Figure 1.

The PCM. A, Sixty-four phase-shifted stimulus exemplars. B, Oriented filters acting as simple cells encoding orientation are convolved with the stimulus exemplars. C, The response of each filter to each exemplar is squared, and then the exemplar responses are summed to make an activity map for each orientation filter. D, The filters' response maps are summed into a single pattern response map, in which each pixel is a “cube” that has a perfectly balanced contribution from each orientation channel, representing an unbiased fMRI voxel.