On the Oscillatory Potentials of the Human Electroretinogram in Light and Dark Adaptation

Abstract

The effect of adaptation to short flashes of light on the oscillatory potentials and the slow potentials (a-and b-wave) of the human ERG as well as the effect on adaptometric visual threshold in response to a series of three flashes were studied. The total energy and the dominant frequency of the oscillatory potentials in response to the third (stimulus) flash were calculated by a combined impulse response and Fourier analysis when the interval between the flashes changed and the intensity of the first two (conditioning) flashes varied. When recorded in response to flashes given at long intervals or conditioning flashes of low intensity the visual threshold recovered to the scotopic branch of the dark adaptation curve and the oscillatory potentials showed a low energy and high frequency (around 150 Hz). On adaptation to flashes at shorter intervals and more intense conditioning flashes [above the threshold for the appearance of the photopic b-wave in response to the second (conditioning) flash], resulting in the recovery of the visual threshold to the photopic branch of the dark adaptation curve, there was an increment of energy and the frequency changed to 105-110 Hz.The slow potentials (a-and b-wave) and the oscillations were differently affected by adaptation to light by previous flashes. The oscillatory potentials showed a 10-fold gain in energy, whereas the amplitudes of the slow potentials were slightly reduced (about 10 Oio). The oscillatory potentials were optimally recorded in the mesopic range

The postnatal development of the oscillatory potentials of the electroretinogram II. Photopic characteristics

“…In humans, the adult, photopic ERG contains fewer wavelets compared to the scotopic one (Wachtmeister 1972). In the present study using very short ISIs, 0, was found to be attenuated and 0, and 0, not to be recordable in the mature animal.…”

“…The oscillatory potentials (OPs) of the electrore-6 tinogram (ERG) reflect rapid adaptational changes and represent neuronal activity in the inner part of the retina (Algvere & Westbeck 1972;Wachtmeister 1972;Wachtmeister & Dowling 1978;Heynen et al 1985). Recently it has been reported that the postnatal development of the OPs generated during relatively more photopic conditions is slower compared to the OPs induced during relatively more scotopic conditions (el Azazi 8c Wachtmeister 1990).…”

The postnatal development of the oscillatory potentials of the electroretinogram IV. Mesopic characteristics

“…Thus, the behaviour of the OPs induced at IS1 30 sec entailed photopic qualities at individual levels, but when summated conformed to a scotopic course of postnatal maturation. This may not be a surprising finding as the OPs have been sug gested to represent both scotopic and photopic mechanisms, probably an interaction between the two in the inner retina (Wachtmeister 1972(Wachtmeister , 1974Stodtmeister 1973), and also because the studied range of adaptation was a relatively mesopic one.…”

“…5A and B). Thus, contrary to the human OPs, the oscillations in the mature rat retina seem not to be augmented by relatively mesopic conditions (Wachtmeister 1972). This could probably be explained by the rat having considerably fewer cones compared to the human retina, and therefore much more intense light stimulation seems to be needed to elicit optimal OPs.…”

“…In the adult human retina the oscillatory activity is most prominent during mesopic conditions (Wachtmeister 1972). Even though the retina of the nocturnal rat contains fewer cones and lacks a well defined area centralis, the spectral sensitivity curves of the adult rat's ERG have similarities to those in humans (Commission International 1'Eclairage 1957; Dodt & Echte 1961;Neitz &Jacobs 1986).…”