Niell Cristopher M, Stryker Michael P
Department of Physiology, W M Keck Foundation Center for Integrative Neuroscience, University of California, San Francisco, San Francisco, California 94143-0444, USA.
J Neurosci. 2008 Jul 23;28(30):7520-36. doi: 10.1523/JNEUROSCI.0623-08.2008.
Genetic methods available in mice are likely to be powerful tools in dissecting cortical circuits. However, the visual cortex, in which sensory coding has been most thoroughly studied in other species, has essentially been neglected in mice perhaps because of their poor spatial acuity and the lack of columnar organization such as orientation maps. We have now applied quantitative methods to characterize visual receptive fields in mouse primary visual cortex V1 by making extracellular recordings with silicon electrode arrays in anesthetized mice. We used current source density analysis to determine laminar location and spike waveforms to discriminate putative excitatory and inhibitory units. We find that, although the spatial scale of mouse receptive fields is up to one or two orders of magnitude larger, neurons show selectivity for stimulus parameters such as orientation and spatial frequency that is near to that found in other species. Furthermore, typical response properties such as linear versus nonlinear spatial summation (i.e., simple and complex cells) and contrast-invariant tuning are also present in mouse V1 and correlate with laminar position and cell type. Interestingly, we find that putative inhibitory neurons generally have less selective, and nonlinear, responses. This quantitative description of receptive field properties should facilitate the use of mouse visual cortex as a system to address longstanding questions of visual neuroscience and cortical processing.
小鼠中可用的遗传方法可能是剖析皮层回路的有力工具。然而，在其他物种中对感觉编码研究最为深入的视觉皮层，在小鼠中基本上被忽视了，这可能是因为它们的空间敏锐度较差，且缺乏诸如方位图等柱状组织。我们现在应用定量方法，通过在麻醉的小鼠中使用硅电极阵列进行细胞外记录，来表征小鼠初级视觉皮层V1中的视觉感受野。我们使用电流源密度分析来确定层状位置，并利用尖峰波形来区分假定的兴奋性和抑制性单元。我们发现，尽管小鼠感受野的空间尺度要大一个或两个数量级，但神经元对诸如方位和空间频率等刺激参数仍表现出与其他物种相近的选择性。此外，典型的反应特性，如线性与非线性空间总和（即简单细胞和复杂细胞）以及对比度不变调谐，在小鼠V1中也存在，并且与层状位置和细胞类型相关。有趣的是，我们发现假定的抑制性神经元通常具有选择性较低且非线性的反应。这种对感受野特性的定量描述应该有助于将小鼠视觉皮层用作一个系统，来解决视觉神经科学和皮层处理方面长期存在的问题。
