Twelve right-handed men participated in two mental
rotation tasks as their regional cerebral blood flow (rCBF)
was monitored using positron emission tomography. In one
task, participants mentally rotated and compared figures
composed of angular branching forms; in the other task,
participants mentally rotated and compared drawings of
human hands. In both cases, rCBF was compared with a baseline
condition that used identical stimuli and required the
same comparison, but in which rotation was not required.
Mental rotation of branching objects engendered activation
in the parietal lobe and Area 19. In contrast, mental rotation
of hands engendered activation in the precentral gyrus
(M1), superior and inferior parietal lobes, primary visual
cortex, insula, and frontal Areas 6 and 9. The results
suggest that at least two different mechanisms can be used
in mental rotation, one mechanism that recruits processes
that prepare motor movements and another mechanism that
does not.