scholarly journals An amplitude code increases the efficiency of information transmission across a visual synapse

2018 ◽  
Author(s):  
Ben James ◽  
Léa Darnet ◽  
José Moya-Díaz ◽  
Sofie-Helene Seibel ◽  
Leon Lagnado
Keyword(s):  
Synaptic Vesicles ◽  
Visual Information ◽  
Dynamic Range ◽  
Bipolar Cells ◽  
Visual Signals ◽  
Temporal Precision ◽  
Ribbon Synapses ◽  
Analogue Signals ◽  
Rate Coding ◽  
The Brain

Most neurons in the brain transmit information digitally using sequences of spikes that trigger release of synaptic vesicles of fixed size. The first stages of vision and hearing are distinct in operating with analogue signals, but it is unclear how these are recoded for synaptic transmission. By imaging the release of glutamate in live zebrafish, we demonstrate how ribbon synapses of retinal bipolar cells transmit analogue visual signals by changes in both the rate and amplitude of synaptic events. Higher contrasts released glutamate packets composed of more vesicles and coding by amplitude often continued after rate coding had saturated. Glutamate packets equivalent to five vesicles transmitted four times as many bits of information per vesicle compared to independent release events. By discretizing analogue signals into sequences of numbers ranging up to eleven, ribbon synapses increase the dynamic range, temporal precision and efficiency with which visual information is transmitted.

scholarly journals Modulation of the vesicle code transmitting the visual signal in the retina

2020 ◽  
Author(s):  
José Moya-Díaz ◽  
Ben James ◽  
Leon Lagnado
Keyword(s):  
Substance P ◽  
Visual Information ◽  
Calcium Influx ◽  
Calcium Transient ◽  
Bipolar Cells ◽  
Visual Signals ◽  
Visual Signal ◽  
Temporal Precision ◽  
Low Pass ◽  
Presynaptic Calcium

SummaryMultivesicular release (MVR) allows retinal bipolar cells to transmit visual signals as changes in both the rate and amplitude of synaptic events. How do neuromodulators reguate this vesicle code? By imaging larval zebrafish, we find that the variability of calcium influx is a major source of synaptic noise. Dopamine increases synaptic gain up to 15-fold while Substance P reduces it 7-fold, both by acting on the presynaptic calcium transient to alter the distribution of amplitudes of multivesicular events. An increase in gain is accompanied by a decrease in the temporal precision of transmission and a reduction in the efficiency with which vesicles transfer visual information. The decrease in gain caused by Substance P was also associated with a shift in temporal filtering from band-pass to low-pass. This study demonstrates how neuromodulators act on the synaptic transformation of the visual signal to alter the way information is coded with vesicles.

scholarly journals Thenob2mouse, a null mutation inCacna1f: Anatomical and functional abnormalities in the outer retina and their consequences on ganglion cell visual responses

2006 ◽  
Vol 23 (1) ◽  
pp. 11-24 ◽  
Author(s):  
BO CHANG ◽  
JOHN R. HECKENLIVELY ◽  
PHILIPPA R. BAYLEY ◽  
NICHOLAS C. BRECHA ◽  
MURIEL T. DAVISSON ◽  
...  
Keyword(s):  
Visual Information ◽  
Synapse Formation ◽  
Dynamic Range ◽  
Outer Nuclear Layer ◽  
Glutamate Release ◽  
Plexiform Layer ◽  
Bipolar Cells ◽  
Null Mutation ◽  
Visual Responses

Glutamate release from photoreceptor terminals is controlled by voltage-dependent calcium channels (VDCCs). In humans, mutations in theCacna1fgene, encoding the α1Fsubunit of VDCCs, underlie the incomplete form of X-linked congenital stationary night blindness (CSNB2). These mutations impair synaptic transmission from rod and cone photoreceptors to bipolar cells. Here, we report anatomical and functional characterizations of the retina in thenob2(no b-wave 2) mouse, a naturally occurring mutant caused by a null mutation inCacna1f. Not surprisingly, theb-waves of both the light- and dark-adapted electroretinogram are abnormal innob2mice. The outer plexiform layer (OPL) is disorganized, with extension of ectopic neurites through the outer nuclear layer that originate from rod bipolar and horizontal cells, but not from hyperpolarizing bipolar cells. These ectopic neurites continue to express mGluR6, which is frequently associated with profiles that label with the presynaptic marker Ribeye, indicating potential points of ectopic synapse formation. However, the morphology of the presynaptic Ribeye-positive profiles is abnormal. While cone pedicles are present their morphology also appears compromised. Characterizations of visual responses in retinal ganglion cellsin vivo, under photopic conditions, demonstrate that ON-center cells have a reduced dynamic range, although their basic center-surround organization is retained; no alteration in the responses of OFF-center cells was evident. These results indicate thatnob2mice are a valuable model in which to explore the pathophysiological mechanisms associated withCacna1fmutations causing CSNB2, and the subsequent effects on visual information processing. Further, thenob2mouse represents a model system in which to define the signals that guide synapse formation and/or maintenance in the OPL.

Temporal Modulation of Scotopic Visual Signals by A17 Amacrine Cells in Mammalian Retina In Vivo

2003 ◽  
Vol 89 (4) ◽  
pp. 2159-2166 ◽  
Author(s):  
Cun-Jian Dong ◽  
William A. Hare
Keyword(s):  
Light Intensity ◽  
Visual Information ◽  
Amacrine Cells ◽  
Bipolar Cells ◽  
Visual Signals ◽  
Temporal Properties ◽  
Mammalian Retina ◽  
Show Evidence ◽  
Light Stimuli

We examined function of the feedback pathway from A17 GABAergic amacrine cells to rod bipolar cells (A17 feedback), a critically located inhibitory circuit in the classic rod pathway of the mammalian retina whose role in processing of scotopic visual information is still poorly understood. We show evidence that this A17 feedback has a profound influence on the temporal properties of rod-driven postphotoreceptoral responses (assessed with the scotopic electroretinogram b-wave). Application of a GABAcantagonist prolonged preferentially the decay of the scotopic b-wave. The degree of prolongation increased as the light intensity decreased. Application of selective GABAa antagonists accelerated the kinetics of the scotopic b-wave. This effect was abolished when the GABAc antagonist was coapplied. Selective ablation of A17 cells mimicked the action of the GABAc antagonist. In A17 cell–ablated retinas, the GABAc antagonist was no longer very effective to slow the decay of the scotopic b-wave. Thus the A17 feedback, activated by light stimulation and mediated mainly by the GABAc receptors, makes the scotopic b-wave more transient by accelerating preferentially its decay. The strength of the feedback can be modulated by GABAa receptor–mediated inhibition and by light intensity. Our results also suggest that in the mammalian retina the feedback may be a novel mechanism that contributes postphotoreceptorally to the termination of rod signals, especially those elicited by very dim light stimuli.

scholarly journals Heterogeneous Presynaptic Distribution of Munc13 Isoforms at Retinal Synapses and Identification of an Unconventional Bipolar Cell Type with Dual Expression of Munc13 Isoforms: A Study Using Munc13-EXFP Knock-in Mice

2020 ◽  
Vol 21 (21) ◽  
pp. 7848 ◽  
Author(s):  
Kaspar Gierke ◽  
Julia von Wittgenstein ◽  
Maike Hemmerlein ◽  
Jenny Atorf ◽  
Anneka Joachimsthaler ◽  
...  
Keyword(s):  
Synaptic Vesicles ◽  
Bipolar Cells ◽  
Visual Signal ◽  
Cell Type ◽  
Future Studies ◽  
Mammalian Retina ◽  
Chemical Synapses ◽  
Important Basis ◽  
The Brain

Munc13 isoforms are constituents of the presynaptic compartment of chemical synapses, where they govern important steps in preparing synaptic vesicles for exocytosis. The role of Munc13-1, -2 and -3 is well documented in brain neurons, but less is known about their function and distribution among the neurons of the retina and their conventional and ribbon-type chemical synapses. Here, we examined the retinae of Munc13-1-, -2-, and -3-EXFP knock-in (KI) mice with a combination of immunocytochemistry, physiology, and electron microscopy. We show that knock-in of Munc13-EXFP fusion proteins did not affect overall retinal anatomy or synapse structure, but slightly affected synaptic transmission. By labeling Munc13-EXFP KI retinae with specific antibodies against Munc13-1, -2 and -3, we found that unlike in the brain, most retinal synapses seem to operate with a single Munc13 isoform. A surprising exception to this rule was type 6 ON bipolar cells, which expressed two Munc13 isoforms in their synaptic terminals, ubMunc13-2 and Munc13-3. The results of this study provide an important basis for future studies on the contribution of Munc13 isoforms in visual signal processing in the mammalian retina.

scholarly journals Cross-Modal Effect of Presenting Visual and Force Feedback That Create the Illusion of Stair-Climbing

2021 ◽  
Vol 11 (7) ◽  
pp. 2987
Author(s):  
Takumi Okumura ◽  
Yuichi Kurita
Keyword(s):  
Visual Information ◽  
Force Feedback ◽  
Activity Level ◽  
Experimental Results ◽  
Stair Climbing ◽  
Mirror Therapy ◽  
Visual Condition ◽  
Stroke Patients ◽  
Head Mount Display ◽  
The Brain

Image therapy, which creates illusions with a mirror and a head mount display, assists movement relearning in stroke patients. Mirror therapy presents the movement of the unaffected limb in a mirror, creating the illusion of movement of the affected limb. As the visual information of images cannot create a fully immersive experience, we propose a cross-modal strategy that supplements the image with sensual information. By interacting with the stimuli received from multiple sensory organs, the brain complements missing senses, and the patient experiences a different sense of motion. Our system generates the sense of stair-climbing in a subject walking on a level floor. The force sensation is presented by a pneumatic gel muscle (PGM). Based on motion analysis in a human lower-limb model and the characteristics of the force exerted by the PGM, we set the appropriate air pressure of the PGM. The effectiveness of the proposed system was evaluated by surface electromyography and a questionnaire. The experimental results showed that by synchronizing the force sensation with visual information, we could match the motor and perceived sensations at the muscle-activity level, enhancing the sense of stair-climbing. The experimental results showed that the visual condition significantly improved the illusion intensity during stair-climbing.

scholarly journals Bio-Inspired Modality Fusion for Active Speaker Detection

2021 ◽  
Vol 11 (8) ◽  
pp. 3397
Author(s):  
Gustavo Assunção ◽  
Nuno Gonçalves ◽  
Paulo Menezes
Keyword(s):  
Superior Colliculus ◽  
Visual Information ◽  
Human Beings ◽  
Validation Process ◽  
Detection Approach ◽  
Wide Range ◽  
Speaker Detection ◽  
The One ◽  
The Brain ◽  
Fusion Ability

Human beings have developed fantastic abilities to integrate information from various sensory sources exploring their inherent complementarity. Perceptual capabilities are therefore heightened, enabling, for instance, the well-known "cocktail party" and McGurk effects, i.e., speech disambiguation from a panoply of sound signals. This fusion ability is also key in refining the perception of sound source location, as in distinguishing whose voice is being heard in a group conversation. Furthermore, neuroscience has successfully identified the superior colliculus region in the brain as the one responsible for this modality fusion, with a handful of biological models having been proposed to approach its underlying neurophysiological process. Deriving inspiration from one of these models, this paper presents a methodology for effectively fusing correlated auditory and visual information for active speaker detection. Such an ability can have a wide range of applications, from teleconferencing systems to social robotics. The detection approach initially routes auditory and visual information through two specialized neural network structures. The resulting embeddings are fused via a novel layer based on the superior colliculus, whose topological structure emulates spatial neuron cross-mapping of unimodal perceptual fields. The validation process employed two publicly available datasets, with achieved results confirming and greatly surpassing initial expectations.

Subcellular Localization and Complements of GABAA and GABAC Receptors on Bullfrog Retinal Bipolar Cells

2000 ◽  
Vol 84 (2) ◽  
pp. 666-676 ◽  
Author(s):  
Jiu-Lin Du ◽  
Xiong-Li Yang
Keyword(s):  
Subcellular Localization ◽  
Receptor Antagonist ◽  
Gaba Receptor ◽  
Drug Application ◽  
Bipolar Cells ◽  
Visual Signals ◽  
Receptor Subtypes ◽  
Inner Retina ◽  
Axon Terminals ◽  
Retinal Bipolar Cells

γ-Aminobutyric acid (GABA) receptors on retinal bipolar cells (BCs) are highly relevant to spatial and temporal integration of visual signals in the outer and inner retina. In the present work, subcellular localization and complements of GABAA and GABACreceptors on BCs were investigated by whole cell recordings and local drug application via multi-barreled puff pipettes in the bullfrog retinal slice preparation. Four types of the BCs (types 1–4) were identified morphologically by injection of Lucifer yellow. According to the ramification levels of the axon terminals and the responses of these cells to glutamate (or kainate) applied at their dendrites, types 1 and 2 of BCs were supposed to be off type, whereas types 3 and 4 of BCs might be on type. Bicuculline (BIC), a GABAA receptor antagonist, and imidazole-4-acetic acid (I4AA), a GABAC receptor antagonist, were used to distinguish GABA receptor-mediated responses. In all BCs tested, not only the axon terminals but also the dendrites showed high GABA sensitivity mediated by both GABAA and GABACreceptors. Subcellular localization and complements of GABAA and GABAC receptors at the dendrites and axon terminals were highly related to the dichotomy of offand on BCs. In the case of off BCs, GABAA receptors were rather evenly distributed at the dendrites and axon terminals, but GABAC receptors were predominantly expressed at the axon terminals. Moreover, the relative contribution of GABAC receptors to the axon terminals was prevalent over that of GABAA receptors, while the situation was reversed at the dendrites. In the case of on BCs, GABAA and GABAC receptors both preferred to be expressed at the axon terminals; relative contributions of these two GABA receptor subtypes to both the sites were comparable, while GABAC receptors were much less expressed than GABAA receptors. GABAA, but not GABAC receptors, were expressed clusteringly at axons of a population of BCs. In a minority of BCs, I4AA suppressed the GABAC responses at the dendrites, but not at the axon terminal, implying that the GABAC receptors at these two sites may be heterogeneous. Taken together, these results suggest that GABAA and GABAC receptors may play different roles in the outer and inner retina and the differential complements of the two receptors on off and on BCs may be closely related to physiological functions of these cells.

Retinal input influences pace of neurogenesis but not cell-type configuration of the visual forebrain

2021 ◽  
Author(s):  
Shachar Sherman ◽  
Koichi Kawakami ◽  
Herwig Baier
Keyword(s):  
Visual Information ◽  
Visual Stimulation ◽  
Ganglion Cells ◽  
Neuronal Cell ◽  
Cell Types ◽  
Vertebrate Brain ◽  
Relative Contribution ◽  
Retinal Input ◽  
And Migration ◽  
The Brain

The brain is assembled during development by both innate and experience-dependent mechanisms1-7, but the relative contribution of these factors is poorly understood. Axons of retinal ganglion cells (RGCs) connect the eye to the brain, forming a bottleneck for the transmission of visual information to central visual areas. RGCs secrete molecules from their axons that control proliferation, differentiation and migration of downstream components7-9. Spontaneously generated waves of retinal activity, but also intense visual stimulation, can entrain responses of RGCs10 and central neurons11-16. Here we asked how the cellular composition of central targets is altered in a vertebrate brain that is depleted of retinal input throughout development. For this, we first established a molecular catalog17 and gene expression atlas18 of neuronal subpopulations in the retinorecipient areas of larval zebrafish. We then searched for changes in lakritz (atoh7-) mutants, in which RGCs do not form19. Although individual forebrain-expressed genes are dysregulated in lakritz mutants, the complete set of 77 putative neuronal cell types in thalamus, pretectum and tectum are present. While neurogenesis and differentiation trajectories are overall unaltered, a greater proportion of cells remain in an uncommitted progenitor stage in the mutant. Optogenetic stimulation of a pretectal area20,21 evokes a visual behavior in blind mutants indistinguishable from wildtype. Our analysis shows that, in this vertebrate visual system, neurons are produced more slowly, but specified and wired up in a proper configuration in the absence of any retinal signals.

scholarly journals Homeostatic plasticity mechanisms in mouse V1

2017 ◽  
Vol 372 (1715) ◽  
pp. 20160504 ◽  
Author(s):  
Megumi Kaneko ◽  
Michael P. Stryker
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Neuronal Activity ◽  
Dynamic Range ◽  
Ocular Dominance ◽  
Homeostatic Plasticity ◽  
Ocular Dominance Plasticity ◽  
The Brain

Mechanisms thought of as homeostatic must exist to maintain neuronal activity in the brain within the dynamic range in which neurons can signal. Several distinct mechanisms have been demonstrated experimentally. Three mechanisms that act to restore levels of activity in the primary visual cortex of mice after occlusion and restoration of vision in one eye, which give rise to the phenomenon of ocular dominance plasticity, are discussed. The existence of different mechanisms raises the issue of how these mechanisms operate together to converge on the same set points of activity. This article is part of the themed issue ‘Integrating Hebbian and homeostatic plasticity’.

Context dependence of receptive field remapping in superior colliculus

2011 ◽  
Vol 106 (4) ◽  
pp. 1862-1874 ◽  
Author(s):  
Jan Churan ◽  
Daniel Guitton ◽  
Christopher C. Pack
Keyword(s):  
Receptive Field ◽  
Superior Colliculus ◽  
Visual Stimulation ◽  
Receptive Fields ◽  
Spatial Location ◽  
Macaque Monkey ◽  
Visual Signals ◽  
Perceptual Stability ◽  
Visual Background ◽  
The Brain

Our perception of the positions of objects in our surroundings is surprisingly unaffected by movements of the eyes, head, and body. This suggests that the brain has a mechanism for maintaining perceptual stability, based either on the spatial relationships among visible objects or internal copies of its own motor commands. Strong evidence for the latter mechanism comes from the remapping of visual receptive fields that occurs around the time of a saccade. Remapping occurs when a single neuron responds to visual stimuli placed presaccadically in the spatial location that will be occupied by its receptive field after the completion of a saccade. Although evidence for remapping has been found in many brain areas, relatively little is known about how it interacts with sensory context. This interaction is important for understanding perceptual stability more generally, as the brain may rely on extraretinal signals or visual signals to different degrees in different contexts. Here, we have studied the interaction between visual stimulation and remapping by recording from single neurons in the superior colliculus of the macaque monkey, using several different visual stimulus conditions. We find that remapping responses are highly sensitive to low-level visual signals, with the overall luminance of the visual background exerting a particularly powerful influence. Specifically, although remapping was fairly common in complete darkness, such responses were usually decreased or abolished in the presence of modest background illumination. Thus the brain might make use of a strategy that emphasizes visual landmarks over extraretinal signals whenever the former are available.

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