Department of Mechano-informatics, Graduate School of Information Science and Technology, The University of Tokyo, Tokyo, Japan.
Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
Sci Rep. 2020 Jun 2;10(1):8932. doi: 10.1038/s41598-020-65745-z.
Neuromodulation achieved by vagus nerve stimulation (VNS) induces various neuropsychiatric effects whose underlying mechanisms of action remain poorly understood. Innervation of neuromodulators and a microcircuit structure in the cerebral cortex informed the hypothesis that VNS exerts layer-specific modulation in the sensory cortex and alters the balance between feedforward and feedback pathways. To test this hypothesis, we characterized laminar profiles of auditory-evoked potentials (AEPs) in the primary auditory cortex (A1) of anesthetized rats with an array of microelectrodes and investigated the effects of VNS on AEPs and stimulus specific adaptation (SSA). VNS predominantly increased the amplitudes of AEPs in superficial layers, but this effect diminished with depth. In addition, VNS exerted a stronger modulation of the neural responses to repeated stimuli than to deviant stimuli, resulting in decreased SSA across all layers of the A1. These results may provide new insights that the VNS-induced neuropsychiatric effects may be attributable to a sensory gain mechanism: VNS strengthens the ascending input in the sensory cortex and creates an imbalance in the strength of activities between superficial and deep cortical layers, where the feedfoward and feedback pathways predominantly originate, respectively.
迷走神经刺激（VNS）实现的神经调节会产生各种神经精神效应，但其作用机制仍知之甚少。神经调节剂的神经支配和大脑皮层的微电路结构使人们假设 VNS 会对感觉皮层产生特定于层的调节，并改变前馈和反馈途径之间的平衡。为了验证这一假设，我们使用一系列微电极对麻醉大鼠的初级听觉皮层（A1）中的听觉诱发电位（AEPs）的层状分布进行了表征，并研究了 VNS 对 AEPs 和刺激特异性适应（SSA）的影响。VNS 主要增加了浅层的 AEPs 幅度，但这种效应随深度而减弱。此外，VNS 对重复刺激的神经反应的调制作用强于对偏差刺激的调制作用，导致 A1 的所有层的 SSA 降低。这些结果可能提供新的见解，即 VNS 诱导的神经精神效应可能归因于感觉增益机制：VNS 增强了感觉皮层中的上行输入，并在浅层和深层皮层之间的活动强度之间造成不平衡，前馈和反馈途径主要起源于这些皮层。
