title: Speech dominance is a better predictor of functional brain asymmetry than handedness: a combined fMRI word generation and behavioral dichotic listening study.
abstract: An unresolved issue in behavioral studies of hemispheric asymmetry is why both left-handers and right-handers show a right ear advantage at the group level. In the present study we screened left-handers for left- versus right-hemisphere speech dominance with fMRI by comparing right versus left hemisphere frontal lobe activity (in Broca's area) in a silent word generation task. A left hemisphere dominant right-handed control group was included as well. All participants took part in a dichotic listening task with consonant-vowel syllables. The results showed that left-handers and right-handers with left-hemisphere speech dominance showed a right ear advantage. However, the left-handers with right hemisphere speech dominance had a left ear advantage. Thus, at the group level the direction of the ear advantage in dichotic listening was predicted by language dominance but not by hand preference. At the individual level, the dichotic task we used showed more variability than the fMRI results. Further research will have to indicate whether this is a feature inherent to dichotic listening, or whether the variability is due to alternative explanations such as a more bilateral representation of speech perception compared to speech production.
authors.affiliation: Department of Experimental Psychology, Ghent University, Henri Dunantlaan 2, Ghent B-9000, Belgium. Lise.VanderHaegen@UGent.be
authors.forename: Lise
authors.initials: L
authors.lastname: Van der Haegen
authors.forename: René
authors.initials: R
authors.lastname: Westerhausen
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hugdahl
authors.forename: Marc
authors.initials: M
authors.lastname: Brysbaert
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001307:Auditory Perception / Q000502:physiology*; D001921:Brain / Q000098:blood supply* / Q000502:physiology*; D004007:Dichotic Listening Tests; D004292:Dominance, Cerebral / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D011930:Reaction Time / Q000502:physiology; D013060:Speech / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen