Fig. 11

ON-OFF opponent ganglion cell spectral patterns. A: in this cell both ON and OFF discharges are prominent particularly with UV excitation (370 nm, 330 nm). At long wavelengths (650 nm, 610 nm, 570 nm) only an OFF discharge is apparent (at ∼500 ms), with a suggestion of impulse silencing during stimulation. Wavelengths appear above each nested set of 3 spike-rate discharge records, which are in response to dim, intermediate, and bright irradiances. The irradiances, selected from 7 total at each wavelength, are matched for comparable quantal stimulation. These are equal quantal responses across wavelengths. The quantal brightness of each monochromatic stimulus is given in log(hν·µm⁻²·s⁻¹) on left of each stimulus trace. B: mean response waveforms for all stimuli at long (650–570 nm), middle (530–490 nm), and short (370–330 nm) wavelengths. At middle wavelengths there is discharge quieting, at long wavelengths an OFF response, and at short wavelength an ON-OFF pattern. ON (C) and OFF (C′) responses are fit by different spectral models, both opponent but employing different numbers of cone opsin signals. All onset model cone signals are included in the offset model, but further cone signals are added. + and − are the probabilities of nonzero excitatory and inhibitory cone opsin signals, following the GraphPad convention for significance (t tests). Modeled discharge amplitude spectra for constant quantal irradiances at ON (D) and OFF (D′): the response onset model (model 36) is trichromatic but generates 4 spectral phases. Long-wavelength excitation is absent. The offset model (model 125) is hexachromatic and pentaphasic. The stimulus protocol is Cs2 (280 stimuli).