Gender differences in lateralization of mismatch negativity in dichotic listening tasks.
OBJECTIVE
With the aim of investigating gender differences in the functional lateralization subserving preattentive processing of language stimuli, we compared auditory mismatch negativities (MMNs) using dichotic listening tasks.


METHODS
Forty-four healthy volunteers, including 23 males and 21 females, participated in the study. MMNs generated by pure-tone and phonetic stimuli were compared, to check for the existence of language-specific gender differences in lateralization. Both EEG amplitude and scalp current density (SCD) data were analyzed.


RESULTS
With phonetic MMNs, EEG findings revealed significantly larger amplitude in females than males, especially in the right hemisphere, while SCD findings revealed left hemisphere dominance and contralateral dominance in males alone. With pure-tone MMNs, no significant gender differences in hemispheric lateralization appeared in either EEG or SCD findings.


CONCLUSIONS
While males exhibited left-lateralized activation with phonetic MMNs, females exhibited more bilateral activity. Further, the contralateral dominance of the SCD distribution associated with the ear receiving deviant stimuli in males indicated that ipsilateral input as well as interhemispheric transfer across the corpus callosum to the ipsilateral side was more suppressed in males than in females.


CONCLUSIONS
The findings of the present study suggest that functional lateralization subserving preattentive detection of phonetic change differs between the genders. These results underscore the significance of considering the gender differences in the study of MMN, especially when phonetic stimulus is adopted. Moreover, they support the view of Voyer and Flight [Voyer, D., Flight, J., 2001. Gender differences in laterality on a dichotic task: the influence of report strategies. Cortex 37, 345-362.] in that the gender difference in hemispheric lateralization of language function is observed in a well-managed-attention condition, which fits the condition adopted in the MMN measurement; subjects are required to focus attention to a distraction task and thereby ignore the phonetic stimuli that elicit MMN.
Ikezawa
Satoru
S
Department of Psychiatry, Showa University School of Medicine, Shinagawa-ku, Tokyo 142-8666, Japan. satoruikezawa@grape.med.tottori-u.ac.jp
Nakagome
Kazuyuki
K
Mimura
Masaru
M
Shinoda
Junko
J
Itoh
Kenji
K
Homma
Ikuo
I
Kamijima
Kunitoshi
K
D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology; D003265:Contingent Negative Variation; D004007:Dichotic Listening Tests; D004192:Discrimination, Psychological / Q000502:physiology*; D005260:Female; D005364:Field Dependence-Independence; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D010700:Phonetics; D012016:Reference Values; D012737:Sex Factors