Right eye use associated with decision to bite in zebrafish.

Cerebral lateralisation is revealed in the zebrafish by preferential eye use, which differs according to the visual stimulus that is being fixated. Past findings [Bisazza A, Pignatti R, Vallortigara G. Behav. Brain Res. 1997b;89:237-242; Miklósi A, Andrew RJ, Savage, H. Physiol. Behav. 1998;63:127 135] suggest that the right eye is used when the stimulus (or scene) is such as to require a careful period of examination in order to decide on a response. The left eye is used when the fish has to check whether an identical stimulus has been seen before. We here show that the same association of right eye use with decision to respond holds for biting at small targets (coloured or black and white beads). Biting and right eye use were both high at the first presentation of both types of bead, and fell together over two further trials with the same type of bead. At the fourth trial the appearance of the bead was changed. A change in colour caused both right eye use and biting to return, whereas a change in orientation of the black stripe on the black and white bead had no effect on either (and seemed to be largely ignored). In the case of the coloured beads, habituation of biting was accompanied by continued interest, shown by increased binocular fixation. The reduction in reliance on right eye viewing thus represents a change in the strategy of analysis rather than coming to ignore the stimulus. It would allow a greater involvement of the left eye system.