Cortical neuromodulation by vibration-induced illusion of movement is observed in older individuals, but not in individuals with acute stroke: a cross-sectional fNIRS study

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BACKGROUND: Together with the aging of the world population, stroke incidence is expected to increase in the coming years. Stroke is frequently associated with sensorimotor impairments of the upper limb, including proprioceptive deficits, that substantially impair motor control and quality of life. Understanding how physiological aging and acute stroke affect proprioceptive processing is therefore crucial for developing targeted rehabilitation strategies. METHODS: Vibration-induced illusion of movement was administered to 28 young, 30 older, and 23 individuals with acute stroke to the distal tendon of the triceps brachii. In healthy participants, vibration was applied to both arms, whereas in participants with acute stroke, it was applied to the paretic left arm. Vibration-induced illusion of movement was delivered either with or without visual feedback of the vibrated arm. Each condition consisted of six 15-s vibrations at 80 Hz. The illusion was quantified using the Standardized Kinesthetic Illusion Procedure scale, while cerebral hemodynamic activity within frontoparietal and sensorimotor areas was assessed using fNIRS through changes in (de)oxyhemoglobin concentrations. Subsequently, activation profiles were established, and group cerebral hemodynamics and functional neural efficiency were compared. RESULTS: Older adults exhibited more extensive bilateral activation in the frontoparietal and sensorimotor cortices compared with young adults, suggesting age-related changes in neural recruitment during proprioceptive processing. In contrast, participants with acute stroke showed no significant task-related cortical activation and displayed an overall reduction in cerebral activity compared with both healthy groups. Despite this reduced activation, neural efficiency in participants with acute stroke was comparable to that observed in older participants. CONCLUSION: Together, these findings suggest that preserved compensatory mechanisms may still be engaged early after stroke, and suggest potential implications of vibration-induced illusion of movement to limit age-related proprioceptive decline and to support early rehabilitation after stroke. CLINICAL TRIAL REGISTRATION: NCT06218563-2024-01-12.

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