Meytlis Marsha, Nichols Zachary, Nirenberg Sheila
Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, NY 10065, United States.
Vision Res. 2012 Oct 1;70:44-53. doi: 10.1016/j.visres.2012.07.007. Epub 2012 Aug 3.
The role of correlated firing in representing information has been a subject of much discussion. Several studies in retina, visual cortex, somatosensory cortex, and motor cortex, have suggested that it plays only a minor role, carrying <10% of the total information carried by the neurons (Gawne & Richmond, 1993; Nirenberg et al., 2001; Oram et al., 2001; Petersen, Panzeri, & Diamond, 2001; Rolls et al., 2003). A limiting factor of these studies, however, is that they were carried out using pairs of neurons; how the results extend to large populations was not clear. Recently, new methods for modeling network firing patterns have been developed (Nirenberg & Pandarinath, 2012; Pillow et al., 2008), opening the door to answering this question for more complete populations. One study, Pillow et al. (2008), showed that including correlations increased information by a modest amount, 20%; however, this work used only a single retina (primate) and a white noise stimulus. Here we performed the analysis using several retinas (mouse) and both white noise and natural scene stimuli. The results showed that correlations added little information when white noise stimuli were used (13%), similar to Pillow et al.'s findings, and essentially no information when natural scene stimuli were used. Further, the results showed that ignoring correlations did not change the quality of the information carried by the population (as measured by comparing the full pattern of decoding errors). These results suggest generalization: the pairwise analysis in several species show that correlations account for very little of the total information. Now, the analysis with large populations in two species show a similar result, that correlations still account for only a small fraction of the total information, and, most significantly, the amount is not statistically significant when natural stimuli are used, making rapid advances in the study of population coding possible.
相关放电在信息表征中的作用一直是诸多讨论的主题。视网膜、视觉皮层、躯体感觉皮层和运动皮层的多项研究表明，它仅起次要作用，携带的信息不到神经元携带的总信息的10%（高恩和里士满，1993年；尼伦伯格等人，2001年；奥勒姆等人，2001年；彼得森、潘泽里和戴蒙德，2001年；罗尔斯等人，2003年）。然而，这些研究的一个限制因素是它们是使用成对神经元进行的；结果如何推广到大量神经元群体尚不清楚。最近，已经开发出了用于模拟网络放电模式的新方法（尼伦伯格和潘达里纳斯，2012年；皮洛等人，2008年），为回答这个关于更完整神经元群体的问题打开了大门。一项研究，皮洛等人（2008年）表明，纳入相关性会使信息适度增加，约20%；然而，这项工作仅使用了单个视网膜（灵长类）和白噪声刺激。在这里，我们使用了多个视网膜（小鼠）以及白噪声和自然场景刺激进行分析。结果表明，当使用白噪声刺激时，相关性增加的信息很少（约13%），与皮洛等人的发现相似，而当使用自然场景刺激时，基本上没有增加信息。此外，结果表明忽略相关性不会改变群体携带信息的质量（通过比较解码错误的完整模式来衡量）。这些结果表明具有普遍性：几个物种中的成对分析表明相关性在总信息中所占比例非常小。现在，对两个物种中大量神经元群体的分析显示了类似的结果，即相关性在总信息中所占比例仍然很小，而且最显著的是，当使用自然刺激时，这个量在统计学上并不显著，这使得群体编码研究有可能取得快速进展。
