Frequency-specific threshold determination with the CERAgram method: basic principle and retrospective evaluation of data.
A method for the objective evaluation of the hearing threshold using cortical evoked response audiometry was developed. The method results in a kind of objective audiogram, visualizing the significance of an auditory evoked potential (AEP) in a scheme similar to a conventional audiogram. In the present implementation of the method, four frequencies are tested quasi-simultaneously (500, 1000, 2000 and 3000 Hz; intensity steps of 5 dB). The significance of an evoked potential is assessed by means of the Rayleigh test, which is applied to the phase values derived from certain time windows of the single-trial epochs. A retrospective analysis of 1, 920 threshold estimations in 240 subjects suggested that the detection threshold (lowest stimulus intensity yielding a significant response) was, on the average, 7.5 dB above the electrophysiological threshold (intensity where the AEP amplitude vanishes). The grand-average amplitude-intensity characteristic was approximated by the function a(1 - exp(-I/b)), with a = 6.25 microV, b = 22.3 dB and I representing the intensity (in decibels) relative to the electrophysiological threshold.
Ross
B
B
Institute of Experimental Audiology, University of Münster, Germany. bernhard.ross@uni-muenster.de
Lütkenhöner
B
B
Pantev
C
C
Hoke
M
M
D001307:Auditory Perception / Q000502:physiology*; D001309:Auditory Threshold / Q000502:physiology*; D004558:Electric Stimulation; D004566:Electrodes; D006801:Humans; D008954:Models, Biological; D012189:Retrospective Studies; D013997:Time Factors