Investigating effortful speech perception using fNIRS and pupillometry measures

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Cognitive Neuroscience

Background:

• Mental effort significantly impacts speech perception, particularly in challenging listening conditions.
• Understanding the neural correlates of listening effort is crucial for diagnosing and treating hearing impairments.
• Pupillometry and functional near-infrared spectroscopy (fNIRS) offer objective measures of cognitive load and neural activity.

Purpose of the Study:

• To investigate the neural mechanisms underlying mental effort in speech perception.
• To examine the correlation between pupillometry, fNIRS measures, and behavioral outcomes (task performance and difficulty).
• To differentiate neural responses related to speech processing versus listening effort.

Main Methods:

• Participants with normal hearing listened to sentences with varying grammatical structure and clarity.
• Objective measures of mental effort included pupillometry (pupil dilation) and fNIRS (cerebral oxygenation).
• Subjective task difficulty was assessed via questionnaire, alongside speech perception task performance.

Main Results:

• Pupil dilation positively correlated with task difficulty and negatively with performance, confirming its role in reflecting effort.
• fNIRS measures in the auditory cortex and lateral frontal cortex correlated with speech processing but not with subjective or objective effort measures.
• A significant negative correlation was found between perceived task demands and task performance.

Conclusions:

• Pupillometry is a valid indicator of listening effort and task demands in speech perception.
• fNIRS, in this paradigm, appears to reflect speech processing rather than the cognitive effort involved.
• Future research should explore complementary neuroimaging techniques to fully capture the neural basis of listening effort.