Angelaki D E
Department of Physiology, University of Minnesota, Minneapolis 55455.
Biol Cybern. 1992;67(1):83-96. doi: 10.1007/BF00201805.
It has been recently demonstrated that some primary otolith afferents and most otolith-related vestibular nuclei neurons encode two spatial dimensions that can be described by two vectors in temporal and spatial quadrature. These cells are called broadly-tuned neurons. They are characterized by a non-zero tuning ratio which is defined as the ratio of the minimum over the maximum sensitivity of the neuron. Broadly-tuned neurons exhibit response gains that do not vary according to the cosine of the angle between the stimulus direction and the cell's maximum sensitivity vector and response phase values that depend on stimulus orientation. These responses were observed during stimulation with pure linear acceleration and can be explained by spatio-temporal convergence (STC) of primary otolith afferents and/or otolith hair cells. Simulations of STC of the inputs to primary otolith afferents and vestibular nuclei neurons have revealed interesting characteristics: First, in the case of two narrowly-tuned input signals, the largest tuning ratio is achieved when the input signals are of equal gain. The smaller the phase difference between the input vectors, the larger the orientation differences that are required to produce a certain tuning ratio. Orientation and temporal phase differences of 30-40 degrees create tuning ratios of approximately 0.10-0.15 in target neurons. Second, in the case of multiple input signals, the larger the number of converging inputs, the smaller the tuning ratio of the target neuron. The tuning ratio depends on the number of input units, as long as there are not more than about 10. For more than 10-20 input vectors, the tuning ratio becomes almost independent of the number of inputs. Further, if the inputs comprise two populations (with different gain and phase values at a given stimulus frequency), the largest tuning ratio is obtained when the larger population has a smaller gain. These findings are discussed in the context of known anatomical and physiological characteristics of innervation patterns of primary otolith afferents and their possible convergence onto vestibular nuclei neurons.
最近的研究表明，一些初级耳石传入神经和大多数与耳石相关的前庭核神经元编码两个空间维度，这两个维度可以用时间和空间正交的两个向量来描述。这些细胞被称为宽调谐神经元。它们的特征是具有非零调谐率，该调谐率定义为神经元最小灵敏度与最大灵敏度之比。宽调谐神经元表现出的反应增益不会根据刺激方向与细胞最大灵敏度向量之间夹角的余弦而变化，其反应相位值则取决于刺激方向。这些反应是在纯线性加速度刺激过程中观察到的，并且可以通过初级耳石传入神经和/或耳石毛细胞的时空汇聚（STC）来解释。对初级耳石传入神经和前庭核神经元输入的STC模拟揭示了一些有趣的特征：首先，在两个窄调谐输入信号的情况下，当输入信号增益相等时，可实现最大调谐率。输入向量之间的相位差越小，产生特定调谐率所需的方向差就越大。30 - 40度的方向和时间相位差在目标神经元中产生的调谐率约为0.10 - 0.15。其次，在多个输入信号的情况下，汇聚输入的数量越多，目标神经元的调谐率越小。只要输入单元数量不超过约10个，调谐率就取决于输入单元的数量。对于超过10 - 20个输入向量，调谐率几乎与输入数量无关。此外，如果输入包括两个群体（在给定刺激频率下具有不同的增益和相位值），当较大群体的增益较小时，可获得最大调谐率。本文将结合初级耳石传入神经支配模式的已知解剖学和生理学特征及其向前庭核神经元可能的汇聚情况对这些发现进行讨论。
