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Abstract:
The study was aimed at examining the cortical representation
of segmental phonemes by means of whole head magnetoencephalography
(MEG) to see whether respective cortical maps are stable or
dynamically organised. We investigated the spatial configuration of
active cortical areas generating the N1m component of the auditory
evoked field during the processing of the synthetic German vowels
[a], [e] and [i] across 10 repeated mesurements in one subject on
different days within 4 weeks. The amplitude of the N1m component
as well as the dipole moment of the estimated equivalent current
dipoles were larger for left hemispheric as compared to right
hemispheric data. The spatial configuration of the N1m sources for
the different vowels could be estimated with a high goodness of fit
(all above 0.95) only for the left hemisphere. Vowels differing
maximally in height and place features, i.e [a] and [i] showed
larger euclidean distances between N1m vowel sources than [a] and
[e] or [e] and [i] which showed the smallest distances. The spatial
configuration of vowel sources around 100ms post stimulus onset in
the left hemisphere was stable across measurements for the given
subject and the given set of synthetic vowels. The spatial-temporal
structure of this cortical map is among others presumably
determined by the distintiveness of phonological features.
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