Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, United Kingdom.
J Neurosci. 2012 Oct 10;32(41):14331-43. doi: 10.1523/JNEUROSCI.3495-11.2012.
Neurons in cortical area MT respond well to transparent streaming motion in distinct depth planes, such as caused by observer self-motion, but do not contain subregions excited by opposite directions of motion. We therefore predicted that spatial resolution for transparent motion/disparity conjunctions would be limited by the size of MT receptive fields, just as spatial resolution for disparity is limited by the much smaller receptive fields found in primary visual cortex, V1. We measured this using a novel "joint motion/disparity grating," on which human observers detected motion/disparity conjunctions in transparent random-dot patterns containing dots streaming in opposite directions on two depth planes. Surprisingly, observers showed the same spatial resolution for these as for pure disparity gratings. We estimate the limiting receptive field diameter at 11 arcmin, similar to V1 and much smaller than MT. Higher internal noise for detecting joint motion/disparity produces a slightly lower high-frequency cutoff of 2.5 cycles per degree (cpd) versus 3.3 cpd for disparity. This suggests that information on motion/disparity conjunctions is available in the population activity of V1 and that this information can be decoded for perception even when it is invisible to neurons in MT.
皮质区 MT 的神经元对不同深度平面上的透明流动物体运动反应良好，例如观察者自身运动引起的运动，但不包含由相反运动方向激发的亚区。因此，我们预测透明运动/视差组合的空间分辨率将受到 MT 感受野大小的限制，就像视差的空间分辨率受到初级视觉皮层 V1 中较小的感受野的限制一样。我们使用一种新颖的“联合运动/视差光栅”来测量这一点，人类观察者在包含两个深度平面上相反方向流动的点的透明随机点图案中检测到运动/视差组合。令人惊讶的是，观察者对这些组合的空间分辨率与纯视差光栅相同。我们估计限制感受野直径为 11 弧分，类似于 V1，远小于 MT。检测联合运动/视差的内部噪声较高，导致高频截止频率略低，为 2.5 个周期/度（cpd），而视差为 3.3 cpd。这表明 V1 中的群体活动中存在关于运动/视差组合的信息，即使这些信息对 MT 中的神经元不可见，也可以对其进行解码以实现感知。
