Reaction times to lateralized visual stimuli in callosal agenesis: stimulus and response factors.
A young acallosal man was intensively tested in a standard simple reaction time (RT) paradigm using briefly-presented lateralized spots for light. In Experiment 1, findings on previous acallosal patients of a large disadvantage for crossed (e.g. right hemifield-left hand) as against uncrossed (e.g. left hemifield-left hand) RTs were replicated. This crossed-uncrossed difference (CUD), as in previous work, turned out to be smaller in a bimanual response task than in the conventional unimanual task. Experiment 2 was a factorial study of unimanual RTs in which (a) stimulus intensity and (b) spatial S-R compatibility, were varied. As in a previously tested patient, decreased intensity resulted in a greatly increased CUD. S-R compatibility on the other hand had no effect on CUD. The results are interpreted as favouring a role for visual commissural neurones in the acallosal CUD, and as evidence against a spatial compatibility hypothesis.
D000328:Adult; D061085:Agenesis of Corpus Callosum; D003337:Corpus Callosum / Q000503:physiopathology; D004292:Dominance, Cerebral / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology*; D014057:Tomography, X-Ray Computed; D014794:Visual Fields; D014796:Visual Perception / Q000502:physiology*