Bodis-Wollner I, Brannan J R, Nicoll J, Frkovic S, Mylin L H
Department of Neurology, Mount Sinai School of Medicine, New York, NY 10029.
Electroencephalogr Clin Neurophysiol. 1992 May-Jun;84(3):201-8. doi: 10.1016/0168-5597(92)90001-r.
Transient evoked potentials were recorded simultaneously over 5 electrodes placed in a horizontal row across the occiput. A range of spatial frequencies were presented as either full-field or hemifield stimuli. Subjects were 11 normal observers and 5 patients with lesions causing a homonymous hemianopic field defect. The shortest latency peak response was at approximately 70 msec, a negative potential (N70). For all spatial frequencies, full-field stimuli evoked a lower amplitude N70 at the midline than the sum of N70 amplitudes to two hemifield stimuli, suggesting partial cancellation. The latency and amplitude of N70 increased as spatial frequency increased. N70 and P100 differed in respect to their response to spatial frequency and field size, further suggesting that they may not be subsets of a unitary response. For hemifield stimulation, N70 had an ipsilateral maximum and attenuated or completely reversed in polarity across the midline. Consistent with the data of normals using hemifield stimuli, in 5 patients a full-field stimulus elicited an N70 lateralized contralaterally to the homonymous hemianopia, i.e., the ipsilateral N70 was absent. The absolute amplitude difference between the left and right electrodes was significant for hemifield stimulation in normals and full-field stimulation in the patients, but not for full-field stimulation in normals. Our results imply that the evaluation of N70 hemispheric distribution is useful for the evaluation of paramacular visual field defects.
瞬态诱发电位在横跨枕骨水平排列的5个电极上同时记录。一系列空间频率以全视野或半视野刺激的形式呈现。受试者包括11名正常观察者和5名患有导致同侧偏盲视野缺损病变的患者。最短潜伏期峰值反应出现在大约70毫秒，为负电位（N70）。对于所有空间频率，全视野刺激在中线诱发的N70波幅低于两个半视野刺激的N70波幅之和，提示部分抵消。N70的潜伏期和波幅随空间频率增加而增加。N70和P100在对空间频率和视野大小的反应方面存在差异，进一步表明它们可能不是单一反应的子集。对于半视野刺激，N70在同侧有最大值，并且在中线处波幅衰减或极性完全反转。与使用半视野刺激的正常人数据一致，在5名患者中，全视野刺激诱发的N70向同侧偏盲的对侧侧化，即同侧N70缺失。正常人群半视野刺激和患者全视野刺激时，左右电极之间的绝对波幅差异显著，但正常人群全视野刺激时不显著。我们的结果表明，评估N70半球分布有助于评估黄斑旁视野缺损。
