May 2003
Volume 44, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2003
The Physiological Origin of Chromatic Response Components in Signals of the Magnocellular Pathway of the Macaque
Author Affiliations & Notes
  • B.B. Lee
    Biological Sciences, SUNY Optometry, New York, NY, United States
  • H. Sun
    Biological Sciences, SUNY Optometry, New York, NY, United States
  • Footnotes
    Commercial Relationships  B.B. Lee, None; H. Sun, None.
  • Footnotes
    Support  EY13112
Investigative Ophthalmology & Visual Science May 2003, Vol.44, 3250. doi:
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      B.B. Lee, H. Sun; The Physiological Origin of Chromatic Response Components in Signals of the Magnocellular Pathway of the Macaque . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3250.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Abstract: : Purpose: Magnocellular (MC) cells show a first-harmonic response to chromatic modulation at low temporal frequencies but at higher frequencies a second-harmonic (2F) response becomes dominant. We attempt to elucidate the physiological basis of these response components. Methods: Responses of MC cells to various mixtures of luminance and chromatic modulation were measured in a variety of spatial configurations. Results: The 2F non-linearity occurs to some degree even with cone isolating stimuli, so that the hypothesis that the 2F response is due to a non-linearity of M and L cone summation is disproven. As the modulation approaches isoluminance, the 2F response develops due to a splitting up of the 1F response peak. This characteristic phase signature can be modelled assuming it represents a rectified chromatic signal to the surround. Both the chromatic response and the 2F response disappear with spot stimuli just covering the center, suggesting a surround origin. However, experiments with annuli showed that both responses derive from a restricted surround region, beyond which the surround is achromatic. Conclusions: The similar spatial extents suggest that the chromatic and the 2F response derive from the same mechanism. This could derive from some form of leaky rectification of chromatic signals, such as might arise from midget bipolars.

Keywords: ganglion cells • receptive fields • color vision 
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