The fact that input from the left and right eyes is very close in the so-called cortical hypercolumns indicates that depth processing occurs very early, aiding the recognition of 3D objects.

Both simple and complex cells are linear operators and are seen as filters because they respond selectively to a large number of patterns.

However, it has been claimed that the Gabor model does not conform to the anatomical structure of the visual system as it short-cuts the LGN and uses the 2D image as it is projected on the retina.

Using simulated reverse correlation, they also demonstrate that the RF map of the CORF model can be divided into elongated excitatory and inhibitory regions typical of simple cells.

Lindeberg [4][5] has derived axiomatically determined models of simple cells in terms of directional derivatives of affine Gaussian kernels over the spatial domain in combination with temporal derivatives of either non-causal or time-causal scale-space kernels over the temporal domain and shown that this theory both leads to predictions about receptive fields with good qualitative agreement with the biological receptive field measurements performed by DeAngelis et al.[6][7] and guarantees good theoretical properties of the mathematical receptive field model, including covariance and invariance properties under natural image transformations.