Two recent dipole models (Michael and Halliday, 1971; Jeffreys and Axford, 1972a, b) for the cortical generators of pattern evoked responses differ both in polarity and to a lesser extent in location of the dipoles. In this paper evidence is presented that these different results, instead of being contradictory, point to different cortical representations for the “contrast-increase” and “contrast-decrease” responses, because the data of Michael and Halliday (1971), obtained with a pattern reversal stimulus, seem to be mainly related to the response to a decrease in contrast, whereas those of Jeffreys and Axford are from the contrast-increase response. It is also shown that the contrast-increase and contrast-decrease responses to foveal stimulation interact.