Purpose. In previous studies we have shown that 4- and 8-week-old infants demonstrate visually-evoked potential (VEP) responses to M- and L-cone isolating stimuli. While these data lend strong support to the hypothesis that M- and L-cones are present and functional within 4-weeks of birth, the evidence is not unequivocal principally because of the possibility that infant spectral sensitivities differ systematically from those of an average adult. In order to resolve this issue we have measured action spectra from infants under conditions of M- and L-cone isolation. Methods. A mixture of either 540 and 610 or 540 and 645 nm light was alternated at 15 Hz in square-wave counterphase with a 570 or 580 nm light, respectively. In separate conditions, the former stimulus was adjusted to modulate the L-cones in isolation (while nulling the response of M-cones and rods) and the latter the M-cones (while nulling the L-cones and rods). The stimulus was presented in a 6 deg disk. The procedure entailed measuring how much light from a superimposed background field of variable wavelength (500-670 nm) was needed to reduce the VEP response to the receptor-isolating stimulus by a criterion voltage. Action spectra were also obtained from two female adults as a control. Results. The VEP action spectra obtained from 7 8-week infants and 2 adults under conditions of M- and L-cone isolation were well fit by the Smith and Pokorny M- and L-cone fundamentals, respectively. Conclusions. We find that VEPs of infants as young as 4-weeks can be driven by M- and L-cone isolating stimuli and that the action spectra of these responses at 8 weeks correspond closely to average adult M- and L-cone spectral sensitivities, respectively.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Feb 15 1996|
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