Visual Neuroscience

Research Articles

Light adaptation, rods, and the human cone flicker ERG

Neal S. Peacheya1a2, Kenneth R. Alexandera3, Deborah J. Derlackia3 and Gerald A. Fishmaa3

a1 Hines VA Hospital

a2 Department of Neurology, Loyola University Medical Center

a3 Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine

Abstract

During the course of light adaptation, the amplitude and implicit time of the human cone ERG change systematically. In the present study, the effect of adapting field luminance on these ERG changes was assessed, and the hypothesis that light adaptation of the rod system is the primary determining factor was evaluated. Cone ERG responses, isolated through the use of 31.1-Hz flicker, were obtained from two visually normal subjects, initially under dark-adapted conditions and then repeatedly for 30 min following the onset of each of a series of ganzfeld adapting fields with luminances that ranged from –1.2 to 2.1 log cd/m. The increase in flicker ERG amplitude and decrease in implicit time during light adaptation were greatest at the highest adapting field luminances. Photopically equivalent achromatic and long-wavelength adapting fields induced comparable increases in flicker ERG amplitude, while scotopically equivalent adapting fields had considerably different effects. This latter finding demonstrates that the rod system is not a major determinant of the adaptation-induced increase in cone ERG amplitude.

(Received April 29 1991)

(Accepted July 01 1991)

Footnotes

Reprint requests to: Neal S. Peachey, 151-E, Hines VA Hospital, Hines, 1L 60141, USA.