Lankheet M J, van Wezel R J, van de Grind W A
Department of Comparative Physiology, Utrecht University, The Netherlands.
Vision Res. 1991;31(7-8):1129-42. doi: 10.1016/0042-6989(91)90039-8.
The frequency transfer properties of horizontal cells in the cat retina were studied as a function of the mean light intensity level and stimulus contrast. To this end, horizontal cell responses to sinusoidally modulated light stimuli were recorded intracellularly in the optically intact, in vivo eye. The light stimulus consisted of a 3.9 deg dia. spot superimposed on a steady background (8.8 deg dia.). A discrete Fourier analysis was performed in order to describe the amplitude and phase characteristics of the linear response component and in order to specify the nonlinear distortion of the response. The amplitude of the fundamental Fourier component was found to increase linearly with the contrast of the sinusoidal light intensity modulation. Increasing the mean light level while keeping the contrast constant caused a frequency dependent increase in response amplitude. The increase was most pronounced at high temporal frequencies and resulted in a conspicuous increase of the flicker fusion frequency. Steady background illumination caused a reduction of the response amplitudes at the lower temporal frequencies. Responses in the high frequency range, however, were not affected. The phase shifts of the fundamental Fourier components were found to diminish at increasing mean illumination levels. The harmonic distortion of horizontal cell responses to sinewave flicker was studied as a function of stimulus frequency and stimulus contrast. By comparing the data obtained using sinusoidal light intensity modulation with the intensity profiles described in a preceding paper it was investigated to what extent the harmonic distortion can be explained by the nonlinearity expressed in the response vs intensity profiles.
研究了猫视网膜水平细胞的频率传递特性与平均光强度水平和刺激对比度的函数关系。为此，在光学完整的活体眼中细胞内记录水平细胞对正弦调制光刺激的反应。光刺激由一个直径3.9度的光斑叠加在一个稳定背景（直径8.8度）上组成。进行离散傅里叶分析以描述线性反应成分的幅度和相位特性，并确定反应的非线性失真。发现基本傅里叶成分的幅度随正弦光强度调制的对比度线性增加。在保持对比度不变的情况下增加平均光水平会导致反应幅度随频率增加。这种增加在高时间频率时最为明显，并导致闪烁融合频率显著增加。稳定的背景照明会导致较低时间频率下反应幅度的降低。然而，高频范围内的反应不受影响。发现基本傅里叶成分的相移随着平均照明水平的增加而减小。研究了水平细胞对正弦波闪烁反应的谐波失真与刺激频率和刺激对比度的函数关系。通过将使用正弦光强度调制获得的数据与前一篇论文中描述的强度分布进行比较，研究了谐波失真在多大程度上可以由反应与强度分布中表达的非线性来解释。
