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Updated: Jun 25, 2026
11:15
fMRI Mapping of Brain Activity Associated with the Vocal Production of Consonant and Dissonant Intervals
Published on: May 23, 2017
Human cortical organization for processing vocalizations indicates representation of harmonic structure as a signal
James W Lewis1, William J Talkington, Nathan A Walker
1Center for Advanced Imaging, West Virginia University, Morgantown, West Virginia 26506, USA. jlewis@hsc.wvu.edu
Summary
Detecting harmonic sounds is crucial for communication and survival. This study reveals specific brain regions sensitive to harmonic structure, supporting the idea of spectral templates for processing vocalizations.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Acoustic Signal Processing
Background:
- Harmonic sounds, common in animal vocalizations and speech, are vital for communication and survival.
- Neurons in the auditory cortex are hypothesized to form 'spectral templates' by detecting specific frequency combinations (harmonics).
Purpose of the Study:
- To investigate how harmonic structure contributes to the activation of spectral templates in the human auditory cortex.
- To determine if the harmonics-to-noise ratio (HNR) is a key acoustic feature processed by the auditory system.
Main Methods:
- Utilized functional MRI (fMRI) to observe brain activity.
- Presented participants with both artificial iterated rippled noises (IRNs) and natural animal vocalizations.
- Quantitatively characterized sounds by calculating their global harmonics-to-noise ratio (HNR).
Main Results:
- Identified specific HNR-sensitive regions in the human auditory cortex.
- Observed activation in areas between primary auditory cortices and regions processing human vocalizations.
- Demonstrated that HNR parametrically activates distinct auditory pathways.
Conclusions:
- The harmonics-to-noise ratio (HNR) is a significant acoustic attribute that activates specific neural pathways.
- Findings provide evidence for the existence of spectral templates in the auditory cortex.
- These templates likely play a key role in the hierarchical processing of vocalizations as behaviorally relevant sounds.
Related Concept Videos
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01:21Perceiving Loudness, Pitch, and Location
The human brain perceives pitch through two primary mechanisms reflected in place theory and frequency theory. Each mechanism describes how sound waves are interpreted as specific pitches by the brain, offering insights into the intricate processes of auditory perception.
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01:13The Cochlea
The cochlea is a coiled structure in the inner ear that contains hair cells—the sensory receptors of the auditory system. Sound waves are transmitted to the cochlea by small bones attached to the eardrum called the ossicles, which vibrate the oval window that leads to the inner ear. This causes fluid in the chambers of the cochlea to move, vibrating the basilar membrane.
01:15Auditory Pathway
Auditory pathways constitute the complex neural circuits responsible for transmitting and interpreting auditory information from the peripheral auditory system to the brain. Sound waves are initially captured by the outer ear, funneled through the ear canal, and reach the tympanic membrane (eardrum). These vibrations are transmitted via the middle ear's ossicles to the inner ear's cochlea.
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01:22Hair Cells
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01:09Harmonic Mean
The arithmetic mean is usually skewed towards the larger values in the data set. Therefore, to avoid this inherent bias towards smaller values, the harmonic mean is used.
Take the example of the speed of a car, which is the measure of the rate of distance traveled. If the vehicle traverses the same distance back-and-forth, its average speed equals the total distance traveled divided by the total time taken. However, if the car moves with varying speeds, then the arithmetic mean is more skewed...
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