A TOPOGRAPHIC STUDY OF OSCILLATORY POTENTIALS IN MAN

The purpose of this study was to evaluate the use of slow multifocal m -sequence stimulation in analyzing the topographic distribution and un derlying mechanisms (including nonlinearities) of the retinal oscillat ory potentials (OPs). In giving us access to the response topography a nd the nonIinear characteristics of the OPs, the m-sequence technique provides us with two important means for the identification and charac terization of the signal sources. In this study, we analyzed the OPs i nto the first- and second-order components and investigated their topo graphies and luminance dependence. The distribution of both the first- and second-order OP components differed significantly from that of th e flicker ERG investigated by Sutter and Tran (1992). At eccentricitie s and luminance levels favoring activity by both rods and cones, the s econd-order OPs were particularly prominent, showing the most clear-de fined and complex waveform. The topographic distribution of the second -order OPs showed combined features of both rod and cone distributions . On a strong rod-bleaching background, the second-order OPs were elim inated and the first-order OPs showed a reduced amplitude and a shifte d latency. These results are consistent with the notion that the secon d-order component of the OPs is dominated by contributions from rod-co ne interactions.