Double-Flash Responses in Different Retinal Layers

Abstract

Stimulating the isolated arterially perfused cat eye with two consecutive flashes (double flashes) we have studied the reduction of the 2nd response recorded from outer (isolated PIII component of the ERG), middle (b-wave) and inner (optic nerve response, ONR) retinal layers. The spectral sensitivity of the mechanism that reduces the amplitude of the 2nd response, determined by a constant threshold of 20% amplitude reduction of the b-wave, could be matched by a 500 nm pigment absorption function. For a given stimulus irradiance the response reduction was largest in the b-wave and smaller in the PIII and ONR. The injection of the dopamine antagonist fluphenazine, which presumably does not influence rod receptor function, changes the ratio between the two b-wave double-flash responses. These data indicate that the reduction of the 2nd response is produced by a rod driven mechanism that has a receptoral as well as a postreceptoral component. The ONR data indicate that mechanisms in the inner retina counteract the amplitude reduction of the 2nd flash, thereby stabilizing the retinal output.

Double-flash electroretinography in human eyes

“…Suppression of the a-wave of the ERG has not been described before, but might be comparable to the suppression of the PIII component as measured in cat [14]. The sensitivity of the suppression mechanism of the a-wave to blue and green flashes indicates a rod origin ( Table 1).…”

“…2 more response suppression with the use of these red flashes than with the green ones. The rod origin of the suppression mechanism as we found in humans has been described before for the b-wave in isolated arterially perfused cat eyes [14] and for the optic tract response in anesthesized cats [15]. The methods in the cat experiments differ from those in our experiments in humans.…”

“…In cats, for instance, these suppression times are much longer. Schneider and Zrenner [14] used 2.2 second interval times in their experiments.…”

“…The methods in the cat experiments differ from those in our experiments in humans. Schneider and Zrenner [14] measured the spectral sensitivity with conditioning and test flashes of equal strength and color. In humans, part of the second response to strong green or red stimuli might be generated by the cone system, and measurement of a reduction of these responses might be influenced by an unchanging cone component.…”

Prolonged Electro-Retinal Response Suppression (PERRS) in patients with stationary subnormal visual acuity and photophobia

“…With this method the influence of preceding stimuli or preceding responses on the excitability of retinal receptors and neuroretinal cells can be studied. Results of measurements in cats [1][2][3], rabbits [4][5][6], frogs [5] and normal human eyes [7][8][9], with and without the use of agonistic or antagonistic drugs, have been published in the last 40 years. In a recent study on patients with Parkinson's disease, decreased suppression of the responses to the test flashes compared to suppression in matched normal subjects was found [10].…”