Visual motion processing investigated using contrast agent-enhanced fMRI in awake behaving monkeys

To reduce the information gap between human neuroimaging and macaque physio logy and anatomy, we mapped fMRI signals produced by moving and stationary stimuli (random dots or lines) in fixating monkeys. Functional sensitivity was increased by a factor of similar to5 relative to the BOLD technique by injecting a contrast agent (monocrystalline iron oxide nanoparticle [MION]) . Areas identified as motion sensitive included V2, V3, MT/V5, vMST, FST, V IP, and FEF (with moving dots), as well as V4, TE, LIP, and PIP (with rando m lines). These regions sensitive for moving dots are largely in agreement with monkey single unit data and (except for V3A) with human fMRI results. Moving lines activate some regions that have not been previously implicated in motion processing. Overall, the results clarify the relationship betwee n the motion pathway and the dorsal stream in primates.