Rod and cone interactions in the retina

Fain, Gordon; Sampath, Alapakkam P.

doi:10.12688/f1000research.14412.1

Cited by 54 publications

(39 citation statements)

References 83 publications

(101 reference statements)

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“…Cones can be identified without the use of fluorescent dyes or any other marking procedure, obviating the need to expose the photoreceptors to light before recording. Recordings can be made not only from dark-adapted WT cones but also from mutant mouse lines, in particular from Gnat −/− cones lacking rod input through rod/cone gap junctions, and from Cx36 −/− cones, which lack gap junctions connecting cones to other photoreceptors (see Fain and Sampath, 2018). We have taken advantage of this preparation to investigate the properties of the membrane conductances of mammalian cone photoreceptors.…”

Section: Resultsmentioning

confidence: 99%

Membrane conductances of mouse cone photoreceptors

Ingram

Sampath

Fain

2020

Journal of General Physiology

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Vertebrate photoreceptor cells respond to light through a closure of CNG channels located in the outer segment. Multiple voltage-sensitive channels in the photoreceptor inner segment serve to transform and transmit the light-induced outer-segment current response. Despite extensive studies in lower vertebrates, we do not know how these channels produce the photoresponse of mammalian photoreceptors. Here we examined these ionic conductances recorded from single mouse cones in unlabeled, dark-adapted retinal slices. First, we show measurements of the voltage dependence of the light response. After block of voltage-gated Ca2+ channels, the light-dependent current was nearly linear within the physiological range of voltages with constant chord conductance and a reversal potential similar to that previously determined in lower vertebrate photoreceptors. At a dark resting membrane potential of −45 mV, cones maintain a standing Ca2+ current (iCa) between 15 and 20 pA. We characterized the time and voltage dependence of iCa and a calcium-activated anion channel. After constitutive closure of the CNG channels by the nonhydrolysable analogue GTP-γ-S, we observed a light-dependent increase in iCa followed by a Ca2+-activated K+ current, both probably the result of feedback from horizontal cells. We also recorded the hyperpolarization-activated cyclic nucleotide-gated (HCN) conductance (ih) and measured its current-voltage relationship and reversal potential. With small hyperpolarizations, ih activated with a time constant of 25 ms; activation was speeded with larger hyperpolarizations. Finally, we characterized two voltage-gated K+-conductances (iK). Depolarizing steps beginning at −10 mV activated a transient, outwardly rectifying iK blocked by 4-AP and insensitive to TEA. A sustained iK isolated through subtraction was blocked by TEA but was insensitive to 4-AP. The sustained iK had a nearly linear voltage dependence throughout the physiological voltage range of the cone. Together these data constitute the first comprehensive study of the channel conductances of mouse photoreceptors.

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Section: Resultsmentioning

confidence: 99%

Membrane conductances of mouse cone photoreceptors

Ingram

Sampath

Fain

2020

Journal of General Physiology

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“…The interaction of rod and cone pathways occurs at virtually every stage in the retina, 93 making difficult the prediction of visual function following the loss of photoreceptors. The imaging of cones nearer vs farther from the fovea (Figure 9) clearly indicates the potential for much more interaction among rods and cones outside the fovea.…”

Section: Discussionmentioning

confidence: 99%

Cones in ageing and harsh environments: the neural economy hypothesis

Elsner

Papay

Johnston

et al. 2020

Ophthalmic Physiologic Optic

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Purpose Cones are at great risk in a wide variety of retinal diseases, especially when there is a harsh microenvironment and retinal pigment epithelium is damaged. We provide established and new methods for assessing cones and retinal pigment epithelium, together with new results. We investigated conditions under which cones can be imaged and could guide light, despite the proximity of less than ideal retinal pigment epithelium. Recent findings We used a variety of imaging methods to detect and localise damage to the retinal pigment epithelium. As age‐related macular degeneration is a particularly widespread disease, we imaged clinical hallmarks: drusen and hyperpigmentation. Using near infrared light provided improved imaging of the deeper fundus layers. We compared confocal and multiply scattered light images, using both the variation of detection apertures and polarisation analysis. We used optical coherence tomography to examine distances between structures and thickness of retinal layers, as well as identifying damage to the retinal pigment epithelium. We counted cones using adaptive optics scanning laser ophthalmoscopy. We compared the results of five subjects with geographic atrophy to data from a previous normative ageing study. Using near infrared imaging and layer analysis of optical coherence tomography, the widespread aspect of drusen became evident. Both multiply scattered light imaging and analysis of the volume in the retinal pigment epithelial layer from the optical coherence tomography were effective in localising drusen and hyperpigmentation beneath the photoreceptors. Cone photoreceptors in normal older eyes were shorter than in younger eyes. Cone photoreceptors survived in regions of atrophy, but with greatly reduced and highly variable density. Regular arrays of cones were found in some locations, despite abnormal retinal pigment epithelium. For some subjects, the cone density was significantly greater than normative values in some retinal locations outside the atrophy. Summary The survival of cones within atrophy is remarkable. The unusually dense packing of cones at some retinal locations outside the atrophy indicates more fluidity in cone distribution than typically thought. Together these findings suggest strategies for therapy that includes preserving cones.

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“…We propose that the mutual information, a measure of association between two discrete spatial points, will determine the perception of how close two spatial points from each other are. Furthermore, since there is direct electrical coupling formed by the gap junctions between the rods and cones in different animals including primates [34][35][36], there will be an increase in the joint probability of their activation, increasing mutual information.…”

Section: Retinal Processing Of Visual Informationmentioning

confidence: 99%

“…We propose that robust increases in mutual information, measuring the association between the characteristics of sensory inputs and neural circuits connectivity patterns, are partly responsible for perception and successful motor interactions with physical surroundings. It is also argued that perception from a sensory input is the result of networking of many circuits to a common circuit that primarily processes the given sensory input.Furthermore, the mutual information processed from the rods and cones will be also affected by other complex interactions within the retinal circuitry as reviewed recently [36], which could help us understand the basis of color, depth or texture perception.…”

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confidence: 99%

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Increase in Mutual Information During Interaction of the Brain with Environment Contributes to Perception

Gupta¹,

Bahmer²

2019

Preprint

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Perception and motor interaction with physical surroundings can be analyzed by the changes in probability laws governing two possible outcomes of neuronal activity, namely the presence or absence of spikes (binary states). Perception and motor interaction with physical environment are accounted partly by the reduction in entropy within the probability distributions of binary states of neurons in distributed neural circuits, given the knowledge about the characteristics of stimuli in physical surroundings. This reduction in the total entropy of multiple pairs of circuits in networks, by an amount equal to the increase of mutual information among them, occurs as sensory information is processed successively from lower to higher cortical areas or between different areas at the same hierarchical level but belonging to different networks. The increase in mutual information is partly accounted by temporal coupling as well as synaptic connections as proposed by Bahmer and Gupta [1]. We propose that robust increases in mutual information, measuring the association between the characteristics of sensory inputs and neural circuits connectivity patterns, are partly responsible for perception and successful motor interactions with physical surroundings. It is also argued that perception from a sensory input is the result of networking of many circuits to a common circuit that primarily processes the given sensory input.

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Rod and cone interactions in the retina

Cited by 54 publications

References 83 publications

Membrane conductances of mouse cone photoreceptors

Membrane conductances of mouse cone photoreceptors

Cones in ageing and harsh environments: the neural economy hypothesis

Increase in Mutual Information During Interaction of the Brain with Environment Contributes to Perception

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