Cortical activations during the mental rotation of different visual objects

Whole-head functional magnetic resonance imaging was applied to nine health y right-handed subjects while they were performing three different mental r otation tasks and two visual control tasks. The mental rotation tasks compr ised 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 lett ers, 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 id entical except that they were rotated in a certain plane. In other cases, t he 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 prev ious studies we found that decision times increased linearly with the degre e of separation between the two objects. Cortical activation converged to d emonstrate bilateral core regions in the superior and inferior parietal lob e (centered on the intraparietal sulcus), which were similarly activated du ring all three mental rotation tasks. Thus, our results suggest that differ ent kinds of stimuli used for mental rotation tasks did not inevitably evok e activations outside the parietal core regions. For example we did not fin d any activation in brain areas known to be involved in lexical or verbal p rocessing nor activations in cortical regions known to be involved in objec t identification or classification. (C) 2001 Academic Press.