9月9日，《神经科学期刊》（Journal of Neuroscience）发表了中科院上海生命科学研究院神经科学研究所姚海珊研究组的研究论文“外膝体感受野的时空频率调谐特征可以提高神经元分辨自然图像的能力”。
理论研究表明，初级视觉系统可以有效地编码自然视觉图像信息。尚未清楚的一个问题是，初级视觉系统能否有选择地放大特定的图像信息成分，从而利于神经元分辨不同的图像。姚海珊研究组研究了外膝体的时空频率调谐特征在处理自然图像中的作用。他们测量外膝体的时空感受野，观察到神经元的时空频率调谐具有不可分特性，该不可分特性与信息论方法计算出来的可以最优化传递自然图像信息的神经元模型相一致。他们分析了自然图像的时空频谱特征，观察到不同图像在时间频率为10 Hz附近的频谱能量变异最大。有趣的是，外膝体神经元的最佳时间频率与该频谱能量变异最大的频率段重合。他们进一步测量了外膝体神经元对自然图像和与自然图像具有相同平均频谱能量的合成图像的反应，观察到外膝体神经元对不同自然图像的分辨能力高于对不同合成图像的分辨能力。这些结果表明，外膝体感受野不仅去除自然图像中的冗余信息，还通过其时空频率调谐特征使得神经元能更好地分辨不同的自然图像。（生物谷Bioon.com）
生物谷推荐原始出处：
The Journal of Neuroscience, September 9, 2009, 29(36):11409-11416; doi:10.1523/JNEUROSCI.1268-09.2009
The Spatiotemporal Frequency Tuning of LGN Receptive Field Facilitates Neural Discrimination of Natural Stimuli
Zhongchao Tan and Haishan Yao
Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
Correspondence should be addressed to Haishan Yao at the above address.
The efficient coding hypothesis suggests that the early visual system is optimized to represent stimuli in the natural environment. While it is believed that LGN processing removes the redundant information of natural scenes, it is not clear whether the early visual processing can selectively amplify important signals in natural stimuli to facilitate discrimination. In this study, we examined the functional role of LGN spatiotemporal frequency tuning in the processing of natural scenes. First, we characterized the relationship between spatial and temporal frequency tuning for LGN receptive fields. We found that LGN neurons exhibit inseparable spatiotemporal frequency tuning in a manner consistent with the feature of optimal filters that can maximize information transmission of natural scenes. Second, we analyzed the spatiotemporal power spectrum of natural scenes and found that some frequencies exhibit larger variation in power across different scenes. Interestingly, the preferred frequency of ensemble LGN neurons matches the range of frequencies in which natural power spectrum varies most. Comparison of neural discrimination for natural stimuli and for artificial stimuli with similar mean power spectra but different variation structure showed that the match between LGN tuning and natural spectra variation enhances neural discrimination for natural stimuli. Our results indicate that, in addition to removing redundancy, the spatiotemporal frequency characteristics of LGN neurons can facilitate neural discrimination of natural stimuli.
