斑馬魚空間記憶學習作業之不對稱行為表現－探討動物腦側化對行為的影響

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

吳曜如(Yao-Ju Wu)

指導教授 ： 呂國棟

國立臺灣師範大學/理學院/生命科學研究所/碩士(2007年)

摘要

隨?基因轉殖斑馬魚製備技術及相關分生檢測技術的不斷進步，斑馬魚用於神經科學的研究日漸增多，近有證據明顯示斑馬魚具有與人類相似的腦側化現象。本研究延續前人的理論基礎，利用改良之斑馬魚T字形迷宮空間記憶學習模式，藉以找出學習過程中，不同學習方向所導致之學習行為差異。並且進一步利用此差異，針對可能與空間記憶有關的端腦部位，進行不可恢復的雙側或單側手術破壞，觀察其於空間記憶學習行為之影響，以探討斑馬魚端腦是否具有類似人類的腦側化現象。

本研究中總共分為三部份實驗，第一部份利用大量未經處理之動物(na?ve animal)進行測試，建立固定的標準訓練程序。此程序以訓練動物學習之方向可分為左側學習與右側學習兩種。實驗結果顯示，動物在往右側學習時，會呈現出學習曲線(p(na?ve-R) < 0.0078)，但往左側學習時，並沒有如此顯著的情況(p(Na?ve-L) = 0.1409)。此外，右側學習組的動物在第一次選擇的表現上，其方向的決定會自高比例選擇左側轉變為高比例選擇右側，然而往左側學習的動物則並表現出接近亂數選擇的情況。

第二部份實驗是對動物進行全端腦的破壞手術，並依照第一部份之標準程序進行訓練。實驗結果顯示經假手術處理的sham組動物，其左側或右側學習結果均和第一部份的結果相似。但雙側端腦遭破壞之lesion組動物，右側學習組的動物並沒有呈現出學習曲線，而左側學習組的動物表現出較快的速度游入目標區，但第一次在交接處進行選擇時，動物並沒有直接選擇向左。第三部份實驗是對動物的單側端腦進行破壞，並和第二部分一樣使用第一部份之標準程序進行訓練，藉此觀察比較動物的學習表現。結果顯示，右側端腦對右側方向的學習，扮演較左側端腦更加關鍵的角色。而左側端腦則可能與動物的情緒處理上較為相關。

近期文獻提出之斑馬魚腦側化現象中，認為右眼系統在斑馬魚決定是否咬取食物與辨識熟悉物體時較為優先；左眼系統的功能則在觀察陌生環境或是辨認新物體。本研究結果顯示，目標區域所在的位置，亦即動物為左側學習組或右側學習組，對於動物的學習表現有其一定的影響。而斑馬魚只有在右側學習時會呈現出較接近傳統學習的模式。我們推測，這樣的差別其原因為斑馬魚的端腦具有功能性腦側化現象，而在右側學習模式，斑馬魚右側的端腦扮演了較為重要的角色。

關鍵字

腦側化 ； 斑馬魚 ； 端腦 ； T字形迷宮 ； 空間記憶學習

並列摘要

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.

並列關鍵字

brain lateralization ； zebrafish ； telecephalon ； t-maze ； spatial memory

參考文獻

Aizawa, H., Bianco, I.H., Hamaoka, T., Miyashita, T., Uemura, O., Concha, M.L., Russell, C., Wilson, S.W., & Okamoto, H. (2005). Laterotopic representation of left-right information onto the dorso-ventral axis of a zebrafish midbrain target nucleus. Curr Biol, 15, 238-243.

Andrew, R.J. (1999). The differential roles of right and left sides of the brain in memory formation. Behav Brain Res, 98, 289-295.

Andrew, R.J., Tommasi, L., & Ford, N. (2000). Motor control by vision and the evolution of cerebral lateralization. Brain Lang, 73, 220-235.

Barth, K.A., Miklosi, A., Watkins, J., Bianco, I.H., Wilson, S.W., & Andrew, R.J. (2005). fsi zebrafish show concordant reversal of laterality of viscera, neuroanatomy, and a subset of behavioral responses. Curr Biol, 15, 844-850.

Brown, C., & Braithwaite, V.A. (2005). Effects of predation pressure on the cognitive ability of the poeciliid Brachyraphis episcopi. Behav. Ecol., 16, 482-487.