Temporal dissociation across the eye-brain-muscle cascade delineates a preparation window before muscle activation in subacute stroke

Upper-limb motor impairment after stroke is compounded by a disrupted sensorimotor cascade linking visual attention, cortical motor preparation, and peripheral muscle activation. Whether these stages are temporally dissociated in subacute stroke, and whether their timing carries information about the preparation and execution of a reaching action, remains unclear. Thirty subacute stroke survivors and 30 healthy controls performed a full-plane nine-grid reaching task while eye-tracking, electroencephalography (EEG), and surface electromyography (EMG) were recorded synchronously. Three neurophysiological latencies were extracted: first fixation on the target, stimulus-locked lateralized readiness potential (s-LRP) onset, and peripheral muscle activation onset. Compared with controls, patients showed a stepwise delay across the cascade, with delayed visual engagement (616.73 ms vs. 367.86 ms) and delayed peripheral muscle activation (1,080 ms vs. 605 ms) bracketing a cortical preparation window. A random-forest classifier was trained on window-level gaze-timing features, computed separately for each target-presentation and inter-target interval of the task. Under participant-level leave-one-subject-out cross-validation, it achieved an area under the receiver operating characteristic curve (AUC) of 0.973 (95% CI 0.958–0.984) and an accuracy of 0.918, numerically the highest among the five classifiers compared. These findings describe a quantifiable temporal organization of the sensorimotor cascade in the subacute stage of stroke and indicate that gaze timing carries discriminative information about the occurrence of an instructed reaching action. They establish a descriptive, testable framework rather than a demonstrated clinical benefit. Validation in chronic stroke and across independent samples is further required.