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Temporal contrast sensitivity function based on cones and melanopsin photoreceptors

35.12, Sunday, 18-May, 5:15 pm - 7:15 pm, Talk Room 1
Session: Color and light: Receptors and mechanisms

Sei-ichi Tsujimura1, Naoshi Hamazono1, Katsunori Okajima2; 1Department of Information Science and Biomedical Engineering, Kagoshima University, 1-21-40, Koorimoto, Kagoshima 890-0065 Japan, 2Faculty of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya, Yokohama 240-8501 Japan

Growing evidence indicates that the recently discovered the intrinsically photoreceptive retinal ganglion cells (ipRGCs) play an important functional role in conventional image-forming pathway as well as in non-image forming pathway, along with the classical photoreceptors rods and cones. Natural lights, therefore, stimulate rods, cones and ipRGCs, which convey visual information through image-forming pathway. However, the functional role of ipRGCs in the image-forming pathway is unclear. Here we show how stimulation of ipRGCs influences temporal contrast sensitivity function. A four-primary illumination system that enables independent stimulation of each photoreceptor class (Tsujimura et al., 2010, Proceedings of the Royal Society B-Biological Sciences, 277, 2485-2492) was used to present the following two types of test stimuli: one varying L-, M- and S-cone stimulation only without change in stimulation of ipRGCs (LMS cone stimulus) and another varying radiant flux of the stimuli without change in spectral composition which reduced/increased the radiant flux uniformly at all wavelengths (Light flux stimulus). The contrast threshold to temporally modulated sinusoidal gratings was measured. It was found that the two thresholds were different between LMS cone stimulus and the Light flux stimulus: the threshold to the LMS cone stimulus and the threshold to the Light flux stimulus became distinct at low temporal frequencies below 5 Hz. On the other hand, the thresholds at high temporal frequency were almost identical between the two stimuli. The difference in threshold at the low temporal frequency can be attributed to the difference in stimulation with or without ipRGCs, suggesting that ipRGCs play an important role in achromatic vision at low temporal frequency.

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