Department of Electronics, Computer Science and Systems, University of Bologna, Bologna, Italy.
Neuroimage. 2010 Sep;52(3):1080-94. doi: 10.1016/j.neuroimage.2009.12.084. Epub 2010 Jan 4.
Rhythms in brain electrical activity are assumed to play a significant role in many cognitive and perceptual processes. It is thus of great value to analyze these rhythms and their mutual relationships in large scale models of cortical regions. In the present work, we modified the neural mass model by Wendling et al. (Eur. J. Neurosci. 15 (2002) 1499-1508) by including a new inhibitory self-loop among GABAA,fast interneurons. A theoretical analysis was performed to demonstrate that, thanks to this loop, GABAA,fast interneurons can produce a gamma rhythm in the power spectral density (PSD) even without the participation of the other neural populations. Then, the model of a whole cortical region, built upon four interconnected neural populations (pyramidal cells, excitatory, GABAA,slow and GABAA,fast interneurons) was investigated by changing the internal connectivity parameters. Results show that different rhythm combinations (beta and gamma, alpha and gamma, or a wide spectrum) can be obtained within the same region by simply altering connectivity values, without the need to change synaptic kinetics. Finally, two or three cortical regions were connected by using different topologies of long range connections. Results show that long-range connections directed from pyramidal neurons to GABAA,fast interneurons are the most efficient to transmit rhythms from one region to another. In this way, PSD with three or four peaks can be obtained using simple connectivity patterns. The model can be of value to gain a deeper insight into the mechanisms involved in the generation of gamma rhythms and provide a better understanding of cortical EEG spectra.
脑电活动节律被认为在许多认知和感知过程中发挥着重要作用。因此，分析皮质区域大尺度模型中的这些节律及其相互关系具有重要意义。在本工作中，我们对 Wendling 等人的神经质量模型进行了修改（Eur. J. Neurosci. 15 (2002) 1499-1508），在 GABAA、快中间神经元中加入了一个新的抑制性自回路。理论分析表明，由于这个回路，GABAA、快中间神经元即使没有其他神经元群体的参与，也可以在功率谱密度（PSD）中产生伽马节律。然后，通过改变内部连接参数，研究了基于四个相互连接的神经元群体（锥体神经元、兴奋性神经元、GABAA、慢中间神经元和 GABAA、快中间神经元）的整个皮质区域模型。结果表明，通过简单地改变连接值，而无需改变突触动力学，可以在同一区域内获得不同的节律组合（β和γ、α和γ或宽谱）。最后，使用不同的长程连接拓扑结构将两个或三个皮质区域连接起来。结果表明，从锥体神经元到 GABAA、快中间神经元的长程连接是将节律从一个区域传输到另一个区域最有效的方式。通过这种方式，使用简单的连接模式可以获得具有三个或四个峰值的 PSD。该模型有助于深入了解产生伽马节律的机制，并更好地理解皮质 EEG 谱。
