Comparison of intermodulation and oddball methods for measuring human cortical color tuning functions using steady-state visually evoked potentials.

Characterization of postreceptoral chromatic mechanisms is an active challenge in color vision research. Adding to evidence from human psychophysics and primate neurophysiology, human neuroimaging using electroencephalography (EEG) in combination with steady-state visually evoked potentials (SSVEPs) has recently been used to investigate the tuning of cortical color mechanisms. We compare the performance of two SSVEP-based methods for measuring the tuning of cortical color mechanisms: an intermodulation component (IM)-based method and an oddball method. Our results support SSVEPs as an effective tool for investigating the tuning of cortical color mechanisms. The intermodulation method is efficient and provides high signal-to-noise ratios, but the oddball method can also yield clear tuning functions if multiple SSVEP harmonics are analyzed in combination.