Evaluating time-reversed speech and signal-correlated noise as auditory baselines for isolating speech-specific...

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Cognitive Neuroscience

Background:

• Established neuroimaging techniques like fMRI and ECoG localize speech-specific cortical responses using auditory baselines.
• Signal-correlated noise (SCN) is often more effective than time-reversed (TR) speech as a baseline.
• Functional near-infrared spectroscopy (fNIRS) is a promising imaging technique for pediatric speech and language research, but optimal baselines are unknown.

Purpose of the Study:

• To determine the most effective auditory baseline (TR speech or SCN) for isolating speech-specific brain activation using fNIRS in children.
• To investigate speech processing in the pediatric brain using fNIRS.

Main Methods:

• Twenty-five normally-hearing children (6-12 years) passively listened to normal speech, TR speech, and SCN in an event-related fNIRS paradigm.
• Brain activity was measured across frontal and temporal regions in both hemispheres.
• Stimuli were contrasted against silence, TR speech, and SCN.

Main Results:

• Significant bilateral superior temporal activation was observed when contrasting any stimulus against silence.
• No significant activation was found in the superior temporal cortex when contrasting normal speech against TR speech or SCN in school-age children.
• A left posterior temporal channel showed significantly greater activity for normal speech versus SCN, suggesting potential lateralization.

Conclusions:

• Neither TR speech nor SCN are suitable auditory baselines for functionally isolating speech processing in 6-12 year old children using fNIRS.
• The findings contrast with previous infant studies and highlight the need for different baseline strategies in pediatric populations.
• Further investigation is required to identify appropriate baselines for pediatric fNIRS speech studies.