No evidence for auditory N1 dishabituation in healthy adults after presentation of rare novel distractors.

Previous studies were not able to show that presentation of change stimuli leads to dishabituation of the auditory evoked potential (AEP) component N1 for repeated stimuli. However, these change stimuli were usually themselves repeatedly presented. Here, we tested whether the presentation of non-repeating distractor stimuli ('novels') would lead to N1 dishabituation. The study sample consisted of 18 healthy participants who had to identify auditory target stimuli (´targets´) among repeated standard stimuli and rare novels. AEPs to standards were separately averaged, depending on the preceding stimulus (standards after standards, standards after targets, and standards after novels) and were compared by F statistics and Bayesian t-test. Moreover, N1 repetition effects within recording blocks were analyzed in single trial analyses. The analyses showed that targets elicited significantly larger N1 amplitudes than standards and standards elicited larger N1 amplitudes than novels. In contrast, the N1 amplitude to standards did not vary with the preceding stimulus. The single trial analyses revealed significant, but similar N1 amplitude decreases within the recording blocks for all standards. The current study revealed no evidence for N1 dishabituation, as the N1 amplitude for standards after novels was not increased as compared to the N1 for standards after standards. Thus, stimulus variation had no impact on the N1 of repeated standards, as also suggested by the single trial analyses. The lack of N1 dishabituation is at odds with the assumption that the N1 amplitude decrease after repeated stimulation results from habituation.