title: Combined functional MRI and diffusion tensor imaging analysis of visual motion pathways.
abstract: BACKGROUND
  Motion perception may be preserved after damage to striate cortex (primary visual cortex, area V1). Awareness and normal discrimination of fast-moving stimuli have been observed even in the complete absence of V1. These facts suggest that motion-sensitive cortex (the V5/MT complex or V5/MT+) may be activated by direct thalamic or collicular inputs that bypass V1. Such projections have been identified previously in monkeys but have not been shown in humans using neuroimaging techniques.
  
  
  METHODS
  We used diffusion tensor imaging (DTI) tractography to visualize white matter fiber tracts connecting with V5/MT+ in 10 healthy volunteers. V5/MT+ was localized for each subject using functional MRI (fMRI). Functional activity maps were overlaid on high-resolution anatomical images and registered with the diffusion-weighted images to define V5/MT+ as the region of interest (ROI) for DTI tractography analysis. Fibers connecting to V1 were excluded from the analysis.
  
  
  RESULTS
  Using conservative tractography parameters, we found connections between the V5/MT+ region and the posterior thalamus and/or superior colliculus in 4 of 10 subjects.
  
  
  CONCLUSIONS
  Connections between the V5/MT+ region and the posterior thalamus and/or superior colliculus may explain visual motion awareness in the absence of a functioning V1.
authors.affiliation: Human Vision and Eye Movement Laboratory, University of British Columbia, Vancouver, British Columbia, Canada. llanyon@eyecarecentre.org
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Lanyon
authors.forename: Deborah
authors.initials: D
authors.lastname: Giaschi
authors.forename: Simon Au
authors.initials: SA
authors.lastname: Young
authors.forename: Kevin
authors.initials: K
authors.lastname: Fitzpatrick
authors.forename: Lu
authors.initials: L
authors.lastname: Diao
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Bjornson
authors.forename: Jason J S
authors.initials: JJ
authors.lastname: Barton
mesh_terms: D000328:Adult; D001931:Brain Mapping; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D013477:Superior Colliculi / Q000098:blood supply / Q000502:physiology; D013788:Thalamus / Q000098:blood supply / Q000502:physiology; D014793:Visual Cortex / Q000098:blood supply* / Q000502:physiology*; D014795:Visual Pathways / Q000098:blood supply* / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen