McCurdy, J. R. | bioRxiv Science

bioRxiv2026

Motor Intention Drives Corticospinal Facilitation during Interception Planning

Intercepting a moving target requires integrating visual motion information with motor preparation, yet how active motor preparation and gaze strategy jointly shape corticospinal excitability during interception planning remains unclear. We applied single-pulse transcranial magnetic stimulation over primary motor cortex to probe corticospinal excitability while participants either prepared to intercept a moving target or passively viewed its motion. Targets moved at one of two speeds, and participants judged target speed relative to a reference after each trial. Across blocks, participants were instructed to either smoothly pursue the target or fixate their eyes on the interception zone. Motor-evoked potentials were elicited at baseline, after task instruction, early during target motion, or shortly before target arrival. Task and gaze strategy interacted to influence both perceptual judgments and corticospinal excitability. Preparing to intercept produced a robust facilitation of corticospinal excitability immediately before movement onset, regardless of gaze strategy. In contrast, corticospinal excitability during passive viewing did not differ from baseline. Smooth pursuit improved perceptual accuracy and reduced interception timing error compared with fixation but did not independently influence corticospinal facilitation. These findings demonstrate that active motor preparation is the primary determinant of the transition to a state of facilitated excitability during interception planning, whereas eye movements modulate perceptual estimates and support behavioral performance. New & NoteworthyThis study dissociates the contributions of visual tracking, eye movements, and active motor preparation to corticospinal excitability during interception. Here, we show that corticospinal facilitation emerges primarily when an action is planned, whereas passive viewing remains at baseline despite identical visual input. Smooth pursuit enhanced perceptual accuracy and interception timing but had a limited effect on corticospinal excitability, highlighting active motor preparation as the key driver of corticospinal output.

neuroscience↗

bioRxiv2025

Corticospinal excitability during timed interception depends on the speed of the moving target

Successfully intercepting a moving object requires precisely timing the optimal moment to act by integrating information about the targets visual motion properties. Neurophysiological evidence indicates that activity in the primary motor cortex (M1) during interception preparation is sensitive to both the targets kinematic features and motor planning. However, how visual motion signals are integrated within M1 to guide interception timing is unclear. In the present study, we applied single-pulse transcranial magnetic stimulation (TMS) over M1 to examine how a targets kinematics influence corticospinal excitability during interception preparation. Participants were instructed to abduct their right index finger to intercept a target moving horizontally at a constant speed toward a fixed interception zone. Target speed (Fast or Slow) and travel distance (Far or Close) were manipulated while controlling motion duration across conditions. Motor-evoked potentials (MEPs) were elicited at five latencies before target arrival at the interception zone. Consistent with previous behavioral findings, movement initiation occurred earlier for faster targets and was delayed when TMS was applied closer to the targets arrival. Though MEPs were generally suppressed relative to baseline at earlier timepoints and facilitated closer to movement initiation, we observed that target speed--but not distance--influenced the time course of MEP modulation. When adjusting for movement initiation times, there was an overall reduced suppression and increased facilitation for faster-moving targets, possibly reflecting a heightened urgency to move. These results suggest M1 activity during interception preparation integrates internal estimates of target motion, which may serve to optimize interception timing and performance. New & NoteworthyWhen intercepting a moving object, like catching a ball, we need to continuously combine visual motion signals to predict the objects future location and enable accurate movement. Here, we show that preparatory suppression and facilitation of corticospinal excitability depends on the speed, but not the distance, of the moving target. These findings reveal that differences in interception timing are closely linked to changes in motor system excitability.

neuroscience↗