Fujisawa Shigeyoshi, Matsuki Norio, Ikegaya Yuji
Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan.
Cereb Cortex. 2006 May;16(5):639-54. doi: 10.1093/cercor/bhj010. Epub 2005 Aug 10.
Fluctuations of membrane potential of cortical neurons, referred to here as internal states, are essential for brain function, but little is known about how these internal states emerge and are maintained, or what determines transitions between these states. We performed intracellular recordings from hippocampal CA3 pyramidal cells ex vivo and found that neurons display multiple and hierarchical internal states, which are linked to cholinergic activity and are characterized by several power law structures in membrane potential dynamics. Multiple recordings from adjacent neurons revealed that the internal states were coherent between neurons, indicating that the internal state of any given cell in a local network could represent the network activity state. Repeated stimulation of single neurons led over time to transitions to different internal states in both the stimulated neuron and neighboring neurons. Thus, single-cell activation is sufficient to shift the state of the entire local network. As the states shift to more active levels, theta- and gamma-frequency components developed in the form of subthreshold oscillations. State transitions were associated with changes in membrane conductance but were not accompanied by a change in reversal potential. These data suggest that the recurrent network organizes the internal states of individual neurons into synchronization through network activity with balanced excitation and inhibition, and that this organization is discrete, heterogeneous and dynamic in nature. Thus, neuronal states reflect the 'phase' of an active network, a novel demonstration of the dynamics and flexibility of cortical microcircuitry.
皮层神经元膜电位的波动，在此称为内部状态，对脑功能至关重要，但对于这些内部状态如何出现和维持，或者是什么决定了这些状态之间的转换，我们却知之甚少。我们对离体海马CA3锥体神经元进行了细胞内记录，发现神经元表现出多种层次化的内部状态，这些状态与胆碱能活动相关，并以膜电位动力学中的几种幂律结构为特征。对相邻神经元的多次记录显示，神经元之间的内部状态是连贯的，这表明局部网络中任何给定细胞的内部状态都可以代表网络活动状态。随着时间的推移，对单个神经元的重复刺激导致受刺激神经元和相邻神经元都转变为不同的内部状态。因此，单细胞激活足以改变整个局部网络的状态。随着状态转变为更活跃的水平，θ波和γ波频率成分以阈下振荡的形式出现。状态转换与膜电导的变化有关，但不伴有反转电位的变化。这些数据表明，递归网络通过具有平衡兴奋和抑制的网络活动将单个神经元的内部状态组织成同步，并且这种组织在性质上是离散的、异质的和动态的。因此，神经元状态反映了活跃网络的“相位”，这是皮层微电路动力学和灵活性的一个新证明。
