Figure 1.

Detection of colour opponent units. (A) Categorisation of all units that were responsive to 67% Michelson contrast stimuli (n = 1,429) based on their response to L- and/or S-cone-selective contrast modulation (0.25 Hz square wave). (B) Spectral composition of the stimulus pairs used to isolate cone-based responses. Dashed filled line: low, solid line: high. (C) Relative photon absorbance (log₁₀ photons) and Michelson contrast for each photopigment under each condition. (D–G) Mean ± SEM responses of example units for each of the cone isolating stimuli shown in (B,C) (n = 100 trials/stimulus); (D) non-opponent S-ON response, (E) non-opponent L-OFF response, (F) S-ON/L-OFF colour-opponent cell, (G) L-ON/S-OFF colour-opponent cell. (H) The mean ± SEM population response of S-ON/L-OFF (n = 36) colour opponent cells.