Cortical activations during the mental rotation of different visual objects.

Whole-head functional magnetic resonance imaging was applied to nine healthy right-handed subjects while they were performing three different mental rotation tasks and two visual control tasks. The mental rotation tasks comprised stimuli pairs derived from the "classical" 3D cube figures first used by R. N. Shepard and J. Metzler (1971, Science 171, 701-703), pairs of letters, and pairs of abstract figures developed by J. Hochberg and L. Gellmann (1977, Memory Cognit. 5, 23-26). In some cases, the paired objects were identical except that they were rotated in a certain plane. In other cases, the two objects were incongruent. Subjects were shown one pair of objects at a time and asked to judge whether the two were the same. In line with previous studies we found that decision times increased linearly with the degree of separation between the two objects. Cortical activation converged to demonstrate bilateral core regions in the superior and inferior parietal lobe (centered on the intraparietal sulcus), which were similarly activated during all three mental rotation tasks. Thus, our results suggest that different kinds of stimuli used for mental rotation tasks did not inevitably evoke activations outside the parietal core regions. For example we did not find any activation in brain areas known to be involved in lexical or verbal processing nor activations in cortical regions known to be involved in object identification or classification. Copyright 2001 Academic Press.