Light adaptation in Drosophila photoreceptors: I. Response dynamics and signaling efficiency at 25 degrees C.
Light adaptation in Drosophila photoreceptors: I. Response dynamics and signaling efficiency at 25 degrees C.
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DOI：
10.1085/jgp.117.1.3
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发表时间：
2001-01
影响因子：
3.8
通讯作者：
Hardie, RC
中科院分区：
文献类型：
--
作者：
Juusola, M;Hardie, RC
除了光子吸收的物理限制外，光导级联和光感受器膜对视觉信息的协同处理决定了光感受器信号的保真度。我们研究了果蝇光感受器对自然样波动光对比刺激和细胞内电流注射的响应动力学和信号传导效率，当细胞适应于4对数单位光强范围在25°C。这种双重刺激使我们能够描述平均光强的增加如何导致光导级联和光感受器膜对给定对比度产生更大、更快和越来越准确的电压响应。使用信号和噪声分析，这似乎与更小和更快的基本响应（即颠簸）的总和增加有关，其延迟分布在不同的平均光强水平下保持相对不变。随着光导级联的增加，信号（光电流）在高适应背景下的大小和速度，以及与光感受器膜的结合，减少了光致电压噪声，并且光感受器信噪比提高并扩展到更高的带宽。由于对光对比的电压响应比电流注入引起的电压响应慢得多，光感受器膜并不限制光导级联的速度，但它过滤了相关的高频噪声。光感受器信息容量随着光适应的增加而增加，并且随着固定数量的转导单元（可能是微绒毛）内的化学反应速度接近其最大值，在~ 200比特/秒时开始饱和。
Besides the physical limits imposed on photon absorption, the coprocessing of visual information by the phototransduction cascade and photoreceptor membrane determines the fidelity of photoreceptor signaling. We investigated the response dynamics and signaling efficiency of Drosophila photoreceptors to natural-like fluctuating light contrast stimulation and intracellular current injection when the cells were adapted over a 4-log unit light intensity range at 25°C. This dual stimulation allowed us to characterize how an increase in the mean light intensity causes the phototransduction cascade and photoreceptor membrane to produce larger, faster and increasingly accurate voltage responses to a given contrast. Using signal and noise analysis, this appears to be associated with an increased summation of smaller and faster elementary responses (i.e., bumps), whose latency distribution stays relatively unchanged at different mean light intensity levels. As the phototransduction cascade increases, the size and speed of the signals (light current) at higher adapting backgrounds and, in conjunction with the photoreceptor membrane, reduces the light-induced voltage noise, and the photoreceptor signal-to-noise ratio improves and extends to a higher bandwidth. Because the voltage responses to light contrasts are much slower than those evoked by current injection, the photoreceptor membrane does not limit the speed of the phototransduction cascade, but it does filter the associated high frequency noise. The photoreceptor information capacity increases with light adaptation and starts to saturate at ∼200 bits/s as the speed of the chemical reactions inside a fixed number of transduction units, possibly microvilli, is approaching its maximum.
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影响因子：
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