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Phase-Amplitude Coupling Reflects Functional Cortical Engagement During Dynamic and Static Motor Tasks

Authors :

Seyed Saman Sajadi¹ Ahmad Reza Keihani² Fateme Karbasi³ Mohammad Amin Fathollahi⁴ Shahriar Nafissi⁵ Erfan Azizi⁶ Amir Homayoun Jafari⁷

1- دانشگاه علوم پزشکی تهران 2- University of Pittsburgh 3- دانشگاه علوم پزشکی تهران 4- دانشگاه علوم پزشکی تهران 5- دانشگاه علوم پزشکی تهران 6- دانشگاه علوم پزشکی تهران 7- دانشگاه علوم پزشکی تهران

Keywords :

Beta-Gamma Coupling،Theta-Gamma Coupling،Electroencephalography،Muscle Contraction،Motor Control

Abstract :

Phase–amplitude coupling (PAC) links slow oscillatory phases with fast rhythmic amplitudes, offering insight into hierarchical brain coordination during movement. We investigated PAC across cortical regions during static and dynamic hand and foot contractions in fifteen healthy adults using EEG. PAC was quantified with the modulation index and validated through surrogate testing across 24 electrodes spanning frontal, premotor, motor, and occipital regions. Results showed clear task- and effector-specific differences. Static tasks were dominated by beta–gamma coupling in motor and premotor areas, reflecting sustained force control. Dynamic tasks elicited stronger theta–gamma PAC, particularly in motor and premotor regions, consistent with sequencing and planning demands. Occipital theta–gamma PAC emerged selectively during dynamic hand movements, suggesting visuomotor integration, while foot tasks engaged mainly midline motor regions. These findings map the spectral and spatial organization of motor PAC, highlighting its role in flexible motor control and potential relevance for neurological disorders.