Rokem Ariel, Watzl Sebastian, Gollisch Tim, Stemmler Martin, Herz Andreas V M, Samengo Inés
Institute for Theoretical Biology, Department of Biology, Humboldt University, Berlin Germany.
J Neurophysiol. 2006 Apr;95(4):2541-52. doi: 10.1152/jn.00891.2005. Epub 2005 Dec 14.
Sensory systems must translate incoming signals quickly and reliably so that an animal can act successfully in its environment. Even at the level of receptor neurons, however, functional aspects of the sensory encoding process are not yet fully understood. Specifically, this concerns the question how stimulus features and neural response characteristics lead to an efficient transmission of sensory information. To address this issue, we have recorded and analyzed spike trains from grasshopper auditory receptors, while systematically varying the stimulus statistics. The stimulus variations profoundly influenced the efficiency of neural encoding. This influence was largely attributable to the presence of specific stimulus features that triggered remarkably precise spikes whose trial-to-trial timing variability was as low as 0.15 ms--one order of magnitude shorter than typical stimulus time scales. Precise spikes decreased the noise entropy of the spike trains, thereby increasing the rate of information transmission. In contrast, the total spike train entropy, which quantifies the variety of different spike train patterns, hardly changed when stimulus conditions were altered, as long as the neural firing rate remained the same. This finding shows that stimulus distributions that were transmitted with high information rates did not invoke additional response patterns, but instead displayed exceptional temporal precision in their neural representation. The acoustic stimuli that led to the highest information rates and smallest spike-time jitter feature pronounced sound-pressure deflections lasting for 2-3 ms. These upstrokes are reminiscent of salient structures found in natural grasshopper communication signals, suggesting that precise spikes selectively encode particularly important aspects of the natural stimulus environment.
感觉系统必须快速且可靠地转换传入信号，以便动物能够在其环境中成功行动。然而，即使在受体神经元层面，感觉编码过程的功能方面仍未被完全理解。具体而言，这涉及到刺激特征和神经反应特性如何导致感觉信息有效传递的问题。为了解决这个问题，我们记录并分析了蚱蜢听觉受体的尖峰序列，同时系统地改变刺激统计量。刺激变化深刻地影响了神经编码的效率。这种影响很大程度上归因于特定刺激特征的存在，这些特征触发了非常精确的尖峰，其逐次试验的时间变异性低至0.15毫秒——比典型的刺激时间尺度短一个数量级。精确的尖峰降低了尖峰序列的噪声熵，从而提高了信息传输速率。相比之下，只要神经放电率保持不变，当刺激条件改变时，量化不同尖峰序列模式多样性的总尖峰序列熵几乎没有变化。这一发现表明，以高信息速率传输的刺激分布不会引发额外的反应模式，而是在其神经表征中表现出异常的时间精度。导致最高信息速率和最小尖峰时间抖动的声学刺激具有持续2 - 3毫秒的明显声压偏转特征。这些上升沿让人联想到在蚱蜢自然通讯信号中发现的显著结构，这表明精确的尖峰选择性地编码了自然刺激环境中特别重要的方面。
