Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030
Department of Neurosurgery, University of Utah, Salt Lake City, Utah 84132.
J Neurosci. 2022 Aug 10;42(32):6285-6294. doi: 10.1523/JNEUROSCI.0050-22.2022. Epub 2022 Jul 5.
Neuronal coherence is thought to be a fundamental mechanism of communication in the brain, where synchronized field potentials coordinate synaptic and spiking events to support plasticity and learning. Although the spread of field potentials has garnered great interest, little is known about the spatial reach of phase synchronization, or neuronal coherence. Functional connectivity between different brain regions is known to occur across long distances, but the locality of synchronization across the neocortex is understudied. Here we used simultaneous recordings from electrocorticography (ECoG) grids and high-density microelectrode arrays to estimate the spatial reach of neuronal coherence and spike-field coherence (SFC) across frontal, temporal, and occipital cortices during cognitive tasks in humans. We observed the strongest coherence within a 2-3 cm distance from the microelectrode arrays, potentially defining an effective range for local communication. This range was relatively consistent across brain regions, spectral frequencies, and cognitive tasks. The magnitude of coherence showed power law decay with increasing distance from the microelectrode arrays, where the highest coherence occurred between ECoG contacts, followed by coherence between ECoG and deep cortical local field potential (LFP), and then SFC (i.e., ECoG > LFP > SFC). The spectral frequency of coherence also affected its magnitude. Alpha coherence (8-14 Hz) was generally higher than other frequencies for signals nearest the microelectrode arrays, whereas delta coherence (1-3 Hz) was higher for signals that were farther away. Action potentials in all brain regions were most coherent with the phase of alpha oscillations, which suggests that alpha waves could play a larger, more spatially local role in spike timing than other frequencies. These findings provide a deeper understanding of the spatial and spectral dynamics of neuronal synchronization, further advancing knowledge about how activity propagates across the human brain. Coherence is theorized to facilitate information transfer across cerebral space by providing a convenient electrophysiological mechanism to modulate membrane potentials in spatiotemporally complex patterns. Our work uses a multiscale approach to evaluate the spatial reach of phase coherence and spike-field coherence during cognitive tasks in humans. Locally, coherence can reach up to 3 cm around a given area of neocortex. The spectral properties of coherence revealed that alpha phase-field and spike-field coherence were higher within ranges <2 cm, whereas lower-frequency delta coherence was higher for contacts farther away. Spatiotemporally shared information (i.e., coherence) across neocortex seems to reach farther than field potentials alone.
神经元相干被认为是大脑中信息传递的基本机制，其中同步的场电位协调突触和尖峰事件，以支持可塑性和学习。尽管场电位的传播引起了广泛的关注，但关于相位同步或神经元相干的空间范围知之甚少。不同脑区之间的功能连接已知发生在长距离，但皮质的同步局部性研究较少。在这里，我们使用皮层电图 (ECoG) 网格和高密度微电极阵列的同步记录，在人类认知任务期间估计前额叶、颞叶和枕叶皮质中神经元相干和尖峰-场相干 (SFC) 的空间范围。我们观察到微电极阵列附近 2-3 厘米范围内最强的相干性，这可能定义了局部通信的有效范围。该范围在不同脑区、频谱频率和认知任务中相对一致。相干性的幅度随着与微电极阵列距离的增加呈幂律衰减，其中微电极阵列之间的相干性最高，其次是微电极阵列和皮质深部局部场电位 (LFP) 之间的相干性，然后是 SFC（即 ECoG>LFP>SFC）。相干性的频谱频率也会影响其幅度。与微电极阵列最近的信号的 alpha 相干性（8-14 Hz）通常高于其他频率，而距离较远的信号的 delta 相干性（1-3 Hz）较高。所有脑区的动作电位与 alpha 振荡的相位最相干，这表明 alpha 波在尖峰定时方面可能比其他频率发挥更大、更局部的作用。这些发现提供了对神经元同步的空间和频谱动态的更深入理解，进一步推进了关于活动如何在人脑内传播的知识。相干性被认为通过提供一种方便的电生理机制来调制时空复杂模式下的膜电位，从而促进大脑空间的信息传递。我们的工作使用多尺度方法来评估人类认知任务期间相位相干性和尖峰-场相干性的空间范围。在局部，相干性可以在给定的新皮质区域周围达到 3 厘米。相干性的频谱特性表明，alpha 相-场和尖峰-场相干性在<2 cm 的范围内更高，而较低频率的 delta 相干性在距离较远的接触点更高。新皮质之间的时空共享信息（即相干性）似乎比场电位本身更远。
