Journal
JOURNAL OF NEUROSCIENCE
Volume 42, Issue 3, Pages 416-434Publisher
SOC NEUROSCIENCE
DOI: 10.1523/JNEUROSCI.0960-21.2021
Keywords
auditory cortex; fMRI; frequency; pitch; timbre; tonotopy
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Funding
- National Institutes of Health (NIH) [R01 DC005216, P41 EB027061, P30 NS076408, S10 RR026783]
- W.M. Keck Foundation
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Tonotopy, an orderly mapping of frequency, is observed throughout the auditory system. Studies have shown evidence for pitch tuning in certain cortical regions that partially overlap with traditional tonotopic maps of spectral content.
Frequency-to-place mapping, or tonotopy, is a fundamental organizing principle throughout the auditory system, from the earliest stages of auditory processing in the cochlea to subcortical and cortical regions. Although cortical maps are referred to as tonotopic, it is unclear whether they simply reflect a mapping of physical frequency inherited from the cochlea, a computation of pitch based on the fundamental frequency, or a mixture of these two features. We used high-resolution functional magnetic resonance imaging (fMRI) to measure BOLD responses as male and female human participants listened to pure tones that varied in frequency or complex tones that varied in either spectral content (brightness) or fundamental frequency (pitch). Our results reveal evidence for pitch tuning in bilateral regions that partially overlap with the traditional tonotopic maps of spectral content. In general, primary regions within Heschl's gyri (HGs) exhibited more tuning to spectral content, whereas areas surrounding HGs exhibited more tuning to pitch. Significance Statement Tonotopy, an orderly mapping of frequency, is observed throughout the auditory system. However, it is not known whether the tonotopy observed in the cortex simply reflects the frequency spectrum (as in the ear) or instead represents the higher -level feature of fundamental frequency, or pitch. Using carefully controlled stimuli and high-resolution functional magnetic resonance imaging (fMRI), we separated these features to study their cortical representations. Our results suggest that tono-topy in primary cortical regions is driven predominantly by frequency, but also reveal evidence for tuning to pitch in regions that partially overlap with the tonotopic gradients but extend into nonprimary cortical areas. In addition to resolving ambigu-ities surrounding cortical tonotopy, our findings provide evidence that selectivity for pitch is distributed bilaterally through-out auditory cortex.
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