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Colloquium on Neuroimaging of Human Brain Function
FIG. 5. Comparison of the ipsilateral activity produced by two different stimuli, within the same unilateral aperture. (A) The typical pattern of activation produced by the moving gratings, in the ipsilateral aperture shown in Fig. 1A (20° in polar angle from the vertical meridian). Significant ipsilateral activity is coded red, and the retinotopic field sign map from the same hemisphere is shown in yellow/blue. As described earlier, this stimulus produces a bifurcating pattern concentrated anterior to V3A/V4v, with the lower branch extending through MT. (B) Data from a similar experiment in the same hemisphere, with the same field sign map for comparison. In this second experiment, naturalistic images were presented within the same ipsilateral apertures, again avoiding the vertical meridian by 20° of polar angle. Activity in response to this stimulus is thresholded as in A and coded green. The upper branch of both ipsilateral activity patterns is similar. However, the lower branch of activity produced by the naturalistic stimuli does not extend anteriorly through MT. Instead it extends further inferior (downward in the figure), compared with that produced by the moving gratings in the same apertures. Similar differences were seen in all subjects tested with these two stimuli.
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