Goode C T, Maney D L, Rubel E W, Fuchs A F
Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, Washington 98195, USA.
J Neurophysiol. 2001 Mar;85(3):1119-28. doi: 10.1152/jn.2001.85.3.1119.
Whenever the head turns, the vestibuloocular reflex (VOR) produces compensatory eye movements to help stabilize the image of the visual world on the retina. Uncompensated slip of the visual world across the retina results in a gradual change in VOR gain to minimize the image motion. VOR gain changes naturally during normal development and during recovery from neuronal damage. We ask here whether visual slip is necessary for the development of the chicken VOR (as in other species) and whether it is required for the recovery of the VOR after hair cell loss and regeneration. In the first experiment, chickens were reared under stroboscopic illumination, which eliminated visual slip. The horizontal and vertical VORs (h- and vVORs) were measured at different ages and compared with those of chickens reared in normal light. Strobe-rearing prevented the normal development of both h- and vVORs. After 8 wk of strobe-rearing, 3 days of exposure to normal light caused the VORs to recover partially but not to normal values. In the second experiment, 1-wk-old chicks were treated with streptomycin, which destroys most vestibular hair cells and reduces hVOR gain to zero. In birds, vestibular hair cells regenerate so that after 8 wk in normal illumination they appear normal and hVOR gain returns to values that are normal for birds of that age. The treated birds in this study recovered in either normal or stroboscopic illumination. Their hVOR and vVOR and vestibulocollic reflexes (VCR) were measured and compared with those of untreated, age-matched controls at 8 wk posthatch, when hair cell regeneration is known to be complete. As in previous studies, the gain of the VOR decreased immediately to zero after streptomycin treatment. After 8 wk of recovery under normal light, the hVOR was normal, but vVOR gain was less than normal. After 8 wk of recovery under stroboscopic illumination, hVOR gain was less than normal at all frequencies. VCR recovery was not affected by the strobe environment. When streptomycin-treated, strobe-recovered birds were then placed in normal light for 2 days, hVOR gain returned to normal. Taken together, the results of these experiments suggest that continuous visual feedback can adjust VOR gain. In the absence of appropriate visual stimuli, however, there is a default VOR gain and phase to which birds recover or revert, regardless of age. Thus an 8-wk-old chicken raised in a strobe environment from hatch would have the same gain as a streptomycin-treated chicken that recovers in a strobe environment.
每当头部转动时，前庭眼反射（VOR）会产生代偿性眼球运动，以帮助稳定视网膜上视觉世界的图像。视觉世界在视网膜上未经补偿的滑动会导致VOR增益逐渐变化，以尽量减少图像运动。在正常发育过程以及从神经元损伤恢复的过程中，VOR增益会自然变化。我们在此探讨视觉滑动对于鸡VOR发育（如同在其他物种中一样）是否必要，以及在毛细胞丧失和再生后VOR恢复是否需要视觉滑动。在第一个实验中，鸡在频闪照明下饲养，这消除了视觉滑动。在不同年龄测量水平和垂直VOR（h-VOR和v-VOR），并与在正常光照下饲养的鸡进行比较。频闪饲养阻止了h-VOR和v-VOR的正常发育。经过8周的频闪饲养后，暴露于正常光照3天导致VOR部分恢复，但未恢复到正常值。在第二个实验中，对1周龄的小鸡用链霉素进行处理，链霉素会破坏大多数前庭毛细胞并使h-VOR增益降至零。在鸟类中，前庭毛细胞会再生，因此在正常光照下8周后它们看起来正常，并且h-VOR增益恢复到该年龄鸟类的正常水平。本研究中接受处理的鸟类在正常或频闪照明下恢复。在孵化后8周，当已知毛细胞再生完成时，测量它们的h-VOR、v-VOR和前庭颈反射（VCR），并与未处理的、年龄匹配的对照进行比较。与之前的研究一样，链霉素处理后VOR增益立即降至零。在正常光照下恢复8周后，h-VOR正常，但v-VOR增益低于正常水平。在频闪照明下恢复8周后，所有频率下h-VOR增益均低于正常水平。VCR恢复不受频闪环境影响。当链霉素处理过的、在频闪环境下恢复的鸟类随后置于正常光照下2天时，h-VOR增益恢复正常。总之，这些实验结果表明持续的视觉反馈可以调节VOR增益。然而，在没有适当视觉刺激的情况下，无论年龄如何，鸟类都会恢复或回归到一个默认的VOR增益和相位。因此，从孵化起就在频闪环境中饲养的8周龄鸡，其增益与在频闪环境中恢复的链霉素处理过的鸡相同。
