title: Mirror-image discrimination and reversal in the disconnected hemispheres.
abstract: Two callosotomized patients and 24 neurologically normal subjects performed simple binary discriminations between upright letters flashed in one or other visual field. Where discrimination of the letters F and R by name either showed a left-hemisphere advantage or no hemispheric effect, discrimination of whether the same letters were normal or backward showed a right-hemisphere advantage. These results suggest that discrimination of mirror-image letters depends on matching to an exemplar, for which the right-hemisphere is dominant, while letter naming depends on abstract category recognition. One commissurotomized patient, DDV, showed systematic left-right reversal of the letters in the left visual field, classifying the normal letters as reversed and reversed ones as normal, and persisted with this reversal when the letters were shown in free vision. This suggests that reversed exemplars of the letters may be laid down the right cerebral hemisphere. There was no such reversal in the other patient (DDC).
authors.affiliation: Department of Psychology, University of Auckland, Private Bag 92019, Auckland 1164, New Zealand. m.corballis@auckland.ac.nz
authors.forename: Michael C
authors.initials: MC
authors.lastname: Corballis
authors.forename: Kylie
authors.initials: K
authors.lastname: Birse
authors.forename: Aldo
authors.initials: A
authors.lastname: Paggi
authors.forename: Tullio
authors.initials: T
authors.lastname: Manzoni
authors.forename: Chiara
authors.initials: C
authors.lastname: Pierpaoli
authors.forename: Mara
authors.initials: M
authors.lastname: Fabri
mesh_terms: D000328:Adult; D003337:Corpus Callosum / Q000503:physiopathology* / Q000601:surgery; D003657:Decision Making / Q000502:physiology; D004193:Discrimination Learning / Q000502:physiology*; D004827:Epilepsy / Q000503:physiopathology / Q000601:surgery; D005260:Female; D006801:Humans; D007092:Imagination / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D014794:Visual Fields / Q000502:physiology*; D055815:Young Adult