Background/Objectives: This study evaluated the effects of a tactile-discrimination compensatory real-time feedback device on hand sensorimotor function in cervical spinal cord injury patients. The study assessed changes in hand numbness, dexterity, and electroencephalogram (EEG) activity, particularly γ-wave power in the sensorimotor area during skilled finger movements. Methods: Three patients with cervical spinal cord injury who presented with hand sensorimotor dysfunction underwent treatment with this device. All cases underwent the intervention using an AB design; A is the exercise task without the system device, and B is the exercise task under the system device. To confirm the reproducibility and minimize the influence of confounding factors, a multiple-baseline design, in which the intervention period was staggered for each subject, was applied. To determine efficacy, the hand numbness numerical rating scale, peg test, and EEG were measured daily, and Tau-U calculations were performed. Results: In two of three cases, moderate or very large changes were observed in numbness in B. In all cases, there was a large or very large change in the peg test results in the B. Regarding EEG activity, the non-skilled participants showed amplification of γ-wave power in the sensorimotor area during the B. Conversely, in the skilled participants, the γ-wave power of the sensorimotor area was attenuated during skillful movements. Conclusions: These findings indicate that the ability of the brain to compare and align predictive control with sensory feedback might be compromised in patients with damage to the afferent pathways of the central nervous system. Moreover, the use of this device appears to have played a role in supporting functional recovery.

Background/Objectives: Post-stroke impairment (PSI) frequently causes upper limb sensorimotor deficits, including reduced ability to perceive fingertip friction, limiting dexterous movements. We evaluated the effects of a tactile sensory substitution device (“Yubi-Reco”) that delivers real-time fingertip friction information to both temporal bones via vibration and explored potential neurophysiological changes in PSI. Methods: This study used a single-case experimental multiple-baseline design. Three participants with PSI completed a 15-day AB-phase protocol. Baseline (A) consisted of daily sensorimotor tasks without Yubi-Reco, while the intervention (B) added real-time friction feedback via Yubi-Reco to the same tasks. Outcomes included electroencephalography (gamma power), the Purdue Pegboard Test, finger numbness Numerical Rating Scale (NRS), Motor Activity Log-14 (Amount of Use [AoU], Quality of Movement [QoM]), and sense of agency (SoA). Effect sizes were calculated using Tau-U. Results: Very large changes were observed in Purdue Pegboard Test performance (Tau-U = 0.80), and large changes were observed in finger numbness NRS scores (Tau-U = 0.79). Case I showed increased gamma power across frontal and central sites, Case II demonstrated relative attenuation near right frontal and parietal sites, and Case III showed bilateral central gamma reduction, suggesting neurophysiological alterations near recorded sites. AoU and SoA improved in all participants. AoU exceeded the minimal clinically important difference (0.5 points) in two cases. Conclusions: Real-time sensory substitution feedback using Yubi-Reco may improve upper-limb sensorimotor function and induce preliminary neurophysiological changes in individuals with PSI. The intervention appeared to enhance dexterous movement ability and SoA, which coincided with preliminary, exploratory neurophysiological shifts across sensorimotor networks.