School of Physics, University of Sydney, New South Wales 2006, Australia.
Neuroimage. 2012 Sep;62(3):1947-55. doi: 10.1016/j.neuroimage.2012.05.054. Epub 2012 May 29.
Strong periodic stimuli such as bright flashing lights evoke nonlinear responses in the brain and interact nonlinearly with ongoing cortical activity, but the underlying mechanisms for these phenomena are poorly understood at present. The dominant features of these experimentally observed dynamics are reproduced by the dynamics of a quantitative neural field model subject to periodic drive. Model power spectra over a range of drive frequencies show agreement with multiple features of experimental measurements, exhibiting nonlinear effects including entrainment over a range of frequencies around the natural alpha frequency f(α), subharmonic entrainment near 2f(α), and harmonic generation. Further analysis of the driven dynamics as a function of the drive parameters reveals rich nonlinear dynamics that is predicted to be observable in future experiments at high drive amplitude, including period doubling, bistable phase-locking, hysteresis, wave mixing, and chaos indicated by positive Lyapunov exponents. Moreover, photosensitive seizures are predicted for physiologically realistic model parameters yielding bistability between healthy and seizure dynamics. These results demonstrate the applicability of neural field models to the new regime of periodically driven nonlinear dynamics, enabling interpretation of experimental data in terms of specific generating mechanisms and providing new tests of the theory.
强烈的周期性刺激，如明亮的闪烁灯光，会在大脑中引发非线性反应，并与皮质活动的持续进行非线性相互作用，但目前对于这些现象的潜在机制还了解甚少。受周期性驱动的定量神经场模型的动力学能够重现这些在实验中观察到的动态的主要特征。在一系列驱动频率下的模型功率谱与多项实验测量结果一致，表现出非线性效应，包括在自然阿尔法频率 f(α)周围的一系列频率上的同步，在 2f(α)附近的次谐波同步，以及谐波产生。对驱动动力学作为驱动参数函数的进一步分析揭示了丰富的非线性动力学，预计在未来的高驱动幅度实验中可以观察到这些动力学，包括倍周期、双稳态锁相、滞后、波混合和正李雅普诺夫指数所表示的混沌。此外，对于产生双稳态的生理现实模型参数，预测了光敏感发作，在健康和发作动力学之间。这些结果表明，神经场模型适用于周期性驱动的非线性动力学的新领域，能够根据特定的生成机制对实验数据进行解释，并为理论提供新的检验。
