Asymmetric behavior of zebrafish in spatial memory learning program - discussing the effects of brain lateralization

Abstract

[[abstract]]By the proving of molecular biological technology, zebrafish has been widely used in transgenic experiments. Recently, results showed that brain lateralization exists both in the small fish’s and human’s brain. In the present study, we use modified T-maze apparatus which is symmetry and able to control opening way to examine the possible direction preference of zebrafish in the spatial memory task. In addition, we give animal irreversible surgical lesion and observe its effect on the spatial memory task. There are three experiments in this study. In experiment-1 we use na?ve animals to develop the standard training procedure. Briefly, there are two training procedure which named right-side learning and left-side learning. Animals were taught to swim direct to the right side and left side respectively. We found that only the right side learning group shows the learning curve, but similar pattern was not found in the left side learning group. Animals of the left side learning group just swam in a randomly manner and kept the speed while enter the target area. In experiment 2, we train the animals which has been bilateral telencephalic ablation on the protocol of T-maze we has made in experiment 1. We found animals in sham group show almost the same pattern and performance with the na?ve groups in experiment 1. However, animals in the lesion group, the right side learning group didn’t show the learning curve. The speed of left side group was faster than the right side group, but animal didn’t choose the left side when animals first arrived the connect area of T-maze. In experiment 3 animals were given one-side telencephalic ablation and saw the learning performance in T-maze. The results showed that the right side telencephalon played an important role in the T-maze task of right side learning, and the left side was more important in emotional progressing. Recent results showed that there were lateralize in zebrafish brain. The right eye system (RES) made decision to bite and the familiar objects. The left eye system (LES) was to use to observe the strange environment or identify new objects. And our results showed that the direction of the target reservoir will confound the learning response. Zebrafish expressed an accumulative learning response when the target reservoir settled on the right hand side. We suggest that the differential learning responses of zebrafish was resulted in the lateralization of zebrafish brain. And the right telecephalon may be play the more important on the spatial learning progress.