Reliability estimates for steady-state evoked potentials.

The steady-state evoked potentials are most efficiently recorded using Fourier analysis. The reliability of this evoked potential is best estimated using either Hotelling's T2 or phase coherence. Using these techniques, the response to 500 Hz tones presented at a rate of 40/sec can be reliably recognized on average down to intensities of below 15 dB SL in an awake subject. Sleep significantly decreases the amplitude of the response and significantly raises the threshold for recognizing the response by 11 dB.