Study on the Correlation between Adult Auditory Language Comprehension and Resting-State Alpha Wave Power

Academic Background and Research Question

Although individual differences in adult language processing have been documented in literature, the neural basis largely remains to be explored. Existing research primarily focuses on how general cognitive abilities, demographics, and other factors affect language comprehension, but how intrinsic brain activity leads to individual differences is less studied. This paper aims to fill this research gap by investigating the relationship between resting-state alpha wave activity and adult sentence comprehension. Alpha wave oscillations regulate cortical excitability, thereby enhancing brain information processing efficiency. Although resting-state alpha wave activity has been shown to correlate with cognitive performance, its association with auditory language comprehension remains unclear. The authors aim to explore the relationship between resting-state alpha wave activity and individual differences in sentence comprehension.

Literature Source and Author Information

This academic paper is authored by Jarrad A.G. Lum, Michael P. Barham, and Aron T. Hill from the Cognitive Neuroscience Unit of the School of Psychology, Deakin University. The paper was accepted on February 12, 2024, and published online on May 21, 2024, in the journal “Cortex.” The publication was executed by Elsevier and released under a CC BY license.

Research Subjects and Methods

The study involved 80 healthy adult participants (mean age 25.8 years, SD = 7.2 years), all native English speakers. Resting-state alpha wave activity was recorded via electroencephalogram (EEG) while participants viewed neutral stimulus images for 3 minutes. Participants then completed a language comprehension task, listening to and understanding “grammatically simple” subject-relative clauses and “grammatically complex” object-relative clauses. Real-time processing demands were recorded using pupillometry, with greater pupil dilation indicating higher processing load.

The study followed these steps: 1) recording resting-state alpha waves, and 2) conducting the sentence comprehension task where sentences were presented via computer speakers while processing demand changes were recorded. Pupillometry was used to monitor real-time changes in processing demand, and EEG recorded brain activity. Additionally, specialized software and algorithms were designed for data analysis.

Experimental Procedure

Participants first underwent a 3-minute resting-state EEG recording, with the EEG electrode system arranged according to the 10-10 international system, and data collected at a sampling rate of 2048Hz. Following this, participants completed 110 sentence comprehension tasks, listening to sentences and judging whether the semantics matched images on the screen. To reduce predictability, semantically congruent and incongruent filler sentences were included in the experimental design.

For the preprocessing of pupillometry data, left and right pupil sizes were averaged, and any missing data at a given time point were not included in subsequent averages. Pupil data were segmented into different time periods, including baseline, pre-relative clause, relative clause, post-relative clause, and response segments. Pupil data from these segments were correlated with resting-state alpha wave power to determine individual differences in sentence comprehension processes across different time periods.

Data Processing and Analysis

EEG data were preprocessed through steps such as resampling, bandpass filtering, and artifact removal. The Welch method was used to convert time series data to the frequency domain for power calculation (mv^2). The FOOOF algorithm was employed to remove non-periodic signals, ultimately extracting 8-13Hz alpha wave power. For pupillometry data, preprocessing steps included baseline correction and averaging for different segments. All statistical analyses were conducted using JASP software, employing Spearman’s correlation coefficient to calculate the relationship between pupillometry data and resting-state alpha wave power, with multiple comparison corrections (FDR correction).

Research Results

Preliminary analyses indicated significantly lower accuracy, longer reaction times, and greater pupil dilation for object-relative clauses compared to subject-relative clauses. Results showed a significant positive correlation between resting-state alpha wave power and pupil size in the post-relative clause segment for subject-relative clauses, with related electrodes mainly concentrated in the occipital region. For object-relative clauses, a positive correlation was found in both the relative clause and post-relative clause segments.

Main Conclusions

The study suggests that resting-state alpha wave power is closely related to individual differences in adult auditory language comprehension, with this association being more pronounced when processing complex sentence structures. Resting-state alpha wave power contributes to understanding how the brain’s intrinsic functional architecture influences individual differences in language processing. These findings lay the groundwork for further exploration of language processing capabilities in populations with language disorders.

Research Highlights

The study reveals the regulatory role of resting-state alpha wave power in sentence comprehension, providing new evidence for the influence of intrinsic brain functional architecture on language understanding. Furthermore, the study combines pupillometry and EEG data, offering a detailed analysis of the relationship between resting-state alpha wave power and online sentence processing load.

Other Valuable Information

Exploratory analyses further confirmed the influence range of resting-state alpha wave power and explored the relationship of other frequency bands (theta and beta waves), reaction time, and accuracy. No significant correlation was found between resting-state alpha wave power and factors such as pupil baseline size and participant handedness, enhancing the reliability of the research results.

Research Contribution and Value

This study provides important insights into how resting-state alpha wave power influences individual differences in language comprehension. It also points out directions for future research involving populations with language disorders, suggesting that resting-state alpha wave power could become a crucial indicator of language processing ability.

Through meticulously designed experimental procedures and rigorous data analysis methods, the research offers comprehensive and detailed evidence of the relationship between brain functional architecture and language comprehension. Future research can further verify the applicability of resting-state alpha wave power in different populations and its potential clinical application value.