The Queensland Brain Institute, The University of Queensland, Saint Lucia, QLD, Australia.
School of Medicine, Medical Sciences, and Nutrition, University of Aberdeen, Aberdeen, United Kingdom.
Front Neural Circuits. 2021 Oct 21;15:748535. doi: 10.3389/fncir.2021.748535. eCollection 2021.
Animals from insects to humans perform visual escape behavior in response to looming stimuli, and these responses habituate if looms are presented repeatedly without consequence. While the basic visual processing and motor pathways involved in this behavior have been described, many of the nuances of predator perception and sensorimotor gating have not. Here, we have performed both behavioral analyses and brain-wide cellular-resolution calcium imaging in larval zebrafish while presenting them with visual loom stimuli or stimuli that selectively deliver either the movement or the dimming properties of full loom stimuli. Behaviorally, we find that, while responses to repeated loom stimuli habituate, no such habituation occurs when repeated movement stimuli (in the absence of luminance changes) are presented. Dim stimuli seldom elicit escape responses, and therefore cannot habituate. Neither repeated movement stimuli nor repeated dimming stimuli habituate the responses to subsequent full loom stimuli, suggesting that full looms are required for habituation. Our calcium imaging reveals that motion-sensitive neurons are abundant in the brain, that dim-sensitive neurons are present but more rare, and that neurons responsive to both stimuli (and to full loom stimuli) are concentrated in the tectum. Neurons selective to full loom stimuli (but not to movement or dimming) were not evident. Finally, we explored whether movement- or dim-sensitive neurons have characteristic response profiles during habituation to full looms. Such functional links between baseline responsiveness and habituation rate could suggest a specific role in the brain-wide habituation network, but no such relationships were found in our data. Overall, our results suggest that, while both movement- and dim-sensitive neurons contribute to predator escape behavior, neither plays a specific role in brain-wide visual habituation networks or in behavioral habituation.
从昆虫到人类的动物都会对逼近的刺激做出视觉逃避行为，而这些反应如果在没有后果的情况下反复呈现逼近刺激，就会习惯化。虽然已经描述了涉及这种行为的基本视觉处理和运动途径，但捕食者感知和感觉运动门控的许多细微差别尚未被揭示。在这里，我们在幼虫斑马鱼中同时进行了行为分析和全脑细胞分辨率钙成像，同时向它们呈现视觉逼近刺激或选择性传递全逼近刺激的运动或变暗特性的刺激。行为上，我们发现，虽然对重复逼近刺激的反应会习惯化，但当重复运动刺激（在没有亮度变化的情况下）呈现时，不会发生这种习惯化。暗刺激很少引起逃避反应，因此不能习惯化。重复运动刺激或重复变暗刺激都不能习惯化对后续全逼近刺激的反应，这表明全逼近刺激是习惯化所必需的。我们的钙成像揭示了大脑中存在大量对运动敏感的神经元，存在但更为罕见的对暗敏感的神经元，以及对两种刺激（和全逼近刺激）有反应的神经元集中在顶盖中。选择性地对全逼近刺激（而不是对运动或变暗）做出反应的神经元不明显。最后，我们探讨了在全逼近刺激习惯化过程中，运动敏感或暗敏感神经元是否具有特征性的反应特征。这种基线反应性和习惯化率之间的功能联系可能暗示了在全脑习惯化网络中的特定作用，但我们的数据中没有发现这种关系。总的来说，我们的结果表明，虽然运动敏感和暗敏感神经元都有助于逃避捕食者的行为，但它们在全脑视觉习惯化网络或行为习惯化中都没有特定作用。
