Neurophysiological Functional Connectivity Changes during Difficult Listening in Older and Younger Adults

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Cognitive Aging

Background:

• Aging is associated with difficulties in understanding speech, particularly in noisy environments.
• These challenges are linked to neurophysiological changes in the aging cortex.
• Speech comprehension depends on coordinated activity and functional connectivity across cortical regions.

Purpose of the Study:

• To investigate age-related changes in cortical functional connectivity during speech comprehension in noise.
• To analyze band-specific (Delta, Theta) neural networks and their reorganization under adverse listening conditions.
• To explore the relationship between neural connectivity and time-locked responses to speech stimuli in older adults.

Main Methods:

• Utilized Network Localized Granger Causality (NLGC) on magnetoencephalography (MEG) data.
• Estimated whole-brain cortical source activity and directed functional connectivity.
• Analyzed band-specific connectivity networks and their evolution with listening difficulty.

Main Results:

• Identified distinct Delta (temporofrontal) and Theta (temporoparietal) band networks consistent with the dual-stream auditory model.
• Observed increased recruitment of frontoparietal attention networks in adverse listening conditions.
• Older adults showed increased connectivity in ventral and dorsal auditory streams across all conditions, indicating greater cortical engagement.

Conclusions:

• Findings demonstrate age- and condition-dependent reorganization of speech-related cortical connectivity.
• Increased connectivity in older adults suggests enhanced cortical recruitment to support speech comprehension.
• Connectivity increases in older adults are not explained by central gain mechanisms but by network reorganization.