Gifford M L, Guinan J J
Hear Res. 1987;29(2-3):179-94. doi: 10.1016/0378-5955(87)90166-3.
Recent anatomical evidence has cast doubt on the interpretation of the neural elements involved in past experiments in which efferents were electrically stimulated. To separate effects produced by medial olivocochlear (MOC) efferents from effects produced by lateral olivocochlear (LOC) efferents, MOC efferents were selectively stimulated by an electrode in the region of the MOC cell bodies in cats. For comparison, efferents were also stimulated with an electrode in the fourth ventricle (OCB stimulation, previously called COCB stimulation). MOC stimulation and fourth-ventricle OCB stimulation both produced qualitatively similar results bilaterally in that auditory-nerve compound action potential (N1) and endocochlear potential were reduced, and cochlear microphonic (CM) was increased. Both efferent-induced changes were affected in similar ways by changes in shock parameters, and were blocked by strychnine. At low sound levels, the decrease in N1 amplitude was approximately equivalent to a shift (decrease) in sound level but the change in N1 latency was not. The ratio of the CM increase to the N1 sound-level shift was independent of shock level or location. MOC stimulation typically produced an N1 sound-level shift of 11-16 dB in the contralateral ear and 4-7 dB in the ipsilateral ear. The ratio of these shifts almost equals the ratio of MOC neurons which had cell bodies on the stimulating-electrode side. Previous results reported by others with 'UOCB stimulation' now seem attributable to excitation of uncrossed MOC efferents rather than to excitation of uncrossed LOC efferents as previously thought. There is no effect reported in the literature or seen by us which can definitely be attributed to LOC neurons. Fourth-ventricle OCB stimulation typically produced an N1 sound-level shift in both ears of 19-22 dB which is approximately the sum of the crossed and uncrossed MOC shifts. Considering also that many uncrossed-MOC fibers course close to the midline (i.e. near the stimulating electrode), it seems likely that fourth-ventricle OCB stimulation excites both crossed and uncrossed MOC efferents. Referring to such stimulation in the cat as 'COCB stimulation' is therefore inaccurate and may lead to wrong conclusions about the functional role of various components of the olivocochlear fibers.
最近的解剖学证据对过去那些通过电刺激传出神经进行的实验中所涉及的神经元件的解释提出了质疑。为了区分内侧橄榄耳蜗（MOC）传出神经产生的效应与外侧橄榄耳蜗（LOC）传出神经产生的效应，在猫的MOC细胞体区域用一个电极选择性地刺激MOC传出神经。作为对照，还用一个电极在第四脑室进行传出神经刺激（OCB刺激，以前称为COCB刺激）。MOC刺激和第四脑室OCB刺激在双侧都产生了定性上相似的结果，即听神经复合动作电位（N1）和内耳蜗电位降低，而耳蜗微音电位（CM）增加。两种传出神经诱导的变化都以相似的方式受到电击参数变化的影响，并且都被士的宁阻断。在低声强水平时，N1振幅的降低大约相当于声强的一个偏移（降低），但N1潜伏期的变化并非如此。CM增加与N1声强偏移的比值与电击水平或位置无关。MOC刺激通常在对侧耳产生11 - 16 dB的N1声强偏移，在同侧耳产生4 - 7 dB的偏移。这些偏移的比值几乎等于其细胞体位于刺激电极一侧的MOC神经元的比值。其他人先前报道的“UOCB刺激”的结果现在看来归因于未交叉的MOC传出神经的兴奋，而不是如先前认为的未交叉的LOC传出神经的兴奋。文献中没有报道或我们也未观察到可明确归因于LOC神经元的效应。第四脑室OCB刺激通常在双耳产生19 - 22 dB的N1声强偏移，这大约是交叉和未交叉MOC偏移之和。还考虑到许多未交叉的MOC纤维靠近中线走行（即靠近刺激电极），似乎第四脑室OCB刺激激发了交叉和未交叉的MOC传出神经。因此，将猫中的这种刺激称为“COCB刺激”是不准确的，并且可能导致关于橄榄耳蜗纤维各个成分功能作用的错误结论。
