Institute of Clinical Neurosciences, LMU München, Munich, Germany.
Exp Brain Res. 2011 May;210(3-4):437-49. doi: 10.1007/s00221-011-2585-3. Epub 2011 Mar 4.
Head/body motion-related sensory signals are transformed in second-order vestibular neurons (2°VN) into commands for appropriate motor reactions that stabilize gaze and posture during locomotion. In all vertebrates, these neurons form functional subgroups with different membrane properties and response dynamics, compatible with the necessity to process a wide range of motion-related sensory signals. In frog, 2°VN subdivide into two well-defined populations with distinctly different intrinsic membrane properties, discharge dynamics and synaptic response characteristics. Tonic 2°VN form low-pass filters with membrane properties that cause synaptic amplification, whereas phasic 2°VN form band-pass filters that cause shunting of repetitive inputs. The different, yet complementary, filter properties render tonic neurons suitable for integration and phasic neurons for differentiation and event detection. Specific insertion of phasic 2°VN into local vestibular networks of inhibitory interneurons reinforces the functional consequences of the intrinsic membrane properties of this particular cell type with respect to the processing of afferent sensory signals. Thus, the combination of matching intrinsic cellular and emerging network properties generates sets of neuronal elements that form adjustable, frequency-tuned filter components for separate transformation of the various dynamic aspects of head motion-related signals. The overall frequency tuning of central vestibular neurons differs between vertebrates along with variations in species-specific locomotor dynamics, thereby illustrating an ecophysiological plasticity of the involved neuronal elements. Moreover, separation into multiple, dynamically different subtypes at any neuronal level along the vestibulo-motor reflex pathways suggests an organization of head motion-related sensory-motor transformation in parallel, frequency-tuned channels.
头部/身体运动相关的感觉信号在二阶前庭神经元（2°VN）中转化为适当运动反应的指令，以在运动过程中稳定注视和姿势。在所有脊椎动物中，这些神经元形成具有不同膜特性和反应动力学的功能亚群，与处理广泛的运动相关感觉信号的必要性相兼容。在青蛙中，2°VN 分为两个具有明显不同的固有膜特性、放电动力学和突触反应特征的明确群体。紧张的 2°VN 形成具有膜特性的低通滤波器，导致突触放大，而相位 2°VN 形成带通滤波器，导致重复输入的分流。不同但互补的滤波特性使紧张神经元适合于整合，而相位神经元适合于分化和事件检测。相位 2°VN 特定地插入到抑制性中间神经元的局部前庭网络中，增强了这种特定细胞类型固有膜特性对传入感觉信号处理的功能后果。因此，匹配的内在细胞和新兴网络特性的组合产生了一组神经元元件，这些元件形成了可调节的、频率调谐的滤波器组件，用于分别转换头部运动相关信号的各种动态方面。中枢前庭神经元的整体频率调谐在脊椎动物之间有所不同，同时也存在物种特异性运动动力学的变化，从而说明了所涉及的神经元元件的生态生理可塑性。此外，在沿前庭运动反射途径的任何神经元水平上分离为多个动态不同的亚型，表明头部运动相关感觉-运动转换的组织是平行的、频率调谐的通道。
