Cone phototransduction and growth of the ERG b-wave during light adaptation

Vision Res. 2006 Oct;46(22):3941-8. doi: 10.1016/j.visres.2006.04.015. Epub 2006 Jun 5.

Abstract

The purpose of this study was to determine whether cone redepolarization accounts for the amplitude increase of the b-wave of the human electroretinogram (ERG) during light adaptation. The time course of the b-wave amplitude increase was compared to the time course of the change in the activation phase of cone phototransduction, as derived from a delayed Gaussian model applied to the leading edge of the ERG a-wave. ERG recordings were obtained from five visually normal subjects, alternately in the presence of the adapting field (adapt-on condition) and 300ms after its temporary extinction (adapt-off condition). The proportional increase in amplitude was less for R(mp3) (maximum amplitude of P3, the massed cone photoreceptor response) than for the b-wave for both adaptation conditions, and the time course of the amplitude increase for R(mp3) was faster than that for the b-wave in the adapt-off condition. The results demonstrate that time-dependent changes in the activation phase of cone phototransduction have only a minimal role in governing the increase in the amplitude of the human cone-derived ERG b-wave during light adaptation. In addition, the systematic increase in b-wave amplitude and the decrease in b-wave implicit time in the adapt-off condition indicates that the ERG response measured shortly after adapting field offset does not necessarily represent the waveform of the dark-adapted cone ERG.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Ocular / physiology*
  • Adult
  • Dark Adaptation
  • Electroretinography / methods
  • Female
  • Humans
  • Middle Aged
  • Photic Stimulation / methods
  • Retinal Cone Photoreceptor Cells / physiology*
  • Time Factors
  • Vision, Ocular / physiology*