title: Dissociated lateralization of transient and sustained blood oxygen level-dependent signal components in human primary auditory cortex.
abstract: Among other auditory operations, the analysis of different sound levels received at both ears is fundamental for the localization of a sound source. These so-called interaural level differences, in animals, are coded by excitatory-inhibitory neurons yielding asymmetric hemispheric activity patterns with acoustic stimuli having maximal interaural level differences. In human auditory cortex, the temporal blood oxygen level-dependent (BOLD) response to auditory inputs, as measured by functional magnetic resonance imaging (fMRI), consists of at least two independent components: an initial transient and a subsequent sustained signal, which, on a different time scale, are consistent with electrophysiological human and animal response patterns. However, their specific functional role remains unclear. Animal studies suggest these temporal components being based on different neural networks and having specific roles in representing the external acoustic environment. Here we hypothesized that the transient and sustained response constituents are differentially involved in coding interaural level differences and therefore play different roles in spatial information processing. Healthy subjects underwent monaural and binaural acoustic stimulation and BOLD responses were measured using high signal-to-noise-ratio fMRI. In the anatomically segmented Heschl's gyrus the transient response was bilaterally balanced, independent of the side of stimulation, while in opposite the sustained response was contralateralized. This dissociation suggests a differential role at these two independent temporal response components, with an initial bilateral transient signal subserving rapid sound detection and a subsequent lateralized sustained signal subserving detailed sound characterization.
authors.affiliation: University Hospital of Clinical Psychiatry, University of Bern, 3000 Bern, Switzerland. lehmann@puk.unibe.ch
authors.forename: Christoph
authors.initials: C
authors.lastname: Lehmann
authors.forename: Marcus
authors.initials: M
authors.lastname: Herdener
authors.forename: Peter
authors.initials: P
authors.lastname: Schneider
authors.forename: Andrea
authors.initials: A
authors.lastname: Federspiel
authors.forename: Dominik R
authors.initials: DR
authors.lastname: Bach
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Esposito
authors.forename: Francesco
authors.initials: F
authors.lastname: di Salle
authors.forename: Klaus
authors.initials: K
authors.lastname: Scheffler
authors.forename: Robert
authors.initials: R
authors.lastname: Kretz
authors.forename: Thomas
authors.initials: T
authors.lastname: Dierks
authors.forename: Erich
authors.initials: E
authors.lastname: Seifritz
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001303:Auditory Cortex / Q000098:blood supply / Q000502:physiology*; D002560:Cerebrovascular Circulation; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010100:Oxygen / Q000097:blood*; D012016:Reference Values
chemical_list: D010100:Oxygen