Oscillatory power and functional connectivity in the speech change detection network

Area of Science:

• Neuroscience
• Auditory Perception
• Speech Processing

Background:

• The mismatch negativity (MMN) is a neurophysiological measure reflecting automatic auditory change detection.
• Speech perception relies on distinguishing between phonetic categories, a process that can be challenging for within-category variations.

Purpose of the Study:

• To investigate how meaningful speech contrasts influence the neural network dynamics underlying the mismatch negativity (MMN).
• To explore the role of different brain regions and their functional connectivity in processing speech deviants.

Main Methods:

• Utilized passive and active oddball paradigms with across-category (AC) and within-category (WC) speech contrasts.
• Employed independent component analysis (ICA) on continuous electroencephalography (EEG) to analyze power changes and functional connectivity (phase synchronization) between brain sources.

Main Results:

• Easily detected AC deviants elicited a left-lateralized MMN response.
• Difficult-to-detect WC deviants did not elicit a MMN response.
• Analysis revealed distinct power changes in brain regions processing standards versus deviants.
• Increased functional connectivity was observed between orbitofrontal cortex, superior temporal gyrus, and left inferior frontal gyrus (Broca's area).

Conclusions:

• The detectability of speech contrasts significantly impacts MMN generation and neural processing.
• The findings highlight the involvement of specific brain networks, including Broca's area, in processing meaningful speech information and generating MMN.
• Functional connectivity patterns provide insights into the neural dynamics underlying speech sound discrimination.