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Dingcai Cao, Andrew J. Zele, Joel Pokorny; Reaction times to rod and cone incremental and decremental stimuli. Journal of Vision 2005;5(12):51. doi: https://doi.org/10.1167/5.12.51.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To measure response times of inferred rod and cone ON and OFF pathways.
Method: A 2-channel, 4-primary colorimetric system provided independent control of rod and cone excitations. A 2° test set within a 13°surround was viewed at a 7.5° eccentricity. Retinal illuminances spanned adaptation levels where rods alone (0.002 – 0. 2 Td), both rods and cones (2 – 20 Td) or cones alone (80 – 200 Td) were active. Reaction times (RTs) were measured for a rod isolating or cone (L+M+S) isolating stimulus at 5 Weber contrasts, using 1 sec duration rapid-on or rapid-off ramp waveforms.
Results: RTs decreased with increasing contrast and retinal illuminance. RTs to incremental and decremental stimuli were similar for cones at all light levels, and for rods at 20 Td. The rod response to decrements was faster than to increments at low light levels (? 0.2 Td). Reaction times for rod and cone stimuli were comparable at 2 Td; cones responded faster than rods at light levels ? 20 Td.
Conclusion: The response times of cone ON and OFF pathways were similar. The rod OFF pathway responses were faster than ON pathway responses at low light levels.
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