The detection of adult cortical auditory evoked potentials (CAEPs) using an automated statistic and visual detection

Abstract

Abstract

The detection of adult cortical auditory evoked potentials (CAEPs) can be challenging when the stimulus is just audible. The effectiveness of a statistic compared with expert examiners in (1) detecting the presence of CAEPs when stimuli were present, and (2) reporting the absence of CAEPs when no stimuli were present, was investigated. CAEPs recorded from ten adults, using two speech-based stimuli, five stimulus presentation levels, and non-stimulus conditions, were given to four experienced examiners who were asked to determine if responses to auditory stimulation could be observed, and their degree of certainty in making their decision. These recordings were also converted to multiple dependent variables and Hotelling's T2 was applied to calculate the probability that the mean value of any linear combination of these variables was significantly different from zero. Results showed that Hotelling's T2 was equally sensitive to the best of individual experienced examiners in differentiating a CAEP from random noise. It is reasonable to assume that the difference in response detection for a novice examiner and Hotelling's T2 would be even greater.

Sumario

La detección de los potenciales evocados auditivos corticales (CAEP) del adulto puede ser un desafío cuando el estímulo es apenas audible. Se investigó la efectividad de una comparación estadística con examinadores expertos para (1) detectar la presencia del CAEP cuando el estimulo estuvo presente, y (2) reportar la ausencia del CAEP cuando ningún estímulo estaba presente. Los CAEP registrados para diez adultos, usando dos estímulos con base en lenguaje, cinco niveles de presentación del estímulo, y condiciones sin estímulo, fueron presentados a cuatro examinadores con experiencia, a quienes se solicitó que determinaran si las respuestas a estímulos auditivos podían ser observadas y su grado de certeza en la toma de sus decisiones. Estos registros fueron también convertidos a múltiples variables dependientes y se aplicó el T2 de Hotelling para calcular la probabilidad de que el valor medio de una combinación lineal de estas variables fuera significativamente diferente de cero. Los resultados mostraron que el T2 de Hotelling era igualmente sensible que lo mejor de los examinadores experimentados individuales para diferenciar un CAEP de un ruido aleatorio. Es razonable asumir que la diferencia en detección de respuestas para un examinador novato y el T2 de Hotelling serían aún mayor.

Key Words:

• Hotelling's T2
• Cortical auditory evoked potentials (CAEP)
• Visual detection
• Sensitivity
• Specificity

Acknowledgements

Selected results from this paper were presented at Audiology Now! in 2006 and at the XX IERASG Biennial Symposium in 2007. The authors would like to acknowledge the instructive comments of Bram Van Dun, regarding the physiological mechanisms of the CAEP.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Appendix

The Hotelling's formula is:

where

S is the covariance matrix of the p variables (the voltage within the nine time bins in our case). n is the number of observations (the number of epochs in our case), μ₀ is the hypothesized array of values (all zero in our case) against which the variables x_i, are tested, and is the mean value across epochs of variable x_i.