從任務實驗探討動物行為在空間記憶中學習過程的神經編碼機制

Abstract

在神經科學的研究中，認知與記憶一直是很重要的一環，而大腦的海馬回區被認為是管理記憶功能的主要區塊，因此想了解記憶學習的產生機制必須從海馬回著手，過去的研究從神經訊號中發現對特定空間的關連，因此假設了海馬回存有空間記憶的特性，並提出認知地圖的架構，但實際空間反應與神經元放電的關連性尚不明確，因此從找出海馬回與空間記憶形成與關係是本研究要探討的議題。 本研究藉由喝水裝置，訓練老鼠在學習環境中自由行走，觀察學習過程中神經元活動的特性。主要發現海馬回區有兩種特定細胞：錐體細胞與中間細胞，其中錐體細胞對於特定地區有穩定的放電特性，並在西塔(θ)頻段4-12Hz發現時序上的放電節奏—相歲差，而中間細胞在轉角處有強烈的放電表現，且中間細胞與錐體細胞單一突觸連結會同步在時序與空間上放電。在地區場電位中發現貝塔(β)頻段15-30Hz對於回饋區的反應，也驗證了西塔(θ)頻段對於動作的反應特性。最後透過電生理訊號，以Q自學式類神經演算法模擬出老鼠行為的軌跡，反應學習行為慣性方向與移動變化。

In neuroscience, cognitive and memory is very important topic. The hippocampus is thought the main function for managing the memory system. Previous study has shown that the neuron activities in hippocampus present spatial information and provide the hypothesis of “cognitive map” for functional hippocampus. However, the correlation between spatial memory and neuron activities are not clearly defined. Therefore, understanding the function of the hippocampus in the formation of spatial memory learning process and describing this mechanism in systemic encode is our purpose. Our research design water reward task to train the rats free running in the environment. Recorded neuron signals through the invaded electrode were examined the relationship with animal behaviors. There are two types of neurons in hippocampus: pyramidal cells and interneurons. The pyramidal cells discharge not only in specific location but also corresponding to theta (4-12Hz) band rhythm, known as phase precession. Interneurons were discovered firing emphasis in corner zone and exhibiting functional monosynaptic coupling in temporal firing and in spatial firing field with pyramidal cell. The low band variance also present in local field potential, where beta band is response to the odor-learning and theta band is response to the movement. Though those feature of neuron signals, we provide a self-organization feature map for learning process to explain animal habitual behavior involved in direction preference and variance in trajectories.