title: Functional localization of the human color center by decreased water displacement using diffusion-weighted fMRI.
abstract: BACKGROUND
  Decreased water displacement following increased neural activity has been observed using diffusion-weighted functional MRI (DfMRI) at high b-values. The physiological mechanisms underlying the diffusion signal change may be unique from the standard blood oxygenation level-dependent (BOLD) contrast and closer to the source of neural activity. Whether DfMRI reflects neural activity more directly than BOLD outside the primary cerebral regions remains unclear.
  
  
  METHODS
  Colored and achromatic Mondrian visual stimuli were statistically contrasted to functionally localize the human color center Area V4 in neurologically intact adults. Spatial and temporal properties of DfMRI and BOLD activation were examined across regions of the visual cortex.
  
  
  RESULTS
  At the individual level, DfMRI activation patterns showed greater spatial specificity to V4 than BOLD. The BOLD activation patterns were more prominent in the primary visual cortex than DfMRI, where activation was localized to the ventral temporal lobe. Temporally, the diffusion signal change in V4 and V1 both preceded the corresponding hemodynamic response, however the early diffusion signal change was more evident in V1.
  
  
  CONCLUSIONS
  DfMRI may be of use in imaging applications implementing cognitive subtraction paradigms, and where highly precise individual functional localization is required.
authors.affiliation: Centre for Advanced Imaging The University of Queensland St Lucia Qld 4067 Australia ; Queensland Brain Institute The University of Queensland St Lucia Qld 4067 Australia ; Centre for Clinical Research The University of Queensland Brisbane Qld 4006 Australia ; Hotchkiss Brain Institute and Department of Radiology University of Calgary Calgary AB T2N 4N1 Canada.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Williams
authors.affiliation: Centre for Advanced Imaging The University of Queensland St Lucia Qld 4067 Australia.
authors.forename: David C
authors.initials: DC
authors.lastname: Reutens
authors.affiliation: School of Psychology and Counselling Queensland University of Technology Kelvin Grove Qld 4059 Australia.
authors.forename: Julia
authors.initials: J
authors.lastname: Hocking
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D003116:Color; D003118:Color Perception / Q000502:physiology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D013702:Temporal Lobe / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology
keywords: Area V4; BOLD; DfMRI; diffusion MRI; fMRI; magnetic resonance imaging