von der Emde G, Schwarz S, Gomez L, Budelli R, Grant K
Institute für Zoologie, Universität Bonn, Germany.
Nature. 1998 Oct 29;395(6705):890-4. doi: 10.1038/27655.
Distance determination in animals can be achieved by visual or non-visual cues. Weakly electric fish use active electrolocation for orientation in the dark. By perceiving self-produced electric signals with epidermal electroreceptors, fish can detect, locate and analyse nearby objects. Distance discrimination, however, was thought to be hardly possible because it was assumed that confusing ambiguity could arise with objects of unknown sizes and materials. Here we show that during electrolocation electric fish can measure the distance of most objects accurately, independently of size, shape and material. Measurements of the 'electric image' projected onto the skin surface during electrolocation revealed only one parameter combination that was unambiguously related to object distance: the ratio between maximal image slope and maximal image amplitude. However, slope-to-amplitude ratios for spheres were always smaller than those for other objects. As predicted, these objects were erroneously judged by the fish to be further away than all other objects at an identical distance. Our results suggest a novel mechanism for depth perception that can be achieved with a single, stationary two-dimensional array of detectors.
动物中的距离测定可以通过视觉或非视觉线索来实现。弱电鱼利用主动电定位在黑暗中定向。通过用表皮电感受器感知自身产生的电信号，鱼可以检测、定位和分析附近的物体。然而，距离辨别被认为几乎是不可能的，因为据推测，对于未知大小和材料的物体可能会产生混淆的模糊性。在这里，我们表明，在电定位过程中，弱电鱼可以准确测量大多数物体的距离，而与物体的大小、形状和材料无关。对电定位过程中投射到皮肤表面的“电图像”的测量揭示了仅与物体距离明确相关的一个参数组合：最大图像斜率与最大图像幅度之间的比率。然而，球体的斜率与幅度比率总是小于其他物体的。正如所预测的，在相同距离下，这些物体被鱼错误地判断为比所有其他物体更远。我们的结果表明了一种可以通过单个固定的二维探测器阵列实现深度感知的新机制。
