Effect of electrical stimulation of the crossed olivocochlear bundle on temporary threshold shifts in auditory sensitivity. I. Dependence on electrical stimulation parameters.
Effect of electrical stimulation of the crossed olivocochlear bundle on temporary threshold shifts in auditory sensitivity. I. Dependence on electrical stimulation parameters.
复制标题
交叉橄榄耳蜗束的电刺激对听觉敏感性临时阈值变化的影响。
作者：
R. Rajan
1.本研究探讨电刺激第四脑室底交叉橄榄耳蜗束（COCB）对听觉脱敏的影响。听觉脱敏是由一个响亮的高频纯音暴露和测量的暂时性阈值偏移（TTS）的敏感性的复合动作电位记录从耳蜗。COCB刺激同时与响亮的声音暴露减少TTS。这种减少取决于COCB刺激在整个暴露持续时间（1分钟）内呈现为连续爆发。2.经士的宁预先给药可消除TTS的降低。士的宁对连续COCB刺激的TTS效应的作用与其对由脉冲短COCB序列引起的经典COCB效应的作用相同。如果士的宁对经典的COCB效应的作用被允许逆转，那么连续的COCB刺激可以像以前一样有效地减少TTS。3.最有效的COCB刺激被认为是一个以高速率的刺激，同时与曝光。COCB对TTS的影响也被发现是一个紧张的，较小的，但显着减少TTS仍然可以获得与暴露COCB刺激后5分钟，虽然不是当延迟10分钟。紧张减少TTS似乎发生在耳蜗没有任何持续的变化。在刺激和暴露之间的延迟中重新测量的正常耳蜗反应没有改变。4.据推测，TTS减少的持续效应并不发生在耳蜗，而是发生在沿COCB纤维的逆向动作电位沿着促进的一些中心部位。随后暴露于响亮的声音将激活由先前的COCB刺激启动的中央部位。这一假设是通过像以前一样单独刺激COCB来测试的，但是在暴露之前损伤纤维。COCB刺激的持续耳蜗效应仍应导致TTS降低。然而，如果持续效应位于更中心的位置，则损伤纤维将允许传入输入在易化中心位置起作用，但不允许随后在耳蜗表达COCB效应。在这种情况下，预计TTS不会降低--这正是这些实验中获得的结果。因此，COCB系统似乎有一个“记忆”的组成部分，促进了先前的刺激和激活的后续曝光。
1. This study examines the effect on auditory desensitization of electrically stimulating the crossed olivocochlear bundle (COCB) at the floor of the fourth ventricle. Auditory desensitization was induced by a loud high-frequency pure tone exposure and measured as temporary threshold shifts (TTS) in the sensitivity of the compound action potential recorded from the cochlea. COCB stimulation simultaneous with the loud sound exposure reduced the TTS. This reduction was contingent on the COCB stimulus being presented as a continuous burst for the entire duration (1 min) of the exposure. 2. The reduction in TTS could be abolished by prior administration of strychnine. The action of strychnine on these TTS effects of continuous COCB stimulation paralleled its action on the classical COCB effects elicited by pulsed short COCB trains. If the action of strychnine on the classical COCB effects was allowed to reverse, then continuous COCB stimulation reduced TTS as effectively as before. 3. The most effective COCB stimulus was found to be one that was presented at a high rate of stimulation simultaneous with the exposure. The COCB effect on TTS was also found to be a tonic one; smaller but significant reductions in TTS could still be obtained with the exposure presented 5 min after COCB stimulation though not when the delay was 10 min. The tonic reductions in TTS appeared to occur without any persisting changes at the cochlea. Normal cochlear responses remeasured in the delay between the stimulus and exposure were not altered. 4. It was hypothesized that the persisting effect responsible for TTS reductions did not occur at the cochlea but at some central site facilitated by antidromic action potentials along the COCB fibers. Subsequent exposure to loud sounds would activate the central site primed by the prior COCB stimulus. This hypothesis was tested by stimulating the COCB alone as before, but then lesioning the fibers before presenting the exposure. Persistent cochlear effects of the COCB stimulus should have still resulted in a reduction in TTS. However, if the persistent effect was at a more central location, lesioning the fibers would allow afferent input to act at the facilitated central location but would not allow subsequent expression of COCB effects at the cochlea. In this case, no reductions in TTS could be expected--precisely the results that were obtained in these experiments. Thus the COCB system appeared to have a "memory" component facilitated by prior stimulation and activated by a subsequent exposure.