MECHANISMS OF DENDRITIC INTEGRATION UNDERLYING GAIN-CONTROL IN FLY MOTION-SENSITIVE INTERNEURONS
MECHANISMS OF DENDRITIC INTEGRATION UNDERLYING GAIN-CONTROL IN FLY MOTION-SENSITIVE INTERNEURONS
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DOI：
10.1007/bf00962705
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发表时间：
1995-03-01
影响因子：
1.2
通讯作者：
HAAG, J
中科院分区：
文献类型：
--
作者：
BORST, A;EGELHAAF, M;HAAG, J
在果蝇的补偿性视运动反应中，Reichardt及其同事已经观察到了增益控制的有趣现象（Reichardt等人，1983年）：响应的幅度随着刺激大小的增加而趋于饱和，但是假设不同的饱和平台具有刺激移动的不同速度。这种特征已经在果蝇视叶的运动敏感性大视野神经元中发现，其在介导这种行为反应中起作用（豪森，1982; Reichardt等人，1983; Egelhaaf，1985; Haag等人，1992年）。为了解释增益控制，提出了一种模型，该模型涉及通过另一个细胞（所谓的池细胞）对这些细胞的分流抑制（Reichardt等人，1983），两个单元共享来自局部运动检测器阵列的公共输入。本文介绍了一种替代模型，它只需要树突集成的输出信号的两种类型的局部运动检测器具有相反的极性。增益控制的解释依赖于最近的发现，这些输入元件不是完美的方向选择性，它们的方向选择性是方向图速度的函数。因此，在整合细胞的树突中产生的突触后电位随着图案尺寸的增加而饱和，处于兴奋性和抑制性逆转电位之间的水平。然后，饱和度的精确值由兴奋性和抑制性输入元件的激活比率来设置，该激活比率又是其他刺激参数（诸如图案速度）的函数。因此，显然是复杂的增益控制现象可以简单地解释与运动敏感的输入元件的属性结合的树突状积分的生物物理学。
In the compensatory optomotor response of the fly the interesting phenomenon of gain control has been observed by Reichardt and colleagues (Reichardt et al., 1983): The amplitude of the response tends to saturate with increasing stimulus size, but different saturation plateaus are assumed with different velocities at which the stimulus is moving. This characteristic can already be found in the motion-sensitive large field neurons of the fly optic lobes that play a role in mediating this behavioral response (Hausen, 1982; Reichardt et al., 1983; Egelhaaf, 1985; Haag et al., 1992). To account for gain control a model was proposed involving shunting inhibition of these cells by another cell, the so-called pool cell (Reichardt et al., 1983), both cells sharing common input from an array of local motion detectors. This article describes an alternative model which only requires dendritic integration of the output signals of two types of local motion detectors with opposite polarity. The explanation of gain control relies on recent findings that these input elements are not perfectly directionally selective and that their direction selectivity is a function of pattern velocity. As a consequence, the resulting postsynaptic potential in the dendrite of the integrating cell saturates with increasing pattern size at a level between the excitatory and inhibitory reversal potentials. The exact value of saturation is then set by the activation ratio of excitatory and inhibitory input elements which in turn is a function of other stimulus parameters such as pattern velocity. Thus, the apparently complex phenomenon of gain control can be simply explained by the biophysics of dendritic integration in conjunction with the properties of the motion-sensitive input elements.