N1 response attenuation and the mismatch negativity (MMN) to within- and across-category phonetic contrasts.
According to the neural adaptation model of the mismatch negativity (MMN), the sensitivity of this event-related response to both acoustic and categorical information in speech sounds can be accounted for by assuming that (a) the degree of overlapping between neural representations of two sounds depends on both the acoustic difference between them and whether or not they belong to distinct phonetic categories, and (b) a release from stimulus-specific adaptation causes an enhanced N1 obligatory response to infrequent deviant stimuli. On the basis of this view, we tested in Experiment 1 whether the N1 response to the second sound of a pair (S2) would be more attenuated in pairs of identical vowels compared with pairs of different vowels, and in pairs of exemplars of the same vowel category compared with pairs of exemplars of different categories. The psychoacoustic distance between S1and S2was the same for all within-category and across-category pairs. While N1 amplitudes decreased markedly from S1to S2, responses to S2were quite similar across pair types, indicating that the attenuation effect in such conditions is not stimulus specific. In Experiment 2, a pronounced MMN was elicited by a deviant vowel sound in an across-category oddball sequence, but not when the exact same deviant vowel was presented in a within-category oddball sequence. This adds evidence that MMN reflects categorical phonetic processing. Taken together, the results suggest that different neural processes underlie the attenuation of the N1 response to S2and the MMN to vowels.
Graduate Program in Neuroscience, Federal University of Minas Gerais, Belo Horizonte, Brazil.
Daniel M R
DM
Silva
Graduate Program in Electrical Engineering, Department of Electrical Engineering, Federal University of Minas Gerais, Belo Horizonte, Brazil.
Danilo B
DB
Melges
Phonetics Lab, Faculty of Letters, Federal University of Minas Gerais, Belo Horizonte, Brazil.
Rui
R
Rothe-Neves
D000161:Acoustic Stimulation; D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology*; D004569:Electroencephalography; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008297:Male; D010700:Phonetics; D011571:Psychoacoustics; D013067:Speech Perception / Q000502:physiology*; D055815:Young Adult
Adaptation; Categorization; ERPs; Language/speech; Mismatch negativity (MMN); N1