title: A problem of overlap.
abstract: Here we propose that earlier-demonstrated details in the primate visual cortical map may account for an otherwise puzzling (and problematic) finding in the current human fMRI literature. Specifically, the well-known regions LO and MT(+) reportedly overlap in the human cortical visual map, when those two regions are localized using standard stimulus comparisons in conventional fMRI experiments. Here we describe evidence supporting the idea that the apparent functional overlap between LO and MT arises from a third area (the MT crescent: "MTc"), which is well known to surround posterior MT based on earlier histological, neuroanatomical, and electrophysiological studies in nonhuman primates. If we assume that MTc also exists in human visual cortex, and that it has a location and functional properties intermediate to those in LO and MT, simplistic modeling confirmed that this arrangement could produce apparent overlap between localizers for LO and MT in conventional fMRI maps in human visual cortex.
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging,Massachusetts General Hospital,Charlestown,Massachusetts.
authors.forename: Roger B
authors.initials: RB
authors.lastname: Tootell
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging,Massachusetts General Hospital,Charlestown,Massachusetts.
authors.forename: Cesar
authors.initials: C
authors.lastname: Echavarria
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging,Massachusetts General Hospital,Charlestown,Massachusetts.
authors.forename: Shahin
authors.initials: S
authors.lastname: Nasr
mesh_terms: D000818:Animals; D001931:Brain Mapping; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D009039:Motion Perception / Q000502:physiology; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D014793:Visual Cortex / Q000098:blood supply / Q000502:physiology*; D014795:Visual Pathways / Q000098:blood supply / Q000502:physiology*
chemical_list: D010100:Oxygen
keywords: LOC; MT; MTc; Visual cortex; fMRI