title: Task-modulated "what" and "where" pathways in human auditory cortex.
abstract: Human neuroimaging studies suggest that localization and identification of relevant auditory objects are accomplished via parallel parietal-to-lateral-prefrontal "where" and anterior-temporal-to-inferior-frontal "what" pathways, respectively. Using combined hemodynamic (functional MRI) and electromagnetic (magnetoencephalography) measurements, we investigated whether such dual pathways exist already in the human nonprimary auditory cortex, as suggested by animal models, and whether selective attention facilitates sound localization and identification by modulating these pathways in a feature-specific fashion. We found a double dissociation in response adaptation to sound pairs with phonetic vs. spatial sound changes, demonstrating that the human nonprimary auditory cortex indeed processes speech-sound identity and location in parallel anterior "what" (in anterolateral Heschl's gyrus, anterior superior temporal gyrus, and posterior planum polare) and posterior "where" (in planum temporale and posterior superior temporal gyrus) pathways as early as approximately 70-150 ms from stimulus onset. Our data further show that the "where" pathway is activated approximately 30 ms earlier than the "what" pathway, possibly enabling the brain to use top-down spatial information in auditory object perception. Notably, selectively attending to phonetic content modulated response adaptation in the "what" pathway, whereas attending to sound location produced analogous effects in the "where" pathway. This finding suggests that selective-attention effects are feature-specific in the human nonprimary auditory cortex and that they arise from enhanced tuning of receptive fields of task-relevant neuronal populations.
authors.affiliation: Harvard Medical School-Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, CNY 149 13th Street, Charlestown, MA 02129, USA. jyrki@nmr.mgh.harvard.edu
authors.forename: Jyrki
authors.initials: J
authors.lastname: Ahveninen
authors.forename: Iiro P
authors.initials: IP
authors.lastname: Jääskeläinen
authors.forename: Tommi
authors.initials: T
authors.lastname: Raij
authors.forename: Giorgio
authors.initials: G
authors.lastname: Bonmassar
authors.forename: Sasha
authors.initials: S
authors.lastname: Devore
authors.forename: Matti
authors.initials: M
authors.lastname: Hämäläinen
authors.forename: Sari
authors.initials: S
authors.lastname: Levänen
authors.forename: Fa-Hsuan
authors.initials: FH
authors.lastname: Lin
authors.forename: Mikko
authors.initials: M
authors.lastname: Sams
authors.forename: Barbara G
authors.initials: BG
authors.lastname: Shinn-Cunningham
authors.forename: Thomas
authors.initials: T
authors.lastname: Witzel
authors.forename: John W
authors.initials: JW
authors.lastname: Belliveau
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001288:Attention / Q000502:physiology; D001303:Auditory Cortex / Q000502:physiology*; D001306:Auditory Pathways / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010700:Phonetics; D013017:Sound Localization / Q000502:physiology; D013037:Spatial Behavior / Q000502:physiology; D013997:Time Factors