The response decrease of auditory evoked potentials by repeated stimulation - Is there evidence for an interplay between habituation and sensitization?

Objectives: To assess whether the response decrement of auditory evoked potentials (AEPs) after stimulus repetition is affected by an interplay between sensitization and habituation. Methods: AEPs were recorded in 18 healthy participants. Stimulation consisted of trains with eight tones. The 6th stimulus of each train was a frequency deviant. The N100 amplitude to the 1st stimulus of the train was quantified in each trial. Trials with initially strong N100 responses and with initially weak N100 responses were averaged separately. Results: For the total trial sample, the N100 and P200 amplitudes decreased from the 1st to the 2nd stimulus of the train but not thereafter. Trials with an initially strong N100 response were qualified by likewise larger N100 amplitudes to the 2nd stimulus, as compared to trials with initially weak N100 responses, and were characterized by a pronounced N100 amplitude decrease from standards to deviants. Conclusion: Our findings are difficult to reconcile with the view that the response decrement of AEP components after stimulus repetition is modulated by sensitization and habituation, as no evidence for either of these two processes could be obtained. Significance: The study provides further evidence against habituation as underlying mechanism for the AEP decrement after stimulus repetition.