Ni Amy M, Murray Scott O, Horwitz Gregory D
National Primate Research Center and Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
Department of Psychology, University of Washington, Seattle, WA 98195, USA.
Curr Biol. 2014 Jul 21;24(14):1653-1658. doi: 10.1016/j.cub.2014.06.003. Epub 2014 Jul 10.
Stimuli that project the same retinal visual angle can appear to occupy very different proportions of the visual field if they are perceived to be at different distances [1-8]. Previous research shows that perceived angular size alters the spatial distribution of activity in early retinotopic visual cortex [7, 9-11]. For example, a sphere superimposed on the far end of a corridor scene appears to occupy a larger visual angle and activates a larger region of primary visual cortex (V1) compared with the same sphere superimposed on the near end of the corridor [7]. These previous results, however, were obtained from human subjects using psychophysics and fMRI, a fact that fundamentally limits our understanding of the underlying neuronal mechanisms. Here, we present an animal model that allows for a finer examination of size perception at the level of single neurons. We first show that macaque monkeys perceive a size-distance illusion similarly to humans. Then, using extracellular recordings, we test the specific hypothesis [12] that neurons in V1 shift the position of their receptive fields (RFs) in response to complex monocular depth cues. Consistent with this hypothesis, we found that when ring-shaped stimuli appeared at the back of the corridor, RFs of V1 neurons shifted toward the center of the rings. When the same stimuli appeared at the front of the corridor, RFs shifted outward. Thus, our results show for the first time that V1 RFs can shift, potentially serving as the neural basis for the perception of angular size.
如果被感知为处于不同距离，投射相同视网膜视角的刺激在视野中所占比例可能会有很大差异[1 - 8]。先前的研究表明，感知到的角大小会改变早期视网膜拓扑视觉皮层中活动的空间分布[7, 9 - 11]。例如，与叠加在走廊近端的相同球体相比，叠加在走廊远端的球体似乎占据更大的视角，并激活初级视觉皮层（V1）的更大区域[7]。然而，这些先前的结果是通过人类受试者的心理物理学和功能磁共振成像获得的，这一事实从根本上限制了我们对潜在神经元机制的理解。在这里，我们提出了一种动物模型，它能够在单个神经元水平上更精细地研究大小感知。我们首先表明，猕猴感知大小 - 距离错觉的方式与人类相似。然后，使用细胞外记录，我们测试了一个具体假设[12]，即V1中的神经元会根据复杂的单眼深度线索移动其感受野（RF）的位置。与该假设一致，我们发现当环形刺激出现在走廊后部时，V1神经元的RF向环的中心移动。当相同刺激出现在走廊前部时，RF向外移动。因此，我们的结果首次表明V1的RF可以移动，这可能是角大小感知的神经基础。
