皮层θ振荡器中灵活相位锁定的动力学机制
Dynamical mechanisms of flexible phase-locking in cortical theta oscillators
AI总结：
研究揭示了皮层θ振荡器通过多时间尺度抑制电流的相互作用实现灵活相位锁定的机制，关键发现包括慢和超慢抑制过程的延迟Hopf现象扩展了同步范围。
摘要：
皮层θ振荡器中的灵活相位锁定动力学机制研究表明，通过多时间尺度抑制电流的相互作用实现了灵活相位锁定。关键发现包括慢和超慢抑制过程的延迟Hopf现象扩展了同步范围。研究在生物物理基础的皮层θ振荡器模型中验证了这一机制，表明θ尺度（4-8 Hz）抑制电流$ I_m $和较慢的delta尺度（1-4 Hz）抑制钾电流$ I_{\ m K_{SS}} $对同步灵活性至关重要。它们的相互作用产生了一个三时间尺度结构，导致与延迟Hopf bifurcation（DHB）相关的明显延迟现象。有趣的是，超慢$ I_{\ m K_{SS}} $和相关的DHB在无外界输入时对振荡动态影响较小，但在外部输入下被招募以支持相位锁定。此外，中间时间尺度的$ I_m $电流而非冗余，通过延长超慢流上的延迟恢复进一步扩展了相位锁定范围。这些结果表明，内在抑制电流在多个时间尺度上的协调可能代表了支持大脑对节奏输入灵活相位锁定的关键机制。
英文摘要：
Oscillatory activity in auditory cortex is thought to play a central role in auditory and speech processing by synchronizing neural rhythms to external acoustic features of the speech stream. To support this function, cortical oscillators must flexibly phase-lock to inputs spanning a wide range of timescales, including rhythms substantially slower than their intrinsic frequency. Here we identify a general dynamical mechanism by which intrinsic inhibitory currents operating on multiple timescales enable such flexible phase-locking. Using tools from dynamical systems theory, we show that interactions between slow and superslow inhibitory processes generate prolonged post-input recovery delays through delayed Hopf phenomena, thereby substantially expanding the frequency range over which entrainment can occur. We demonstrate this mechanisms in a biophysically grounded cortical theta oscillator model for speech segmentation. Specifically, we show that both a theta-timescale (4-8 Hz) inhibitory current $I_m$ and a slower delta-timescale (1-4 Hz) inhibitory potassium current $I_{\rm K_{SS}}$ are crucial for entrainment flexibility. Their interaction creates a three-timescale structure that gives rise to pronounced delay phenomena associated with a delayed Hopf bifurcation (DHB). Interestingly, the superslow $I_{\rm K_{SS}}$ and the associated DHB play little role in the unforced oscillatory dynamics, but are recruited to support phase locking under external forcing. Moreover, the intermediate-timescale current $I_m$, rather than being redundant, further expands the phase-locking range by prolonging delayed recovery along the superslow manifold. Together, these results suggest that coordination among intrinsic inhibitory currents operating on multiple timescales may represent a key mechanism supporting flexible phase locking to rhythmic inputs in the brain.
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