以大鼠初級體感覺皮質各層神經活性 評估植入式多通道神經探針

Abstract

擷取清醒狀態大腦電生理訊號並且進行分析是目前研究趨勢，但過往電生理研究在技術上以及實驗上的考量，幾乎是使用麻醉狀態之動物進行研究。目前已有文獻指出麻醉和清醒狀態下神經元運作有差異，甚至不同的麻藥有不同的影響。因此，我們若要瞭解大腦功能性的反應，勢必在清醒狀態下進行實驗。本論文即是實驗室轉型之基礎研究，藉此設計出適合未來清醒狀態研究的實驗架構，並且探討可植入式多通道神經探針是否適用於本實驗室未來的實驗目標。 本論文選用大鼠大腦初級體感覺皮質區（primary somatosensory cortex, S1）作為記錄之核區。藉由該皮質區的特性，以及所選用之多通道神經探針的架構，我們透過分析大鼠後肢區同一柱狀結構（column）內各分層（laminar）神經群對於機械性刺激的反應，來評估植入式多通道神經探針於長期記錄下之可行性。 於神經探針植入後三個月之觀察，將所記錄的誘發性神經動作電位（evoked action potential）由三個面向進行分析。從波形來看，長期記錄下所收集之訊號振幅皆有變小，但不同皮質深度所收集之訊號變小程度不盡相同，且其中棘波（spike）發生重疊可能性升高。延遲時間來看，長期記錄下依然是第IV層最短，符合文獻中短期記錄之結果。由積分結果來看，各層數值皆有下降之趨勢，其中又以第V層下降幅度最大。另外，由積分結果進行統計分析後發現，長期記錄下依然可區分第II/III層以及第IV層之活性。由此可知，雖然本論文所選用之神經探針在植入後會影響神經元活性，但依然足以進行相關分析。況且該電極擁有十六通道之優勢，對於研究清醒狀態下初級體感覺皮質區各層活性差異有莫大的助益。

Presently, electrophysiological studies focus primarily on recording and analyzing signals while testing animals are in conscious state. New research suggests the idea that differences in state of brain as well as type of anesthetics could result in different activity of neurons. In addition, some research studies point out the limitations of doing animal testing under states of anesthesia since higher brain function will be inhibited at the time. Thus research animals should be maintained consciousness. The purpose of this study is to design a protocol of electrophysiological study with animals in conscious states and evaluate the feasibility of applying implantable multi-channel neuroprobe in future studies. In this study, signals were recorded from hindpaw region of the primary somatosensory cortex (S1) in adult rats. Due to the response properties of neurons in primary somatosensory cortex and the conformation of multi-channel neuroprobe, the responses to mechanical stimuli of neurons were recorded in same column, however, in different laminar in order to evaluate the usability of the implantable multi-channel neuroprobe. After implantation, the changes of evoked action potential were examined for three months. The results recorded were analyzed in three different ways: (1) amplitude of signals; (2) latency of evoked action potential; and (3) statistical analysis on layers. First of all, although the decline was different in laminar, the amplitude of the signal was found becoming smaller over time. Additionally, the probability of signal overlap increased. Secondly, regarding to the latency of evoked action potential, in long-term recording, the shortest one was found in layer IV which corresponded to the previous studies. Last but not least, there was a declining trend of signal integration in laminar, and the greatest decline was in layer V. Moreover, in long-term recording, the differences between the activity of layer II/III and layer IV could be distinguished utilizing statistical analysis. Therefore, although neuroprobe would influence the activity of neurons after implantation, it could be utilized to record signals for analysis. Furthermore, since there are multi-channels in one neuroprobe, this will be the superiority on studying differences in activity in S1 laminar with animals in conscious states.