Grabska-Barwińska Agnieszka, Zygierewicz Jarosław
Department of Biomedical Physics, Institute of Experimental Physics, Warsaw University, Hoza 69, 00-681 Warsaw, Poland.
J Theor Biol. 2006 Feb 21;238(4):901-13. doi: 10.1016/j.jtbi.2005.07.001. Epub 2005 Aug 15.
During preparation, execution and recovery from simple movements, the EEG power spectrum undergoes a sequence of changes. The power in the beta band (13-25 Hz) decreases during preparation and execution of movement, but during recovery it reaches a level higher than that in the reference period (not affected by the event). These effects are known as event-related beta desynchronization and beta rebound. The power in the gamma band (>30 Hz) increases significantly just before the onset of the movement. This effect is known as event-related gamma synchronization. There are numerous observations concerning these effects but the underlying physiological mechanisms and functional role are not clear. We propose a lumped computational model of a cortical circuit. The model consists only of a pyramidal and an interneuronal population. Each population represents averaged properties of constituting neurons. The output of the model represents a local field potential, with a power spectrum peak either in the beta or in the gamma band. The model elucidates the mechanisms of transition between slower and faster rhythms, gamma synchronization and beta desynchronization and rebound effects. The sufficient conditions to observe the effects in the model are changes of the external excitation level and of the connection strength between excitatory and inhibitory populations attributed to short-time plasticity. The present model presents the role of the pyramidal neurons to interneuron connection in the oscillatory behavior of the two populations. We conclude that the pronounced facilitation of the pyramidal to fast spiking interneuron connections, initiated by robust excitation of the motor cortex neurons, may be essential for the effect of beta rebound. Further experiments concerning short-time plasticity during behavioral tasks would be of great value in studies of functional local cortical circuits.
在简单运动的准备、执行和恢复过程中，脑电图功率谱会经历一系列变化。在运动准备和执行期间，β波段（13 - 25赫兹）的功率下降，但在恢复期间，它会达到高于参考期（不受该事件影响）的水平。这些效应被称为事件相关β去同步化和β反弹。在运动开始前，γ波段（>30赫兹）的功率会显著增加。这种效应被称为事件相关γ同步化。关于这些效应有许多观察结果，但潜在的生理机制和功能作用尚不清楚。我们提出了一个皮质回路的集总计算模型。该模型仅由一个锥体神经元群体和一个中间神经元群体组成。每个群体代表构成神经元的平均特性。模型的输出代表局部场电位，其功率谱峰值要么在β波段，要么在γ波段。该模型阐明了慢节律和快节律之间转换、γ同步化、β去同步化以及反弹效应的机制。在模型中观察到这些效应的充分条件是外部兴奋水平的变化以及归因于短时可塑性的兴奋性和抑制性群体之间连接强度的变化。本模型展示了锥体神经元与中间神经元连接在这两个群体振荡行为中的作用。我们得出结论，由运动皮层神经元的强烈兴奋引发的锥体神经元与快速发放中间神经元连接的显著促进作用，可能对β反弹效应至关重要。关于行为任务期间短时可塑性的进一步实验，在功能性局部皮质回路的研究中将具有重要价值。
