Department of Psychology.
Department of Neuroscience.
Behav Neurosci. 2020 Dec;134(6):516-528. doi: 10.1037/bne0000416.
Hippocampal theta oscillations have a temporally asymmetric waveform shape, but it is not known if this theta asymmetry extends to all other cortical regions involved in spatial navigation and memory. Here, using both established and improved cycle-by-cycle analysis methods, we show that theta waveforms in the postrhinal cortex are also temporally asymmetric. On average, the falling phase of postrhinal theta cycles lasts longer than the subsequent rising phase. There are, however, rapid changes in both the instantaneous amplitude and instantaneous temporal asymmetry of postrhinal theta cycles. These rapid changes in amplitude and asymmetry are very poorly correlated, indicative of a mechanistic disconnect between these theta cycle features. We show that the instantaneous amplitude and asymmetry of postrhinal theta cycles differentially encode running speed. Although theta amplitude continues to increase at the fastest running speeds, temporal asymmetry of the theta waveform shape plateaus after medium speeds. Our results suggest that the amplitude and waveform shape of individual postrhinal theta cycles may be governed by partially independent mechanisms and emphasize the importance of employing a single cycle approach to understanding the genesis and behavioral correlates of cortical theta rhythms. (PsycInfo Database Record (c) 2021 APA, all rights reserved).
海马体θ 振荡具有时间不对称的波形形状，但尚不清楚这种θ 不对称是否扩展到所有其他参与空间导航和记忆的皮质区域。在这里，我们使用已建立和改进的逐周期分析方法，表明在旁海马皮层中，θ 波也具有时间不对称性。平均而言，旁海马θ 周期的下降阶段持续时间长于随后的上升阶段。然而，旁海马θ 周期的瞬时幅度和瞬时时间不对称性都发生了快速变化。这些幅度和不对称性的快速变化相关性很差，表明这些θ 周期特征之间存在机制上的脱节。我们表明，旁海马θ 周期的瞬时幅度和不对称性可区分地编码运行速度。尽管θ 幅度在最快的运行速度下继续增加，但θ 波形形状的时间不对称性在中等速度后趋于平稳。我们的结果表明，单个旁海马θ 周期的幅度和波形形状可能由部分独立的机制控制，并强调采用单个周期方法来理解皮质θ 节律的产生和行为相关性的重要性。（PsycInfo 数据库记录（c）2021 APA，保留所有权利）。
