Electrophysiological measurements of the spectral sensitivity of three types of cones in the carp retina.

The spectral sensitivities of red-, green-, and blue-sensitive cones were measured by intracellular recording in the carp retina. The responses from all cones were univariant, i.e., the waveform of a response to any wavelength and at any intensity could be superimposed on the response to other wavelengths if the intensity was properly selected. Red-sensitive cones showed a maximum sensitivity at about 620 nm, green-sensitive cones at about 520 nm, and blue-sensitive cones at about 460 nm. The peak wavelengths and general forms of the spectral sensitivity curves agreed with those of the spectral absorption curves measured by microspectrophotometry (MSP), but the sensitivity of red-sensitive cones at both ends of the spectrum was significantly lower than the spectral absorption determined by MSP.