Nonlinear Signal Transfer from Mouse Rods to Bipolar Cells and Implications for Visual Sensitivity

Field, Greg D.; Rieke, Fred

doi:10.1016/s0896-6273(02)00700-6

Cited by 285 publications

(392 citation statements)

References 33 publications

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“…9 The synapse from the rod photoreceptor is reliably able to transmit the discrete quantal responses to the rod bipolar cell (RBC), as discovered from measurements of ERG b-wave sensitivity 12 and from single-cell recordings. 13,14 The postsynaptic terminal at this synapse utilises a metabotropic mechanism involving a high-gain G protein-coupled cascade (reviewed in Morgans et al 15 ). Remarkably, this cascade is broadly similar to that used in phototransduction and, as in the case of rhabdomeric photoreceptors, the final stage involves a TRP ion channel.…”

Section: Contrast Sensitivitymentioning

confidence: 99%

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Why rods and cones?

Lamb

2015

Eye

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Under twenty-first-century metropolitan conditions, almost all of our vision is mediated by cones and the photopic system, yet cones make up barely 5% of our retinal photoreceptors. This paper looks at reasons why we additionally possess rods and a scotopic system, and asks why rods comprise 95% of our retinal photoreceptors. It considers the ability of rods to reliably signal the arrival of individual photons of light, as well as the ability of the retina to process these singlephoton signals, and it discusses the advantages that accrue. Drawbacks in the arrangement, including the very slow dark adaptation of scotopic vision, are also considered. Finally, the timing of the evolution of cone and rod photoreceptors, the retina, and the camera-style eye is summarised.

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Section: Contrast Sensitivitymentioning

confidence: 99%

“…This rod synapse appears to operate in a thresholding mode, substantially removing the ongoing photoreceptor dark noise. [12][13][14] As a result, the response of the RBC comprises discrete single-photon events from each of the rods that synapse onto it, so that it too functions in a 'photon detecting mode'.…”

Section: Contrast Sensitivitymentioning

confidence: 99%

Why rods and cones?

Lamb

2015

Eye

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“…Photon densities measured at the preparation were converted to photoisomerizations per rod (Rh*/rod) assuming a collecting area of 0.5 μm 2 (ref. 25). All experiments were at 35-37 °C.…”

Section: Recordings From Rods and Rod Bipolar Cellsmentioning

confidence: 99%

Essential role of Ca2+-binding protein 4, a Cav1.4 channel regulator, in photoreceptor synaptic function

et al. 2004

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CaBP1-8 are neuronal Ca 2+ -binding proteins with similarity to calmodulin (CaM). Here we show that CaBP4 is specifically expressed in photoreceptors, where it is localized to synaptic terminals. The outer plexiform layer, which contains the photoreceptor synapses with secondary neurons, was thinner in the Cabp4 −/− mice than in control mice. Cabp4 −/− retinas also had ectopic synapses originating from rod bipolar and horizontal cells that extended into the outer nuclear layer. Responses of Cabp4 −/− rod bipolars were reduced in sensitivity about 100-fold. Electroretinograms (ERGs) indicated a reduction in cone and rod synaptic function. The phenotype of Cabp4 −/− mice shares similarities with that of incomplete congenital stationary night blindness (CSNB2) patients. CaBP4 directly associated with the C-terminal domain of the Ca v 1.4 α 1 -subunit and shifted the activation of Ca v 1.4 to hyperpolarized voltages in transfected cells. These observations indicate that CaBP4 is important for normal synaptic function, probably through regulation of Ca 2+ influx and neurotransmitter release in photoreceptor synaptic terminals.L-type Ca 2+ channels are involved in neuronal differentiation and outgrowth and in synaptic plasticity 1,2 . At many ribbon synapses, Ca 2+ influx through L-type Ca 2+ channels triggers neurotransmitter release 3-5 . The α 1 -subunit of the L-type Ca v 1.4 channel (Ca v 1.4α1) is specific to photoreceptors and is present at highest density in the synaptic terminals 5,6 . Compared with other L-type Ca 2+ channels, Ca v 1.4 channels are activated at relatively more negative voltages and show slow inactivation 7-9 , important properties for the ability of photoreceptors to sustain continual glutamate release in the dark 4,10 . Null mutations in Ca v 1.4α1 are responsible for an X-linked disorder, CSNB2 (refs. 11 ,12 ). ERGs of these patients indicate that a deficit may occur in transmission of signals from rod photoreceptors to bipolar cells. In mice, deletion of the β 2 -subunit, another component of the photoreceptor L-type channel, alters the expression of Ca v 1.4 and produces a phenotype similar to that seen in CSNB2 patients 13 .CaBPs, a subfamily of calmodulin (CaM)-like neuronal Ca 2+ -binding proteins 14 , modulate voltage-dependent Ca 2+ channels (VDCCs) and inositol triphosphate receptors 15-17 . Here we show that CaBP4, which has only been partially characterized in silico 14 , is found specifically

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“…However, the cost of discarded signals is more than compensated for by the benefits of eliminating noise. The net effect of the thresholding nonlinearity at this synapse is a several-hundred-fold increase in SNR [45].…”

Section: How Do Retinal Circuits Relay Single-photon Responses To Retmentioning

confidence: 99%

“…As described above, continuous noise is omnipresent in the rod photocurrent and threatens to swamp rare photon detection events when signals from many rods are pooled in the retina and brain. Unless rod signals are processed with an appropriately set nonlinearity, visual threshold will be degraded by continuous noise such that limits imposed by the spontaneous activation of rhodopsin cannot be reached [38,45,51]. This raises the question, does continuous noise or discrete noise limit vision?…”

Section: What Is the Limiting Noise Source?mentioning

confidence: 99%

Behavioural and physiological limits to vision in mammals

Field

Sampath²

2017

Phil. Trans. R. Soc. B

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Human vision is exquisitely sensitive-a dark-adapted observer is capable of reliably detecting the absorption of a few quanta of light. Such sensitivity requires that the sensory receptors of the retina, rod photoreceptors, generate a reliable signal when single photons are absorbed. In addition, the retina must be able to extract this information and relay it to higher visual centres under conditions where very few rods signal single-photon responses while the majority generate only noise. Critical to signal transmission are mechanistic optimizations within rods and their dedicated retinal circuits that enhance the discriminability of single-photon responses by mitigating photoreceptor and synaptic noise. We describe behavioural experiments over the past century that have led to the appreciation of high sensitivity near absolute visual threshold. We further consider mechanisms within rod photoreceptors and dedicated rod circuits that act to extract single-photon responses from cellular noise. We highlight how these studies have shaped our understanding of brain function and point out several unresolved questions in the processing of light near the visual threshold.This article is part of the themed issue 'Vision in dim light'.

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Nonlinear Signal Transfer from Mouse Rods to Bipolar Cells and Implications for Visual Sensitivity

Cited by 285 publications

References 33 publications

Why rods and cones?

Why rods and cones?

Essential role of Ca2+-binding protein 4, a Cav1.4 channel regulator, in photoreceptor synaptic function

Behavioural and physiological limits to vision in mammals

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