Discipline of Physiology, School of Medical Sciences and Bosch Institute, The University of Sydney, New South Wales, Australia.
J Neurophysiol. 2011 Sep;106(3):1310-21. doi: 10.1152/jn.00943.2010. Epub 2011 Jun 8.
Prolonged exposure to an effective stimulus generally reduces the sensitivity of neurons early in the visual pathway. Yet eye and head movements bring about frequent changes in the retinal image, and it is less clear that exposure to brief presentations will produce similar desensitization. To address this, we made extracellular recordings from single neurons in the lateral geniculate nucleus of anesthetized marmosets, a New World primate. We measured the contrast response for drifting gratings before and after 0.5-s exposure to a high-contrast drifting grating, a stationary grating, or a blank screen. Prior exposure to the drifting grating reduced the contrast sensitivity of cells in the magnocellular pathway, on average by 23%; this reduction remained strong when the adapting and test stimuli were separated by 0.4 s. Exposure to a stationary grating of the preferred spatial phase did not change the contrast response; exposure to the opposite spatial phase did. None of the brief adaptors reduced the sensitivity of parvocellular cells. We conclude that brief periods of high contrast, such as those that would be expected to occur during a normal visual fixation, are sufficient to reduce the sensitivity of magnocellular-pathway cells.
长时间暴露于有效刺激通常会降低视觉通路早期神经元的敏感性。然而，眼睛和头部的运动会使视网膜图像频繁发生变化，目前尚不清楚短暂呈现的刺激是否会产生类似的脱敏作用。为了解决这个问题，我们在麻醉的狨猴外侧膝状体核中单神经元进行了细胞外记录，这是一种新世界灵长类动物。我们在高对比度的漂移光栅、静止光栅或空白屏幕之前和之后测量了漂移光栅的对比度响应。在 0.5 秒内暴露于漂移光栅会降低大细胞通路细胞的对比度敏感度，平均降低 23%；当适应刺激和测试刺激之间的间隔为 0.4 秒时，这种降低仍然很强。暴露于最佳空间相位的静止光栅不会改变对比度响应；暴露于相反的空间相位会。短暂的适应器都没有降低小细胞的敏感度。我们的结论是，高对比度的短暂时期，例如在正常视觉注视期间可能发生的时期，足以降低大细胞通路细胞的敏感性。
