Escape behavior and neuronal responses to looming stimuli in the crab Chasmagnathus granulatus (Decapoda: Grapsidae)
Escape behavior and neuronal responses to looming stimuli in the crab Chasmagnathus granulatus (Decapoda: Grapsidae)
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DOI：
10.1242/jeb.02707
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发表时间：
2007-03
影响因子：
2.8
通讯作者：
Damián Oliva;Violeta Medan;D. Tomsic
中科院分区：
文献类型：
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作者：
Damián Oliva;Violeta Medan;D. Tomsic
在许多脊椎动物和无脊椎动物物种中已经研究了对隐现刺激的行为反应，但是在极少数动物中研究了对隐现敏感的神经元。在本文中，我们介绍了一个新的实验模型，使用螃蟹Chasmagnathus颗粒，它允许调查的过程中，迫在眉睫的检测和逃避决定在行为和神经元水平。通过分析蟹类在步行模拟装置中的逃避反应，我们发现：（1）计算机产生的隐现刺激能在所有被试动物中引起稳健可靠的逃避反应：（2）逃避的距离、速度、时间和方向等参数在步行模拟装置中易于精确记录和量化;（iii）尽管动物和刺激呈现之间的逃避幅度不同，但反应的时间是显著一致的，并且在3分钟的刺激间隔下不习惯。然后，我们研究了神经元的反应，从大脑的螃蟹通过细胞内记录在完整的动物，并表明：（iv）两个子类的先前确定的运动检测神经元从小叶（第三视神经元）对触发行为反应的相同隐现刺激表现出稳健和可靠的反应;（v）神经元通过以与图像扩展的动态紧密匹配的方式增加其放电速率来响应对象接近。最后，我们比较了神经元的行为反应表明：（六）神经元的反应，隐现，后退或横向移动的刺激的差异密切反映了这种刺激的行为差异;（七）在隐现，螃蟹开始运行后不久，隐现敏感的神经元开始，以增加其发射率。在刺激接近过程中，跑步速度的增加忠实地遵循放电率的增加，直到最大刺激扩展的时刻。此后，神经元突然停止放电，动物立即减速奔跑。结果进行了讨论，在蝗虫迫在眉睫的刺激反应的研究。
SUMMARY Behavioral responses to looming stimuli have been studied in many vertebrate and invertebrate species, but neurons sensitive to looming have been investigated in very few animals. In this paper we introduce a new experimental model using the crab Chasmagnathus granulatus, which allows investigation of the processes of looming detection and escape decision at both the behavioral and neuronal levels. By analyzing the escape response of the crab in a walking simulator device we show that: (i) a robust and reliable escape response can be elicited by computer-generated looming stimuli in all tested animals; (ii) parameters such as distance, speed, timing and directionality of the escape run, are easy to record and quantify precisely in the walking device; (iii) although the magnitude of escape varies between animals and stimulus presentations, the timing of the response is remarkably consistent and does not habituate at 3 min stimulus intervals. We then study the response of neurons from the brain of the crab by means of intracellular recordings in the intact animal and show that: (iv) two subclasses of previously identified movement detector neurons from the lobula (third optic neuropil) exhibit robust and reliable responses to the same looming stimuli that trigger the behavioral response; (v) the neurons respond to the object approach by increasing their rate of firing in a way that closely matches the dynamics of the image expansion. Finally, we compare the neuronal with the behavioral response showing that: (vi) differences in the neuronal responses to looming, receding or laterally moving stimuli closely reflect the behavioral differences to such stimuli; (vii) during looming, the crab starts to run soon after the looming-sensitive neurons begin to increase their firing rate. The increase in the running speed during stimulus approach faithfully follows the increment in the firing rate, until the moment of maximum stimulus expansion. Thereafter, the neurons abruptly stop firing and the animal immediately decelerates its run. The results are discussed in connection with studies of responses to looming stimuli in the locust.