Abstract
Introduction. Recent observations of retinotopically organized areas within the human MT/V5 complex suggest two conflicting models for the relationship of these areas to neighboring areas LO1/2: a discontinuous model (Georgieva et al., 2009), with separated central representations and distinct eccentricity distributions in hMT/V5+ and lateral occipital complex (LOC), and a continuous model (Amano et al., 2009), in which LO1/2, MT/V5, and MST share a common eccentricity distribution. Methods. We used functional magnetic resonance imaging (fMRI) at 3T to identify areas within hMT/V5+ and the LOC and recorded responses to motion and shape localizers and to hand action for their characterization. We correlated the functional responses across subjects through the retinotopic data in each subject instead of using an anatomical registration, which resulted in a specificity of the group analysis near the resolution of the functional volumes of (2mm)3. Results.We consistently located areas LO1 and LO2 within the LOC and four retinotopic areas, the likely homologues V4t, MT/V5, MSTv, and FST, within hMT/V5+. Responses in the hand action vs. static hand condition were strong in all areas of the hMT/V5 complex but weak and not significant in the LOC. We found significant shape sensitivity in all areas of both complexes. MT/V5 and MSTv, however, showed half the sensitivity compared to all other areas. Conclusion. The four areas of the hMT/V5 complex share a common central representation distinct from the LOC and their topological organization closely resembles the organization recently observed in the MT/V5 field map cluster of the macaque monkey (Kolster et al., 2009). Areas V4t and FST, located between MT/V5 and LO1/2, show equally strong shape sensitivity as the areas within the LOC. They are, in terms of functional properties as well as topological location, consistent with the previously reported LO-ML overlap (Kourtzi, et al. 2002).
IUAP 6/29, EF/05/014, and FWO G.0730.09.