Functional Neurobiology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands.
Hum Brain Mapp. 2009 Dec;30(12):3970-80. doi: 10.1002/hbm.20822.
Recently, evidence has emerged for a radial orientation bias in early visual cortex. These results predict that in early visual cortex a tangential bias should be present for motion direction. We tested this prediction in a human imaging study, using a translating random dot pattern that slowly rotated its motion direction 360 degrees in cycles of 54 s. In addition, polar angle and eccentricity mapping were performed. This allowed the measurement of the BOLD response across the visual representations of the different retinotopic areas. We found that, in V1, V2, and V3, BOLD responses were consistently enhanced for centrifugal and centripetal motion, relative to tangential motion. The relative magnitude of the centrifugal and centripetal response biases changed with visual eccentricity. We found no motion direction biases in MT+. These results are in line with previously observed anisotropies in motion sensitivity across the visual field. However, the observation of radial motion biases in early visual cortex is surprising considering the evidence for a radial orientation bias. An additional experiment was performed to resolve this apparent conflict in results. The additional experiment revealed that the observed motion direction biases most likely originate from anisotropies in long range horizontal connections within visual cortex.
最近，早期视觉皮层存在放射状方向偏向的证据已经出现。这些结果预测，在早期视觉皮层中，运动方向应该存在切向偏向。我们在一项人类成像研究中检验了这一预测，使用了一个平移的随机点模式，该模式以 54 秒为一个周期缓慢地旋转其运动方向 360 度。此外，还进行了极角和偏心映射。这允许在不同视网膜区域的不同视觉表示中测量 BOLD 反应。我们发现，在 V1、V2 和 V3 中，相对于切向运动，BOLD 反应对于离心和向心运动始终增强。离心和向心反应偏差的相对幅度随视觉偏心度而变化。我们在 MT+ 中没有发现运动方向偏差。这些结果与以前在整个视野中观察到的运动敏感性各向异性一致。然而，考虑到存在放射状方向偏向的证据，早期视觉皮层中观察到的径向运动偏向令人惊讶。进行了一项额外的实验来解决结果中的这种明显冲突。额外的实验表明，观察到的运动方向偏差很可能源自视觉皮层内长程水平连接的各向异性。
