title: Handedness, dichotic-listening ear advantage, and gender effects on planum temporale asymmetry--a volumetric investigation using structural magnetic resonance imaging.
abstract: Previous research has often examined whether the asymmetrical structure of the planum temporale (PT) represents an anatomical correlate of lateralized language-processing functions, gathering diverging empirical evidence by comparing PT asymmetry in subjects with differing handedness, gender, or speech lateralization. Apart from other methodological problems, direct comparisons between studies are hampered by insufficient assessment and consideration of all three potential determinants of structural cerebral asymmetry. Based on volumetric assessment of structural Magnetic Resonance Imaging (MRI) scans of 104 healthy subjects, the present study replicated earlier observations of an overall leftward PT asymmetry, which was found to prevail irrespective of handedness, gender, or dichotic-listening ear advantage. However, the mean magnitude of this leftward asymmetry was not determined by either one of these factors in itself, but varied depending on their specific combination. A clear correspondence between structural and functional asymmetry was only observed among right-handed males. In this particular subgroup, more pronounced structural asymmetry was associated with an enlarged PT on the left side, while the enhanced leftward asymmetry of female sinistrals resulted from smaller adjusted volumes of their right PT. The existence of such complex interactions suggests that future research in this area can only be expected to overcome past inconsistencies by adequately considering handedness, gender, and speech lateralization.
authors.affiliation: Center for Neuropsychological Research, University of Trier, Johanniterufer 15, D-54290 Trier, Germany.
authors.forename: Sarah
authors.initials: S
authors.lastname: Dos Santos Sequeira
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Woerner
authors.forename: Christof
authors.initials: C
authors.lastname: Walter
authors.forename: Frank
authors.initials: F
authors.lastname: Kreuder
authors.forename: Ulrike
authors.initials: U
authors.lastname: Lueken
authors.forename: René
authors.initials: R
authors.lastname: Westerhausen
authors.forename: Ralf Arne
authors.initials: RA
authors.lastname: Wittling
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Schweiger
authors.forename: Werner
authors.initials: W
authors.lastname: Wittling
mesh_terms: D001303:Auditory Cortex / Q000033:anatomy & histology; D001931:Brain Mapping; D004007:Dichotic Listening Tests; D004292:Dominance, Cerebral / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008432:Mathematical Computing; D012016:Reference Values; D012737:Sex Factors; D013067:Speech Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000033:anatomy & histology*