The influence of the detection paradigm in recording auditory steady-state responses.

OBJECTIVES

The purpose of this study was to evaluate the risks of uncontrolled use of an objective detection criterion in recording auditory steady-state responses (ASSRs). The influence of decisions such as when to accept a response and stop the recording was assessed by analyzing the number of false- and true-detected responses.

DESIGN

A large sample of 500 multiple-stimulus ASSR recordings of normal-hearing and hearing-impaired adults and babies was processed offline. Three types of detection paradigms were evaluated. A first type had a fixed recording length with significance testing after the last sweep. A second type allowed a variable recording length and implied sequential application of the statistical decision criterion. The recording was stopped after significance was reached for y consecutive sweeps. The third type was analogous to the second, with the additional requirement of a minimum of eight recorded sweeps. Furthermore, the effect of significance level and averaging procedure were assessed. Error rates were calculated for the different detection paradigms at eight control frequencies. At the signal frequencies, detection rates and recording times were determined, keeping the error rates fixed. Moreover, ASSR thresholds were compared for a selection of detection paradigms.

RESULTS

When a variable recording length was allowed and a significance level of p = 0.05 was applied, the error rate increased to unacceptable levels because of the effect of repeated testing. The error rate decreased as the required number of consecutive significant sweeps increased and approximated 5% only when eight consecutive significant sweeps were required (with a maximum of 32 recorded sweeps). With an error rate of 5%, the highest detection rate was associated with a fixed recording length of 32 sweeps combined with weighted averaging. A substantial decrease in detection rate was noted when less than 24 sweeps were recorded per intensity. All paradigms with a variable recording length had rather comparable detection rates and recording times. With an error rate of only 1%, small responses could not be distinguished from the noise. The reduction in recording time using a variable instead of a fixed recording length was very limited when a conventional multiple-stimulus approach was used. Test duration would be reduced considerably when the test set-up would allow an independent presentation and recording of the eight signals and responses. Differences in overall detection rate had a small effect on the ASSR thresholds.

CONCLUSIONS

The error rate, detection rate, and recording time can improve or deteriorate significantly, even with small adaptations of the detection protocol. When a variable recording length is allowed, the acceptance criterion of the statistical test needs to be adjusted to ensure a tolerable error rate. However, most commercial devices do not offer this option. Then, it is advisable to use a fixed recording length and to judge the significance of the responses at the end of the recording. Although response detection is objective, the measurement protocol has to be well-considered and a critical approach is required when interpreting the responses.