Changes in perceived contrast,reaction time,and pattern-specific evoked potentials due to stimulus duration

Using patterned stimulation without luminance change, the authors manipulated the stimulus duration and measured three variables: the magnitude of contrast experience, simple reaction time, and the amplitude of pattern-specific visual evoked potentials. While contrast experience, measured by the scaling method, indicated no saturation below 85 msec, the other two variables saturated below 40 msec. The lower saturation value of the pattern-specific evoked potential is considered as the limit of the correlation between psychophysical measures and brain electric activity. This suprathreshold divergence can be seen as evidence that processes underlying the pattern-specific visual evoked potential components cannot be considered as mechanisms mediating subjective experience of spatial contrast.