Nadler Jacob W, Angelaki Dora E, DeAngelis Gregory C
Department of Anatomy and Neurobiology, Washington University School of Medicine, St Louis, Missouri 63110, USA.
Nature. 2008 Apr 3;452(7187):642-5. doi: 10.1038/nature06814. Epub 2008 Mar 16.
Perception of depth is a fundamental challenge for the visual system, particularly for observers moving through their environment. The brain makes use of multiple visual cues to reconstruct the three-dimensional structure of a scene. One potent cue, motion parallax, frequently arises during translation of the observer because the images of objects at different distances move across the retina with different velocities. Human psychophysical studies have demonstrated that motion parallax can be a powerful depth cue, and motion parallax seems to be heavily exploited by animal species that lack highly developed binocular vision. However, little is known about the neural mechanisms that underlie this capacity. Here we show, by using a virtual-reality system to translate macaque monkeys (Macaca mulatta) while they viewed motion parallax displays that simulated objects at different depths, that many neurons in the middle temporal area (area MT) signal the sign of depth (near versus far) from motion parallax in the absence of other depth cues. To achieve this, neurons must combine visual motion with extra-retinal (non-visual) signals related to the animal's movement. Our findings suggest a new neural substrate for depth perception and demonstrate a robust interaction of visual and non-visual cues in area MT. Combined with previous studies that implicate area MT in depth perception based on binocular disparities, our results suggest that area MT contains a more general representation of three-dimensional space that makes use of multiple cues.
深度感知是视觉系统面临的一项基本挑战，对于在其所处环境中移动的观察者而言尤为如此。大脑利用多种视觉线索来重建场景的三维结构。一种有效的线索——运动视差，在观察者移动过程中经常出现，因为不同距离物体的图像以不同速度在视网膜上移动。人类心理物理学研究表明，运动视差可以是一种强大的深度线索，而且缺乏高度发达双眼视觉的动物物种似乎大量利用了运动视差。然而，对于这种能力背后的神经机制却知之甚少。在这里，我们通过使用虚拟现实系统让猕猴（恒河猴）在观看模拟不同深度物体的运动视差显示时进行平移，发现颞中区（MT区）的许多神经元在没有其他深度线索的情况下根据运动视差信号深度的正负（近与远）。为了实现这一点，神经元必须将视觉运动与与动物运动相关的视网膜外（非视觉）信号相结合。我们的研究结果表明了深度感知的一种新神经基础，并证明了MT区视觉和非视觉线索之间强大的相互作用。结合之前暗示MT区基于双眼视差参与深度感知的研究，我们的结果表明MT区包含利用多种线索的更通用的三维空间表征。
