Purchase this article with an account.
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.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
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.
This PDF is available to Subscribers Only