Abstract

We offer a model of dual rod pathways that incorporate recent psychophysical, physiological, and anatomical work. Flicker sensitivity studies suggest that one rod pathway, π₀, has greater absolute sensitivity but poorer high temporal frequency responses than the other pathway, π₀ (Conner, 1982; Connor and MacLeod, 1977; Sharpe, Stockman, and MacLeod, in press). The dual pathways may arise from differential electrical coupling of rods and cones via gap junctions as a function of adaptation level (Yang and Wu, 1989), so that π₀ signals travel through rod pathways and π₀ signals travel through cone pathways (Smith, Freed, and Sterling, 1986) before being recombined at ganglion cells or beyond. So far, the importance of dual rod pathways for processing other than temporal information is unclear. Our model of dual rod pathways generalizes their role to incremental and spatial processing and makes testable predictions to challenge the model. Predictions include more conelike spatial sensitivity for π₀, differential dependence of π₀ and π₀ increment sensitivity on spatial and temporal parameters, and different interactions of cone signals with π₀ and π₀ in detection and adaptation. Support for the model comes in part from kinks in increment t.v.i. curves observed in various labs at –2 to 0 log scot td (the same as for flicker data).

© 1989 Optical Society of America