Pack Christopher C, Livingstone Margaret S, Duffy Kevin R, Born Richard T
Harvard Medical School, Department of Neurobiology, 220 Longwood Avenue, Boston, MA 02115, USA.
Neuron. 2003 Aug 14;39(4):671-80. doi: 10.1016/s0896-6273(03)00439-2.
Our perception of fine visual detail relies on small receptive fields at early stages of visual processing. However, small receptive fields tend to confound the orientation and velocity of moving edges, leading to ambiguous or inaccurate motion measurements (the aperture problem). Thus, it is often assumed that neurons in primary visual cortex (V1) carry only ambiguous motion information. Here we show that a subpopulation of V1 neurons is capable of signaling motion direction in a manner that is independent of contour orientation. Specifically, end-stopped V1 neurons obtain accurate motion measurements by responding only to the endpoints of long contours, a strategy which renders them largely immune to the aperture problem. Furthermore, the time course of end-stopping is similar to the time course of motion integration by MT neurons. These results suggest that cortical neurons might represent object motion by responding selectively to two-dimensional discontinuities in the visual scene.
我们对精细视觉细节的感知依赖于视觉处理早期阶段的小感受野。然而，小感受野往往会混淆移动边缘的方向和速度，导致运动测量结果模糊或不准确（孔径问题）。因此，人们通常认为初级视觉皮层（V1）中的神经元仅携带模糊的运动信息。在此我们表明，V1神经元的一个亚群能够以独立于轮廓方向的方式传递运动方向信号。具体而言，终端抑制的V1神经元仅对长轮廓的端点做出反应，从而获得准确的运动测量结果，这一策略使它们在很大程度上不受孔径问题的影响。此外，终端抑制的时间进程与MT神经元进行运动整合的时间进程相似。这些结果表明，皮层神经元可能通过选择性地对视觉场景中的二维不连续性做出反应来表征物体运动。
