Magnocellular channel subserves the human contrast-sensitivity function.
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.
Plainis
Sotiris
S
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
Murray
Ian J
IJ
D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D011601:Psychophysics; D011930:Reaction Time; D012165:Retinal Ganglion Cells / Q000502:physiology*; D012684:Sensory Thresholds; D014795:Visual Pathways / Q000502:physiology*