that the capacity to compute motion direction is present in the retina, which is earlier in the primate visual system than classically thought.


Assuntos
Células Amácrinas , Conectoma , Células Amácrinas/fisiologia , Animais , Dendritos/fisiologia , Mamíferos , Primatas , Retina/fisiologia , Células Ganglionares da Retina/fisiologia , Sinapses/fisiologia
6.
J Neural Eng ; 19(3)2022 05 27.
Artigo em Inglês | MEDLINE | ID: mdl-35561667

RESUMO

Optoelectronic semiconducting polymer material interfaced with a blind-developing chick-retina (E13-E18) in subretinal configuration reveals a response to full-field flash stimulus that resembles an elicited response from natural photoreceptors in a neonatal chick retina. The response manifests as evoked-firing of action potentials and was recorded using a multi-electrode array in contact with the retinal ganglion layer. Characteristics of increasing features in the signal unfold during different retina-development stages and highlight the emerging network mediated pathways typically present in the vision process of the artificial photoreceptor interfaced retina.


Assuntos
Polímeros , Retina , Potenciais de Ação , Humanos , Recém-Nascido , Células Fotorreceptoras , Retina/fisiologia , Células Ganglionares da Retina/fisiologia
7.
Nat Commun ; 13(1): 2862, 2022 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-35606344

RESUMO

From mouse to primate, there is a striking discontinuity in our current understanding of the neural coding of motion direction. In non-primate mammals, directionally selective cell types and circuits are a signature feature of the retina, situated at the earliest stage of the visual process. In primates, by contrast, direction selectivity is a hallmark of motion processing areas in visual cortex, but has not been found in the retina, despite significant effort. Here we combined functional recordings of light-evoked responses and connectomic reconstruction to identify diverse direction-selective cell types in the macaque monkey retina with distinctive physiological properties and synaptic motifs. This circuitry includes an ON-OFF ganglion cell type, a spiking, ON-OFF polyaxonal amacrine cell and the starburst amacrine cell, all of which show direction selectivity. Moreover, we discovered that macaque starburst cells possess a strong, non-GABAergic, antagonistic surround mediated by input from excitatory bipolar cells that is critical for the generation of radial motion sensitivity in these cells. Our findings open a door to investigation of a precortical circuitry that computes motion direction in the primate visual system.


Assuntos
Conectoma , Macaca , Retina , Células Amácrinas/fisiologia , Animais , Potenciais Evocados Visuais/fisiologia , Macaca/fisiologia , Mamíferos , Camundongos , Primatas/fisiologia , Retina/fisiologia , Células Ganglionares da Retina/fisiologia , Sinapses/fisiologia
8.
Nat Commun ; 13(1): 2613, 2022 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-35551183

RESUMO

Neuromodulators adapt sensory circuits to changes in the external world or the animal's internal state and synapses are key control sites for such plasticity. Less clear is how neuromodulation alters the amount of information transmitted through the circuit. We investigated this question in the context of the diurnal regulation of visual processing in the retina of zebrafish, focusing on ribbon synapses of bipolar cells. We demonstrate that contrast-sensitivity peaks in the afternoon accompanied by a four-fold increase in the average Shannon information transmitted from an active zone. This increase reflects higher synaptic gain, lower spontaneous "noise" and reduced variability of evoked responses. Simultaneously, an increase in the probability of multivesicular events with larger information content increases the efficiency of transmission (bits per vesicle) by factors of 1.5-2.7. This study demonstrates the multiplicity of mechanisms by which a neuromodulator can adjust the synaptic transfer of sensory information.


Assuntos
Transmissão Sináptica , Peixe-Zebra , Animais , Neurotransmissores , Retina/fisiologia , Sinapses/fisiologia , Transmissão Sináptica/fisiologia
9.
J Neurosci ; 42(21): 4231-4249, 2022 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-35437278

RESUMO

Signal integration of converging neural circuits is poorly understood. One example is in the retina where the integration of rod and cone signaling is responsible for the large dynamic range of vision. The relative contribution of rods versus cones is dictated by a complex function involving background light intensity and stimulus temporal frequency. One understudied mechanism involved in coordinating rod and cone signaling onto the shared retinal circuit is the hyperpolarization activated current (I h) mediated by hyperpolarization-activated cyclic nucleotide-gated 1 (HCN1) channels expressed in rods and cones. I h opposes membrane hyperpolarization driven by activation of the phototransduction cascade and modulates the strength and kinetics of the photoreceptor voltage response. We examined conditional knock-out (KO) of HCN1 from mouse rods using electroretinography (ERG). In the absence of HCN1, rod responses are prolonged in dim light which altered the response to slow modulation of light intensity both at the level of retinal signaling and behavior. Under brighter intensities, cone-driven signaling was suppressed. To our surprise, conditional KO of HCN1 from mouse cones had no effect on cone-mediated signaling. We propose that I h is dispensable in cones because of the high level of temporal control of cone phototransduction. Thus, HCN1 is required for cone-driven retinal signaling only indirectly by modulating the voltage response of rods to limit their output.SIGNIFICANCE STATEMENT Hyperpolarization gated hyperpolarization-activated cyclic nucleotide-gated 1 (HCN1) channels carry a feedback current that helps to reset light-activated photoreceptors. Using conditional HCN1 knock-out (KO) mice we show that ablating HCN1 from rods allows rods to signal in bright light when they are normally shut down. Instead of enhancing vision this results in suppressing cone signaling. Conversely, ablating HCN1 from cones was of no consequence. This work provides novel insights into the integration of rod and cone signaling in the retina and challenges our assumptions about the role of HCN1 in cones.


Assuntos
Nucleotídeos Cíclicos , Células Fotorreceptoras Retinianas Bastonetes , Animais , Eletrorretinografia , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/genética , Camundongos , Camundongos Knockout , Canais de Potássio/genética , Retina/fisiologia , Células Fotorreceptoras Retinianas Cones/fisiologia , Células Fotorreceptoras Retinianas Bastonetes/fisiologia
10.
Int J Mol Sci ; 23(8)2022 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-35456959

RESUMO

The full-field ERG is useful for index rod- or cone-mediated retinal function in rodent models of retinal degeneration. However, the relationship between the ERG response amplitudes and visually guided behavior, such as flicker detection, is not well understood. A comparison of ERG to behavioral responses in a light-damage model of retinal degeneration allows us to better understand the functional implications of electrophysiological changes. Flicker-ERG and behavioral responses to flicker were used to determine critical flicker frequency (CFF) under scotopic and photopic conditions before and up to 90 d after a 10-day period of low-intensity light damage. Dark- and light-adapted ERG flash responses were significantly reduced after light damage. The a-wave was permanently reduced, while the b-wave amplitude recovered over three weeks after light damage. There was a small, but significant dip in scotopic ERG CFF. Photopic behavioral CFF was slightly lower following light damage. The recovery of the b-wave amplitude and flicker sensitivity demonstrates the plasticity of retinal circuits following photopic injury.


Assuntos
Visão de Cores , Degeneração Retiniana , Animais , Aves , Eletrorretinografia , Estimulação Luminosa , Ratos , Retina/fisiologia , Degeneração Retiniana/etiologia
12.
Cells ; 11(8)2022 04 18.
Artigo em Inglês | MEDLINE | ID: mdl-35456052

RESUMO

Zebrafish show an extraordinary potential for regeneration in several organs from fins to central nervous system. Most impressively, the outcome of an injury results in a near perfect regeneration and a full functional recovery. Indeed, among the various injury paradigms previously tested in the field of zebrafish retina regeneration, a perfect layered structure is observed after one month of recovery in most of the reported cases. In this study, we applied cryoinjury to the zebrafish eye. We show that retina exposed to this treatment for one second undergoes an acute damage affecting all retinal cell types, followed by a phase of limited tissue remodeling and regrowth. Surprisingly, zebrafish developed a persistent retinal dysplasia observable through 300 days post-injury. There is no indication of fibrosis during the regeneration period, contrary to the regeneration process after cryoinjury to the zebrafish cardiac ventricle. RNA sequencing analysis of injured retinas at different time points has uncovered enriched processes and a number of potential candidate genes. By means of this simple, time and cost-effective technique, we propose a zebrafish injury model that displays a unique inability to completely recover following focal retinal damage; an outcome that is unreported to our knowledge. Furthermore, RNA sequencing proved to be useful in identifying pathways, which may play a crucial role not only in the regeneration of the retina, but in the first initial step of regeneration, degeneration. We propose that this model may prove useful in comparative and translational studies to examine critical pathways for successful regeneration.


Assuntos
Retina , Peixe-Zebra , Animais , Ventrículos do Coração , Regeneração Nervosa/fisiologia , Retina/fisiologia , Peixe-Zebra/fisiologia
13.
Curr Biol ; 32(10): 2130-2143.e3, 2022 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-35395192

RESUMO

The sensory periphery is responsible for detecting ethologically relevant features of the external world, using compact, predominantly feedforward circuits. Visual motion is a particularly prevalent sensory feature, the presence of which can be a signal to enact diverse behaviors ranging from gaze stabilization reflexes to predator avoidance or prey capture. To understand how the retina constructs the distinct neural representations required for these behaviors, we investigated two circuits responsible for encoding different aspects of image motion: ON and ON-OFF direction-selective ganglion cells (DSGCs). Using a combination of two-photon targeted whole-cell electrophysiology, pharmacology, and conditional knockout mice, we show that distinct inhibitory pathways independently control tuning for motion velocity and motion direction in these two cell types. We further employ dynamic clamp and numerical modeling techniques to show that asymmetric inhibition provides a velocity-invariant mechanism of directional tuning, despite the strong velocity dependence of classical models of direction selectivity. We therefore demonstrate that invariant representations of motion features by inhibitory interneurons act as computational building blocks to construct distinct, behaviorally relevant signals at the earliest stages of the visual system.


Assuntos
Percepção de Movimento , Células Ganglionares da Retina , Animais , Camundongos , Percepção de Movimento/fisiologia , Estimulação Luminosa/métodos , Retina/fisiologia , Células Ganglionares da Retina/fisiologia , Vias Visuais/fisiologia
14.
J Neurosci ; 42(20): 4101-4115, 2022 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-35396331

RESUMO

Aversive responses to bright light (photoaversion) require signaling from the eye to the brain. Melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) encode absolute light intensity and are thought to provide the light signals for photoaversion. Consistent with this, neonatal mice exhibit photoaversion before the developmental onset of image vision, and melanopsin deletion abolishes photoaversion in neonates. It is not well understood how the population of ipRGCs, which constitutes multiple physiologically distinct types (denoted M1-M6 in mouse), encodes light stimuli to produce an aversive response. Here, we provide several lines of evidence that M1 ipRGCs that lack the Brn3b transcription factor drive photoaversion in neonatal mice. First, neonatal mice lacking TRPC6 and TRPC7 ion channels failed to turn away from bright light, while two photon Ca2+ imaging of their acutely isolated retinas revealed reduced photosensitivity in M1 ipRGCs, but not other ipRGC types. Second, mice in which all ipRGC types except for Brn3b-negative M1 ipRGCs are ablated exhibited normal photoaversion. Third, pharmacological blockade or genetic knockout of gap junction channels expressed by ipRGCs, which reduces the light sensitivity of M2-M6 ipRGCs in the neonatal retina, had small effects on photoaversion only at the brightest light intensities. Finally, M1s were not strongly depolarized by spontaneous retinal waves, a robust source of activity in the developing retina that depolarizes all other ipRGC types. M1s therefore constitute a separate information channel between the neonatal retina and brain that could ensure behavioral responses to light but not spontaneous retinal waves.SIGNIFICANCE STATEMENT At an early stage of development, before the maturation of photoreceptor input to the retina, neonatal mice exhibit photoaversion. On exposure to bright light, they turn away and emit ultrasonic vocalizations, a cue to their parents to return them to the nest. Neonatal photoaversion is mediated by intrinsically photosensitive retinal ganglion cells (ipRGCs), a small percentage of the retinal ganglion cell population that express the photopigment melanopsin and depolarize directly in response to light. This study shows that photoaversion is mediated by a subset of ipRGCs, called M1-ipRGCs. Moreover, M1-ipRGCs have reduced responses to retinal waves, providing a mechanism by which the mouse distinguishes light stimulation from developmental patterns of spontaneous activity.


Assuntos
Retina , Opsinas de Bastonetes , Animais , Animais Recém-Nascidos , Junções Comunicantes , Camundongos , Retina/fisiologia , Células Ganglionares da Retina/fisiologia , Opsinas de Bastonetes/genética , Visão Ocular
15.
J Vis Exp ; (181)2022 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-35404354

RESUMO

Müller glia (MG) are the predominant glia in the neural retina and can function as a regenerative source for retinal neurons. In lower vertebrates such as fish, MG-driven regeneration occurs naturally; in mammals, however, stimulation with certain factors or genetic/epigenetic manipulation is required. Since MG comprise only 5% of the retinal cell population, there is a need for model systems that allow the study of this cell population exclusively. One of these model systems is primary MG cultures that are reproducible and can be used for a variety of applications, including molecule/factor screening and identification, testing of compounds or factors, cell monitoring, and/or functional tests. This model is used to study the potential of murine MG to convert into retinal neurons after supplementation or inhibition of microRNAs (miRNAs) via transfection of artificial miRNAs or their inhibitors. The use of MG-specific reporter mice in combination with immunofluorescent labeling and single-cell RNA sequencing (scRNA-seq) confirmed that 80%-90% of the cells found in these cultures are MG. Using this model, it was discovered that miRNAs can reprogram MG into retinal progenitor cells (RPCs), which subsequently differentiate into neuronal-like cells. The advantages of this technique are that miRNA candidates can be tested for their efficiency and outcome before their usage in in vivo applications.


Assuntos
MicroRNAs , Regeneração Nervosa , Neuroglia , Animais , Proliferação de Células/fisiologia , Células Ependimogliais , Camundongos , MicroRNAs/genética , Regeneração Nervosa/fisiologia , Cultura Primária de Células , Retina/fisiologia , Células-Tronco
16.
Brain Res ; 1785: 147875, 2022 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-35271821

RESUMO

Retinal stimulation has become a widely utilized approach to restore visual function for individuals with retinal degenerative diseases. Although the rectangular electrical pulse is the primary stimulus waveform used in retinal neuromodulation, it remains unclear whether alternate waveforms may be more effective. Here, we used the optical intrinsic signal imaging system to assess the responses of cats' visual cortex to sinusoidal electrical stimulation through contact lens electrode, analyzing the response to various stimulus parameters (frequency, intensity, pulse width). A comparison between sinusoidal and rectangular stimulus waveform was also investigated. The results indicated that the optimal stimulation frequency for sinusoidal electrical stimulation was approximately 20 Hz, supporting the hypothesis that low-frequency electrostimulation induces more responsiveness in retinal neurons than high-frequency electrostimulation in case of sinusoidal stimulation. We also demonstrated that for low-frequency retinal neuromodulation, sinusoidal pulses are more effective than rectangular ones. In addition, we found that compared to current intensity, the effect of the sinusoidal pulse width on cortical responses was more prominent. These results suggested that sinusoidal electrical stimulation may provide a promising strategy for improved retinal neuromodulation in clinical settings.


Assuntos
Degeneração Retiniana , Córtex Visual , Estimulação Elétrica/métodos , Humanos , Retina/fisiologia , Córtex Visual/fisiologia
17.
Opt Express ; 30(6): 9035-9052, 2022 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-35299342

RESUMO

Brightness is one of the most important perceptual correlates of color appearance models (CAMs) when self-luminous stimuli are targeted. However, the vast majority of existing CAMs adopt the presence of a uniform background surrounding the stimulus, which severely limits their practical application in lighting. In this paper, a study on the brightness perception of a neutral circular stimulus surrounded by a non-uniform background consisting of a neutral ring-shaped luminous area and a dark surround is presented. The ring-shaped luminous area is presented with 3 thicknesses (0.33 cm, 0.67 cm and 1.00 cm), at 4 angular distances to the edge of the central stimulus (1.2°, 6.4°, 11.3° and 16.1°) and at 3 luminance levels (90 cd/m2, 335 cd/m2, 1200 cd/m2). In line with the literature, the results of the visual matching experiments show that the perceived brightness decreases in presence of a ring and the effect is maximal at the highest luminance of the ring, for the largest thickness and at the closest distance. Based on the observed results, an image-based model inspired by the physiology of the retina is proposed. The model includes the calculation of cone-fundamental weighted spectral radiance, scattering in the eye, cone compression and receptive field post-receptor organization. The wide receptive field assures an adaptive shift determined by both the adaptation to the stimulus and to the background. It is shown that the model performs well in predicting the matching experiments, including the impact of the thickness, the distance and the intensity of the ring, showing its potential to become the basic framework of a Lighting Appearance Model.


Assuntos
Luz , Visão Ocular , Iluminação , Retina/fisiologia , Percepção Visual/fisiologia
18.
Elife ; 112022 03 14.
Artigo em Inglês | MEDLINE | ID: mdl-35285798

RESUMO

Neural circuits are constructed from nonlinear building blocks, and not surprisingly overall circuit behavior is often strongly nonlinear. But neural circuits can also behave near linearly, and some circuits shift from linear to nonlinear behavior depending on stimulus conditions. Such control of nonlinear circuit behavior is fundamental to neural computation. Here, we study a surprising stimulus dependence of the responses of macaque On (but not Off) parasol retinal ganglion cells: these cells respond nonlinearly to spatial structure in some stimuli but near linearly to spatial structure in others, including natural inputs. We show that these differences in the linearity of the integration of spatial inputs can be explained by a shift in the balance of excitatory and inhibitory synaptic inputs that originates at least partially from adaptation in the cone photoreceptors. More generally, this highlights how subtle asymmetries in signaling - here in the cone signals - can qualitatively alter circuit computation.


Assuntos
Células Fotorreceptoras Retinianas Cones , Células Ganglionares da Retina , Animais , Macaca , Estimulação Luminosa/métodos , Primatas , Retina/fisiologia , Células Fotorreceptoras Retinianas Cones/fisiologia , Células Ganglionares da Retina/fisiologia
19.
Brain Struct Funct ; 227(4): 1507-1522, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35325293

RESUMO

Retinotopic map, the mapping between visual inputs on the retina and neuronal responses on the cortical surface, is one of the central topics in vision science. Typically, human retinotopic maps are constructed by analyzing functional magnetic resonance responses to designed visual stimuli on the cortical surface. Although it is widely used in visual neuroscience, retinotopic maps are limited by the signal-to-noise ratio and spatial resolution of fMRI. One promising approach to improve the quality of retinotopic maps is to register individual subject's retinotopic maps to a retinotopic template. However, none of the existing retinotopic registration methods has explicitly quantified the diffeomorphic condition, that is, retinotopic maps shall be aligned by stretching/compressing without tearing up the cortical surface. Here, we developed Diffeomorphic Registration for Retinotopic Maps (DRRM) to simultaneously align retinotopic maps in multiple visual regions under the diffeomorphic condition. Specifically, we used the Beltrami coefficient to model the diffeomorphic condition and performed surface registration based on retinotopic coordinates. The overall framework preserves the topological condition defined in the template. We further developed a unique evaluation protocol and compared the performance of the new method with several existing registration methods on both synthetic and real datasets. The results showed that DRRM is superior to the existing methods in achieving diffeomorphic  registration in synthetic and empirical data from 3T and 7T MRI systems. DRRM may improve the interpretation of low-quality retinotopic maps and facilitate applications of retinotopic maps in clinical settings.


Assuntos
Córtex Visual , Mapeamento Encefálico/métodos , Humanos , Imageamento por Ressonância Magnética/métodos , Retina/fisiologia , Razão Sinal-Ruído , Córtex Visual/diagnóstico por imagem , Córtex Visual/fisiologia , Vias Visuais/diagnóstico por imagem , Vias Visuais/fisiologia
20.
Sci Rep ; 12(1): 4785, 2022 03 21.
Artigo em Inglês | MEDLINE | ID: mdl-35314724

RESUMO

Altered retinal dopamine and ON-pathway activity may underlie myopia development. It has been shown that the stimulation of the blind spot with short-wavelength light increases the electroretinogram (ERG) b-wave amplitude of myopic eyes and may engage the retinal dopaminergic system. This study evaluated the impact of various durations of blind spot stimulation on the electrophysiological response of the myopic retina and their relationship to axial length. Six myopic individuals underwent three short-wavelength blue light blind spot stimulation protocols (10 s, 1 min, 10 min) using a virtual reality headset. As a control condition, no stimulation was shown for 1 min. The b-wave amplitude of the photopic full-field ERG was measured at baseline and 10, 20, 30, 40, 50, and 60 min after each condition. A significant increase in b-wave amplitude was observed for all stimulation protocols compared to the control. The peak b-wave amplitude was observed 20 min after the 1-min stimulation protocol and 60 min after the 10-min stimulation protocol. A significant positive correlation was found between axial length of the eye and percent change in b-wave amplitude for the 10-min stimulation protocol. A rapid and a delayed b-wave time course responses were observed following 1 min and 10 min of blind spot stimulation, respectively. Overall, these results indicate that light stimulation of the blind spot for various durations elevates ON-bipolar cell activity in the retina and as such is assumed to reduce the myopic response. These findings could have implications for future myopia treatment.


Assuntos
Visão de Cores , Miopia , Eletrorretinografia/métodos , Humanos , Luz , Miopia/terapia , Estimulação Luminosa/métodos , Retina/fisiologia
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