title: Neuromagnetic functional coupling during dichotic listening of speech sounds.
abstract: The present magnetoencephalography (MEG) study tested the hypothesis of a phase synchronization (functional coupling) of cortical alpha rhythms (about 6-12 Hz) within a "speech" cortical neural network comprising bilateral primary auditory cortex and Wernicke's areas, during dichotic listening (DL) of consonant-vowel (CV) syllables. Dichotic stimulation was done with the CV-syllable pairs /da/-/ba/ (true DL, yielded by stimuli having high spectral overlap) and /da/-/ka/ (sham DL, obtained with stimuli having poor spectral overlap). Whole-head MEG activity (165 sensors) was recorded from 10 healthy right-handed non-musicians showing right ear advantage in a speech DL task. Functional coupling of alpha rhythms was defined as the spectral coherence at the following bands: alpha 1 (about 6-8 Hz), alpha 2 (about 8-10 Hz), and alpha 3 (about 10-12) with respect to the peak of individual alpha frequency. Results showed an inverse pattern of functional coupling: during DL of speech sounds, spectral coherence of the high-band alpha rhythms increased between left auditory and Wernicke's areas with respect to sham DL, whereas it decreased between left and right auditory areas. The increase of functional coupling within the left hemisphere would underlie the processing of the syllable presented to the right ear, which arrives to the left auditory cortex without the interference of the other syllable presented to the left ear. Conversely, the decrease of inter-hemispherical coupling of the high-band alpha might be due to the fact that the two auditory cortices do not receive the same information from the ears during DL. These results suggest that functional coupling of alpha rhythms can constitute a neural substrate for the lateralization of auditory stimuli during DL.
authors: Dipartimento di Scienze Biomediche, Università G. D'Annunzio, Chieti, Italy. alfredo.brancucci@uniroma1.it
authors: Alfredo
authors: A
authors: Brancucci
authors: Stefania Della
authors: SD
authors: Penna
authors: Claudio
authors: C
authors: Babiloni
authors: Fabrizio
authors: F
authors: Vecchio
authors: Paolo
authors: P
authors: Capotosto
authors: Davide
authors: D
authors: Rossi
authors: Raffaella
authors: R
authors: Franciotti
authors: Kathya
authors: K
authors: Torquati
authors: Vittorio
authors: V
authors: Pizzella
authors: Paolo M
authors: PM
authors: Rossini
authors: Gian Luca
authors: GL
authors: Romani
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology; D015982:Bias; D001931:Brain Mapping; D004007:Dichotic Listening Tests; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006309:Hearing; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods; D008297:Male; D010700:Phonetics; D013057:Spectrum Analysis; D013067:Speech Perception / Q000502:physiology*