Diverse speed response properties of motion sensitive neurons in the fly's optic lobe
Diverse speed response properties of motion sensitive neurons in the fly's optic lobe
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DOI：
10.1007/s00359-006-0185-7
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发表时间：
2007-02-01
影响因子：
2.1
通讯作者：
Strausfeld, Nicholas J.
中科院分区：
文献类型：
--
作者：
Douglass, John K.;Strausfeld, Nicholas J.
速度和加速度是视觉运动的基本组成部分，动物可以用它们来解释世界。行为研究已经证实，昆虫在很大程度上独立于对比和空间频率来区分速度，生理学记录表明，运动前下行神经元的一个子集在这种意义上是速度选择的。然而，昆虫速度选择的神经基础和机制尚不清楚。利用丝毛费尼索蝇，从髓质和小叶复合体神经元中获得细胞内记录和染料填充，这些神经元虽然本身不一定具有速度选择性，但它们被定位于参与在下行神经元中产生速度选择性的回路。正弦变化光栅运动（0-200度/秒）的刺激提供了一系列瞬时速度和加速度。由此产生的速度响应曲线表明了四个不同的速度范围，支持了中等水平神经元的时空调节包含足够多样性的假设，以解释在下降神经元水平上出现的速度选择性。这种类型的机制已经被提出来解释昆虫和哺乳动物的速度歧视，但由于可能受到小大脑的限制，昆虫似乎不太可能。另外两个记录提示加速选择性，这是一种潜在有用的视觉能力，对节肢动物的功能意义尚不确定。
Speed and acceleration are fundamental components of visual motion that animals can use to interpret the world. Behavioral studies have established that insects discriminate speed largely independently of contrast and spatial frequency, and physiological recordings suggest that a subset of premotor descending neurons is in this sense speed-selective. Neural substrates and mechanisms of speed selectivity in insects, however, are unknown. Using blow flies Phaenicia sericata, intracellular recordings and dye-fills were obtained from medulla and lobula complex neurons which, though not necessarily speed-selective themselves, are positioned to participate in circuits that produce speed-selectivity in descending neurons. Stimulation with sinusoidally varied grating motion (0-200 degrees/s) provided a range of instantaneous velocities and accelerations. The resulting speed response profiles are indicative of four distinct speed ranges, supporting the hypothesis that the spatiotemporal tuning of mid-level neurons contains sufficient diversity to account for the emergence of speed selectivity at the descending neuron level. This type of mechanism has been proposed to explain speed discrimination in both insects and mammals, but has seemed less likely for insects due to possible constraints on small brains. Two additional recordings are suggestive of acceleration-selectivity, a potentially useful visual capability that is of uncertain functional significance for arthropods.