Steady State Average Evoked Potentials as a Measure of Tracking Difficulty

Abstract

The utility of steady state average evoked potentials (AEPs) to measure the difficulty of a tracking task will be reported. Medium (14 Hz) and high (50–56 Hz) frequency sine wave modulated light was used to evoke steady state AEPs while subjects performed a tracking task. Three levels of difficulty, based upon each subject's ability, were used in the single axis visual tracking task. The phase lag between stimulus input and the AEP waveform was found to be significantly related to task difficulty. Increasing difficulty levels were associated with greater amounts of phase lag of the AEPs during the high frequency stimulation. Neither the phase lag nor the amplitude of the medium frequency AEPs were significantly affected by the level of tracking difficulty.

Each subject was found to have one particular frequency of stimulation in the high range which produced an enhanced AEP amplitude. This suggests that researchers using high frequency stimulation with sine wave modulated light should test each subject to find the frequency which produces the maximal amplitude.