A new statistic for steady-state evoked potentials

Steady-state evoked potentials are often characterized by the amplitude and phase of the Fourier component at one or more frequencies of interest. We introduce a new statistic for the evaluation of these Fourier components. This statistic, denoted T_circ², is based on the same physiologic assumptions concerning the sources of variability of a Fourier component that are made in the use of the Rayleigh relationship between the real and imaginary components of Fourier estimates, which is not exploited by T², and utilizes amplitude information, which is ignored by the Rayleigh criterion. For these reasons, the T_circ² statistic is more efficient than previously used criteria for detection and quantitation of steady-state responses, both in principle and in practice.