Chen-Huang Chiju, Peterson Barry W
Department of Physiology, Northwestern University, Chicago, IL 60611, USA.
Exp Brain Res. 2006 Jan;168(3):410-26. doi: 10.1007/s00221-005-0098-7. Epub 2005 Sep 29.
Spatio-temporal convergence (STC) properties of 19 vestibular only neurons' responses to translational head movements were examined in an alert, behaving squirrel monkey. In addition to standard tests that included 1.2 Hz yaw/pitch/roll rotations and inter-aural/naso-occipital/dorso-ventral translations, we also observed responses to translations along multiple directions in several orthogonal planes. Neural responses were fitted first by a model that permitted STC in all planes, characterized by a non-zero minimum and a gradual shift of phase. We then evaluated statistically whether models with fewer independent dynamic parameters yielded equally satisfactory results. The responses of 13 neurons were adequately fit by simple cosine models (1-D) as well as models that allowed complex STC behavior. Of the six neurons exhibiting STC, five could be modeled with two independent phase parameters (2-D) while the remaining neuron required a model with three independent phase parameters (3-D). The maximum translation sensitivity and phase, Smax and varphimax, and minimum translation sensitivity and phase, Smin and varphimin, were estimated from the reconstructed sensitivity and phase surfaces. The tuning ratio, Smin/Smax, in STC neurons was>0.40 while in 1-D neurons it was <0.25. Furthermore, the maximum response vectors of most 1-D neurons lay within 20 degrees of either the horizontal or sagittal plane while those of STC neurons lay >20 degrees from both planes. No difference in other response properties, such as varphimax or rotational responses, was found between neurons exhibiting STC and the simple cosine tuning. Our results suggest that the STC behavior observed in otolith-related vestibular neurons probably arises from summing inputs from afferents, with diverse response dynamics, innervating different otolith macula.
在一只警觉的、行为活跃的松鼠猴身上，研究了19个仅对前庭刺激有反应的神经元对头部平移运动的时空收敛（STC）特性。除了包括1.2 Hz偏航/俯仰/翻滚旋转以及耳间/鼻枕/背腹平移的标准测试外，我们还观察了在几个正交平面上沿多个方向平移时的反应。首先用一个允许在所有平面上进行STC的模型拟合神经反应，该模型的特征是具有非零最小值和相位的逐渐偏移。然后，我们统计评估了具有较少独立动态参数的模型是否能产生同样令人满意的结果。13个神经元的反应可以用简单余弦模型（一维）以及允许复杂STC行为的模型进行充分拟合。在表现出STC的6个神经元中，5个可以用两个独立相位参数（二维）建模，而其余1个神经元需要一个具有三个独立相位参数（三维）的模型。根据重建的灵敏度和相位表面估计最大平移灵敏度和相位（Smax和varphimax）以及最小平移灵敏度和相位（Smin和varphimin）。STC神经元的调谐比（Smin/Smax）>0.40，而一维神经元的调谐比<0.25。此外，大多数一维神经元的最大反应向量位于水平或矢状面的20度范围内，而STC神经元的最大反应向量与这两个平面的夹角均>20度。在表现出STC的神经元和简单余弦调谐的神经元之间，未发现其他反应特性（如varphimax或旋转反应）存在差异。我们的结果表明，在与耳石相关的前庭神经元中观察到的STC行为可能源于对来自传入神经的输入进行求和，这些传入神经具有不同的反应动力学，支配着不同的耳石斑。
