LOCALIZATION AND FUNCTIONAL-ANALYSIS OF HUMAN CORTICAL AREA V5 USING MAGNETO-ENCEPHALOGRAPHY

Using a multi-channel SQUID-based neuromagnetometer, we have determine d the location, temporal dynamics and functional response properties o f the human homologue of the primate cortical area V5 (MT). We provide evidence that area V5 in humans is located near the occipito-temporal border in a minor sulcus immediately below the superior temporal sulc us. This area is selective for low spatial frequencies (less than or e qual to 4.0 c/deg), responds to a wide range of temporal frequencies ( less than or equal to 35 Hz) and shows response saturation for stimulu s contrasts greater than 10%. In addition, we find that this area is n ot responsive to purely chromatic patterns but is responsive to motion -contrast stimuli. Our results are consistent with the hypothesis that area V5 in humans represents a stage of processing within the magnoce llular pathway. We discuss our results in relation to the widespread b elief that area V5 in humans is specifically concerned with motion per ception.