title: The topography of frequency and time representation in primate auditory cortices.
abstract: Natural sounds can be characterised by their spectral content and temporal modulation, but how the brain is organized to analyse these two critical sound dimensions remains uncertain. Using functional magnetic resonance imaging, we demonstrate a topographical representation of amplitude modulation rate in the auditory cortex of awake macaques. The representation of this temporal dimension is organized in approximately concentric bands of equal rates across the superior temporal plane in both hemispheres, progressing from high rates in the posterior core to low rates in the anterior core and lateral belt cortex. In A1 the resulting gradient of modulation rate runs approximately perpendicular to the axis of the tonotopic gradient, suggesting an orthogonal organisation of spectral and temporal sound dimensions. In auditory belt areas this relationship is more complex. The data suggest a continuous representation of modulation rate across several physiological areas, in contradistinction to a separate representation of frequency within each area.
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Simon
authors.initials: S
authors.lastname: Baumann
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Olivier
authors.identifier: http://orcid.org/0000-0002-5818-6552
authors.initials: O
authors.lastname: Joly
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Adrian
authors.initials: A
authors.lastname: Rees
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Petkov
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Li
authors.initials: L
authors.lastname: Sun
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Alexander
authors.initials: A
authors.lastname: Thiele
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Griffiths
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001303:Auditory Cortex / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D008251:Macaca; D008297:Male; D013997:Time Factors
keywords: amplitude modulation; auditory cortex; fMRI; macaque; neuroscience; tonotopy; topography