Magnocellular channel subserves the human contrast-sensitivity function |
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Authors: | Plainis Sotiris Murray Ian J |
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Institution: | Vardinoyiannion Eye Institute of Crete (VEIC), Department of Ophthalmology, School of Medicine, University of Crete, PO Box 2208, Heraklion, Crete, Greece. plainis@med.uoc.gr |
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Abstract: | There is evidence that the human contrast-sensitivity function (CSF) is mediated by the spatiotemporal characteristics of magno and parvo neurons early in the visual pathway. In this study we use a measure of contrast gain derived from simple reaction times, to investigate the neural substrates of suprathreshold performance. The results reveal the activity of two mechanisms having distinctly different contrast-gain characteristics. Comparing these to neurophysiological data, we find that the magnocellular system dominates close-to-threshold detection and probably forms the basis of the achromatic CSF, whereas the parvocellular system dominates detection at higher contrasts, when the magnocellular system saturates. |
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