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Abstract:
Visual changes in feature movies, like in real-live, can be partitioned into global flow due to self/camera motion, local/differential flow due to object motion, and residuals, for example,
due to illumination changes. We correlated these measures with
brain responses of human volunteers viewing movies in an fMRI
scanner. Early visual areas responded only to residual changes,
thus lacking responses to equally large motion-induced changes,
consistent with predictive coding. Motion activated V51 (MT1),
V3A, medial posterior parietal cortex (mPPC) and, weakly, lateral
occipital cortex (LOC). V51 responded to local/differential motion
and depended on visual contrast, whereas mPPC responded to
global flow spanning the whole visual field and was contrast
independent. mPPC thus codes for flow compatible with unbiased
heading estimation in natural scenes and for the comparison of
visual flow with nonretinal, multimodal motion cues in it or
downstream. mPPC was functionally connected to anterior portions
of V51, whereas laterally neighboring putative homologue of
lateral intraparietal area (LIP) connected with frontal eye fields.
Our results demonstrate a progression of selectivity from local and
contrast-dependent motion processing in V51 toward global and
contrast-independent motion processing in mPPC. The function,
connectivity, and anatomical neighborhood of mPPC imply several
parallels to monkey ventral intraparietal area (VIP).
