Pollen D A, Ronner S F
Vision Res. 1982;22(1):101-18. doi: 10.1016/0042-6989(82)90172-9.
Simple and complex cells have been tested with drifting sine-wave and square-wave gratings. Despite the known differences in the response pattern of each cell type to drifting sine-wave gratings, the tuning curves for square-wave gratings for both cell types show a similar secondary response band peaking at one-third the preferred spatial frequency as determined from sine-wave studies. These results establish that both cell types respond predominantly to the third harmonic of square-wave gratings in this frequency range. At the simple cell stage, all the information required to specify the amplitude and phase for channel at a given orientation, direction and spatial frequency can be conveyed by four cells for a given subsection of visual space. At the complex cell stage, the cell's mean firing rate appears to represent the amplitude of a local Fourier coefficient, but phase information is not conveyed in the action potential code.
