D'Souza Dany V, Auer Tibor, Strasburger Hans, Frahm Jens, Lee Barry B
Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
J Vis. 2011 Jul 13;11(8):8. doi: 10.1167/11.8.8.
Psychophysical sensitivity to isoluminant chromatic modulation declines at temporal frequencies beyond 4 Hz, whereas chromatically opponent cells of the afferent visual pathway (long- to middle-wavelength (L-M) cone-opponent or short-wavelength (S) cone cells) show responses at much higher temporal frequencies, indicating a central limitation in temporal processing capacity. Here, we sought to localize this limit in cortical retinotopic visual areas. We used fMRI to investigate responses of lateral geniculate nucleus and cortical visual areas in humans to isoluminant chromatic modulation as a function of temporal frequency (2-12 Hz). Our results suggest that L-M cone-opponent and S-cone signals are processed in LGN up to 12 Hz. In all visual areas except MT (middle temporal) and V3a, S-cone responses declined steeply with temporal frequency, implying that psychophysical sensitivity loss to blue-yellow modulation might occur early within these areas. While V1 showed robust L-M responses up to 12 Hz, there was a progressive falloff of responses with temporal frequency as information is transferred from V1 to higher areas (V2, V3, and V4), suggesting that, in humans, temporal limitation in perception of red-green chromatic modulation likely results from limited processing capacity of higher ventral extrastriate areas.
对等亮度颜色调制的心理物理敏感性在时间频率超过4Hz时会下降，而传入视觉通路的颜色拮抗细胞（长至中波长（L-M）视锥细胞拮抗或短波长（S）视锥细胞）在高得多的时间频率下仍有反应，这表明时间处理能力存在中枢限制。在此，我们试图在皮质视网膜拓扑视觉区域中定位这一限制。我们使用功能磁共振成像来研究人类外侧膝状体核和皮质视觉区域对等亮度颜色调制的反应，该反应是时间频率（2-12Hz）的函数。我们的结果表明，L-M视锥细胞拮抗和S视锥细胞信号在外侧膝状体核中可处理至12Hz。在除MT（颞中区）和V3a之外的所有视觉区域中，S视锥细胞反应随时间频率急剧下降，这意味着在这些区域内早期可能就会出现对蓝黄调制的心理物理敏感性丧失。虽然V1在高达12Hz时表现出强烈的L-M反应，但随着信息从V1传递到更高区域（V2、V3和V4），反应会随时间频率逐渐下降，这表明在人类中，对红绿颜色调制感知的时间限制可能是由于更高的腹侧纹外区域处理能力有限所致。
