Merigan W H
Department of Ophthalmology, University of Rochester Medical Center, NY 14642, USA.
Vis Neurosci. 1996 Jan-Feb;13(1):51-60. doi: 10.1017/s0952523800007124.
Ibotenic acid lesions were made in four macaque monkeys in a region of cortical area V4 that corresponds to the lower quadrant of one hemifield. For visual testing, fixation locus was monitored with scleral search coils and controlled behaviorally to place test stimuli either in the lesioned quadrant or in a control location in the opposite hemifield. Some basic visual capacities were slightly altered by the lesions; there was a two-fold reduction of luminance contrast sensitivity as well as red-green chromatic contrast sensitivity, both tested with stationary gratings. On the other hand, little or no loss was found when contrast sensitivity for detection or direction discrimination was tested with 10-Hz drifting gratings nor was there a reliable change in visual acuity. Hue and luminance matching were tested with a spatially more complex matching-to-sample task, but monkeys could not learn this task in the visual field locus of a V4 lesion. If previously trained at this locus, performance was not affected by the lesion. In contrast to the small effects on basic visual capabilities, performance on two form discrimination tasks was devastated by V4 lesions. The first involved discriminating the orientation of colinear groups of dots on a background of randomly placed dots. The second involved discriminating the orientation of a group of three line segments surrounded by differently oriented line segments. Some selectivity of the deficits for form discrimination was shown by the lack of an effect of the lesions on a global motion discrimination. These results show that while V4 lesions cause only slight disruptions of basic visual capacities, they profoundly disrupt form discriminations.
在四只猕猴的大脑皮层V4区对应一个半视野下象限的区域制造了鹅膏蕈氨酸损伤。为了进行视觉测试，用巩膜搜索线圈监测注视位置，并通过行为控制将测试刺激置于损伤象限或对侧半视野的对照位置。损伤使一些基本视觉能力略有改变；用静止光栅测试时，亮度对比敏感度以及红-绿颜色对比敏感度降低了两倍。另一方面，用10赫兹漂移光栅测试检测或方向辨别对比敏感度时，几乎没有发现损失，视力也没有可靠变化。用空间上更复杂的样本匹配任务测试色调和亮度匹配，但猴子在V4损伤的视野位置无法学会这项任务。如果之前在这个位置受过训练，表现不受损伤影响。与对基本视觉能力的微小影响形成对比的是，V4损伤严重破坏了两项形状辨别任务的表现。第一项任务是在随机排列的点的背景中辨别共线点组的方向。第二项任务是辨别被不同方向线段包围的一组三条线段的方向。损伤对整体运动辨别没有影响，这表明在形状辨别缺陷方面存在一定的选择性。这些结果表明，虽然V4损伤仅轻微扰乱基本视觉能力，但却严重扰乱形状辨别。
