Short-term neurovascular and electrophysiological responses to combined visual and vibration stimulation in older...

Mild cognitive impairment (MCI) is associated with age-related alterations in neural oscillatory activity and cerebral hemodynamics, while mobility limitations often restrict participation in conventional exercise-based interventions. This study investigated exploratory, single-arm, within-subject short-term neurovascular and electrophysiological responses to a combined visual and vibration stimulation protocol in older adults with MCI. Cerebral blood flow was assessed using near-infrared spectroscopy (NIRS) in 27 participants, and electroencephalography (EEG) was additionally recorded in a subgroup of nine participants (n = 9) drawn from the same cohort. The intervention consisted of simultaneous 40 Hz visual flicker and low-frequency mechanical vibration delivered during a seated condition. Changes in total hemoglobin concentration and EEG power in predefined frequency bands were analyzed before and after the intervention, with additional time-window analyses to examine temporal dynamics. At baseline, NIRS revealed higher total hemoglobin levels in the left prefrontal cortex compared with the right. Following the intervention, total hemoglobin decreased significantly in both hemispheres, with a larger reduction observed in the right hemisphere. Time-resolved analyses demonstrated an earlier hemodynamic response in the right hemisphere, followed by a delayed response in the left. EEG analyses showed a reduction in frontal gamma-band power accompanied by an increase in theta-band power in temporoparietal regions after the intervention. These electrophysiological changes were stable across time windows. Together, these findings suggest that short-term combined visual and vibration stimulation was associated with asymmetric and time-dependent changes in cerebral hemodynamics and neural oscillatory activity in older adults with MCI. This non-volitional stimulation approach may provide a feasible experimental framework for investigating brain responses in aging populations with limited mobility. Given the exploratory, uncontrolled design, acute measurement window, and small EEG subgroup, these findings should be interpreted as hypothesis-generating rather than as evidence of clinical or neuroplastic efficacy.