Psychology Department, Helen Wills Neuroscience Institute, and Physics Department, University of California, Berkeley, Berkeley, California 94720-1650, USA.
J Neurosci. 2010 Feb 10;30(6):2102-14. doi: 10.1523/JNEUROSCI.4099-09.2010.
Area V2 is a major visual processing stage in mammalian visual cortex, but little is currently known about how V2 encodes information during natural vision. To determine how V2 represents natural images, we used a novel nonlinear system identification approach to obtain quantitative estimates of spatial tuning across a large sample of V2 neurons. We compared these tuning estimates with those obtained in area V1, in which the neural code is relatively well understood. We find two subpopulations of neurons in V2. Approximately one-half of the V2 neurons have tuning that is similar to V1. The other half of the V2 neurons are selective for complex features such as those that occur in natural scenes. These neurons are distinguished from V1 neurons mainly by the presence of stronger suppressive tuning. Selectivity in these neurons therefore reflects a balance between excitatory and suppressive tuning for specific features. These results provide a new perspective on how complex shape selectivity arises, emphasizing the role of suppressive tuning in determining stimulus selectivity in higher visual cortex.
V2 区是哺乳动物视觉皮层中的一个主要视觉处理阶段，但目前对于 V2 在自然视觉中如何编码信息知之甚少。为了确定 V2 如何表示自然图像，我们使用了一种新颖的非线性系统识别方法，对大量 V2 神经元的空间调谐进行了定量估计。我们将这些调谐估计与在 V1 区获得的调谐估计进行了比较，V1 区的神经编码相对较为清楚。我们发现 V2 区有两个神经元亚群。大约一半的 V2 神经元的调谐类似于 V1。V2 区的另一半神经元对复杂特征（如自然场景中出现的特征）具有选择性。这些神经元与 V1 神经元的区别主要在于抑制性调谐更强。这些神经元的选择性反映了特定特征的兴奋性和抑制性调谐之间的平衡。这些结果为复杂形状选择性如何产生提供了一个新的视角，强调了抑制性调谐在确定高级视觉皮层中刺激选择性方面的作用。
