Sheliga B M, Quaia C, FitzGibbon E J, Cumming B G
Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Vision Res. 2015 Apr;109(Pt A):11-9. doi: 10.1016/j.visres.2015.02.015. Epub 2015 Mar 2.
Using sinusoidal gratings we show that an increase in stimulus size confined to the dimension orthogonal to the axis of motion leads to stronger Ocular Following Responses (OFRs) up to a certain optimal size. An increase beyond this optimum produces smaller responses, indicating suppressive interactions. In sharp contrast, when the stimulus growth occurs parallel to the axis of motion OFR magnitudes increase monotonically both for horizontal and vertical directions of motion. Similar results are obtained with 1D white noise patterns. However, the OFR spatial anisotropy is minimal with 2D white noise patterns, revealing a pivotal role of orientation-selective (i.e., cortical) mechanisms in mediating this phenomenon. The lack of anisotropy for 2D patterns suggests that directional signals alone are not sufficient to elicit this suppression. The OFR spatial anisotropy is potentiated if a stationary grating is presented for 600-1000ms before its motion commences, further emphasizing the importance of static orientation signals. These results suggest that the strength of cortical spatial interactions is asymmetric-i.e., larger in the direction of the ends than the flanks of an orientation-selective receptive field-which corroborates the existing neurophysiological evidence.
我们使用正弦光栅表明，在与运动轴正交的维度上，刺激大小的增加会导致更强的眼动跟随反应（OFRs），直至达到某个最佳大小。超过此最佳值的增加会产生较小的反应，表明存在抑制性相互作用。与之形成鲜明对比的是，当刺激在与运动轴平行的方向上增长时，无论是水平还是垂直运动方向，OFR的幅度都会单调增加。对于一维白噪声模式也获得了类似的结果。然而，二维白噪声模式下的OFR空间各向异性最小，这揭示了方向选择性（即皮层）机制在介导这一现象中的关键作用。二维模式缺乏各向异性表明仅方向信号不足以引发这种抑制。如果在运动开始前呈现一个静止光栅600 - 1000毫秒，OFR空间各向异性会增强，这进一步强调了静态方向信号的重要性。这些结果表明，皮层空间相互作用的强度是不对称的——即在方向选择性感受野的两端方向上比边缘更大——这证实了现有的神经生理学证据。
