title: Early Visual Processing is Affected by Clinical Subtype in Patients with Unilateral Spatial Neglect: A Magnetoencephalography Study.
abstract: OBJECTIVE
  To determine whether visual evoked magnetic fields (VEFs) elicited by right and left hemifield stimulation differ in patients with unilateral spatial neglect (USN) that results from cerebrovascular accident.
  
  
  METHODS
  Pattern-reversal stimulation of the right and left hemifield was performed in three patients with left USN. Magnetoencephalography (MEG) was recorded using a 160-channel system, and VEFs were quantified in the 400 ms after each stimulus. The presence or absence of VEF components at around 100 ms (P100m component) and 145 ms (N145m component) after stimulus onset was determined. The source of the VEF was determined using a single equivalent current dipole model for spherical volume conduction. All patients were evaluated using the behavioral inattention test (BIT).
  
  
  RESULTS
  In response to right hemifield stimulation, the P100m and N145m components of the VEF were evident in all three patients. In response to left hemifield stimulation, both components were evident in Patient 3, whereas only the P100m component was evident in Patient 1 and only the N145m component was evident in Patient 2. Patient 1 exhibited impairments on the line bisection and cancelation tasks of the BIT, Patient 2 exhibited impairments on the copying, drawing and cancelation tasks of the BIT, and Patient 3 exhibited impairments on the cancelation task of the BIT.
  
  
  CONCLUSIONS
  These results demonstrate that early VEFs are disrupted in patients with USN and support the concept that deficits in visual processing differ according to the clinical subtype of USN and the lesion location. This study also demonstrates the feasibility of using MEG to explore subtypes of neglect.
authors.affiliation: Department of Rehabilitation Medicine, Keio University School of Medicine , Tokyo , Japan ; ImpAct Team, INSERM U1028, CNRS UMR5292, Lyon Neuroscience Research Center , Bron , France ; National Sanatorium Tama Zenshoen , Tokyo , Japan.
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Mizuno
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tsuji
authors.forename: Yves
authors.initials: Y
authors.lastname: Rossetti
authors.forename: Laure
authors.initials: L
authors.lastname: Pisella
authors.forename: Hisao
authors.initials: H
authors.lastname: Ohde
authors.forename: Meigen
authors.initials: M
authors.lastname: Liu
keywords: attention network; diagnosis of unilateral spatial neglect; neglect subtypes; pattern-reversal stimulation; stimulus-centered neglect; viewer-centered neglect; visual attention networks; visual evoked magnetic field
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