Eysteinsson T, Barris M C, Denny N, Frumkes T E
Department of Ophthalmology, University of Iceland, Reykjavik.
Invest Ophthalmol Vis Sci. 1993 Jul;34(8):2443-8.
Psychophysical studies have shown that a dark-adapted eye exerts a tonic interocular suppression (TIS) upon spatial vision mediated by the contralateral eye. The present study was designed to demonstrate TIS by means of visual evoked potential (VEP) procedures.
Evoked cortical potentials were obtained in response to reversing checkerboard patterns with fundamental Fourier frequencies between 3 and 12 cycles per degree. Responses were obtained under monocular viewing conditions when the contralateral "adapting" eye was dark adapted, under monocular viewing conditions when the adapted state of the adapting eye was experimentally manipulated, or under binocular viewing conditions. Data were collected from three healthy young men, two native regarding purpose of experimentation.
Regardless of spatial frequency, monocular responses evoked by stimulating a "test eye" were always smaller in amplitude when the contralateral adapting eye was dark adapted than when adapted to a dim, homogeneous field. The monocular evoked response obtained in the presence of an interocular adapting field was similar in amplitude to the binocular evoked response. During dark adaptation of the contralateral adapting eye, the amplitude of the monocular evoked response decreased: the time course of this decline follows that of psychophysically measured rod thresholds in the directly adapted eye.
TIS is easily demonstrated by means of VEP as well as psychophysical procedures. The well-known increase in VEP amplitude resulting from binocular viewing may be attributable to the removal of TIS rather than to "physiologic, binocular summation."
心理物理学研究表明，暗适应眼对由对侧眼介导的空间视觉施加持续性眼间抑制（TIS）。本研究旨在通过视觉诱发电位（VEP）程序来证明TIS。
以每度3至12个周期的基本傅里叶频率对反转棋盘图案做出反应，从而获得诱发的皮质电位。在对侧“适应”眼处于暗适应状态的单眼观察条件下、在实验性操纵适应眼的适应状态的单眼观察条件下或在双眼观察条件下获得反应。数据收集自三名健康年轻男性，其中两名受试者知晓实验目的。
无论空间频率如何，当对侧适应眼处于暗适应状态时，刺激“测试眼”诱发的单眼反应的幅度始终比对适应于昏暗均匀视场时小。在存在眼间适应场的情况下获得的单眼诱发反应在幅度上与双眼诱发反应相似。在对侧适应眼的暗适应过程中，单眼诱发反应的幅度下降：这种下降的时间进程与直接适应眼中通过心理物理学测量的视杆阈值的时间进程一致。
通过VEP以及心理物理学程序很容易证明TIS。双眼观察导致的VEP幅度的众所周知的增加可能归因于TIS的消除，而不是“生理性双眼总和”。
