Varying the degree of acoustic and perceptual category overlap should in that case lead to varying degrees of N1 repetition-attenuation. We further investigate whether N1 attenuation occurs for both acoustic and perceptual category overlap. If N1 attenuation is a result of neural refractoriness, attenuation should be demonstrated even in the face of acoustic variation, provided stimuli are similar enough that they activate overlapping groups of neurons. In the present study, we test the neural refractoriness hypothesis of N1 repetition-attenuation by examining the impact of acoustic and perceptual category variation on N1 attenuation. The amplitude of the N1 wave 1 of the event-related potential (ERP) decreases with repeated stimulation ( Näätänen and Picton, 1987). It remains unclear if the attenuation of the N1 wave is reduced as a result of stimuli being perceived as belonging to perceptual categories or as a result of some other characteristic of speech. Speech stimuli resulted in less attenuation than the acoustically matched non-speech stimuli, which is in line with previous findings. Findings show N1 repetition-attenuation in the face of acoustic and perceptual category variability, but no impact of the degree of variability on the degree of N1 attenuation. In the rotated speech condition, the spectrally rotated counterparts of the vowels were presented. In the speech condition, participants ( n = 19) listened to stimulus trains consisting of either the same vowel exemplar (no variability condition), different exemplars of the same vowel (low variability condition), or different exemplars of two different vowels (high variability condition). In the present study, N1 repetition-attenuation was investigated for speech and spectrally rotated speech with varying degrees of acoustic and perceptual category variation. perceptual category repetition been studied. This repetition-attenuation has not previously been investigated in response to variable auditory stimuli, nor has the relative impact of acoustic vs. The amplitude of the event-related N1 wave decreases with repeated stimulation. Phonetics Laboratory, Department of Linguistics, Stockholm University, Stockholm, Sweden.Ellen Marklund *, Lisa Gustavsson, Petter Kallioinen and Iris-Corinna Schwarz
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