F-mri reveals that selective attention to one way translation activates vi while attention to expansion activates higher cortices

Purposes. By means of both psychophysics and the f-MRI technique, Watanabe (1994, 1995, ARVO) showed that attention to local component motion activates VI while attention to an integrated motion activates MT. These findings suggest the activated area depends on a feature to which attention is directed, In order to confirm the task dependency of an effect of attention to a motion feature on a cortical area of activation, the same stimulus was used in different attention conditions. Methods. Two superimposed groups of moving random dots comprised the test stimulus. All the dots in one group moved rightwards (one-way translation) while those in the other group moved outward radially from the center of the display (expansion). Six subjects participated in the experiment. In the first of three conditions subjects were instructed to direct attention selectively to the one-way translation, in the second to the expansion, and in the third to no particular motion, all while fixating the cross presented at the center of the display. Functional images were collected with echoplanar imaging using a 1.5 T whole body scanner (Siemens Vision) with a CP head coil. Eye-movements were measured using an Ober II system with three of the subjects while the brain was being scanned. Results. VI was more active when the one-way motion was attended than in the no-attention condition, whereas extrastriate cortical areas including MT/MST were more active when expansion was attended to. No significant eye movements were found in any of the three conditions. Conclusions. The results confirm the assumption that the activated area depends on the feature of motion to which attention is directed (Watanabe & Miyauchi, Higher-level Motion, in press).