David Marr’s Concept of a Computational Theory for Understanding an Information Processing Task in the Brain

Therefore, even if some day we had complete knowledge of every molecule in the brain, and could record the electrical activities of every cell at any time, we would still not understand how the brain processes information.  We need, in addition, a computational theory which specifies how the electrical signals carried by a large number of neurons could act in concert to solve a certain perceptual problem.