Carandini Matteo, Heeger David J, Senn Walter
Institute of Neuroinformatics, University of Zurich and Swiss Federal Institute of Technology, CH-8057 Zurich, Switzerland.
J Neurosci. 2002 Nov 15;22(22):10053-65. doi: 10.1523/JNEUROSCI.22-22-10053.2002.
The responses of neurons in the primary visual cortex (V1) are suppressed by mask stimuli that do not elicit responses if presented alone. This suppression is widely believed to be mediated by intracortical inhibition. As an alternative, we propose that it can be explained by thalamocortical synaptic depression. This explanation correctly predicts that suppression is monocular, immune to cortical adaptation, and occurs for mask stimuli that elicit responses in the thalamus but not in the cortex. Depression also explains other phenomena previously ascribed to intracortical inhibition. It explains why responses saturate at high stimulus contrast, whereas selectivity for orientation and spatial frequency is invariant with contrast. It explains why transient responses to flashed stimuli are nonlinear, whereas spatial summation is primarily linear. These results suggest that the very first synapses into the cortex, and not the cortical network, may account for important response properties of V1 neurons.
初级视觉皮层（V1）中的神经元反应会受到掩蔽刺激的抑制，这些掩蔽刺激单独呈现时不会引发反应。人们普遍认为这种抑制是由皮质内抑制介导的。作为一种替代解释，我们提出它可以用丘脑皮质突触抑制来解释。这种解释正确地预测了抑制是单眼的，不受皮质适应的影响，并且发生在那些在丘脑中引发反应但在皮质中不引发反应的掩蔽刺激情况下。抑制也解释了先前归因于皮质内抑制的其他现象。它解释了为什么反应在高刺激对比度下会饱和，而对方向和空间频率的选择性却与对比度无关。它解释了为什么对闪光刺激的瞬态反应是非线性的，而空间总和主要是线性的。这些结果表明，进入皮层的最初突触，而非皮层网络，可能是V1神经元重要反应特性的原因。
