Magnetic oscillatory responses to lateralization changes of natural and artificial sounds in humans

Abstract

Oscillatory signals in human magnetoencephalogram were investigated as correlates of cortical network activity in response to sound lateralization changes. Previously, we found lateralized presentations of a monosyllabic word to elicit posterior temporo-parietal gamma-band activity, possibly reflecting synchronization of neuronal assemblies in putative auditory dorsal stream areas. In addition, beta activity was decreased over sensorimotor regions, suggesting the activation of motor networks involved in orientating. The present study investigated responses to lateralization changes of both a barking dog sound and a distorted noise to test whether beta desynchronization would depend on the sound's relevance for orientating. Eighteen adults listened passively to 900 samples of each sound in separate location mismatch paradigms with midline standards and both right- and left-lateralized deviants. Lateralized distorted noises were accompanied by enhanced spectral amplitude at 58-73 Hz over right temporo-parietal cortex. Left-lateralized barking dog sounds elicited right and right-lateralized sounds elicited bilateral temporo-parietal spectral amplitude increases at approximately 77 Hz. This replicated the involvement of posterior temporo-parietal areas in auditory spatial processing. Only barking dog sounds, but not distorted noises, gave rise to 30 Hz desynchronization over contralateral sensorimotor areas, parieto-frontal gamma coherence increases and beta coherence reductions between sensorimotor and prefrontal sensors. Apparently passive listening to lateralized natural sounds with a potential biological relevance led to an activation of motor networks involved in the automatic preparation for orientating. Parieto-frontal coherence increases may reflect enhanced coupling of networks involved in the integration of auditory spatial and motor processes.