Horwitz Gregory D
Department of Physiology and Biophysics, Washington National Primate Research Center, University of Washington, 1959 N.E. Pacific Street, HSB I-714, Box 357290, Seattle, WA 98195, USA.
iScience. 2021 May 18;24(6):102536. doi: 10.1016/j.isci.2021.102536. eCollection 2021 Jun 25.
Contrast sensitivity peaks near 10 Hz for luminance modulations and at lower frequencies for modulations between equiluminant lights. This difference is rooted in retinal filtering, but additional filtering occurs in the cerebral cortex. To measure the cortical contributions to luminance and chromatic temporal contrast sensitivity, signals in the lateral geniculate nucleus (LGN) were compared to the behavioral contrast sensitivity of macaque monkeys. Long wavelength-sensitive (L) and medium wavelength-sensitive (M) cones were modulated in phase to produce a luminance modulation (L + M) or in counterphase to produce a chromatic modulation (L - M). The sensitivity of LGN neurons was well matched to behavioral sensitivity at low temporal frequencies but was approximately 7 times greater at high temporal frequencies. Similar results were obtained for L + M and L - M modulations. These results show that differences in the shapes of the luminance and chromatic temporal contrast sensitivity functions are due almost entirely to pre-cortical mechanisms.
对于亮度调制，对比敏感度在10赫兹附近达到峰值；而对于等亮度光之间的调制，对比敏感度在较低频率时达到峰值。这种差异源于视网膜滤波，但在大脑皮层中还会发生额外的滤波。为了测量皮层对亮度和色度时间对比敏感度的贡献，将外侧膝状体核（LGN）中的信号与猕猴的行为对比敏感度进行了比较。对长波长敏感（L）和中波长敏感（M）的视锥细胞进行同相调制以产生亮度调制（L + M），或进行反相调制以产生色度调制（L - M）。LGN神经元的敏感度在低时间频率下与行为敏感度匹配良好，但在高时间频率下大约高7倍。对于L + M和L - M调制，获得了类似的结果。这些结果表明，亮度和色度时间对比敏感度函数形状的差异几乎完全归因于皮层下机制。
