The components of the retinal action potential in mammals and their relation to the discharge in the optic nerve

[13] Electroretinographic determination of human Rod flash response in vivo

“…If the prevailing rate of change of the test-flash-induced response at time t is relatively small, little if any change in this test flash response will occur in the brief interval between time t and attainment of the a-wave peak of the probe response. Under these conditions, the peak amplitude of the probe response as referred to the pre-probe baseline will approximate the circulating current at time t. From this determination of the probe response amplitude, and from the maximal amplitude exhibited by the probe-alone response, one obtains by subtraction an amplitude A that represents the rod response to the test flash at time t. That is, (1) where A m (t) is the probe response amplitude determined in the paired-flash trial, A mo is the amplitude of the probe-alone response, and A(t) is the amplitude at time t of the derived response to the test flash. The family of determinations of A(t) obtained with variation of the interflash interval t (Fig.…”

“…1 The first component of the ERG elicited by a brief flash of moderate or high intensity is a cornea-negative response, termed the a-wave, that in mammals reaches its (negative) peak at ~5-20 msec after flash presentation. Abundant evidence indicates that the leading edge (rising phase) of the rod-mediated a-wave closely monitors the massed photocurrent response of the rod photoreceptors, i.e., the flash-induced reduction of rod circulating current.…”

The Rat Electroretinogram

“…This amplitude is conventionally measured from the bottom of the a-wave to partially correct for the reduction in the b-wave (Granit's PII) amplitude caused by the opposing a-wave (Granit's PIII; see Fig. 4) (14). However, because the amplitudes of both the PII and PIII components increase rapidly in time at the point where the observable a-wave reaches its maximum size, slight changes in the latencies of these two ERG components would apparently lead to large changes in a-wave amplitude.…”

Electroretinography in dogs: a review

“…Granit noted that PII and PIII components are strongly correlated with the light stimulus. Due to the short implicit time, Granit believed that the PIII component was associated with photoreceptor activity (Granit 1933). In the mid-20 th century, Karpe (1945) reported that electroretinography was an examination used to determine retinal function.…”