Appendix鋰鹽去除酬賞價值程序對兩種標誌系統空間行為的影響

Effects of Lithium Chloride Induced Reward Devaluation on Two Types of Spatial Behavior of the Taxon System

本研究透過鋰鹽去除酬賞物誘因價值及改變環境刺激的操弄對大白鼠在輻射型八角迷津的行為影響之測試，探討標誌系統空間行為下之線索導引及體位導向兩策略（O'Keefe & Nadel, 1978）是否分屬不同學習內涵之行為系統。剝奪食物之大白鼠在學習輻射型八角迷津之線索學習作業及自我中心作業後，前者作業要求受試從八個跑道中選擇進入由實驗者所任選的兩個佈有砂紙跑道以獲得食餌，後者作業要求置於只用四個跑道的十字型迷津中的任一跑道末端之受試以特定方向轉九十度進入另一跑道獲得食餌。俟兩作業的行為基準線形成後，受試先接受改變環境刺激之反應依據測試，再接受鋰鹽去除酬賞價值程序的操弄。反應依據測試結果發現習得線索學習作業的大白鼠在砂紙線索被移除狀況中會明顯的延宕選擇跑道的時間，而在自我中心作業的大白鼠則不受作業起始點轉換之環境刺激改變影響該行為表現。食餌的誘因價值因鋰鹽去除酬賞價值程序的施予而降低後，這個操弄只會影響自我中心作業的行為表現，即其作業正確率降低及平均完成時間延長；反之，大白鼠在線索學習作業的行為表現則不受到食餌誘因價值降低的影響。綜合上述結果，大白鼠習得線索學習作業與自我中心作業後分別會形成刺激－反應（S-R）與反應一酬賞物（R-S*）的聯結學習型態，意即標誌系統下的線索導引及體位導向兩策略確實為兩種不同學習內涵之空間行為。

In order to investigate the potential differences between the spatial behavior derived from the guidance and the orientation hypotheses in the taxon system (O'Keefe & Nadel, 1978), the present study examined the behavioral performance in the radial eightarm maze in rats under lithium chloride (LiCl) devaluation and context stimulus alteration. Food-deprived rats were separately trained to perform in the cue-learning and egocentric tasks in maze. The cue-learning task required the subject to enter two randomly chosen (out of eight) arms each cued with a piece of sandpaper on the arm entrance. When only four arms were used, the egocentric task required the subject to start from the end of a randomly chosen arm and turned into a baited arm with a specific direction of 90°. After reaching the baseline level, behavioral measures on two tasks were conducted first under the response probe test of the context stimulus alteration and followed by the LiCl devaluation procedure. Removal of sandpaper significantly enhanced the time the rat stayed on the central platform of the maze before entering the arms in the cue-learning task. In contrast, performance on the egocentric task remained intact when the starting point was shifted. The incentive value of the reinforcer baited in the maze was clearly reduced by the LiCl devaluation procedure. This manipulation significantly impaired performance on the egocentric task by decreasing the percent of correct choice and increasing the time to complete the task. In contrast, the performance on cue-learning task was not affected by LiCl devaluation. Together, these data indicate that the rats acquire the cue-learning and egocentric tasks based on the learning associations of stimulus-response (S-R) and response-reinforcement (R-S*), respectively. It is suggested that the guidance and orientation can be the two hypothetical strategies the different spatial behaviors in the taxon system.