Hoffmann Michael B, Seufert Petra S
Visual Processing Lab, Universitäts-Augenklinik, Leipziger Str. 44, 39120 Magdeburg, Germany.
Clin Neurophysiol. 2005 Jul;116(7):1723-32. doi: 10.1016/j.clinph.2005.03.010.
In patients with nystagmus conventional pattern-reversal visual evoked potentials are severely degraded, while sizeable pattern-onset VEPs can often still be obtained. We tested whether this differential effect of retinal image motion on pattern-reversal and pattern-onset responses also applies to multifocal VEPs (mfVEPs).
In eight subjects with normal oculomotor behaviour and vision we recorded pattern-reversal and pattern-onset mfVEPs from an occipital electrode pair to 60 locations of a scaled dartboard-pattern, and to 64 locations of a uniform checkerboard-pattern. Subjects viewed the stimulus monocularly via a mirror, which was placed close to the eye and driven by a scanner with a 4 Hz sawtooth waveform at an amplitude of 2 degrees to simulate horizontal jerk nystagmus and of 0 degrees for the reference condition.
For the scaled dartboard-stimulus we observed an eccentricity-dependent effect of induced retinal image motion on mfVEP responses: in the central visual field (0-0.5 degrees), pattern-reversal and pattern-onset responses were reduced by 73 and 42%, respectively. In the periphery (10-16 degrees), only pattern-reversal responses were reduced (by 27%), while pattern-onset responses were enhanced by 39%. Pattern-onset responses to the uniform checkerboard stimulus were enhanced by 17%, while pattern-reversal responses were reduced by 27%.
Pattern-onset mfVEPs are more efficient than pattern-reversal mfVEPs, if retinal image motion is superimposed onto the stimulus. This is in close correspondence to previous reports on conventional VEPs.
This study demonstrates a differential effect of retinal image motion on pattern-reversal and pattern-onset mfVEPs and thus suggests stimulus conditions to enhance the efficiency of mfVEP recordings in patients with moderate nystagmus.
在眼球震颤患者中，传统的模式翻转视觉诱发电位严重退化，而通常仍可获得相当可观的模式起始视觉诱发电位。我们测试了视网膜图像运动对模式翻转和模式起始反应的这种差异效应是否也适用于多焦视觉诱发电位（mfVEP）。
在八名眼动行为和视力正常的受试者中，我们从枕部电极对记录了模式翻转和模式起始mfVEP，刺激为缩放飞镖靶图案的60个位置以及均匀棋盘图案的64个位置。受试者通过靠近眼睛放置的镜子单眼观看刺激，镜子由扫描仪驱动，以4Hz锯齿波波形、2度幅度模拟水平急动性眼球震颤，参考条件下为0度。
对于缩放飞镖靶刺激，我们观察到诱导的视网膜图像运动对mfVEP反应有偏心度依赖性效应：在中心视野（0 - 0.5度），模式翻转和模式起始反应分别降低了73%和42%。在周边（10 - 16度），仅模式翻转反应降低（27%），而模式起始反应增强了39%。对均匀棋盘刺激的模式起始反应增强了17%，而模式翻转反应降低了27%。
如果视网膜图像运动叠加在刺激上，模式起始mfVEP比模式翻转mfVEP更有效。这与先前关于传统视觉诱发电位的报道密切相符。
本研究证明了视网膜图像运动对模式翻转和模式起始mfVEP的差异效应，从而提出了提高中度眼球震颤患者mfVEP记录效率的刺激条件。
