The study focuses on a set of “pitch-sensitive” regions in human auditory cortex that respond approximately twice as strongly to sounds with a pitch compared with a non-pitch control such as gaussian noise. Although many studies have investigated neural responses to pitch, the large majority of neuroimaging studies have used stimuli with so-called “unresolved harmonics”, which produce a weak pitch percept. Here, we show that pitch-sensitive regions throughout auditory cortex respond mainly to resolved harmonics, the dominant cue for human pitch perception. We also show that when tested with resolved harmonics, pitch-sensitive regions exhibit a distinctive anatomical profile relative to tonotopic landmarks.
Abstract: Pitch is a defining perceptual property of many real-world sounds, including music and speech. Classically, theories of pitch perception have differentiated between temporal and spectral cues. These cues are rendered distinct by the frequency resolution of the ear, such that some frequencies produce “resolved” peaks of excitation in the cochlea, while others are “unresolved”, providing a pitch cue only via their temporal fluctuations. Despite longstanding interest, the neural structures that process pitch, and their relationship to these cues, have remained controversial. Here, using fMRI in humans, we report: 1) Consistent with previous reports, all subjects exhibited pitch-sensitive cortical regions that responded substantially more to harmonic tones than frequency-matched noise. 2) The response of these regions was mainly driven by spectrally resolved harmonics, although they also exhibited a weak but consistent response to unresolved harmonics relative to noise. 3) The response of pitch-sensitive regions to a parametric manipulation of resolvability tracked psychophysical discrimination thresholds for the same stimuli. 4) Pitch-sensitive regions were localized to specific tonotopic regions of anterior auditory cortex, extending from a low-frequency region of primary auditory cortex into a more anterior and less frequency-selective region of nonprimary auditory cortex. These results demonstrate that cortical pitch responses are located in a stereotyped region of anterior auditory cortex, and are predominantly driven by resolved frequency components, in a way that mirrors behavior.