A longitudinal study of visual evoked responses to tritan stimuli in human infants

The principal goal of this study was to assess the development of the S-cone pathway in human infants. For comparison, development of the L-M opponent pathway was also assessed. Visual evoked responses were measured to chromatic (tritan and red-green) and luminance-modulated (yellow-black) sinusoidal gratings of 0.2 cpd, viewed binocularly at a distance of 40 cm. For each type of chromatic stimulus, responses were recorded at a range of color ratios around the adult isoluminant point, as determined using standard flicker photometry criteria. Presentation was by abrupt pattern-onset with a stimulus duration of 100 ms and an interstimulus interval of 400 ms. Responses were recorded from Oz, referred to Cz, by averaging 30 sweeps. Infants were examined between the ages of 4 weeks and 3 months. Reliable visual evoked responses were recorded to isoluminant tritan stimuli from as early as 4 weeks of age, and to red-green stimuli from 6 weeks. Responses to the luminance-modulated stimuli were evident in all infants at 4 weeks of age (the earliest age examined). Our results provide evidence that the rate of development for pathways mediating information about tritan stimuli, red-green stimuli, and luminance-modulated stimuli is similar.