大鼠恐懼增益驚跳反應作業及雙向主動躲避作業之社會學習

Abstract

動物為了生存，終其一生必須不斷學習如何應對外界的刺激，動物可藉由自身承受刺激之親身學習(self learning)來改變行為；然而藉由觀察(observation)或是與其他個體進行社會互動(social interaction)之社會學習(social learning)能夠更快速的獲得資源以及避開危險，是一種較有效率的學習方式。本論文試圖對機制較清楚之個別學習模式建立社會觀察學習模型：訓練大鼠利用社會觀察學習從事恐懼增益驚跳反應作業及雙向主動躲避作業。在恐懼增益驚跳反應作業之三個實驗中，大白鼠觀察同伴進行燈光以及電擊的聯結，檢視此一社會觀察經驗對於展現新行為或是對後續之個別親身學習是否有幫助效果。研究結果顯示，在恐懼增益驚跳反應作業中，大鼠並無法僅憑著社會觀察學習而產生新的行為，然而觀察同類學習此一作業的經驗會使動物有較高的激動度(arousal)，且對於兩個月後的個別親身訓練有促進效果。於雙向主動躲避作業之三個實驗中，大鼠觀察不同學習階段的示範者後進行個別親身學習，藉以探討促進社會觀察學習的重要因子。在雙向主動躲避作業下，社會觀察經驗可促進事後大鼠的個別親自學習該作業，但但助益效果僅明顯出現於觀察初始學習階段的觀察者。相對的，觀察熟練階段的觀察者反而會減慢觀察者親身學習出期的反應時間。這些結果顯示，動物在觀察同類學習時，能否獲得被觀察者行為與環境刺激間的對應關係是產生觀察學習效果的重要因素之一。本研究建立了恐懼增益驚跳反應作業以及雙向主動作業之社會觀察學習模型，於此作業下大鼠可經由觀察學習獲得行為改變，且觀察學習的成立必須倚賴各種因素的介入；這些結果可作為未來對於社會觀察學習神經機制研究的基礎。

Animals can learn and change their behavior directly through interacting with the world around them, which is commonly known as individual or self learning. Also, they can learn from simply observing or interacting with another animal, which is denoted as social learning. Social learning is a very useful way for adaptation because animal can learn without experiencing potential danger, which is extremely important for its survival. However, experimental models for socially acquired fear have not yet been well established for laboratory animals. This thesis intended to build a model for social/observational learning by using fear potentiated startle and two-way active avoidance tasks, of which the neural mechanisms have been well documented in the literature. In the fear potentiated startle task, Wistar rats observed a conspecific being shocked along with light and was subsequently tested directly for startle potentiation caused by the light, or for saving on a self-experienced paradigm to relearning the same task. The results showed that, in the direct test, rats with pure observation experience showed no significant behavior change compared with control group in response to the warning signal. But the arousal level of observers conditioned to the context (as indicated by the difference of startle elicited in the context before and after observation) was higher than that of controls after the observation experience. Similar results were also obtained in rats tested for saving in a self-learning paradigm given 1 day after observation. However, if the observing rats received the saving test 2 months later, they did show higher fear potentiated startle responses to moderate noise bursts in the presence of light, suggesting the observation created saving long time after the experience. In the two-way active avoidance task, the observer rat either observed a novice to demonstrate at the early stage of learning (the first two days), or an expert to demonstrate at the final stage of learning (the last two days). The results showed that rats who observed a novice-demonstrator showed higher learning speed than both the control and expert-observation groups when they experienced self-learning in a saving paradigm. In this research we have built a model for social/observational learning by using fear potentiated startle and two-way active avoidance tasks, and rats could change their behavior by observing others only if some condition has been satisfied. These observational learning models can become foundation for the research of neural mechanism for observation learning.