我們研究大白老鼠腦皮質層之二維腦神經網路，於低鎂離子濃度下的同步發火現象。利用鈣離子螢光染色指示計，共軛焦雷射掃瞄顯微技術，與電子倍增式影像顯微系統，使神經元網路之鈣離子動力學行為得以量測。腦皮質神經元細胞於高密度下，形成以粗大絲狀神經元捆束相互連接之三維巨大團簇，以組成二維神經元網路。因著腦神經元網路之時空異質性，此神經網路可展現豐富之同步發火動力學行為。第一，導致神經網路中，同步發火領先團簇與同步發火落後團簇之自動性發生。藉著調控團簇間之聯結強度與環境干擾程度，神經元團簇同步發火之順序可被翻轉。第二，在成長後期展現有一長時間的間歇時期與高頻同步發火動力共存，形成一緩慢之調幅效應。根據非線性動力學之分析手法，以及藥理學之實驗測試，我們提出並驗證幾種可能的機制。 Synchronization is investigated in the two-dimensional clusterized cortical neuronal network in vitro. The firing activity of the network is stained by fluorescence calcium indicator under the depletion of magnesium ions and monitored by the confocal microscopy with 10 Hz EMCCD. At high density (» 9000 cells/mm2), neurons self-organize into the two-dimensional clusterized neuronal network interconnected by three-dimensional clusters. Due to the spatial heterogeneity of the clusterized network at high density, the cortical neuronal network has rich spatiotemporal firing dynamics. It has been identified that the envelopes of bursting neurons within clusters are synchronous. At inter-cluster level, the firing delay between clusters is investigated at fine temporal scale. The firing order between these clusters exists on 8th day in vitro (DIV). Through tuning the mutual coupling strength and stochastic noise in the environment, it is found that not only the firing delay is enhanced, but also the firing order between clusters is exchanged. As day goes by, the firing burst rate increases, because the stronger coupling strength between clusters enhance. In the presence of the spatial heterogeneous neuronal network, the slower time scale dynamics, the burst of action potential burst, is explored on 14th»17th DIV. Standing on the nonlinear dynamics, several mechanisms are proposed and verified. This phenomenon still calls for more biological assays to verify.
