猫外膝体细胞和视网膜神经节细胞对正弦调制光刺激反应的相位特性

记录了猫外膝体细胞和视交叉纤维对正弦调制光点刺激的反应,作成反应时间直方图(PSTH)。用博里叶分析方法测量不同时间频率下反应的基波相位,作相位-频率特性曲线(PFC)。在暗适应条件下用锥系统的阈下刺激分离出杆系统的反应,这时外膝体细胞的相-频特性为一条负斜率的直线。由斜率所推算的潜伏期平均为81ms。在间视条件下,用 Stiles的二色阈法,分离出锥系统的反应,在这种情况下,相-频特性出现一个十分明显的转折。低频段回归线所对应的潜伏期平均为 107ms,高频段为 39ms。用同样方法分析了神经节细胞(视交叉纤维)的相位-频率特性,结果与外膝体细胞相似,说明与锥系统及杆系统活动有关的时间频率通道在视网膜就已经形成。

PHASE CHARACTERISTICS OF RESPONSES TO SINUSOIDAL LIGHT STIMULATION IN LGN AND RETINAL GANGLION CELLS OF CAT

Single unit responses to a sinusoidally modulated punctiform light stimulationat different frequencies were recorded from the lateral geniculate nucleus (LGN)and the optic chiasma. By Fourier analysis, the phases of the first harmonic of theperistimulus-time-histograms were measured at different temporal frequenciesand the phase-frequency characteristics (PFC) was investigated. Under darkadaptation, rod response was isolated by using weak luminance below cone threshold.The PFC exhibited a straight line with a negative slope. The corresponding latencycalculated from the slope was 81 ms on the average. The neurones were thenadapted by a green-blue (480 nm) background to mesopic-photopic range as testedwith a red (630 nm) spot. Cone system was selectively stimulated under this condi-tion. A clear cut turning appeared unexceptionally on the PFC of LGN neurones.The calculated latency for the lower frequency range of the regression line was 107ms and for the higher frequency range, 39 ms on the average. The same experimentswere done in retinal ganglion cells by recordings from optic chiasma. The resultswere similar to those obtained in LGN neurones. This fact shows that the rod-and cone- dependent temporal frequency channels were formed at the retinallevel.