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Abstract:
The magnetic mismatch field (MMF) has been defined as a
correlate of the brain response to a deviating stimulus in a series
of standard stimuli. Furthermore, it is widely acknowledged that
MMF varies according to the dimension of deviancy (e.g. duration,
intensity as well as phonological or lexical wellformedness). The
present study employed a German single word uttered by a male
speaker as standard stimulus and investigated the following types
of deviants: a) deviating WORD b) deviating (female) SPEAKER c)
BOTH (i.e. another word uttered by a female speaker). Brain
responses were collected from 6 female and 3 male subjects using a
148 channel wholehead magnetometer. Event-related surface current
densities (SCD) were calculated. All stimuli showed a mismatch
response peaking around 130-220 ms post onset. The SCD maps of the
brain response to the deviating WORD were lateralized to the left
hemisphere. In contrast, the SPEAKER deviancy led to a
significantly higher current density in the right hemisphere.
Stimuli deviating in BOTH dimensions elicited a generally stronger
response and a tendency of being lateralized to the left hemiphere,
suggesting that the perceptual system might be tuned to phonetic
deviancy rather than voice information, even in early stages of
auditory processing.
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