SPATIAL-TEMPORAL INTERACTIONS IN THE STEADY-STATE PATTERN ELECTRORETINOGRAM

It is currently assumed that steady-state pattern electroretinograms c an be obtained only at high rates of pattern reversal. However, steady -state responses can also be obtained at very low temporal frequencies (less than 1 Hz), provided that the reversal is sinusoidal. In five h ealthy volunteers, we studied the frequency characteristics of the pat tern-reversal electroretinogram in response to sinusoidal gratings of 0.4 and 4 c/deg, reversed sinusoidally in contrast at frequencies rang ing from 1 to 27 Hz. Steady-state responses dominated by the second ha rmonic component were obtained at all temporal frequencies tested; the amplitude of the second harmonic changed with stimulus temporal frequ ency. In the low-temporal-frequency range, stimuli of high spatial fre quency appear to elicit larger contribution of generators with sustain ed or tonic characteristics compared with stimuli of low spatial frequ ency.