Relationships between transient and steady-state AEPs, and AEMFs determined from SQUID measurements
Alan J. Klein, Arnold Tubis, Kenneth Jones, Edward McN. Burns · The Journal of the Acoustical Society of America · 1984
When an auditory stimulus is presented at a repetition rate fr of about 40/s, a robust steady-state auditory evoked potential (AEP) is recordable [R. Galambos et al., Proc. Natl. Acad. Sci. (USA) 78, 2643–2647 (1981)], and has an approximate sinusoidal waveform with frequency fr. A similar phenomenon is encountered when auditory evoked magnetic fields (AEMFs) are measured at the scalp with a SQUID magnetometer. We have determined the fr dependence of the steady-state AEPs and AEMFs for the same human subjects. Using the assumption of a sandwich system (linear transformation-zero memory nonlinear transformation-linear transformation) response, we have also produced computer simulations of the fr dependence of steady-state responses from measured transient-response data. The simulations account fairly well for the steady-state data. The stimulus was a 500-Hz tone pip presented with fr varying from 3-50/s. The AEMF was recorded from a point around the T4 location, and the AEP was recorded between electrodes at CZ and the mastoid process of the test ear. Preliminary results for optimal fr's are 40-45/s for the AEPs and 30-35/s for the AEMFs. [Work supported by NINCDS, NSF, and the Purdue University Biomedical Support Fund.]