The Role of Alpha- and Delta-Band Oscillations in Speech Perception Under Visual Interference
Poster No:
821
Submission Type:
Late-Breaking Abstract Submission
Authors:
Kaile Zhang1, Gang Peng1
Institutions:
1The Hong Kong Polytechnic University, Hong Kong, China
First Author:
Co-Author:
Introduction:
Speech perception often relies on context cues to resolve ambiguity, such as interpreting Cantonese level tones based on a speaker's pitch height (Wong et al., 2003). This context-dependent calibration, extracting pitch from contexts to adjust target perception, is cognitively demanding (Nusbaum et al., 1997). Yet, listeners often succeed even in multitasking conditions (e.g., conversing while monitoring traffic). This study investigates how brain oscillations support context-dependent speech perception with visual interference.
Methods:
Thirty-two native Cantonese speakers (mean age: 20.52) completed a dual-task experiment. In the primary task, participants identified an ambiguous Cantonese word with mid-level tone (/ji33/, "meaning," 450 ms) embedded in auditory contexts (呢個字係 "this word is …") spoken in high, mid, or low pitch heights. Context-dependent perception was expected: /ji22/ (low tone) in high- and /ji55/ (high tone) in low- pitch contexts. Simultaneously, they did a visual search task, detecting a white diamond in a 4×4 (low load) or 8×8 (high load) grid of shapes (Bosker et al., 2017). Auditory context together with visual picture preceded the target word. Participants did the auditory task first, then the visual task. EEG was recorded using a 64-channel cap. Event-related spectral perturbation (ERSP) was computed via Fast Fourier Transform with Hanning tapering, time-locked to target onset (-500 to 800 ms; baseline: -300 to -100 ms), across 1–50 Hz (1-Hz steps).
Results:
Participants' tone identification was context-dependent: /ji55/ dominated in low-, /ji33/ in mid-, and /ji22/ in high-pitch contexts (ps < 0.001). Visual task accuracy exceeded chance (50%) under low (M = 0.91, SE = 0.013) and high (M = 0.70, SE = 0.013) loads, confirming secondary task engagement. Tone perception was comparable across conditions, unaffected by visual tasks (ps > 0.05). Non-parametric permutation tests on ERSP revealed that, without visual task, tone perception elicited alpha-band (8–13 Hz) desynchronization in prefrontal and parietal-occipital regions (0–415 ms). With visual distraction, alpha-band synchronization emerged in parietal-occipital areas (low load: 246–800 ms; high load: 159–800 ms), with stronger activation in high load (515–665 ms, p < 0.05). High-load conditions also showed delta-band (1–3 Hz) inhibition in the prefrontal cortex (303–565 ms).
Conclusions:
Our findings underscore that the dynamic modulation of alpha and delta oscillations is critical for robust speech perception in multitasking. Alpha power decreases signify cortical activation, while increases reflect inhibition of irrelevant processes (Klimesch, 2012). Here, context-dependent tone identification without visual task induced alpha desynchronization in prefrontal and parietal-occipital regions, indicating focused auditory process. However, when paired with visual task, the parietal–occipital region, integral to visual sensory process, exhibited pronounced alpha synchrony in an auditory task. This alpha increase likely represents an inhibition of visual process, thereby mitigating their disruptive impact. The graded enhancement in the high-load condition (notably between 515 and 665 ms), reveals how the brain scales its inhibitory response in accordance with the degree of interference.
In addition, high-load tone calibration showed delta-band (1–3 Hz) inhibition in the prefrontal cortex (303–565 ms). Delta enhancement signals internal focus, but its suppression is linked to heightened attention to external environment (Jiang et al., 2021). Thus, In the prefrontal cortex, key for attention and multitasking (Burgess et al., 2005; Koechlin et al., 1999), this delta reduction likely shifts resources from internal visual processing to external auditory demands. Together, parietal-occipital alpha synchrony inhibits irrelevant visual processes, while prefrontal delta suppression prioritizes auditory process, supporting a robust speech perception amidst visual interference.
In addition, high-load tone calibration showed delta-band (1–3 Hz) inhibition in the prefrontal cortex (303–565 ms). Delta enhancement signals internal focus, but its suppression is linked to heightened attention to external environment (Jiang et al., 2021). Thus, In the prefrontal cortex, key for attention and multitasking (Burgess et al., 2005; Koechlin et al., 1999), this delta reduction likely shifts resources from internal visual processing to external auditory demands. Together, parietal-occipital alpha synchrony inhibits irrelevant visual processes, while prefrontal delta suppression prioritizes auditory process, supporting a robust speech perception amidst visual interference.
Language:
Speech Perception 1
Novel Imaging Acquisition Methods:
EEG 2
Keywords:
Electroencephaolography (EEG)
Hearing
Language
Perception
1|2Indicates the priority used for review
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Provide references using APA citation style.
Burgess, P. W. (2005). The gateway hypothesis of rostral prefrontal cortex (area 10) function. In Measuring the Mind: Speed, control, and age (Vol. 15, Issue 1, pp. 217–248). Oxford University Press.
Jiang, Y. (2021). Changes in delta and theta oscillations in the brain indicate dynamic switching of attention between internal and external processing. ACM International Conference Proceeding Series, 25–31.
Klimesch, W. (2012). Alpha-band oscillations, attention, and controlled access to stored information. Trends in Cognitive Sciences, 16(12), 606–617.
Koechlin, E. (1999). The role of the anterior prefrontal cortex in human cognition. Nature, 399(6732), 148–151.
Nusbaum, H. (1997). Talker Normalization : Phonetic Constancy as a Cognitive Process. In K. A. Johnson & J. W. Mullennix (Eds.), Talker variability and speech processing (pp. 109–132). Academic Press.
Wong, P. C. M. (2003). Perceptual normalization for inter- and intratalker variation in cantonese level tones. Journal of Speech, Language, and Hearing Research, 46(2), 413–421.