Waespe W, Cohen B
Exp Brain Res. 1983;51(1):23-35. doi: 10.1007/BF00236799.
Activity of neurons in the vestibular nuclei of alert monkeys was recorded extracellularly after total unilateral and bilateral flocculectomy and partial paraflocculectomy. Type 1 horizontal cells that were encountered after flocculectomy responded to visual and vestibular stimuli and to conflict stimulation, i.e., to rotation in a subject-stationary visual surround, as do vestibular neurons in the normal animal. The major difference between neurons in the normal and lesioned animals was that more time was needed to reach steady state firing levels during optokinetic stimulation at a constant velocity after operation. As shown previously (Waespe et al. 1983) the longer time course is related to increased initial retinal slip velocities that occur after flocculectomy as a result of an inability to change eye velocity rapidly in response to visual stimulation. It does not signify a change in the dynamics of neurons in the vestibular nuclei that mediate the vestibulo-ocular reflex (VOR). The similarity in modulation of horizontal Type 1 vestibular neurons in normal and flocculectomized monkeys makes it unlikely that floccular Purkinje cells suppress the horizontal VOR in the monkey during conflicting visual and vestibular stimuli by inhibiting or disfacilitating secondary or tertiary vestibular neurons. This is consistent with earlier findings that indicate that visual-oculomotor pathways responsible for ocular pursuit or for rapid changes in OKN do not go through the vestibular nuclei. Rather the point of interaction of the flocculus output with the VOR appears to be external to the vestibular nuclei. There was a close correspondence between the slow phase velocity of nystagmus and unit activity in the vestibular nuclei under a wide variety of test conditions after flocculectomy. This is consistent with the postulate that frequencies of vestibular nuclei neurons represent a summation of activity in direct vestibulo-oculomotor pathways and indirect pathways that include the velocity storage mechanism. These are the major remaining sources of activity that generate slow phases of nystagmus after the direct visual-oculomotor pathways have been partially interrupted by flocculectomy (Waespe et al. 1983). Horizontal Type 1 neurons which responded to vestibular and optokinetic stimulation with increases in frequency above 1 spike/s/degree/s were rarely encountered after flocculectomy. These cells were present on the normal side in a monkey after unilateral flocculectomy. We infer that vestibular nuclei neurons that project mossy fibers to the flocculus are inactivated or disappear as a result of surgical ablation of their axons. This could also contribute to the reduced gain of vestibular nystagmus, OKAN and off-vertical nystagmus that was observed in some of the animals after lesion.
在完全单侧和双侧绒球切除术以及部分旁绒球切除术后，对清醒猴子前庭核中的神经元活动进行了细胞外记录。绒球切除术后遇到的1型水平细胞对视觉和前庭刺激以及冲突刺激有反应，即在受试者静止的视觉环境中旋转时的反应，与正常动物中的前庭神经元一样。正常动物和损伤动物中神经元的主要区别在于，术后在以恒定速度进行视动刺激时，达到稳定放电水平需要更多时间。如先前所示（Waespe等人，1983年），较长的时间过程与绒球切除术后由于无法对视觉刺激快速改变眼速度而出现的初始视网膜滑动速度增加有关。这并不意味着介导前庭眼反射（VOR）的前庭核中神经元的动力学发生了变化。正常和绒球切除术后猴子中1型水平前庭神经元调节的相似性使得在视觉和前庭刺激冲突期间，绒球浦肯野细胞不太可能通过抑制或减弱次级或三级前庭神经元来抑制猴子的水平VOR。这与早期的研究结果一致，即负责眼球追踪或视动性眼震快速变化的视觉动眼神经通路不经过前庭核。相反，绒球输出与VOR的相互作用点似乎在前庭核之外。绒球切除术后，在各种测试条件下，眼震慢相速度与前庭核中的单位活动之间存在密切对应关系。这与前庭核神经元频率代表直接前庭动眼神经通路和包括速度存储机制的间接通路中活动总和的假设一致。这些是在直接视觉动眼神经通路因绒球切除术而部分中断后（Waespe等人，1983年）产生眼震慢相的主要剩余活动来源。绒球切除术后很少遇到对前庭和视动刺激频率增加超过1个峰电位/秒/度/秒有反应的1型水平神经元。在单侧绒球切除术后的猴子中，这些细胞存在于正常一侧。我们推断，向前庭投射苔藓纤维的前庭核神经元由于其轴突的手术切除而失活或消失。这也可能导致在一些动物损伤后观察到的前庭眼震、视动性眼震后慢相和垂直离眼性眼震增益降低。
