Department of Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Neurosci. 2010 Jan 13;30(2):439-48. doi: 10.1523/JNEUROSCI.3192-09.2010.
To understand the roles of the vestibular system in perceptual detection and discrimination of self-motion, it is critical to account for response variability in computing the sensitivity of vestibular neurons. Here we study responses of neurons with no eye movement sensitivity in the vestibular (VN) and rostral fastigial nuclei (FN) using high-frequency (2 Hz) oscillatory translational motion stimuli. The axis of translation (i.e., heading) varied slowly (1 degrees /s) in the horizontal plane as the animal was translated back and forth. Signal detection theory was used to compute the threshold sensitivity of VN/FN neurons for discriminating small variations in heading around all possible directions of translation. Across the population, minimum heading discrimination thresholds averaged 16.6 degrees +/- 1 degrees SE for FN neurons and 15.3 degrees +/- 2.2 degrees SE for VN neurons, severalfold larger than perceptual thresholds for heading discrimination. In line with previous studies and theoretical predictions, maximum discriminability was observed for directions where firing rate changed steeply as a function of heading, which occurs at headings approximately perpendicular to the maximum response direction. Forward/backward heading thresholds tended to be lower than lateral motion thresholds, and the ratio of lateral over forward heading thresholds averaged 2.2 +/- 6.1 (geometric mean +/- SD) for FN neurons and 1.1 +/- 4.4 for VN neurons. Our findings suggest that substantial pooling and/or selective decoding of vestibular signals from the vestibular and deep cerebellar nuclei may be important components of further processing. Such a characterization of neural sensitivity is critical for understanding how early stages of vestibular processing limit behavioral performance.
为了理解前庭系统在自我运动知觉和辨别中的作用，在计算前庭神经元的敏感性时，必须考虑到反应变异性。在这里，我们使用高频（2 Hz）振荡平移运动刺激来研究前庭（VN）和延髓fastigial 核（FN）中没有眼动敏感性的神经元的反应。当动物被前后平移时，平移的轴（即朝向）以缓慢的速度（1 度/s）在水平面变化。信号检测理论用于计算 VN/FN 神经元在辨别朝向周围所有可能平移方向的小变化时的阈值敏感性。在整个群体中，FN 神经元的最小朝向辨别阈值平均为 16.6 度 +/- 1 度 SE，VN 神经元的最小朝向辨别阈值平均为 15.3 度 +/- 2.2 度 SE，比朝向辨别感知阈值大几个数量级。与之前的研究和理论预测一致，最大可辨别性出现在作为朝向函数的放电率急剧变化的方向，这发生在朝向大约垂直于最大响应方向的方向上。前后朝向的阈值往往低于侧向运动的阈值，而侧向运动与前后朝向的阈值比平均为 2.2 +/- 6.1（几何均值 +/- SD）的 FN 神经元和 1.1 +/- 4.4 的 VN 神经元。我们的发现表明，从前庭和深部小脑核对前庭信号的大量池化和/或选择性解码可能是进一步处理的重要组成部分。这种神经敏感性的特征对于理解前庭处理的早期阶段如何限制行为表现至关重要。
