PDF(Pubmed)
Abstract：
In animal species ranging from invertebrate to mammals, visually guided escape behaviours have been studied using looming stimuli, the two-dimensional expanding projection on a screen of an object approaching on a collision course at constant speed. The peak firing rate or membrane potential of neurons responding to looming stimuli often tracks a fixed threshold angular size of the approaching stimulus that contributes to the triggering of escape behaviours. To study whether this result holds more generally, we designed stimuli that simulate acceleration or deceleration over the course of object approach on a collision course. Under these conditions, we found that the angular threshold conveyed by collision detecting neurons in grasshoppers was sensitive to acceleration whereas the triggering of escape behaviours was less so. In contrast, neurons in goldfish identified through the characteristic features of the escape behaviours they trigger, showed little sensitivity to acceleration. This closely mirrored a broader lack of sensitivity to acceleration of the goldfish escape behaviour. Thus, although the sensory coding of simulated colliding stimuli with non-zero acceleration probably differs in grasshoppers and goldfish, the triggering of escape behaviours converges towards similar characteristics. Approaching stimuli with non-zero acceleration may help refine our understanding of neural computations underlying escape behaviours in a broad range of animal species. KEY POINTS: A companion manuscript showed that two mathematical models of collision-detecting neurons in grasshoppers and goldfish make distinct predictions for the timing of their responses to simulated objects approaching on a collision course with non-zero acceleration. Testing these experimental predictions showed that grasshopper neurons are sensitive to acceleration while goldfish neurons are not, in agreement with the distinct models proposed previously in these species using constant velocity approaches. Grasshopper and goldfish escape behaviours occurred after the stimulus reached a fixed angular size insensitive to acceleration, suggesting further downstream processing in grasshopper motor circuits to match what was observed in goldfish. Thus, in spite of different sensory processing in the two species, escape behaviours converge towards similar solutions. The use of object acceleration during approach on a collision course may help better understand the neural computations implemented for collision avoidance in a broad range of species.
摘要：
在从无脊椎动物到哺乳动物的动物物种中，已经使用迫在眉睫的刺激研究了视觉引导的逃生行为，物体在屏幕上以恒定速度接近碰撞路线的二维扩展投影。响应于迫在眉睫的刺激的神经元的峰值放电速率或膜电位通常跟踪接近刺激的固定阈值角度大小，这有助于触发逃避行为。为了研究这一结果是否更普遍地适用，我们设计了模拟碰撞过程中物体接近过程中加速或减速的刺激。在这些条件下,我们发现，蝗虫中碰撞检测神经元传递的角度阈值对加速度敏感，而逃避行为的触发则不那么敏感。相比之下,金鱼中的神经元通过它们触发的逃避行为的特征来识别，对加速度几乎不敏感。这紧密地反映了对金鱼逃生行为的加速缺乏敏感性的广泛缺乏。因此，虽然模拟的非零加速度碰撞刺激的感官编码可能在蝗虫和金鱼中有所不同，逃生行为的触发趋于相似的特征。以非零加速度接近刺激可能有助于完善我们对广泛动物物种中逃避行为的神经计算的理解。关键点：一份伴随手稿表明，两个碰撞检测神经元的数学模型在蝗虫和金鱼中做出了不同的预测，它们对模拟物体以非零加速度接近碰撞过程的时间做出了不同的预测。测试这些实验预测表明，蝗虫神经元对加速度敏感，而金鱼神经元则不敏感，与以前在这些物种中使用恒定速度方法提出的不同模型一致。在刺激达到对加速度不敏感的固定角度大小后，发生了蝗虫和金鱼的逃逸行为，建议在蝗虫电机电路中进行进一步的下游处理，以匹配金鱼中观察到的情况。因此，尽管这两个物种的感官处理不同，逃避行为趋于相似的解决方案。在接近碰撞过程中使用物体加速度可以帮助更好地理解为在广泛的物种中避免碰撞而实现的神经计算。
