| Retinal ganglion cell adaptation to small luminance fluctuations. | |
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MedLine Citation:
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PMID: 20538771 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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To accommodate the wide input range over which the visual system operates within the narrow output range of spiking neurons, the retina adjusts its sensitivity to the mean light level so that retinal ganglion cells can faithfully signal contrast, or relative deviations from the mean luminance. Given the large operating range of the visual system, the majority of work on luminance adaptation has involved logarithmic changes in light level. We report that luminance gain controls are recruited for remarkably small fluctuations in luminance as well. Using spike recordings from the rat optic tract, we show that ganglion cell responses to a brief flash of light are modulated in amplitude by local background fluctuations as little as 15% contrast. The time scale of the gain control is rapid (<125 ms), at least for on cells. The retinal locus of adaptation precedes the ganglion cell spike generator because response gain changes of on cells were uncorrelated with firing rate. The mechanism seems to reside within the inner retinal network and not in the photoreceptors, because the adaptation profiles of on and off cells differed markedly. The response gain changes follow Weber's law, suggesting that network mechanisms of luminance adaptation described in previous work modulates retinal ganglion cell sensitivity, not just when we move between different lighting environments, but also as our eyes scan a visual scene. Finally, we show that response amplitude is uniformly reduced for flashes on a modulated background that has spatial contrast, indicating that another gain control that integrates luminance signals nonlinearly over space operates within the receptive field center of rat ganglion cells. |
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Authors:
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Daniel K Freeman; Gilberto Graña; Christopher L Passaglia |
Publication Detail:
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Type: Journal Article Date: 2010-06-10 |
Journal Detail:
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Title: Journal of neurophysiology Volume: 104 ISSN: 1522-1598 ISO Abbreviation: J. Neurophysiol. Publication Date: 2010 Aug |
Date Detail:
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Created Date: 2010-08-16 Completed Date: 2010-12-01 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0375404 Medline TA: J Neurophysiol Country: United States |
Other Details:
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Languages: eng Pagination: 704-12 Citation Subset: IM |
Affiliation:
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Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Action Potentials
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physiology Adaptation, Physiological / physiology* Animals Contrast Sensitivity / physiology* Models, Neurological Nonlinear Dynamics Photic Stimulation / methods Rats Retina / cytology Retinal Ganglion Cells / physiology* |
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