Estimating chromatic contrast thresholds from the transient visual evoked potential.

Chromatic contrast thresholds may be estimated from transient VEPs by measuring the peak-to-peak amplitude at a range of stimulus levels followed by extrapolation to zero amplitude. However, there have been reports of failure of this technique when applied to the transient chromatic VEP due to variability of amplitude, difficulties with component identification and poor correlation of amplitude with stimulus level. The aim of our study was to compare methods of transient VEP chromatic contrast threshold estimation in terms of success rate and comparison with psychophysical threshold. We found each of the methods we investigated to have a high success rate, and in most cases VEP and psychophysical thresholds did not differ significantly.