Pfeiffer Keram, Kinoshita Michiyo, Homberg Uwe
Department of Biology, Animal Physiology, University of Marburg, Germany.
J Neurophysiol. 2005 Dec;94(6):3903-15. doi: 10.1152/jn.00276.2005. Epub 2005 Jul 27.
Many migrating animals use a sun compass for long-range navigation. One of the guiding cues used by insects is the polarization pattern of the blue sky. In the desert locust Schistocerca gregaria, neurons of the central complex, a neuropil in the center of the brain, are sensitive to polarized light and might serve a key role in compass navigation. Visual pathways to the central complex include signal processing in the upper and lower units of the anterior optic tubercle. To determine whether these pathways carry polarization-vision signals, we have recorded the responses of interneurons of the optic tubercle of the locust to visual stimuli including polarized light. All neurons of the lower unit but only one of five recorded neurons of the upper unit of the tubercle were sensitive to linearly polarized light presented in the dorsal visual field. These neurons showed polarization opponency, or a sinusoidal modulation of activity, during stimulation through a rotating polarizer. Two types of bilateral interneurons preferred particular e-vector orientations, reflecting the presence of bilateral pairs of these neurons in the brain. We show here for the first time neurons with projections to the lateral accessory lobe that are suited to provide polarization input to the central complex. All neurons of the tubercle, furthermore, responded to unpolarized light, mostly with tonic activity changes. These responses strongly depended on stimulus position and might reflect navigation-relevant signals such as direct sunlight or visual landmarks that are integrated with polarization responses in neurons of the lower unit.
许多迁徙动物利用太阳罗盘进行远距离导航。昆虫使用的一种引导线索是蓝天的偏振模式。在沙漠蝗虫沙漠飞蝗中，中央复合体（位于大脑中心的神经纤维网）的神经元对偏振光敏感，可能在罗盘导航中起关键作用。通向中央复合体的视觉通路包括前视结节上下单元中的信号处理。为了确定这些通路是否携带偏振视觉信号，我们记录了蝗虫视结节中间神经元对包括偏振光在内的视觉刺激的反应。视结节下部单元的所有神经元，但上部单元记录的五个神经元中只有一个对背侧视野中呈现的线偏振光敏感。在通过旋转偏振器进行刺激时，这些神经元表现出偏振对立，即活动的正弦调制。两种类型的双侧中间神经元偏好特定的电场矢量方向，这反映了大脑中这些神经元存在双侧配对。我们首次在此展示了投射到外侧副叶的神经元，它们适合为中央复合体提供偏振输入。此外，视结节的所有神经元对非偏振光都有反应，大多伴随着紧张性活动变化。这些反应强烈依赖于刺激位置，可能反映了与导航相关的信号，如直射阳光或视觉地标，它们与下部单元神经元中的偏振反应整合在一起。
