The influence of spatial frequency on the reaction times and evoked potentials recorded to grating pattern stimuli.

The simple reaction times recorded to sine-wave and square-wave grating stimulus patterns of both constant physical contrast and of constant suprathreshold contrast were appreciably delayed by an increase in spatial frequency from 0.5 to 10 c/deg. There was no comparable increase, however, in the peak latency of the initial visual evoked potential component, C1, recorded to the same stimulus patterns. In view of the evidence that C1 has a striate cortical origin, these results suggest that the large spatial-frequency dependent variations in RT do not reflect delays of stimulus-induced neuronal responses in the primary visual pathway from retina to striate cortex.