视觉诱发电位(VEP)方位效应与刺激位置的关系

以人视觉诱发电位(VEP)反应为指标,在视野的不同位置测定了VEP对四个方位的闪烁方波光栅刺激(时间频率2.9Hz,空间频率1.4c/deg,对比度0.94)的反应幅度。在距中央凹20°视角同心圆的八个刺激位置上,VEP反应幅度对与向心线垂直方位的光栅刺激(同心圆的切线方向),有统计意义上的优势。这一规律在垂直、水平向心线上尤为明显。从总体上未发现VEP反应幅度与刺激光栅方位有着明显的关系。这说明在人视野周边区,VEP反应幅度与光栅方位和向心线的夹角(偏向角)相关,而与光栅的绝对方位无关。在相同的刺激条件下,中央区的VEP反应幅度与刺激光栅方位之间也未发现明显关系。

ORIENTATION EFFECT OF VISUAL EVOKED POTENTIAL FOR DIFFERENT STIMULUS LOCATIONS ON THE HUMAN RETINA

Visual evoked potentials (VEP) to square-wave gratings (spatial frequency 1.4 c/deg. , flickering frequency 2.9 Hz, contrast 0.94) at various stimulus locations on the retina were recorded from human occipital scalp. At eccentricities of 20 degree, VEP yielded the largest responses to gratings perpendicular to the visual field meridians through stimulus locus and the lowest responses to meridionally oriented gratings. No obvious relation between VEP amplitude and grating orientation found implies that VEP ampltude was only relative to deviating angle (i. e. the angle between the optimum orientation and visual field meridian) in peripheral vision. For central vision, VEP response to the same grating was independent of orientation.