Selective activation of human cortical area V5A by a rotating visual stimulus in fMRI; implication of attentional mechanisms.

The human homologue of area V5A of rotation-selective cells in the monkey medial superior temporal area (MST) was identified using functional magnetic resonance imaging (fMRI). It was located within the border region of occipito-temporo-parietal cortex, in four of 10 subjects on both sides, and on the right or left side in three subjects each. The stimulus was a black-and-white sine-modulated windmill presented either stationary or in rotation phases of 1 s duration. Areas V1-V3 did not show up with this paradigm. Focusing attention by mentally counting the number of rotation phases ensured high signal intensity in V5A, whereas moving attention away by counting electric stimuli to the wrist diminished it despite persistent fixation of gaze to the centre of the windmill.