Clarke Robert J, Zhang Hongyu, Gamlin Paul D R
Vision Science Research Center, University of Alabama, Birmingham, Alabama 35294, USA.
J Neurophysiol. 2003 Jun;89(6):3168-78. doi: 10.1152/jn.01130.2002. Epub 2003 Jan 15.
This study examined the response properties of luminance neurons found within the pretectal olivary nucleus (PON), which is the pretectal nucleus that mediates the primate pupillary light reflex. We recorded the activity of 121 single units in alert, behaving rhesus monkeys trained to fixate a back-projected laser spot while a luminance stimulus was presented. The change in the firing rate of luminance neurons was measured as a function of changes in the size, retinal illuminance, and position of the stimulus. We found that these neurons possessed large receptive fields, which were sufficiently distinct that they could be placed into three classes. Approximately 40% of the PON luminance neurons responded well to stimuli presented in either the contralateral or ipsilateral hemifield. These neurons were classified as "bilateral" neurons. In the primate, retinal projections to the pretectum and other retinorecipient nuclei are organized such that direct retinal input can only account for the contralateral hemifield responses of these neurons. Thus the representation of the ipsilateral hemifield in "bilateral" PON cells must result from input from a nonretinal source. Approximately 30% of PON neurons responded only to stimuli presented in the contralateral hemifield. These neurons were classified as "contralateral" neurons. Finally, approximately 30% of PON neurons responded to stimuli presented at or near the animal's fixation point. These neurons were classified as "macular" neurons. The mean firing rates of all classes of neurons increased with increases in stimulus size and luminance within their receptive fields. The thresholds and magnitude of these responses closely matched those that would be appropriate for mediating the pupillary light reflex. In summary, these results suggest that all three classes of PON neurons contribute to the behaviorally observed pupillomotor field characteristics in which stimuli at the macular produce substantially larger pupillary responses than more peripheral stimuli. The contributions of "bilateral" and "contralateral" cells account for pupillary responses evoked by peripheral changes in luminance, whereas the contributions of all three cell classes account for the larger pupillary responses evoked by stimuli in the central visual field.
本研究检测了顶盖前橄榄核（PON）内亮度神经元的反应特性，顶盖前橄榄核是介导灵长类动物瞳孔光反射的顶盖前核。我们记录了121个单神经元的活动，这些神经元来自警觉且行为正常的恒河猴，训练它们在呈现亮度刺激时注视后投射激光点。亮度神经元放电率的变化作为刺激大小、视网膜照度和位置变化的函数进行测量。我们发现这些神经元具有大的感受野，其差异足够明显，可分为三类。大约40%的PON亮度神经元对在对侧或同侧半视野呈现的刺激反应良好。这些神经元被归类为“双侧”神经元。在灵长类动物中，视网膜向顶盖前区和其他视网膜接受核的投射是有组织的，使得直接的视网膜输入仅能解释这些神经元的对侧半视野反应。因此，“双侧”PON细胞中同侧半视野的表征必定来自非视网膜来源的输入。大约30%的PON神经元仅对对侧半视野呈现的刺激有反应。这些神经元被归类为“对侧”神经元。最后，大约30%的PON神经元对在动物注视点或其附近呈现的刺激有反应。这些神经元被归类为“黄斑”神经元。所有类型神经元的平均放电率随其感受野内刺激大小和亮度的增加而增加。这些反应的阈值和幅度与介导瞳孔光反射的阈值和幅度紧密匹配。总之，这些结果表明，所有三类PON神经元都对行为观察到的瞳孔运动场特征有贡献，其中黄斑处的刺激比更外周的刺激产生的瞳孔反应大得多。“双侧”和“对侧”细胞的贡献解释了由外周亮度变化引起的瞳孔反应，而所有三类细胞的贡献解释了由中央视野刺激引起的更大瞳孔反应。
