Functional dissociation of the hemispheres in the discrimination of complex gratings near the vertical meridian.
It was previously shown that the discrimination of complex gratings differing in the spatial phase of their harmonic components is performed more accurately when the stimuli are presented in the left than in the right visual hemifield, provided that the stimuli are separated at least 2 deg from the vertical meridian (VM) and/or their spatial frequency exceeds 2 c/deg. Here we report measurements of reaction times (RT) for the discrimination of complex gratings presented laterally at various distances from the VM. The (choice) RTs are found to be longer in the right than in the left hemifield even for stimuli of low spatial frequency at 1 deg from the VM. This rules out the possibility that a naso-temporal overlap in the retino-cortical projection in man is exploited in "bridging the gap" between the two hemispheres in the discrimination of complex gratings.
Berardi
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Istituto di Neurofisiologia del CNR, Pisa, Italy.
Fiorentini
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Gravina
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A
D003337:Corpus Callosum / Q000502:physiology; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D014794:Visual Fields