Form and motion coherence activate independent, but not dorsal/ventral segregated, networks in the human brain

There is much evidence in primates' visual processing for distinct mechanis ms involved in object recognition and encoding object position and motion, which have been identified with 'ventral' and 'dorsal' streams, respectivel y, of the extra-striate visual areas [1-3]. This distinction may yield insi ghts into normal human perception, its development and pathology. Motion co herence sensitivity has been taken as a test of global processing in the do rsal stream [4,5]. We have proposed an analogous 'form coherence' measure o f global processing in the ventral stream [6]. In a functional magnetic res onance imaging (fMRI) experiment, we found that the cortical regions activa ted by form coherence did not overlap with those activated by motion cohere nce in the same individuals. Areas differentially activated by form coheren ce included regions in the middle occipital gyrus, the ventral occipital su rface, the intraparietal sulcus, and the temporal lobe, Motion coherence ac tivated areas consistent with those previously identified as vs and V3a, th e ventral occipital surface, the intraparietal sulcus, and temporal structu res. Neither form nor motion coherence activated area V1 differentially. Fo rm and motion foci in occipital, parietal, and temporal areas were nearby b ut showed almost no overlap. These results support the idea that form and m otion coherence test distinct functional brain systems, but that these do n ot necessarily correspond to a gross anatomical separation of dorsal and ve ntral processing streams. (C) 2000 Elsevier Science Ltd. All rights reserve d.