Abstract
SummaryContrast 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.
Highlights
Signal processing in the visual system preserves some types of information while eliminating others
Visual stimuli were constructed on the basis of this model and used to measure the signal-to-noise ratio (SNR) of lateral geniculate nucleus (LGN) neuronal responses (Figure 1B)
Each recorded neuron was stimulated with Gabor patterns centered on its receptive field (RF) that varied across trials in temporal frequency and L and M cone modulation phase
Summary
Signal processing in the visual system preserves some types of information while eliminating others. A salient example of information loss in the visual system is the dependence of the visibility of a periodic stimulus on its temporal frequency. This relationship, the temporal contrast sensitivity function, plays important roles in industry (Legall, 1991) and medicine (Owsley, 2011; Tyler, 1981), but its biological basis is incompletely understood. This uncertainty is due in part to methodological differences between neurophysiological and behavioral studies. Care was taken to match these factors between neurophysiological and behavioral measurements, providing a clearer picture of their relationship than has previously been available
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