Left: Fourier space comparison. Modulation transfer function measured in a simple cortical cell (De Valois et al, in Frontiers of Visual Science, Springer, 1978) compared to the appropriate Gabor elementary signal. Right: Direct space comparison. Measured spatial sensitivity of the same cell, compared to the same elementary signal. From: S. Marcelja, Mathematical description of the responses of simple cortical cells, Journal of the Optical Society of America 70 (1980) 1297-1300.

By the end of 1970's there were many published accurate measurements of single cell responses from the primary visual cortex. They suggested to me that the visual information is represented in the particular basis set, known in physics since the time of Heisenberg and Von Neumann. Basis vectors are formed as a product of a Gaussian and a sine or cosine functions and have the property that they minimise Heisenberg uncertainty. Gabor called them 'elementary signals' and emphasised their suitability for communication.

Today, the representation seen in the visual cortex in 1980 would be considered an example of multiresolution image decomposition. This particular basis has found many applications in signal and image processing.