Seeing patterns in human visual cortex.

world through the relatively small windows of their receptive fields. This creates a perceptual dilemma known as the ‘aperture problem’, in which the locally ambiguous views of individual cells must be resolved into higher-order percepts that are consistent with the whole. When cells in V1 see a moving plaid (grid), for example, they respond to the direction and orientation of the component lines. They are referred to as ‘componentmotion’ cells. Cells higher up in the visual hierarchy must integrate this component information and respond to the direction of movement of the pattern. Such ‘pattern-motion’ cells (as they are called) are found in visual area MT of macaque monkeys. Using fMRI, Huk and Heeger have been able to infer the existence of subpopulations of these pattern-motion cells in area MT+ of humans [1]. Two sets of plaids were composed from a common set of moving grid patches. One set was constructed so that the pattern-motion of the plaids was in a single direction. Cells sensitive to pattern-motion should adapt to this unidirectional set.