Properties of Vestibular Neurons Mediating Vertical Canal Reflexes.

研究了警觉性猫参与前庭-眼垂直通路的前庭次级核神经元的放电特性和投射模式。前庭神经刺激后单突触激活的轴突在滑车核附近的内侧纵束（MLF）中进行单单元记录。许多人发现，当头部静止时，与垂直眼球运动有关的轴突放电。在注视过程中，这些轴突中的大多数增加了眼向下位置的放电速率。在光线下进行俯仰旋转时，所有被测试的DPVs都随着头部向上旋转而增加了放电速率，这表明它们接受了来自后半圆形管的单突触输入。dpv根据其射击规律可分为两类。与不规则DPVs相比，规则DPVs有更高的发射速率、更高的速率-位置关系、更大的相位滞后和更小的增益-头速度的趋势。Spike-triggered average method和轴突内HRP技术表明，同侧投射（i-） dppv与眼外向上运动神经元形成抑制性连接，而对侧投射（c-） dppv与眼外向下运动神经元形成兴奋性连接。几乎所有i- dpv均为规则型，而c- dpv包括规则型和不规则型。在腹侧水平刺激尾侧MLF表明，所有不规则的c- dpv和一些规则的c- dpv都有脊髓侧支，而规则的i- dpv都没有这样的侧支。

The firing properties and projection patterns of secondary vestibular nucleus neurons involved in the vertical vestibulo-ocular pathways were investigated in alert cats. Single unit recordings were made in the medial longitudinal fasciculus (MLF) near the trochlear nucleus from axons that were monosynaptically activated following stimulation of the vestibular nerve. Many identified axons discharged in relation to vertical eye movements when the head was still. The majority of these axons increased their firing rate for downward eye position during fixation (DPVs). During pitch rotation in the light, all the DPVs tested increased their firing rate with upward head rotation, suggesting that they received monosynaptic input from the posterior semicircular canal. DPVs could be divided into two groups on the basis of their firing regularity. There was a tendency for regular DPVs to have a higher firing rate, a higher correlation for the rate-position relationship, and a larger phase lag and a smaller gain re head velocity than irregular DPVs. Spike-triggered average method and intraaxonal HRP techniques demonstrated that ipsilaterally projecting (i-) DPVs made inhibitory connections with up-on extraocular motoneurons, and contralaterally projecting (c-) DPVs made excitatory connections with down-on motoneurons. Virtually all i-DPVs were of regular type, while c-DPVs included both regular and irregular types. Stimulation of the caudal MLF at the level of the obex indicated that all the irregular c-DPVs and some of the regular c-DPVs had a collateral to the spinal cord, while none of the regular i-DPVs had such a collateral.