Department of Neurology, Case Western Reserve University, Cleveland, OH 44106-5040, USA.
Cerebellum. 2013 Feb;12(1):97-107. doi: 10.1007/s12311-012-0401-7.
Vestibular velocity storage enhances the efficacy of the angular vestibulo-ocular reflex (VOR) during relatively low-frequency head rotations. This function is modulated by GABA-mediated inhibitory cerebellar projections. Velocity storage also exists in perceptual pathway and has similar functional principles as VOR. However, it is not known whether the neural substrate for perception and VOR overlap. We propose two possibilities. First, there is the same velocity storage for both VOR and perception; second, there are nonoverlapping neural networks: one might be involved in perception and the other for the VOR. We investigated these possibilities by measuring VOR and perceptual responses in healthy human subjects during whole-body, constant-velocity rotation steps about all three dimensions (yaw, pitch, and roll) before and after 10 mg of 4-aminopyridine (4-AP). 4-AP, a selective blocker of inward rectifier potassium conductance, can lead to increased synchronization and precision of Purkinje neuron discharge and possibly enhance the GABAergic action. Hence 4-AP could reduce the decay time constant of the perceived angular velocity and VOR. We found that 4-AP reduced the decay time constant, but the amount of reduction in the two processes, perception and VOR, was not the same, suggesting the possibility of nonoverlapping or partially overlapping neural substrates for VOR and perception. We also noted that, unlike the VOR, the perceived angular velocity gradually built up and plateau prior to decay. Hence, the perception pathway may have additional mechanism that changes the dynamics of perceived angular velocity beyond the velocity storage. 4-AP had no effects on the duration of build-up of perceived angular velocity, suggesting that the higher order processing of perception, beyond the velocity storage, might not occur under the influence of mechanism that could be influenced by 4-AP.
前庭速度储存增强了在相对低频头部旋转期间角前庭眼反射（VOR）的功效。该功能受 GABA 介导的抑制性小脑投射调制。速度储存也存在于感知途径中，具有与 VOR 相似的功能原理。然而，尚不清楚感知和 VOR 的神经基础是否重叠。我们提出了两种可能性。首先，VOR 和感知都有相同的速度储存；其次，存在非重叠的神经网络：一个可能涉及感知，另一个可能涉及 VOR。我们通过在服用 10 毫克 4-氨基吡啶（4-AP）前后，在三个维度（偏航、俯仰和滚动）上对所有三个维度进行全身匀速旋转步骤，测量了健康人体受试者的 VOR 和感知反应，来研究这些可能性。4-AP，一种内向整流钾电导的选择性阻断剂，可导致浦肯野细胞放电的同步性和精度增加，并可能增强 GABA 能作用。因此，4-AP 可以降低感知角速度和 VOR 的衰减时间常数。我们发现，4-AP 降低了衰减时间常数，但这两个过程（感知和 VOR）的减少量并不相同，这表明 VOR 和感知的神经基础可能是不重叠的或部分重叠的。我们还注意到，与 VOR 不同，感知角速度在衰减之前逐渐建立并达到平台。因此，感知途径可能具有改变感知角速度动态的附加机制，而不仅仅是速度储存。4-AP 对感知角速度的建立时间没有影响，这表明感知的更高阶处理，超出了速度储存，可能不会受到可能受到 4-AP 影响的机制的影响。
