Rudduck G A, Harding G F
Department of Vision Sciences, Aston University, Birmingham, UK.
Int J Psychophysiol. 1994 May;16(2-3):209-18. doi: 10.1016/0167-8760(89)90048-2.
We have previously reported on the development of black/white pattern reversal VEPs in premature babies of more than 30 weeks post-menstrual age (PMA). Unlike the flash VEP, the pattern reversal VEP shows a similar morphology to that of the full term infant and the major positive component (P1) decreased in latency with increasing PMA. The N1 and N2 components were more likely to be present with increasing maturity. In our present study we are examining the development of the transient chromatic pattern VEP. In order to produce a purely chromatic stimulus it is necessary to remove luminance cues. Based on forced choice preferential looking we developed a method of determining the isoluminant point for infants. Preference was tested for a flickering sinusoidal red and green grating over the uniform field. As sensitivity for chromatic flicker is much poorer than for luminance flicker, sensitivity is expected to be least when the residual luminance variation in the stimulus is at a minimum. The red/green luminance ratio at which this occurs represents the isoluminant point. From this method we found the subjective isoluminant point for infants of 2-3 months of age to be very close to the objective measure of isoluminance. Using this information, pattern reversal VEPs to 20 chromatic red/green and achromatic checks were studied and it would appear that pattern reversal VEPs cannot be obtained to isoluminant stimuli before 7 weeks chronological age.
我们之前曾报道过孕龄超过30周的早产儿黑白模式翻转视觉诱发电位（VEP）的发育情况。与闪光VEP不同，模式翻转VEP的形态与足月儿相似，其主要正波成分（P1）的潜伏期随着孕龄增加而缩短。随着成熟度增加，N1和N2成分更易出现。在我们目前的研究中，我们正在研究瞬态彩色模式VEP的发育情况。为了产生纯彩色刺激，有必要去除亮度线索。基于强迫选择优先注视，我们开发了一种确定婴儿等亮度点的方法。通过在均匀场中测试对闪烁正弦红绿光栅的偏好来进行测试。由于对彩色闪烁的敏感度远低于对亮度闪烁的敏感度，预计当刺激中的残余亮度变化最小时，敏感度最低。发生这种情况时的红/绿亮度比代表等亮度点。通过这种方法，我们发现2至3个月大婴儿的主观等亮度点与等亮度的客观测量值非常接近。利用这些信息，我们研究了对20种彩色红/绿和非彩色方格的模式翻转VEP，似乎在实际年龄7周之前无法获得对等亮度刺激的模式翻转VEP。
