Electrophysiological correlates of vernier and relative motion mechanisms in human visual cortex.
Electrophysiological correlates of vernier and relative motion mechanisms in human visual cortex.
复制标题
人类视觉皮层游标和相对运动机制的电生理相关性。
DOI：
10.1017/s0952523899166124
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发表时间：
1999
影响因子：
1.9
通讯作者：
Manny,RE
中科院分区：
文献类型：
--
作者：
Norcia,AM;Wesemann,W;Manny,RE
游标起始/偏移阈值测量心理和稳态VEP通过引入一系列的垂直方波亮度光栅的水平中断。几个诊断测试表明，偏移光栅的周期性调制产生的诱发反应的第一谐波分量抽头编码的空间特征的相对位置的机制。在第一个测试中，一个第一谐波分量只发现与目标，包含共线和非共线状态之间的过渡。中心凹观察获得的VEP游标起始/偏移阈值在15-22弧秒的范围内。控制实验与对称，非共线模式（相对运动）之间的过渡没有产生第一谐波分量，也没有全场运动的共线光栅。第二系列的实验表明，VEP阈值的基础上的游标开始/偏移响应的第一谐波分量的偏心率的依赖性，这是非常相似的心理物理歧视任务，需要一个左/右位置判断（游标敏锐度）。其他记录显示，游标起始/偏移VEP的第一谐波由于在刺激元件之间引入间隙而劣化，位移阈值也是如此。游标起始/偏移目标还产生了与相对运动刺激产生的谐波几乎相同的二次谐波分量。与游标偏移引起的第一谐波分量相比，基于这些第二谐波分量的位移阈值随着视网膜偏心率的下降更加缓慢。游标起始/偏移VEP的二次谐波相对不受刺激元件之间的间隙的引入的影响。游标起始/偏移VEP的第一和第二谐波分量因此分接不同的机制，这两者都支持比由光感受器的间距设置的分辨率限制更精细的位移阈值（超敏度）。
Vernier onset/offset thresholds were measured both psychophysically and with the steady-state VEP by introducing a series of horizontal breaks in a vertical square-wave luminance grating. Several diagnostic tests indicated that the first harmonic component of the evoked response generated by periodic modulation of offset gratings taps mechanisms that encode the relative position of spatial features. In the first test, a first harmonic component was only found with targets that contained transitions between collinear and noncollinear states. VEP vernier onset/offset thresholds obtained with foveal viewing were in the range of 15–22 arc sec. Control experiments with transitions between symmetrical, noncollinear patterns (relative motion) did not produce first harmonic components, nor did full-field motion of a collinear grating. A second series of experiments showed that VEP thresholds based on the first harmonic component of the vernier onset/offset response had an eccentricity dependence that was very similar to that found in a psychophysical discrimination task that required a left/right position judgment (vernier acuity). Other recordings showed that the first harmonic of the vernier onset/offset VEP was degraded by the introduction of a gap between stimulus elements, as is the displacement threshold. The vernier onset/offset target also produced a second harmonic component that was virtually identical to the one produced by a relative motion stimulus. Displacement thresholds based on these second harmonic components showed a more gradual decline with retinal eccentricity than did the first harmonic component elicited by vernier offsets. The second harmonic of the vernier onset/offset VEP was relatively unaffected by the introduction of gaps between the stimulus elements. The first and second harmonic components of the vernier onset/offset VEP thus tap different mechanisms, both of which support displacement thresholds that are finer than the resolution limits set by the spacing of the photoreceptors (hyperacuity).