Yen Shih-Cheng, Baker Jonathan, Gray Charles M
Center for Computational Biology and Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT, USA.
J Neurophysiol. 2007 Feb;97(2):1326-41. doi: 10.1152/jn.00747.2006. Epub 2006 Nov 1.
When presented with simple stimuli like bars and gratings, adjacent neurons in striate cortex exhibit shared selectivity for multiple stimulus dimensions, such as orientation, direction, and spatial frequency. This has led to the idea that local averaging of neuronal responses provides a more reliable representation of stimulus properties. However, when stimulated with complex, time-varying natural scenes (i.e., movies), striate neurons exhibit highly sparse responses. This raises the question of how much response heterogeneity the local population exhibits when stimulated with movies, and how it varies with separation distance between cells. We investigated this question by simultaneously recording the responses of groups of neurons in cat striate cortex to the repeated presentation of movies using silicon probes in a multi-tetrode configuration. We found, first, that the responses of striate neurons to movies are brief (tens of milliseconds), decorrelated, and exhibit high population sparseness. Second, we found that adjacent neurons differed significantly in their peak firing rates even when they responded to the same frames of a movie. Third, pairs of adjacent neurons recorded on the same tetrodes exhibited as much heterogeneity in their responses as pairs recorded by different tetrodes. These findings demonstrate that complex natural scenes evoke highly heterogeneous responses within local populations, suggesting that response redundancy in a cortical column is substantially lower than previously thought.
当面对诸如线条和光栅等简单刺激时，纹状皮层中的相邻神经元对多个刺激维度表现出共同的选择性，如方向、运动方向和空间频率。这导致了一种观点，即神经元反应的局部平均提供了更可靠的刺激特性表征。然而，当用复杂的、随时间变化的自然场景（即电影）进行刺激时，纹状神经元表现出高度稀疏的反应。这就提出了一个问题，即当用电影进行刺激时，局部神经元群体表现出多大程度的反应异质性，以及它如何随细胞间的间隔距离而变化。我们通过使用多电极配置的硅探针同时记录猫纹状皮层中神经元群体对电影重复呈现的反应，来研究这个问题。我们首先发现，纹状神经元对电影的反应是短暂的（几十毫秒），不相关的，并且表现出高群体稀疏性。其次，我们发现即使相邻神经元对电影的同一帧做出反应，它们的峰值放电率也存在显著差异。第三，在同一电极上记录的相邻神经元对之间的反应异质性与在不同电极上记录的相邻神经元对之间的反应异质性一样大。这些发现表明，复杂的自然场景在局部神经元群体中引发了高度异质性的反应，这表明皮层柱中的反应冗余度比之前认为的要低得多。
