Neurophysiology Unit, Department of Brain and Behavioral Sciences, University of Pavia Pavia, Italy ; Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia Modena, Italy.
Front Neural Circuits. 2013 Apr 10;7:64. doi: 10.3389/fncir.2013.00064. eCollection 2013.
The neuronal circuits of the brain are thought to use resonance and oscillations to improve communication over specific frequency bands (Llinas, 1988; Buzsaki, 2006). However, the properties and mechanism of these phenomena in brain circuits remain largely unknown. Here we show that, at the cerebellum input stage, the granular layer (GRL) generates its maximum response at 5-7 Hz both in vivo following tactile sensory stimulation of the whisker pad and in acute slices following mossy fiber bundle stimulation. The spatial analysis of GRL activity performed using voltage-sensitive dye (VSD) imaging revealed 5-7 Hz resonance covering large GRL areas. In single granule cells, resonance appeared as a reorganization of output spike bursts on the millisecond time-scale, such that the first spike occurred earlier and with higher temporal precision and the probability of spike generation increased. Resonance was independent from circuit inhibition, as it persisted with little variation in the presence of the GABAA receptor blocker, gabazine. However, circuit inhibition reduced the resonance area more markedly at 7 Hz. Simulations with detailed computational models suggested that resonance depended on intrinsic granule cells ionic mechanisms: specifically, K slow (M-like) and KA currents acted as resonators and the persistent Na current and NMDA current acted as amplifiers. This form of resonance may play an important role for enhancing coherent spike emission from the GRL when theta-frequency bursts are transmitted by the cerebral cortex and peripheral sensory structures during sensory-motor processing, cognition, and learning.
大脑的神经元回路被认为利用共振和振荡来改善特定频带的信息传递（Llinas，1988；Buzsaki，2006）。然而，这些现象在脑回路中的特性和机制在很大程度上仍然未知。在这里，我们表明，在小脑输入阶段，颗粒层（GRL）在体内对胡须垫进行触觉感觉刺激后和在急性切片中对苔藓纤维束刺激后，在 5-7 Hz 时产生最大响应。使用电压敏感染料（VSD）成像进行的 GRL 活动的空间分析显示，5-7 Hz 的共振覆盖了大的 GRL 区域。在单个颗粒细胞中，共振表现为输出尖峰爆发在毫秒时间尺度上的重新组织，使得第一个尖峰更早发生，具有更高的时间精度，并且尖峰发生的概率增加。共振与电路抑制无关，因为在存在 GABA A 受体阻滞剂 Gabazine 的情况下，它几乎没有变化而持续存在。然而，电路抑制在 7 Hz 时更显著地减小了共振区域。使用详细的计算模型进行的模拟表明，共振取决于内在颗粒细胞的离子机制：具体而言，K 慢（M 样）和 KA 电流充当共振器，而持续的 Na 电流和 NMDA 电流充当放大器。当感觉运动处理、认知和学习期间大脑皮层和外周感觉结构传输θ频率爆发时，这种形式的共振可能在增强 GRL 中相干尖峰发射方面发挥重要作用。
