title: Hemisphere-dependent ipsilesional deficits in hemianopia: Sightblindness in the 'intact' visual field.
abstract: OBJECTIVE
  In addition to exhibiting a severe contralesional deficit, hemianopic patients may also show a subtle ipsilesional visual deficit, called sightblindness (the reverse case of 'blindsight). We have tested for the presence, nature and extent of such an ipsilesional visual field (IVF) deficit in hemianopic patients that we assigned to perform two visual tasks. Namely, we aimed to ascertain any links between this ipsilesional deficit, the lesion side, and the tasks performed or the stimuli used.
  
  
  METHODS
  We tested left and right homonymous hemianopic (right brain-damaged RBD and left brain-damaged LBD, respectively) patients and healthy controls. Natural-scene images, either non-filtered or filtered in low or high spatial frequency (LSF or HSF, respectively) were presented in the IVF of each subject. For the two tasks, detection ("Is an image present?") and categorization ("Is the image of a forest or a city?"), accuracy and response time were recorded.
  
  
  RESULTS
  In the IVF the RBD (left hemianopes) patients made more errors on the categorization task than did their matched controls, regardless of image type. In contrast, the only task in which the LBD (right hemianopes) patients made more errors than did the controls was the HSF-images task. Furthermore, in both tasks (detection and categorization), the RBD patients performed worse than did the LBD patients.
  
  
  CONCLUSIONS
  Homonymous hemianopic patients do indeed exhibit a specific visual deficit in their IVF, which was previously thought to be unaffected. We have demonstrated that the nature and severity of this ipsilesional deficit is determined by the side of the occipital lesion as well as by the tasks and the stimuli. Our findings corroborate the idea of hemispheric specialization at the occipital level, which might determine the nature and severity of ipsilesional deficits in hemianopic patients.
authors.affiliation: Laboratoire Vision, Action, Cognition - EAU 01, Université Paris Descartes - Sorbonne Paris Cité, Boulogne-Billancourt, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Cavézian
authors.affiliation: Service de Neurologie, Fondation Ophtalmologique Rothschild, Paris, France; Unité Vision et Cognition, Fondation Ophtalmologique Rothschild, Paris, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Perez
authors.affiliation: CNRS, LPNC UMR 5105, Grenoble, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Peyrin
authors.affiliation: Service de Neurologie, Fondation Ophtalmologique Rothschild, Paris, France; Unité Vision et Cognition, Fondation Ophtalmologique Rothschild, Paris, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Gaudry
authors.affiliation: Service de Neurologie, Fondation Ophtalmologique Rothschild, Paris, France.
authors.forename: Michaël
authors.initials: M
authors.lastname: Obadia
authors.affiliation: Service de Neurologie, Fondation Ophtalmologique Rothschild, Paris, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Gout
authors.affiliation: Service de Neurologie, Fondation Ophtalmologique Rothschild, Paris, France; Unité Vision et Cognition, Fondation Ophtalmologique Rothschild, Paris, France; Laboratoire de Psychologie de la Perception, UMR 8242, CNRS & Université Paris-Descartes, Paris, France. Electronic address: sylvie.chokron@gmail.com.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Chokron
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006423:Hemianopsia / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D014794:Visual Fields / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
keywords: Categorization; Detection; Hemianopia; Natural scenes; Spatial frequency