RETINAL PROCESSING NEAR ABSOLUTE THRESHOLD: From Behavior to Mechanism

Field, Greg D.; Sampath, Alapakkam P.; Rieke, Fred

doi:10.1146/annurev.physiol.67.031103.151256

Cited by 190 publications

(211 citation statements)

References 92 publications

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“…This value is well below the background light required for background adaptation of mammalian rods (equivalent to~30 to 50 Meta-II Rho per rod cell per second) (33). Moreover, if signaling of free opsin, like the continuous noise, exhibits high frequency and low amplitude, it may be filtered by the nonlinearity of rod-to-rod bipolar synapses (30). In earlier studies, exogenous supply of 11CR to dark-adapted rod cells failed to enhance rod sensitivity, suggesting that the small population of free opsin indeed does not cause elevated threshold (3).…”

Section: The Physiological Implications Of Free Opsin In Rod Cell Sigmentioning

confidence: 91%

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Measurement of Slow Spontaneous Release of 11-cis-Retinal from Rhodopsin

Tian

Sakmar

Huber

2017

Biophysical Journal

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The vertebrate visual photoreceptor rhodopsin (Rho) is a unique G protein-coupled receptor as it utilizes a covalently tethered inverse agonist (11-cis-retinal) as the native ligand. Previously, electrophysiological studies showed that ligand binding of 11-cis-retinal in dark-adapted Rho was essentially irreversible with a half-life estimated to be 420 years, until after thermal isomerization to all-trans-retinal, which then slowly dissociates. This long lifetime of 11-cis-retinal binding was considered to be physiologically important for minimizing background signal (dark noise) of the visual system. However, in vitro biochemical studies on the thermal stability of Rho showed that Rho decays with a half-life on the order of days. In this study, we resolve the discrepancy by measuring the chromophore exchange rate of the bound 11-cis-retinal chromophore with free 9-cis-retinal from Rho in an in vitro phospholipid/detergent bicelle system. We conclude that the thermal decay of Rho primarily proceeds through spontaneous breaking of the covalent linkage between opsin and 11-cis-retinal, which was overlooked in the electrophysiological recording. We estimate that this slow spontaneous release of 11-cis-retinal from Rho should result in 10 4 to 10 5 free opsin molecules in a dark-adapted rod cell-a number that is three orders of magnitude higher than previously expected. We also discuss the physiological implications of these findings on the basal activity of opsins and the associated dark noise in the visual system.

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Section: The Physiological Implications Of Free Opsin In Rod Cell Sigmentioning

confidence: 91%

“…In salamander rods, the continuous component was shown to be independent of G protein (29). The discrete component corresponding to the thermal isomerization events is thought to set the rod visual threshold (30).…”

Section: The Physiological Implications Of Free Opsin In Rod Cell Sigmentioning

confidence: 99%

Measurement of Slow Spontaneous Release of 11-cis-Retinal from Rhodopsin

Tian

Sakmar

Huber

2017

Biophysical Journal

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“…Previous work has led to the hypothesis that the main neural limit to visual sensitivity is physiological noise caused by spontaneous activation of rhodopsin in the rods (for review, see Field et al, 2005); this noise is indistinguishable from the signal produced by photon absorption. This hypothesis, if true, indicates that downstream processing of rod signals is efficient and nearly noiseless.…”

Section: Introductionmentioning

confidence: 99%

Detection Sensitivity and Temporal Resolution of Visual Signals near Absolute Threshold in the Salamander Retina

Chichilnisky¹,

Rieke²

2005

J. Neurosci.

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Several studies have suggested that the visual system can detect dim lights with a fidelity limited only by Poisson fluctuations in photon absorption and spontaneous activation of rhodopsin. If correct, this implies that neural processing of responses produced by rod photoreceptors is efficient and effectively noiseless. However, experimental uncertainty makes this conclusion tenuous. Furthermore, previous work provided no information about how accurately stimulus timing is represented. Here, the detection sensitivity and temporal resolution of salamander rods and retinal ganglion cells (RGCs) are compared in nearly matched experimental conditions by using recorded responses to identify the time of a flash. At detection threshold, RGCs could reliably signal the absorption of 20 -50 photons, but the rods within the RGC receptive field could signal stimuli 3-10 times weaker. For flash strengths 10 times higher than detection threshold, some RGCs could distinguish stimulus timing with a resolution finer than 100 msec, within a factor of 2 of the rod limit. The relationship between RGC and rod sensitivity could not be explained by added noise in the retinal circuitry but could be explained by a threshold acting after pooling of rod signals. Simulations of rod signals indicated that continuous noise, rather than spontaneous activation of rhodopsin or fluctuations in the single-photon response, limited temporal resolution. Thus, detection of dim lights was limited by retinal processing, but, at higher light levels, synaptic transmission, cellular integration of synaptic inputs, and spike generation in RGCs faithfully conveyed information about the time of photon absorption.

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“…However, visual information processing is complex, even in its early stages; this fact is very clear when considering that although photoreceptors compute photons, human beings see much more complex visual entities. Indeed, an individual is unable to tell the amount of photons present in things he sees (Field, Sampath, & Rieke, 2005;Hecht, Shlaer, & Pirenne, 1942).…”

Section: The Computational Brainmentioning

confidence: 99%

A neurociência computacional no estudo dos processos cognitivos

Leopoldo

Joselevitch

2018

Psicol. USP

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Abstract:In recent decades the study of cognitive processes has been influenced by two tendencies: legitimation of several forms and levels of study and the attempt of multidisciplinary integration. The first had great importance in the second half of the 20th century, when research lines in cognitive psychology and neuroscience were strengthened. In this sense, Marr's three levels of analysis (computational, algorithmic, and implementation) are one way to structure the study of cognitive processes. The second tendency is more recent and, supported by the first one, seeks to deepen the understanding of cognitive processes in their different scales and to integrate several paradigms of studies in order to reach theoretical consilience. This article aims to introduce computational neuroscience and its possible contributions to cognitive psychology, articulating, through Marr's three levels, a theoretical basis that explains the role of each of the disciplines and their possible interactions.

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RETINAL PROCESSING NEAR ABSOLUTE THRESHOLD: From Behavior to Mechanism

Cited by 190 publications

References 92 publications

Measurement of Slow Spontaneous Release of 11-cis-Retinal from Rhodopsin

Measurement of Slow Spontaneous Release of 11-cis-Retinal from Rhodopsin

Detection Sensitivity and Temporal Resolution of Visual Signals near Absolute Threshold in the Salamander Retina

A neurociência computacional no estudo dos processos cognitivos

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