scholarly journals Pitch of Harmonic Complex Tones: Rate Coding of Envelope Repetition Rate in the Auditory Midbrain

2018 ◽  
Vol 104 (5) ◽  
pp. 860-864 ◽  
Author(s):  
Yaqing Su ◽  
Bertrand Delgutte
Keyword(s):  
Repetition Rate ◽  
Auditory Midbrain ◽  
Harmonic Complex ◽  
Complex Tones ◽  
Rate Coding

scholarly journals Pitch of harmonic complex tones: rate and temporal coding of envelope repetition rate in inferior colliculus of unanesthetized rabbits

2019 ◽  
Vol 122 (6) ◽  
pp. 2468-2485 ◽  
Author(s):  
Yaqing Su ◽  
Bertrand Delgutte
Keyword(s):  
Inferior Colliculus ◽  
Repetition Rate ◽  
Temporal Coding ◽  
Broadband Noise ◽  
Temporal Code ◽  
Rate Code ◽  
Harmonic Complex ◽  
Phase Lock ◽  
Wide Range ◽  
Complex Tones

Harmonic complex tones (HCTs) found in speech, music, and animal vocalizations evoke strong pitch percepts at their fundamental frequencies. The strongest pitches are produced by HCTs that contain harmonics resolved by cochlear frequency analysis, but HCTs containing solely unresolved harmonics also evoke a weaker pitch at their envelope repetition rate (ERR). In the auditory periphery, neurons phase lock to the stimulus envelope, but this temporal representation of ERR degrades and gives way to rate codes along the ascending auditory pathway. To assess the role of the inferior colliculus (IC) in such transformations, we recorded IC neuron responses to HCT and sinusoidally modulated broadband noise (SAMN) with varying ERR from unanesthetized rabbits. Different interharmonic phase relationships of HCT were used to manipulate the temporal envelope without changing the power spectrum. Many IC neurons demonstrated band-pass rate tuning to ERR between 60 and 1,600 Hz for HCT and between 40 and 500 Hz for SAMN. The tuning was not related to the pure-tone best frequency of neurons but was dependent on the shape of the stimulus envelope, indicating a temporal rather than spectral origin. A phenomenological model suggests that the tuning may arise from peripheral temporal response patterns via synaptic inhibition. We also characterized temporal coding to ERR. Some IC neurons could phase lock to the stimulus envelope up to 900 Hz for either HCT or SAMN, but phase locking was weaker with SAMN. Together, the rate code and the temporal code represent a wide range of ERR, providing strong cues for the pitch of unresolved harmonics. NEW & NOTEWORTHY Envelope repetition rate (ERR) provides crucial cues for pitch perception of frequency components that are not individually resolved by the cochlea, but the neural representation of ERR for stimuli containing many harmonics is poorly characterized. Here we show that the pitch of stimuli with unresolved harmonics is represented by both a rate code and a temporal code for ERR in auditory midbrain neurons and propose possible underlying neural mechanisms with a computational model.

scholarly journals Pitch of Harmonic Complex Tones: Rate-Place Coding of Resolved Components in Harmonic and Inharmonic Complex Tones in Auditory Midbrain

2019 ◽  
Author(s):  
Yaqing Su ◽  
Bertrand Delgutte
Keyword(s):  
Primary Auditory Cortex ◽  
Auditory Pathway ◽  
Sound Level ◽  
Auditory Midbrain ◽  
Harmonic Complex ◽  
Local Maxima ◽  
Firing Rates ◽  
Sound Levels ◽  
Complex Tones ◽  
Frequency Components

AbstractHarmonic complex tones (HCT) commonly occurring in speech and music evoke a strong pitch at their fundamental frequency (F0), especially when they contain harmonics individually resolved by the cochlea. When all frequency components of an HCT are shifted by the same amount, the pitch of the resulting inharmonic tone (IHCT) also shifts although the envelope repetition rate is unchanged. A rate-place code whereby resolved harmonics are represented by local maxima in firing rates along the tonotopic axis has been characterized in the auditory nerve and primary auditory cortex, but little is known about intermediate processing stages. We recorded single neuron responses to HCT and IHCT with varying F0 and sound level in the inferior colliculus (IC) of unanesthetized rabbits. Many neurons showed peaks in firing rates when a low-numbered harmonic aligned with the neuron’s characteristic frequency, demonstrating “rate-place” coding. The IC rate-place code was most prevalent for F0>800 Hz, was only moderately dependent on sound level over a 40 dB range, and was not sensitive to stimulus harmonicity. A spectral receptive-field model incorporating broadband inhibition better predicted the neural responses than a purely excitatory model, suggesting an enhancement of the rate-place representation by inhibition. Some IC neurons showed facilitation in response to HCT, similar to cortical “harmonic template neurons” (Feng and Wang 2017), but to a lesser degree. Our findings shed light on the transformation of rate-place coding of resolved harmonics along the auditory pathway, and suggest a gradual emergence of harmonic templates from low to high processing centers.Significance statementHarmonic complex tones are ubiquitous in speech and music and produce strong pitch percepts in human listeners when they contain frequency components that are individually resolved by the cochlea. Here, we characterize a “rate-place” code for resolved harmonics in the auditory midbrain that is more robust across sound levels than the peripheral rate-place code and insensitive to the harmonic relationships among frequency components. We use a computational model to show that inhibition may play an important role in shaping the rate-place code. We also show that midbrain auditory neurons can demonstrate similar properties as cortical harmonic template neurons. Our study fills a gap in understanding the transformation in neural representations of resolved harmonics along the auditory pathway.

Rabbits use both spectral and temporal cues to discriminate the fundamental frequency of harmonic complexes with missing fundamentals

2021 ◽  
Author(s):  
Joseph D Wagner ◽  
Alice Gelman ◽  
Kenneth E. Hancock ◽  
Yoojin Chung ◽  
Bertrand Delgutte
Keyword(s):  
Fundamental Frequency ◽  
Human Performance ◽  
Spectral Composition ◽  
Pitch Perception ◽  
Wide Frequency Range ◽  
Spatial Gradient ◽  
Harmonic Complex ◽  
Complex Tones ◽  
Behavioral Paradigm ◽  
Animal Vocalizations

The pitch of harmonic complex tones (HCT) common in speech, music and animal vocalizations plays a key role in the perceptual organization of sound. Unraveling the neural mechanisms of pitch perception requires animal models but little is known about complex pitch perception by animals, and some species appear to use different pitch mechanisms than humans. Here, we tested rabbits' ability to discriminate the fundamental frequency (F0) of HCTs with missing fundamentals using a behavioral paradigm inspired by foraging behavior in which rabbits learned to harness a spatial gradient in F0 to find the location of a virtual target within a room for a food reward. Rabbits were initially trained to discriminate HCTs with F0s in the range 400-800 Hz and with harmonics covering a wide frequency range (800-16,000 Hz), and then tested with stimuli differing either in spectral composition to test the role of harmonic resolvability (Experiment 1), or in F0 range (Experiment 2), or both F0 and spectral content (Experiment 3). Together, these experiments show that rabbits can discriminate HCTs over a wide F0 range (200-1600 Hz) encompassing the range of conspecific vocalizations, and can use either the spectral pattern of harmonics resolved by the cochlea for higher F0s or temporal envelope cues resulting from interaction between unresolved harmonics for lower F0s. The qualitative similarity of these results to human performance supports using rabbits as an animal model for studies of pitch mechanisms providing species differences in cochlear frequency selectivity and F0 range of vocalizations are taken into account.

Influence of peripheral resolvability on the perceptual segregation of harmonic complex tones differing in fundamental frequency

2000 ◽  
Vol 108 (1) ◽  
pp. 263-271 ◽  
Author(s):  
Nicolas Grimault ◽  
Christophe Micheyl ◽  
Robert P. Carlyon ◽  
Patrick Arthaud ◽  
Lionel Collet
Keyword(s):  
Fundamental Frequency ◽  
Harmonic Complex ◽  
Complex Tones

Forward masking patterns for harmonic complex tones

1983 ◽  
Vol 73 (5) ◽  
pp. 1682-1685 ◽  
Author(s):  
Brian C. J. Moore ◽  
Brian R. Glasberg
Keyword(s):  
Forward Masking ◽  
Harmonic Complex ◽  
Complex Tones

scholarly journals Distortion products and their influence on representation of pitch-relevant information in the human brainstem for unresolved harmonic complex tones

2012 ◽  
Vol 292 (1-2) ◽  
pp. 26-34 ◽  
Author(s):  
Christopher J. Smalt ◽  
Ananthanarayan Krishnan ◽  
Gavin M. Bidelman ◽  
Saradha Ananthakrishnan ◽  
Jackson T. Gandour
Keyword(s):  
Relevant Information ◽  
Harmonic Complex ◽  
Distortion Products ◽  
Complex Tones
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