A hemispherically asymmetrical MEG response to vowels

NEUROMAGNETIC fields elicited by vowels and tones were recorded and sources were modeled as single equivalent current dipoles (ECDs) in 1ms steps 80-4 00ms post stimulus. To vowels, the left hemisphere (LH) auditory cortex had nearly twice as many satisfactory ECD fits as the right hemisphere (RH). T ones did not evoke such asymmetry. In particular, in the late field (150-40 0 ms) the LH had more than twice as many ECDs as the RH, and the spatial di stribution of LH sources was more clustered than in the RH. An asymmetrical , focal cortical mechanism for vowel processing was identified that intensi fied in later auditory processing stages. These data suggest that MEG might be used for non-invasive, language laterality determination with simple vo wel-like stimuli. NeuroReport 10:2481-2486 (C) 1999 Lippincott Williams & W ilkins.