Understanding the functional organization of the human primary auditory cortex (PAC) is an essential step in elucidating the neural mechanisms underlying the perception of sound, including speech and music. Based on invasive research in animals, it is believed that neurons in human PAC that respond selectively with respect to the spectral content of a sound form one or more maps in which neighboring patches on the cortical surface respond to similar frequencies (tonotopic maps). The number and the cortical layout of such tonotopic maps in the human brain, however, remain unknown. Here we use silent, event-related functional magnetic resonance imaging at 7 Tesla and a cortex-based analysis of functional data to delineate with high spatial resolution the detailed topography of two tonotopic maps in two adjacent subdivisions of PAC. These maps share a low-frequency border, are mirror symmetric, and clearly resemble those of presumably homologous fields in the macaque monkey.
Bibliographical noteFunding Information:
Work performed at the University of Minnesota was supported by NIH grants RR08079, EB00331, the Keck Foundation, and the MIND Institute. The authors are grateful to Gregor Adriany for building the surface coil, Frederic Humbert for helping with 7 Tesla measurements, Noam Harel for insightful discussions, and Nikolaus Kriegeskorte and the reviewers for useful comments on the manuscript.