The L/M-Opponent Channel Provides a Distinct and Time-Dependent Contribution towards Visual Recognition

The visual pathway has been successfully modelled as containing separate channels consisting of one achromatically opponent mechanism and two chromatically opponent mechanisms. However, little is known about how time affects the processing of chromatic information. Here, parametrically defined objects were generated. Reduced-colour objects were interleaved with full-colour objects and measures of recognition performance (d′) were compared by the continuous serial recognition paradigm. Measures were taken at multiple delay intervals (1, 4, 7, and 10 s). When chromatic variations were removed, recognition performance was impaired, but at the 1 s and 10 s intervals only. When luminance variations were removed, no impairment resulted. When only L/M-opponent modulations were removed, a deficit in performance was produced only at the 1 s and 10 s intervals, similar to the removal of chromatic variation. When only S-opponent modulations were removed, no impairment was observed. The results suggest that the L/M-opponent pathway provides a specialised contribution to visual recognition, but that its effect is modulated by time. A three-stage process model is proposed to explain the data.