Fig. 3.

A, Activated voxels evoked by covertly counted targets and identified by correlation with the time function of McCarthy et al. (1997) are shown inred–yellow overlay on T1-weighted anatomical images for the six slices through prefrontal cortex. Activated voxels are clearly evident in the MFG bilaterally, although the activation is greater in the right MFG. This individual's data typify the general pattern of results. B, MFG activation evoked by targets to which the subject made a button press are shown in red–yellowoverlay on T1-weighted anatomical images. As in A, activation is bilateral but greatest in the right hemisphere. In this and all following images, the right hemisphere (R) is depicted on the left, and the left hemisphere (L) is depicted on theright.