Barmack N H, Fagerson M, Fredette B J, Mugnaini E, Shojaku H
R.S. Dow Neurological Sciences Insitute, Good Samaritan Hospital and Medical Center, Portland, Oregon 97209.
Exp Brain Res. 1993;94(2):203-15. doi: 10.1007/BF00230288.
The inferior olive (IO) appears to be organized functionally in discrete subnuclei that receive transmitter-specific inputs. In particular, the IO receives a GABAergic input that is most densely concentrated in the beta-nucleus. In this experiment, we examined the functional specificity of neurons in the beta-nucleus of the IO of rabbits by recording their activity during natural vestibular and optokinetic stimulation. Rabbits were anesthetized and positioned in a triaxial servo- controlled rate table with the head fixed at the center of rotation. Contour-rich visual stimuli were rear-projected onto a 70 deg tangent screen and moved at constant velocities. Recording sites in the beta-nucleus were verified by subsequent histological analysis of marking microlesions. Neurons in the beta-nucleus responded to roll vestibular stimulation about the longitudinal axis. These neurons were excited when the rabbit was rolled onto the side which was contralateral to the recording site, and inhibited when the rabbit was rolled ipsilaterally. Thirty-eight of the 75 beta-nucleus neurons that were responsive to roll vestibular stimulation also responded to static tilt, indicating an otolithic as well as a vertical semicircular canal origin of the vestibular input. The modulated activity of none of the neurons could be attributed to stimulation of the horizontal semicircular canals. All the recorded neurons were found in a region of the beta-nucleus that was retrogradely labeled following HRP injections into the cerebellar nodulus. Using a "null point" technique, we found that there was a differential projection of information from the anterior and posterior semicircular canals onto to the beta-nucleus. Stimulation of the ipsilateral anterior-contralateral posterior semicircular canals modulates activity of the neurons in the caudal 500 microns of the beta-nucleus. Stimulation of the ipsilateral posterior-contralateral anterior semicircular canals modulates activity of neurons located more rostrally. beta-nucleus neurons and the olivocerebellar circuits in which they participate may constitute an important pathway for the control and adaptive modification of postural reflexes.
下橄榄核（IO）在功能上似乎是由接受特定递质输入的离散亚核组成。特别是，IO接受一种γ-氨基丁酸能输入，这种输入在β核中最为密集。在本实验中，我们通过记录家兔IO的β核神经元在自然前庭和视动刺激期间的活动，研究了其功能特异性。家兔麻醉后置于三轴伺服控制的速率台上，头部固定在旋转中心。轮廓丰富的视觉刺激被后投射到一个70度的正切屏幕上并以恒定速度移动。β核中的记录位点通过对标记微损伤的后续组织学分析得以验证。β核中的神经元对围绕纵轴的侧倾前庭刺激有反应。当兔子向与记录位点对侧的一侧翻滚时，这些神经元被兴奋，而当兔子同侧翻滚时则被抑制。75个对侧倾前庭刺激有反应的β核神经元中有38个也对静态倾斜有反应，这表明前庭输入既有耳石起源也有垂直半规管起源。没有一个神经元的调制活动可归因于水平半规管的刺激。所有记录的神经元都位于β核的一个区域，该区域在将辣根过氧化物酶注射到小脑小结后被逆行标记。使用“零点”技术，我们发现来自前半规管和后半规管的信息向β核的投射存在差异。刺激同侧前半规管 - 对侧后半规管可调节β核尾端500微米处神经元的活动。刺激同侧后半规管 - 对侧前半规管可调节更靠前位置的神经元的活动。β核神经元及其参与的橄榄小脑回路可能构成姿势反射控制和适应性调节的重要途径。
