Neural correlates of visuospatial imagery.

We studied changes in regional cerebral blood flow (rCBF) in 10 healthy right-handed subjects during a visuospatial imagery task. The subject's task consisted of drawing imagined lines connecting encircled numbers in ascending order and estimating the number of lines crossing. Compared with a control task in which there were no crossed lines, there were significant rCBF increases in the cingulate gyrus, the adjacent superior frontal gyrus and in the left inferior parietal cortex. The rCBF changes of the latter area correlated with task performance time. Since these activation areas are close to those in imagery of movement trajectories, we concluded that they appear to be a subsystem for processing mental visuospatial images.