Generation of the auditory steady state responses (ASSR) is commonly explained by the linear combination of random background noise activity and the stationary response. Based on this model, the decrease of amplitude that occurs over the sequential averaging of epochs of the raw data has been exclusively linked to the cancelation of noise. Nevertheless, this behavior might also reflect the non-stationary response of the ASSR generators. We tested this hypothesis by characterizing the ASSR time course in rats with different auditory maturational stages. ASSR were evoked by 8-kHz tones of different supra-threshold intensities, modulated in amplitude at 115 Hz. Results show that the ASSR amplitude habituated to the sustained stimulation and that dishabituation occurred when deviant stimuli were presented. ASSR habituation increased as animals became adults, suggesting that the ability to filter acoustic stimuli with no-relevant temporal information increased with age. Results are discussed in terms of the current model of the ASSR generation and analysis procedures. They might have implications for audiometric tests designed to assess hearing in subjects who cannot provide reliable results in the psychophysical trials.

Abstract-This paper presents an algorithm for detecting auditory brainstem responses elicited by click stimuli at low intensities. Feature extraction is focused on peak V detection including analysis of the instantaneous energy and comparison with a template constructed from a reference dataset. All detection methods were validated and adjusted using ROC curve analysis. The algorithm was implemented in MatLab and evaluated in 135 ABR recordings. The combination of sensitivity, specificity and ROC area values exceeding 95 % with a 35 ms running time validates this approach for fast and accurate ABR detection.

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