Articulation-based sound perception in verbal repetition: a functional NIRS study
1R&D Team, Health and Medical Equipment Business, Samsung Electronics Suwon, South Korea.
Frontiers in Human Neuroscience
|September 19, 2013
Summary
The left inferior frontal gyrus (IFG) processes articulatory codes for verbal repetition. This brain region also shows distinct hemodynamic responses to both speech and non-speech sounds, suggesting sensorimotor integration.
Area of Science:
- Neuroscience
- Cognitive Science
- Psycholinguistics
Background:
- Verbal repetition links listening and speaking.
- Previous research implicated the left inferior frontal gyrus (IFG) in articulation-based codes for speech sound repetition.
- The role of IFG in sound perception alongside articulation requires further investigation.
Purpose of the Study:
- To confirm the role of the left IFG in processing articulatory codes during verbal repetition.
- To investigate whether neural circuits in the IFG are involved in sound perception as well as articulation.
- To explore the neural processing of both speech and non-speech sounds in the IFG.
Main Methods:
- Functional near-infrared spectroscopy (fNIRS) was used to monitor hemoglobin concentration changes in the IFG bilaterally.
- Participants verbally repeated pseudowords and words.
- Participants passively listened to various sounds, including environmental, animal, and human non-speech sounds.
Main Results:
- Repetition of pseudowords, compared to words, led to a significant increase in oxygenated hemoglobin (O2Hb) over total Hb at the left IFG, confirming articulatory code processing.
- Both speech and non-speech sounds elicited hemodynamic modulations in both left and right IFG during passive listening.
- Specifically, O2Hb increased in the left IFG and decreased in the right IFG for both sound types.
Conclusions:
- The left IFG is confirmed to process articulatory codes essential for verbal repetition.
- The IFG appears to be involved in sensorimotor integration for both speech and non-speech sound processing.
- Findings suggest a shared neural mechanism in the left IFG for processing auditory information and articulatory representations.
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