Lesica Nicholas A, Stanley Garrett B
Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
J Neurosci. 2004 Nov 24;24(47):10731-40. doi: 10.1523/JNEUROSCI.3059-04.2004.
The role of the lateral geniculate nucleus (LGN) of the thalamus in visual encoding remains an open question. Here, we characterize the function of tonic and burst spikes in cat LGN X-cells in signaling features of natural stimuli. A significant increase in bursting was observed during natural stimulation (relative to white noise stimulation) and was linked to the strong correlation structure of the natural scene movies. Burst responses were triggered by specific stimulus events consisting of a prolonged inhibitory stimulus, followed by an excitatory stimulus, such as the movement of an object into the receptive field. LGN responses to natural scene movies were predicted using an integrate-and-fire (IF) framework and compared with experimentally observed responses. The standard IF model successfully predicted LGN responses to natural scene movies during tonic firing, indicating a linear relationship between stimulus and response. However, the IF model typically underpredicted the LGN response during periods of bursting, indicating a nonlinear amplification of the stimulus in the actual response. The addition of a burst mechanism to the IF model was necessary to accurately predict the entire LGN response. These results suggest that LGN bursts are an important part of the neural code, providing a nonlinear amplification of stimulus features that are typical of the natural environment.
丘脑外侧膝状体核（LGN）在视觉编码中的作用仍是一个悬而未决的问题。在此，我们描述了猫LGN X细胞中紧张性发放和爆发性发放对自然刺激特征进行信号编码的功能。在自然刺激期间（相对于白噪声刺激）观察到爆发性发放显著增加，且与自然场景电影的强相关结构有关。爆发性反应由特定的刺激事件触发，这些事件包括一个持续的抑制性刺激，随后是一个兴奋性刺激，比如一个物体移入感受野。使用积分发放（IF）框架预测LGN对自然场景电影的反应，并与实验观察到的反应进行比较。标准的IF模型成功预测了紧张性发放期间LGN对自然场景电影的反应，表明刺激与反应之间存在线性关系。然而，IF模型通常在爆发性发放期间对LGN反应预测不足，这表明在实际反应中刺激存在非线性放大。在IF模型中添加爆发机制对于准确预测整个LGN反应是必要的。这些结果表明，LGN爆发是神经编码的重要组成部分，可以对自然环境中典型的刺激特征进行非线性放大。
