小腦經視丘至前扣帶迴皮質的神經連結

Abstract

小腦除了在運動功能上扮演重要角色，近期行為及電生理研究也發現小腦參與了認知和情緒等功能，但在解剖上的證據較不明確。本研究在大鼠腦中注射神經追蹤劑，來觀察小腦及和情緒功能高度相關的大腦邊緣系統之間的連結。本實驗分為四個部分：(1)在大鼠小腦深部核(deep cerebellar nuclei, DCN)注射順行性神經追蹤劑;(2)在大鼠視丘中央部位注射反行性神經追蹤劑;(3)在大鼠前扣帶迴皮質區(anterior cingulate cortex, ACC)注射反行性神經追蹤劑;(4)同時在大鼠小腦注射順行性神經追蹤劑，並在大腦邊前扣帶迴皮質區注射反行性神經追蹤劑。使存活一段時間後，將動物犧牲灌流並將腦固定後取出，以冷凍切片並進行觀察。在此研究中發現:(1)小腦除了投射至腹前側核(ventral anterior thalamic nucleus, VA),腹外側核(ventrolateral thalamic nucleus, VL),腹內側核(ventromedial, VM)等運動相關核區，也會投射到內背側核外側部分(lateral part of mediodorsal thalamic nucleus, MDL),中央旁核(paracentral thalamic nucleus, PC),中央外側核(centrolateral thalamic nucleus, CL),中央內側核(central medial thalamic nucleus, CM)等位於視丘的核區，其中以齒狀核(dentate nuclei, DN)的投射最多。(2)靠近尾端的內背側核, 板內側核(intralaminar nuclei, ILN)等視丘核區傾向投射到靠近頭側的前扣帶迴皮質區，而較頭側的視丘核區則會投射到靠近尾端的前扣帶皮質區。(3)在小腦及前扣帶迴皮質區分別注射順行及反行性的神經追蹤劑實驗中，發現在小腦齒狀核及中間核(interposed nuclei, IN)注射追蹤劑的大鼠中，可以在視丘內背側核外側部分,中央旁核,中央外側核等區域發現被標定的神經細胞被從小腦投射而來的軸突末端包圍。說明小腦中神經元可能通過丘腦中的這些核區作為中繼站進而和前扣帶迴皮質區進行連結與功能協調。本結果在解剖上提供小腦在認知、情緒等非運動功能上也扮演了協調的可能。

Cerebellum has long been thought as a main area for motor executive control. Recent studies of electrophysiology and behavior reveal that cerebellum also participates in cognitive and emotional functions. However, there is still no sufficient anatomical evidence. The study includes four parts: we (1) injected anterograde neuronal tracer in the rat deep cerebellar nuclei (DCN); (2) injected retrograde tracer in the mid thalamus; (3) injected retrograde tracer in anterior cingulate cortex (ACC); (4) simultaneously injected anterograde tracer in the DCN and retrograde tracer in ACC. After several days of survival, the animal was sacrificed for perfusion and the brain was fixed and removed for further frozen section. The results show: (1) Except for ventral anterior thalamic nucleus (VA), ventrolateral thalamic nucleus (VL) and ventromedial thalamic nucleus (VM), cerebellar also projects to non-motor nuclei, such as lateral part of mediodorsal thalamic nucleus (MDL), paracentral thalamic nucleus (PC), centrolateral thalamic nucleus (CL) and central medial thalamic nucleus (CM), and dentate nuclei (DN) is the main output. (2) The retrograde tracing of ACC injection of fluoro-gold shows a tendency that rostral medial thalamus preferentially projects to A2 and caudal medial thalamus to A4 level of ACC. (3) In MDL, PC, and CL, many retrograde tracer labeled neurons can be seen and anterograde tracer labeled axon fiber and boutons around those neurons. Our results indicate that the cerebellum may have connections with anterior cingulate cortex through mediodorsal thalamic nucleus, paracentral nucleus, or central lateral nucleus and provide anatomical data showing the role of emotional coordination by the cerebellum.