Photoreceptor inputs to cat lateral geniculate nucleus cells

The spectral sensitivities of single on- and off-centre, brisk sustained and brisk transient cells recorded from the A laminae of the lateral geniculate nucleus (LGNd) in cats anaesthetised with nitrous oxide and oxygen supplemented with halothane were measured under photopic and mesopic achromatic adapting conditions. All cells possessed spectral sensitivity functions with a single peak at about 556 nm under photopic conditions. Intense chromatic adapting fields superimposed on the photopic background affected neither the shape of the spectral sensitivity functions nor the position of the peak wavelength. Under mesopic adapting conditions cells possessed spectral sensitivities with two peaks, one at 507 nm and one at 556 nm. These results are interpreted as suggesting that the cells of the A laminae of the LGNd receive inputs from rods with maximum sensitivity at 507 nm and a single class of cones maximally sensitive at 556 nm.