Manzoni D, Pompeiano O, Marchand A R
Dipartimento di Fisiologia e Biochimica, Università di Pisa, Italy.
Pflugers Arch. 1993 Apr;423(1-2):121-32. doi: 10.1007/BF00374969.
In decerebrate cats, rotation about the longitudinal axis of the animal, leading to sinusoidal stimulation of labyrinth receptors, produces a tonic contraction of limb extensors during side-down tilt (alpha responses) and of dorsal neck extensors during side-up tilt (beta responses). These changes in posture are mediated, at least in part, by lateral vestibular nucleus (LVN) neurons, with response characteristics to stimulation of macular and/or canal receptors that have so far been evaluated at the level of either unidentified vestibulospinal (VS) neurons or vestibulo-collic neurons projecting to the upper cervical cord. In the present study we investigated the dynamics of the responses of VS neurons projecting to the lumbosacral segments of the spinal cord to increasing frequencies of tilt (from 0.026 to 0.32 Hz, +/- 10 degrees). All the recorded units showed an average phase lead with respect to position of +25.6 +/- 5.5 degrees (SE) at the tilt frequency of 0.026 Hz. Most of these neurons (n = 32) were particularly activated during side-down tilt (alpha responses) and showed either a stable phase or an increase in phase lead of the responses with increasing frequency of tilt. At the tilt frequency of 0.026 Hz, the smaller the phase lead of the responses, the larger was the response gain. Moreover, the smaller the phase lead of the responses at that frequency of tilt, the smaller the increase in gain but the larger was the increase in lead of the responses obtained by increasing the stimulation frequency up to 0.32 Hz. Through this set of finely organized changes in unit response characteristics, the overall output of this population of neurons increased, while the phase angle of the responses reached the mean value of +64.9 +/- 2.6 degrees (SE), thus becoming more related to the velocity than to the positional signal. The remaining units (n = 7), which were mainly activated during side-up tilt (beta responses), displayed an increase in phase lag of the responses to increasing frequency of stimulation, which reached the mean value of -118.9 +/- 14.5 degrees (SE) at 0.32 Hz. The differences in the dynamic properties of these VS neurons projecting to the lumbosacral cord, with respect to those of previously recorded populations of VS neurons, are discussed.
在去大脑猫中，动物绕其纵轴旋转，导致迷路感受器受到正弦刺激，在侧卧向下倾斜时会引起肢体伸肌的强直性收缩（α反应），在侧卧向上倾斜时会引起颈背伸肌的强直性收缩（β反应）。这些姿势变化至少部分是由外侧前庭核（LVN）神经元介导的，其对黄斑和/或半规管感受器刺激的反应特性，目前是在未鉴定的前庭脊髓（VS）神经元或投射至上颈髓的前庭-颈神经元水平上进行评估的。在本研究中，我们研究了投射到脊髓腰骶段的VS神经元对逐渐增加的倾斜频率（从0.026至0.32Hz，±10度）的反应动力学。所有记录的单位在0.026Hz的倾斜频率下，相对于位置显示出平均相位超前+25.6±5.5度（标准误）。这些神经元中的大多数（n = 32）在侧卧向下倾斜时（α反应）特别活跃，并且随着倾斜频率的增加，其反应显示出稳定的相位或相位超前增加。在0.026Hz的倾斜频率下，反应的相位超前越小，反应增益越大。此外，在该倾斜频率下反应的相位超前越小，增益增加越小，但通过将刺激频率增加至0.32Hz所获得的反应超前增加越大。通过这组单位反应特性的精细组织变化，这群神经元的总体输出增加，而反应的相位角达到+64.9±2.6度（标准误）的平均值，因此与速度的相关性比与位置信号的相关性更高。其余的单位（n = 7）主要在侧卧向上倾斜时（β反应）被激活，随着刺激频率的增加，其反应的相位滞后增加，在0.32Hz时达到-118.9±14.5度（标准误）的平均值。本文讨论了这些投射到腰骶脊髓的VS神经元与先前记录的VS神经元群体在动态特性上的差异。
