Alpha rhythms in the left auditory cortex set the speed limit for speech comprehension
Abstract
Human cognition operates within distinct temporal windows spanning from very short to extremely long. Each cognitive function has its own processing speed range, beyond which performance deteriorates or even becomes impossible. Speech comprehension, as one of the most important cognitive functions in civilized societies, exemplifies this constraint: Performance declines markedly when speech rates exceed about 10 syllables per second. However, the neural mechanisms underlying this speed limit remain unclear. Here, by combining psychophysics, scalp-electroencephalography, transcranial alternating current stimulation (tACS), repetitive sensory stimulation, and stereo-electroencephalography (sEEG), we showed that the intrinsic alpha band activity determined the maximum rate of speech comprehension. In healthy participants, individual alpha frequency (IAF) precisely predicted the speech recognition rate threshold. Crucially, causally accelerating endogenous alpha rhythms via high-definition tACS and rhythmic auditory stimulation shifted this threshold, enhancing comprehension of ultrafast speech. Furthermore, sEEG recordings from the human auditory cortex revealed that this speed-limiting mechanism was locally determined: Faster alpha band activity in the left auditory cortex facilitated stronger neural entrainment to the speech envelope. These findings identify alpha band activity as a fundamental, malleable temporal bottleneck for linguistic processing, suggesting that the brain’s intrinsic sampling rate sets the physiological limit on human communication.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (17)
Yayue Gao
School of Humanities and Social Sciences, Beihang University
Jianing Fan
School of Humanities and Social Sciences, Beihang University
Na Xu
Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, Nanjing Drum Tower Hospital, College of Chemistry and Materials Science
Libo Zhao
Lifang Deng
School of Humanities and Social Sciences, Beihang University
Ruolin Yang
School of Psychological and Cognitive Sciences and Beijing Key Laboratory of Brain-Computer Interface and Mental Health Modulation, Peking University
Luyao Chen
School of Psychological and Cognitive Sciences and Beijing Key Laboratory of Brain-Computer Interface and Mental Health Modulation, Peking University
Zhiwei Jing
Aesthetic Education Center, Beihang University
Tingting Huang
Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary, IRDR International Center of Excellence on Risk Interconnectivity and Governance on Weather, Department of Environmental Science & Engineering
Xiongfei Wang
Department of Neurosurgery, Laboratory for Clinical Medicine, Sanbo Brain Hospital, Capital Medical University
Jing Wang
Hunan Cancer Hospital Changsha China
Pengfei Teng
Center for Functional Neurosurgery and Epilepsy, Sanbo Brain Hospital, Capital Medical University
Peng Cai
School of Psychological and Cognitive Sciences and Beijing Key Laboratory of Brain-Computer Interface and Mental Health Modulation, Peking University
Guoming Luan
Department of Neurosurgery, Laboratory for Clinical Medicine, Sanbo Brain Hospital, Capital Medical University
Yi Du
State Key Laboratory of Cognitive Science and Mental Health, Institute of Psychology, Chinese Academy of Sciences
Qian Wang
Fang Fang