Temporal downscaling of movement reveals duration-dependent modulation of motor preparatory potentials in humans.

Abstract

Voluntary movement requires the coordination of neural circuits that prepare, initiate, and execute motor actions. A well characterized neural marker of this process is the Readiness Potential, a slow negative deflection in scalp recorded electroencephalography that precedes voluntary movement. While the readiness potential has been extensively studied in brief and discrete actions, its temporal and spectral dynamics under conditions of increased movement duration remain poorly understood. In this study, we investigated how the readiness potential is modulated by the duration of voluntary forearm flexions lasting 2, 4, or 6 s. Electroencephalography, electromyographic, and kinematic data were collected from participants performing voluntary movements guided by visual countdown cues. The amplitude and frequency domain characteristics were analysed across multiple motor related cortical sites. Results showed that shorter movement durations elicited greater readiness potential amplitudes and stronger low frequency spectral components. In contrast, longer movements were associated with attenuated readiness potential responses and reduced spectral power, suggesting a more gradual recruitment of preparatory networks. These effects were consistent across participants and independent of inter movement interval variability. Statistical analysis confirmed significant modulation of both early and late readiness potential components across conditions. This study provides novel evidence that the cortical dynamics of motor preparation scale with the temporal demands of the intended action. Our findings establish a foundation for future research exploring the contribution of oscillatory activity, including beta band synchronization, to movement planning. Overall, our results emphasize the importance of time as a functional variable shaping preparatory brain states in voluntary action.