Abstract from "Lateralization of visuspatial processing in the bottlenosed dolphin (Tursiops truncatus)".
Two adult female bottlenosed dolphins were tested for cerebral assymetries in the visuo spatial domain. The animal learned under binocular conditions a three-choice spatial discrimintion task with three hoops positionned along a line in the middle of the tank. During a correct trial the dolphins had to swim from a sterting position at the tanks wall through one of the hoops, come back to the starting position, chosse another hoop, swim back to start and finally swim trough the third hoop. For such a trial to be correct, the animals had to swim through all three hoops in an any sequence without omitting or re-using one of them. After reaching criterion binocularly, monocular trials (one eyed covered with an adherent succion cup) were introduced where the dolphins was carried out the same task alternatingly under right or left eye seeing conditions.For both animals, the right eye performance was clearly superior tot that of the left eye. Binocular and right eye superiority suggests a left-hemispheric dominance for the processing of visuospatial information. This is a remarkable deviation from the usual right hemisphere advantage for these kind of tasks found in different species of mammal and birds.
(c) 2000 Elsevier Science B.V. All right reserved.
Keywords: Cetacea, Cerebral Assymetry, Working memory, Visual system, Evolution.
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