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  • 學位論文

小腦浦金耶氏細胞於自主平衡控制中的訊息編碼可塑性

Information Coding Plasticity of Cerebellar Purkinje Cells in Voluntary Balance Control

指導教授 : 嚴震東
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摘要


維持平衡涉及小腦的神經元可塑性。然而,在同時具有主動與被動運動的自然學習過程中,感覺訊息輸入的計算調整依然不清楚。本論文中,我們研究大鼠於高懸短桿上嘗試維持身體平衡時,小腦浦金耶氏細胞(PC)的峰電位活動。我們發現頭部的擺動隨著大鼠於桿上的適應逐漸下降(十八隻大鼠),暗示著平衡控制中存在短期運動學習。PC的簡單(SS;二十六顆神經元中的十七顆)與複雜峰電位(CS;十二顆中的七顆)均有發現對頭部角運動編碼的情形。在這些編碼神經元中,大多數(十七顆中的十四顆)SS放電頻率與頭部運動的角速度呈線性相關。對於CS訊息編碼的PC,其SS以互逆(七顆中的五顆)或同向(七顆中的兩顆)的關係編碼相同的訊息。SS放電頻率與頭部角運動的相關性與站桿時的運動程度呈現正相關。選用運動程度相近的時間區間,我們發現其中大部分(十七顆中的十顆)PC的編碼能力於站桿任務中隨著時間顯著下降,並伴隨著SS與CS之間互動的減弱。這種編碼能力在提供非預期性擾動而增加被動運動,或在動物被麻醉後又恢復。因此,我們推論濾除主動運動所帶來之感覺輸入的神經可塑性發生在維持平衡的學習過程中。我們的發現首度揭示小腦皮質對主動與被動運動所造成感覺輸入計算的學習動態。

並列摘要


Maintenance of balance involves neuronal plasticity in the cerebellum. However, plasticity mechanisms underlying the adjustment in the computation of sensory afference during a natural learning process with both active and passive motions still remain unclear. In this thesis, we investigated the readout of the cerebellar cortex, the Purkinje cell (PC) spiking, when the rat tried to balance itself on a short beam high above the ground. We found the fluctuation of the head gradually decreased as the rat adapted on the beam (n = 18 rats), suggesting a short-term motor learning of balance control. Both simple (SSs; n=17 of 26 neurons) and complex spikes (CSs; n=7 of 12) of Purkinje cells were shown to code head motion in the sagittal plane. Among the coding neurons, most (n = 14 of 17 neurons) had their SS firing frequency linearly correlated with the angular velocity of the head motion. PCs with CS information coding had their SS code the same information in either a reciprocal (n=5 of 7) or a one-sided manner (n=2 of 7). The correlation between SS firing frequency and the angular motions of the head correlated positively with the motion level during beam standing. Using periods with comparable motion level, we found the SS coding capability in most PCs (n = 10 of 17) decreased significantly during the beam standing task, with the reduction in the interaction between simple and complex spikes. SS coding capability of these PCs was recovered under unexpected perturbations or under anesthesia. Hence, we demonstrate that neural plasticity for filtering out sensory afference of active motions happened in the learning process of balance maintenance. Our findings reveal, for the first time, the learning dynamics of sensory afference computation between active and passive motions in the cerebellar cortex.

參考文獻


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