以雄性敘利亞倉鼠為模式探討社會訊息襲取的行為效果與當下的腦部神經活動反應

Investigation of behavioral consequence and functional neural activity during social eavesdropping - using male Syrian hamsters as a model

劉璟儀(Ching-Yi Liu)

指導教授 ： 賴文崧

國立臺灣大學/理學院/心理學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201600867

摘要

社會訊息襲取（social eavesdropping）是一種特定的社會學習行為，被定義為「自訊息發送者的社會互動中取得與被觀察者有關的訊息」。近年來已經有越來越多研究關注動物的社會訊息襲取行為，但是這些研究大多著重於行為機制的探討，少有神經生理機制方面的研究。因此，本研究利用敘利亞倉鼠的社會訊息襲取模式，探討社會訊息襲取當下的腦部活動。本研究共包含三個實驗，每個實驗都採用具有一次社會挫敗經驗的成年雄性敘利亞倉鼠為受試者。每個實驗都具有三組操弄：打鬥事件組（受試者觀看兩隻示範者倉鼠打鬥）、中性互動事件組（有兩隻示範者倉鼠，但輸家示範者被關在鐵籠中，因此不會有直接的肢體接觸）、以及沒有社會互動事件的控制組（實驗一和實驗三中為場地控制組，實驗二為社交刺激物控制組）。在實驗一中，首先採用c-Fos免疫染色法來找出可能參與在社會訊息襲取過程中的腦區，包含梨狀皮質（piriform cortex）、扣帶迴皮質（cingulate cortex）、海馬迴（hippocampus）、以及杏仁核（amygdala）。結果顯示，打鬥事件組受試者在前中扣帶迴皮質（the anterior midcingulate cortex，aMCC）有更多的c-Fos染色細胞表現。根據實驗一的發現，在第二個實驗中，我們記錄了aMCC的場電位、探討在社會訊息襲取當下的神經反應模式。在本實驗中的社會刺激物控制組，由兩隻完全被隔開、無法產生肢體與視線接觸的倉鼠做為示範者。功率頻譜密度分析（Power spectral density）顯示，打鬥事件組及中性互動事件組的受試者會比社會刺激物組受試者，於社會訊息襲取當下有更多的delta共振產生於aMCC。並且，當示範者間沒有社會互動事件發生時，這樣的差異又會消失，顯示aMCC可能參與了偵測社會訊息的功能。由於實驗二的結果顯示，第一次到第三次的社會訊息襲取經驗有神經活動反應動態的改變，因此，於實驗三中進一步比較一次性與三次社會訊息襲取經驗之後受試者的行為表現。實驗三的結果顯示，一天的社會訊息襲取就足以讓受試者的行為產生影響，但三天的學習經驗造成的行為改變更明顯。透過本研究，我們可以更了解社會訊息襲取的運作機制，並也因此幫助我們更了解社會學習的神經機制。

關鍵字

社會訊息襲取 ； 敘利亞倉鼠 ； c-Fos免疫染色法 ； 扣帶迴皮質 ； 社會學習

並列摘要

Social eavesdropping is a specific type of social learning. It is defined as extracting information about the relative content of signalers from the interactions between the signalers. Social eavesdropping has advantage in information gathering and has attracted increasing attention. Though many studies have investigated behavioral and developmental consequences of social eavesdropping in animals, the underlying neural mechanisms remain much unclear. Taking advantage of the established social eavesdropping model in Syrian hamsters, we investigated the neural activity of the brain underlying social eavesdropping in hamsters with a single defeated experience. There are three experiments in this study. Adult male Syrian hamsters were randomly assigned into the following three groups: the fight group (subjects exposed to two fighting male hamsters), the neutral group (subjects exposed to an indirect social interaction in which one hamster was constrained in a metal basket), or the non-social control group (an empty arena in Experiment 1 and 3, or social stimuli control group). In Experiment 1, immunochemistry was adopted to map neuronal activities in the selected brains, including piriform cortex, cingulate cortex, hippocampus, and amygdala. We found that males in the fight group had more c-Fos labeled neurons in the anterior mid-cingulate cortex (aMCC) compared with males in the other two groups. Based on the findings in Experiment 1, local field potential was recorded in the aMCC of behaving hamsters to reveal neural activity patterns during social eavesdropping in Experiment 2. The non-social control group was the social stimuli control group in which two demonstrators had no physical and visual contacts with each other. Compared with the social stimuli control group, power spectral density analysis revealed that delta oscillation was increased in the fight group and the neutral group when subjects eavesdropped on the interactions of the demonstrators across the three-day social learning. When there were no demonstrators or social interaction, no difference in the patterns of neural activity was found. Based on the result of Experiment 2, we further investigated the behavioral consequences of one-time and three-time social eavesdropping. Our result demonstrated that 1-day social eavesdropping was sufficient to induce behavioral changes in the bystander even though the learning effect is more pronounced for 3-day social eavesdropping. Collectively, our data suggest that the aMCC might play an important role in social signal detection. This study provides further details regarding social eavesdropping and its neural activity, which may also shed lights on understanding neural mechanisms of social learning.

並列關鍵字

social eavesdropping ； hamsters ； c-Fos ； cingulate cortex ； social learning

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