[Blue-sensitive mechanisms in pattern ERG and VEP]

Pattern onset-offset ERGs and VEPs in response to square-wave stripe patterns of different wavelengths and spatial frequencies under chromatic yellow adaptation (two-channel Maxwellian view) were studied in three subjects. One channel provided a steady homogeneous adapting field of 570 nm, while the other channel, containing the patterns, was superimposed on the adapting field (33 degrees). The spectral sensitivity curve of the ERG had a prominent peak in the blue (460 nm) and a shoulder in the red and green (above 500 nm). For wavelengths below 500 nm the shape of the psychophysically determined sensitivity curve to the onset and offset of the pattern was in close agreement with the electroretinal sensitivity curves determined for a low-amplitude criterion. With almost all wavelengths there were two components in the same VEP response at the same time: a slow negative wave with maximum sensitivity at 460 nm and an earlier fast positive component with maximum sensitivity in the red-green region. When the spatial frequency of a 460 nm test pattern was varied under yellow adaptation the onset response in the ERG showed only very slight spatial tuning. In the onset response of the VEP, however, the slow component showed prominent spatial tuning (around 2 c/deg) under the same conditions.