fMRI and its interpretations: an illustration on directional selectivity in area V5/MT.
fMRI is a tool to study brain function noninvasively that can reliably identify sites of neural involvement for a given task. However, to what extent can fMRI signals be related to measures obtained in electrophysiology? Can the blood-oxygen-level-dependent signal be interpreted as spatially pooled spiking activity? Here we combine knowledge from neurovascular coupling, functional imaging and neurophysiology to discuss whether fMRI has succeeded in demonstrating one of the most established functional properties in the visual brain, namely directional selectivity in the motion-processing region V5/MT+. We also discuss differences of fMRI and electrophysiology in their sensitivity to distinct physiological processes. We conclude that fMRI constitutes a complement, not a poor-resolution substitute, to invasive techniques, and that it deserves interpretations that acknowledge its stand as a separate signal.
Bartels
Andreas
A
Max Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany. andreas.bartels@tuebingen.mpg.de
Logothetis
Nikos K
NK
Moutoussis
Konstantinos
K
D000222:Adaptation, Physiological; D001931:Brain Mapping / Q000295:instrumentation*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D009039:Motion Perception / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D012039:Regional Blood Flow; D014278:Trigeminal Nuclei / Q000098:blood supply / Q000378:metabolism; D014793:Visual Cortex / Q000098:blood supply / Q000378:metabolism*; D014795:Visual Pathways / Q000098:blood supply / Q000378:metabolism*
D010100:Oxygen