Evidence has shown that a variety of vertebrates, including fish, can discriminate collections of visual items on the basis of their numerousness using an evolutionarily conserved system for approximating numerical magnitude (the so-called Approximate Number System, ANS). Here we combine a habituation/dishabituation behavioural task with molecular biology assays to start investigating the neural bases of the ANS in zebrafish. Separate groups of zebrafish underwent a habituation phase with a set of 3 or 9 small red dots, associated with a food reward. The dots changed in size, position and density from trial to trial but maintained their numerousness, and the overall areas of the stimuli was kept constant. During the subsequent dishabituation test, zebrafish faced a change (i) in number (from 3 to 9 or vice versa with the same overall surface), or (ii) in shape (with the same overall surface and number), or (iii) in size (with the same shape and number). A control group of zebrafish was shown the same stimuli as during the habituation. RT-qPCR revealed that the telencephalon and thalamus were characterized by the most consistent modulation of the expression of the immediate early genes c-fos and egr-1 upon change in numerousness; in contrast, the retina and optic tectum responded mainly to changes in stimulus size.

有证据表明，包括鱼类在内的各种脊椎动物都可以使用进化保守的近似数值系统（所谓的近似数系统，ANS），根据视觉物品的数量来区分视觉物品的集合。在这里，我们将习惯性/适应性行为任务与分子生物学分析相结合，以开始研究斑马鱼中ANS的神经基础。单独的斑马鱼群经历了一个适应阶段，该阶段带有一组3或9个小红点，与食物奖励有关。在不同的试验中，点的大小，位置和密度都发生了变化，但是保持了许多点，并且刺激的总面积保持恒定。在随后的适应测试中，斑马鱼的数量（i）从3变到9或反之亦然，或者（ii）形状（具有相同的总体表面和数量），或者（iii）尺寸（具有相同的形状和数量）。斑马鱼对照组显示出与习惯化过程相同的刺激。RT-qPCR揭示，端脑和丘脑的特征是，随着数量的变化，立即早期基因c-fos和egr-1的表达得到最一致的调节。相反，视网膜和视神经支架主要对刺激大小的变化作出反应。