Flinders Health and Medical Research Institute, Flinders University, Adelaide 5001, Australia.
Flinders Health and Medical Research Institute, Flinders University, Adelaide 5001, Australia
eNeuro. 2023 Jul 24;10(7). doi: 10.1523/ENEURO.0188-23.2023. Print 2023 Jul.
Responding rapidly to visual stimuli is fundamental for many animals. For example, predatory birds and insects alike have amazing target detection abilities, with incredibly short neural and behavioral delays, enabling efficient prey capture. Similarly, looming objects need to be rapidly avoided to ensure immediate survival, as these could represent approaching predators. Male hoverflies are nonpredatory, highly territorial insects that perform high-speed pursuits of conspecifics and other territorial intruders. During the initial stages of the pursuit, the retinal projection of the target is very small, but this grows to a larger object before physical interaction. Supporting such behaviors, and other insects have both target-tuned and loom-sensitive neurons in the optic lobes and the descending pathways. We here show that these visual stimuli are not necessarily encoded in parallel. Indeed, we describe a class of descending neurons that respond to small targets, to looming and to wide-field stimuli. We show that these descending neurons have two distinct receptive fields where the dorsal receptive field is sensitive to the motion of small targets and the ventral receptive field responds to larger objects or wide-field stimuli. Our data suggest that the two receptive fields have different presynaptic input, where the inputs are not linearly summed. This novel and unique arrangement could support different behaviors, including obstacle avoidance, flower landing, and target pursuit or capture.
快速响应视觉刺激对于许多动物来说是至关重要的。例如，掠食性鸟类和昆虫都具有令人惊叹的目标检测能力，其神经和行为延迟非常短，从而能够有效地捕捉猎物。同样，需要迅速避开逼近的物体，以确保即时生存，因为这些物体可能代表着逼近的捕食者。雄性食蚜蝇是一种非掠食性的、高度领地性的昆虫，它们会对同种个体和其他领地入侵者进行高速追逐。在追逐的初始阶段，目标的视网膜投影非常小，但在物理相互作用之前，它会变成更大的物体。支持这种行为，以及其他昆虫在视叶和下行通路上都有目标调谐和逼近敏感神经元。我们在这里表明，这些视觉刺激不一定是并行编码的。事实上，我们描述了一类下行神经元，它们对小目标、逼近和宽视野刺激做出反应。我们表明，这些下行神经元有两个不同的感受野，其中背侧感受野对小目标的运动敏感，而腹侧感受野对较大物体或宽视野刺激做出反应。我们的数据表明，这两个感受野具有不同的突触前输入，输入不是线性相加的。这种新颖而独特的排列方式可能支持不同的行为，包括躲避障碍物、降落在花朵上以及追逐或捕捉目标。
