Assessment of visual acuity by evoked potential recording: Ambiguity caused by temporal dependence of spatial frequency selectivity

The spatial-frequency selectivity of pattern evoked potentials depends on the stimulus repetition rate: responses to low spatial frequencies are emphasized by stimulating at 16–20 Hz, while responses to high spatial frequencies are emphasized at 5–8 Hz. These findings are consistent with the suggestion that pattern EP's are a mixture of pattern responses and responses to local flicker. To a first approximation the “local flicker” responses resemble EP's produced by flickering a light similar to the patterned stimulis in all respects except for absence of pattern. Any developmental changes in the temporal tuning of pattern responses and/or local flicker responses might distort the results of studies in which pattern EP's have been used as an index of either (a) the development of visual acuity or (b) acuity changes due to visual deprivation. Methods of minimizing this problem are suggested.