Hoffmann K, Witte H, Niedner H, Vollandt R
Institute of Medical Statistics, Computer Sciences and Documentation, Friedrich Schiller University, Jena, Germany.
Electroencephalogr Clin Neurophysiol. 1998 Nov;108(6):560-6. doi: 10.1016/s0168-5597(98)00035-5.
Left and right hemifield pattern-reversal visual evoked potentials (PVEP) at P100 latency are characterised by typical field distributions of potential and the spectral parameter instantaneous frequency (IF). Both parameters can be utilised for the correct identification of the stimulated hemiretina in healthy volunteers (Hoffmann, K. et al. Electroenceph. clin. Neurophysiol., 100, 1996: 569-578). The aim of this study was the investigation of the robustness of instantaneous frequency for reduced numbers of averages. Hemifield PVEP of 15 volunteers (20 channel records) were analysed. The number of averages was reduced step-by-step (64-32-16-8-4-1). For each average, the time of P100 latency was determined by the Global field power maximum between 90 and 125 ms. The stimulated hemifield was identified using the potential or instantaneous frequency values at the occipital electrode positions O1 and O2: by maximal potential and instantaneous frequency on the stimulus-contralateral side. In summary, by reduced numbers of averages (as well as by single trials) the stimulated hemiretina was correctly identified more frequently on the basis of instantaneous frequency than of potential distribution. A number of 8 averages seems to be sufficient for the correct identification of the stimulus condition. Consequently, for the identification of left and right hemifield stimulations the recording time could be reduced immensely. Instantaneous frequency is suggested as an additional and robust parameter for the selective averaging of artefact-free trials during the recording of hemifield PVEP.
P100潜伏期的左右半视野模式翻转视觉诱发电位（PVEP）具有典型的电位场分布和频谱参数瞬时频率（IF）。这两个参数都可用于在健康志愿者中正确识别受刺激的半视网膜（霍夫曼，K.等人，《脑电图临床神经生理学》，100，1996：569 - 578）。本研究的目的是调查减少平均次数时瞬时频率的稳健性。分析了15名志愿者的半视野PVEP（20通道记录）。平均次数逐步减少（64 - 32 - 16 - 8 - 4 - 1）。对于每个平均值，通过90至125毫秒之间的全局场功率最大值确定P100潜伏期的时间。使用枕叶电极位置O1和O2处的电位或瞬时频率值来识别受刺激的半视野：通过刺激对侧的最大电位和瞬时频率。总之，通过减少平均次数（以及单次试验），基于瞬时频率比基于电位分布更频繁地正确识别受刺激的半视网膜。8次平均似乎足以正确识别刺激条件。因此，对于识别左右半视野刺激，记录时间可以大幅减少。建议将瞬时频率作为在记录半视野PVEP期间对无伪迹试验进行选择性平均的一个额外且稳健的参数。
