Abstract

The human spectral luminosity function (Vλ) can be modeled as the linear sum of signals from long-wavelength-selective (L) and middle-wavelength-selective (M) cones, with L cones being weighted by a factor of ∼2. This factor of ∼2 is thought to reflect an approximate 2:1 ratio of L:M cones in the human retina, which has been supported by studies that allow for more direct counting of different cone types in the retina. In contrast to humans, several lines of retinally based evidence in macaques suggest an L:M ratio closer to 1:1. To investigate the consequences of differences in L:M cone ratios between humans and macaques, red–green equiluminance matches obtained psychophysically in humans (n=11) were compared with those obtained electrophysiologically from single neurons in the extrastriate middle temporal visual area of macaques (M. mulatta, n=5). Neurons in the middle temporal visual area were tested with sinusoidal red–green moving gratings across a range of luminance contrasts, with equiluminance being defined as the red–green contrast yielding a response minimum. Human subjects were tested under analogous conditions, by a minimally distinct motion technique, to establish psychophysical equiluminance. Although red–green equiluminance points in both humans and macaques were found to vary across individuals, the means across species differed significantly; compared with humans, macaque equiluminance points reflected relatively greater sensitivity to green. By means of a simple model based on equating the weighted sum of L and M cone signals, the observed red–green equiluminance points were found to be consistent with L:M cone ratios of approximately 2:1 in humans and 1:1 in macaques. These data thus support retinally based estimates of L:M cone ratios and further demonstrate that the information carried in the cone mosaic has functional consequences for red–green spectral sensitivity revealed perceptually and in the dorsal stream of visual cortex.

© 2000 Optical Society of America

Full Article  |  PDF Article

References

You do not have subscription access to this journal. Citation lists with outbound citation links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Cited By

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Figures (3)

You do not have subscription access to this journal. Figure files are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Tables (3)

You do not have subscription access to this journal. Article tables are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Equations (2)

You do not have subscription access to this journal. Equations are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Metrics

You do not have subscription access to this journal. Article level metrics are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription