Contribution of post-receptoral cells to the a-wave of the human photopic electroretinogram.
ERGs were recorded to red flashes (0.01-50 phcdsm(2)) presented against a steady background (2000 sctd) or 0-300 ms after its suppression. The cone a-wave was altered in form and increased in amplitude in the dark. Peak amplitudes were doubled when the dark period was 50-100 ms and also when it was 150-200 ms. Measurement of the a-wave at fixed times showed that amplitude increase occurred at times later than 6-8 ms. The a-wave receives a significant negative-signal contribution from two post-receptoral mechanisms. These are adapted by weak backgrounds and recover their sensitivity extremely rapidly in the dark. The cone photocurrent alone contributes 40-70% of peak amplitude depending on stimulus intensity.
Bradshaw
Keith
K
Vision Science, Ophthalmology Department, Addenbrookes Hospital, Hills Road, Cambridge CB2 2QQ, UK. keith.bradshaw@addenbrookes.nhs.uk
D000328:Adult; D003118:Color Perception / Q000502:physiology*; D003623:Dark Adaptation / Q000502:physiology; D004596:Electroretinography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology