Figure 2. Voxel-wise tuning vectors are measured from BOLD responses evoked by natural movies.

Tuning changes in single voxels are a unique, diagnostic aspect of the tuning-shift hypothesis. Therefore, to test this hypothesis we measured changes in voxel tuning during covert visual search for either ‘humans’ or ‘vehicles’ in complex natural movies. A separate category model was fit to each voxel within each attention condition, in order to optimally predict evoked BOLD responses (predicted response: dashed lines, measured response: solid lines). The category model gives voxel tuning under each condition, and tuning shifts can be identified by comparing tuning across conditions.