Cite as:
Shapiro A G, Baldwin L A, Mollon J D, 2002, "The S and L - M chromatic systems have matched temporal processing characteristics only at low-light levels" Perception 31 ECVP Abstract Supplement

The S and L - M chromatic systems have matched temporal processing characteristics only at low-light levels

A G Shapiro, L A Baldwin, J D Mollon

McKeefry et al (2001 Vision Research 41 245 - 255) found that the S and L - M chromatic systems are matched in sensitivity for temporal modulation, whereas earlier studies claimed that the L - M system has a faster response than the S system. McKeefry et al took great care to eliminate luminance artifacts; it is therefore possible that previous measurements of chromatic sensitivity are contaminated at high frequencies by L - M signals entering the magnocellular pathway. However, it is also possible that differences between the S and L - M temporal response are light-level dependent. We measured temporal sensitivity functions for S and L - M lights at three different light levels (6, 20, and 60 cd m^-2) on a CRT monitor. The test light was an annulus with a 3 deg outer diameter divided into four segments. To control for luminance artifacts, one of the segments contained a temporally modulated chromatic signal embedded in a field of broadband noise; the other three segments contained noise only. We confirm the McKeefry et al finding that the S and L - M chromatic systems have matched temporal responses at 6 cd m^-2 (approximately the same luminance as was used in their study). At higher light levels, however, the L - M system is faster than the S system in some conditions.

[Supported by NEI grant R15-EY12946.]

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