Spatial distribution of inputs and local receptive field properties of a wide-field, looming sensitive neuron
Spatial distribution of inputs and local receptive field properties of a wide-field, looming sensitive neuron
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DOI：
10.1152/jn.00965.2004
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发表时间：
2005-04-01
影响因子：
2.5
通讯作者：
Gabbiani, F
中科院分区：
文献类型：
--
作者：
Krapp, HG;Gabbiani, F
蝗虫视觉系统中的巨额运动检测器（LGMD）及其目标神经元下行对侧运动检测器（DCMD）对接近的物体做出反应。因此，它们为研究细胞和网络机制对这类特定行为相关刺激的敏感性提供了一个很好的模型。我们确定了整个蝗虫眼的光轴密度分布，描述了视觉系统局部输入的空间组织，并将其与LGMD/DCMD对局部运动刺激的灵敏度分布进行了比较。光轴密度在前眼的赤道区达到峰值。然而，局部运动敏感度在尾侧视野的赤道区域达到峰值，并且仅与光轴的背-腹侧密度呈正相关。在局部刺激下，LGMD/DCMD的速度调整和响应延迟都取决于刺激在视野中的位置。在空间和时间整合实验中，多个局部运动刺激同时或以固定延迟激活，表明LGMD以一种强烈的亚线性方式处理局部运动。因此，神经元的整合特性似乎取决于几个因素，包括其树突形态，传入纤维输入的局部特征，以及由不同途径或电压门控电导介导的抑制。我们的研究表明，这种迫在眉睫的敏感神经元对接近物体的选择性依赖于比以前认为的更复杂的生物物理机制。
The lobula giant movement detector (LGMD) in the locust visual system and its target neuron, the descending contralateral movement detector (DCMD), respond to approaching objects looming on a collision course with the animal. They thus provide a good model to study the cellular and network mechanisms underlying the sensitivity to this specific class of behaviorally relevant stimuli. We determined over an entire locust eye the density distribution of optical axes describing the spatial organization of local inputs to the visual system and compared it with the sensitivity distribution of the LGMD/DCMD to local motion stimuli. The density of optical axes peaks in the equatorial region of the frontal eye. Local motion sensitivity, however, peaks in the equatorial region of the caudolateral visual field and only correlates positively with the dorso-ventral density of optical axes. On local stimulation, both the velocity tuning and the response latency of the LGMD/DCMD depend on stimulus position within the Visual field. Spatial and temporal integration experiments in which several local motion stimuli were activated either simultaneously or at fixed delays reveal that the LGMD processes local motion in a strongly sublinear way. Thus the neuron's integration properties seem to depend on several factors including its dendritic morphology, the local characteristics of afferent fiber inputs, and inhibition mediated by different pathways or by voltage-gated conductances. Our study shows that the selectivity of this looming sensitive neuron to approaching objects relies on more complex biophysical mechanisms than previously thought.