Cortical representation of vowels reflects acoustic dissimilarity determined by formant frequencies

We studied neuromagnetic correlates of the processing of German vowels [a], [e] and [i]. The aim was (i) to show an influence of acoustic/phonetic features on timing and mapping of the N100m component and (ii) to demonstrate the retest reliability of these parameters. To assess the spatial configuration of the N100m generators, Euclidean distances between vowel sources were computed. Latency, amplitude, and source locations of the N100m component differed between vowels. The acoustically most dissimilar vowels [a] and [i] showed more distant source locations than the more similar vowels [e] and [i]. This pattern of results was reliably found in a second experimental session after at least 5 days. The results suggest the preservation of spectral dissimilarities as mapped in a F₁-F₂ vowel space in a cortical representation.