Multiplicative computation in a visual neuron sensitive to looming
Multiplicative computation in a visual neuron sensitive to looming
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DOI：
10.1038/nature01190
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发表时间：
2002-11-21
期刊：
影响因子：
64.8
通讯作者：
Laurent, G
中科院分区：
文献类型：
--
作者：
Gabbiani, F;Krapp, HG;Laurent, G
乘法运算在感觉处理中很重要（1-5），但它们的生物物理实现在很大程度上仍然未知（5-10）。我们研究了一个确定的神经元（小叶巨大的运动检测器，LGMD，蝗虫），其输出的发射率在响应迫在眉睫的视觉刺激已被描述为两个模型，其中之一涉及乘法。在这个模型中，LGMD在突触后增加两个输入（一个兴奋性，一个抑制性），并汇聚到其树突树（11，12）;在另一个模型中，抑制是突触前LGMD（13，14）。通过使用选择性激活和失活的突触前和突触后抑制，我们表明，突触后抑制具有主导作用，这表明乘法是在神经元本身。我们的药理学实验和放电率与膜电位的测量也表明，钠通道既能及时推进LGMD的反应，又能以接近指数的方式将膜电位映射到放电率。这些结果与基于树状减法的乘法的实现一致，所述树状减法是对两个收敛输入进行算术编码，然后通过活性膜电导求幂。
Multiplicative operations are important in sensory processing(1-5), but their biophysical implementation remains largely unknown(5-10). We investigated an identified neuron ( the lobula giant movement detector, LGMD, of locusts) whose output firing rate in response to looming visual stimuli has been described by two models, one of which involves a multiplication. In this model, the LGMD multiplies postsynaptically two inputs ( one excitatory, one inhibitory) that converge onto its dendritic tree(11,12); in the other model, inhibition is presynaptic to the LGMD(13,14). By using selective activation and inactivation of pre- and postsynaptic inhibition, we show that postsynaptic inhibition has a predominant role, suggesting that multiplication is implemented within the neuron itself. Our pharmacological experiments and measurements of firing rate versus membrane potential also reveal that sodium channels act both to advance the response of the LGMD in time and to map membrane potential to firing rate in a nearly exponential manner. These results are consistent with an implementation of multiplication based on dendritic subtraction of two converging inputs encoded logarithmically, followed by exponentiation through active membrane conductances.