Plant G T, Nakayama K
Smith Kettlewell Eye Research Institute, San Francisco.
Brain. 1993 Dec;116 ( Pt 6):1337-53. doi: 10.1093/brain/116.6.1337.
Unilateral damage to the lateral occipital region in humans can give rise to impaired motion perception in the contralateral visual field [Plant et al. (1993), Brain, 116, 1303-1335]. We report the following characteristics of the residual vision. (i) Spatial acuity and spatial frequency discrimination are not affected. (ii) Contrast thresholds for direction-of-motion (DOM) discrimination of luminance modulated (LMod) sine-wave gratings is unaffected regardless of drift temporal frequency and the effect of spatial and temporal frequency on drifting/counterphase sensitivity ratios is normal (providing further evidence that cortical directionally selective mechanisms are intact). (iii) Contrast thresholds for DOM discrimination of contrast modulated (CMod) gratings are elevated by a log unit across a range of drift velocities. (iv) The residual motion perception shows neither a directional nor a naso-temporal asymmetry. (v) Weber fractions for velocity discrimination are shown in one patient in whom this measurement was carried out, to be elevated by around a factor of three but the functions relating velocity discrimination to stimulus contrast and to the velocity of the standard are parallel in the affected and unaffected hemifields. (vi) Weber fractions for temporal frequency discrimination using counterphase modulated gratings are also elevated. We conclude that the degraded motion perception is mediated by mechanisms which have similar contrast and temporal properties to those subserving normal motion perception. Mechanisms subserving DOM discrimination of LMod gratings may be spared because they are more widely distributed in extra-striate cortex than mechanisms subserving non-Fourier (second-order) motion perception or velocity discrimination. The anomaly resembles that described in some recent animal studies of impaired motion perception after extra-striate cortical damage.
人类枕叶外侧区域的单侧损伤可导致对侧视野中运动感知受损[普兰特等人（1993年），《大脑》，第116卷，第1303 - 1335页]。我们报告了残余视觉的以下特征。（i）空间敏锐度和空间频率辨别不受影响。（ii）无论漂移时间频率如何，亮度调制（LMod）正弦波光栅的运动方向（DOM）辨别对比度阈值不受影响，并且空间和时间频率对漂移/反相灵敏度比率的影响是正常的（这进一步证明了皮质方向选择性机制是完整的）。（iii）在一系列漂移速度范围内，对比度调制（CMod）光栅的DOM辨别对比度阈值提高了一个对数单位。（iv）残余运动感知既没有方向不对称也没有鼻颞不对称。（v）在进行此测量的一名患者中，速度辨别韦伯分数提高了约三倍，但受影响和未受影响半视野中速度辨别与刺激对比度以及标准速度之间的函数是平行的。（vi）使用反相调制光栅的时间频率辨别韦伯分数也提高了。我们得出结论，退化的运动感知是由与正常运动感知机制具有相似对比度和时间特性的机制介导的。服务于LMod光栅DOM辨别的机制可能未受影响，因为它们在纹外皮层中的分布比服务于非傅里叶（二阶）运动感知或速度辨别的机制更广泛。这种异常类似于最近一些动物研究中描述的纹外皮层损伤后运动感知受损的情况。
