Electrotactile Frequency, Amplitude, and Temporal Gap Discrimination in Young Adults, Older Adults, and Stroke Survivors

The purpose of this study is to evaluate and compare sensory discrimination ability for electrotactile stimulation among young adults, older adults, and patients with stroke. Participants will receive non-invasive electrotactile stimulation through electrodes attached to the skin of the upper limb, such as the fingertip, palm, elbow, or shoulder, depending on the stimulation condition. The study will assess discrimination thresholds for changes in stimulation frequency, stimulation amplitude, and temporal gaps in stimulation, together with task accuracy and reaction time. The results are expected to provide foundational data for sensory assessment, electrotactile feedback design, and sensory-based rehabilitation technologies for older adults and stroke patients.

Inclusion Criteria: * Young Adult Group: * Age 19 to 54 years. * Has tactile sensation in the hands and fingers. * Provides voluntary written informed consent personally or through a legally authorized representative, if applicable. Older Adult Group: * Age 55 to 70 years. * Has tactile sensation in the hands and fingers. * Provides voluntary written informed consent personally or through a legally authorized representative, if applicable. Stroke Patient Group: * Age 19 years or older. * Diagnosis of ischemic or hemorrhagic stroke. * Stroke confirmed by CT or MRI. * Stroke accompanied by proprioceptive sensory impairment. * Residual tactile sensation in the fingertip. * Provides voluntary written informed consent personally or through a legally authorized representative, Exclusion Criteria: * Young and Older Adult Groups: * Absence of tactile sensation in the hands or fingers. * Congenital deformity of the hands or fingers. * Presence of a major pre-existing neurogenic disease. * Presence of a major psychiatric disorder, such as major depressive disorder, schizophrenia, bipolar disorder, or dementia. * Implanted pacemaker. Stroke Patient Group: * Difficulty communicating due to K-MMSE score \< 23, severe language impairment, or similar condition. * Absence of tactile sensation in the hands or fingers. * Congenital deformity of the hands or fingers. * Severe pain during elbow joint or finger movement. * Progressive or unstable stroke. * Presence of hemispatial neglect. * Presence of a major pre-existing neurogenic disease. * Presence of a major psychiatric disorder, such as major depressive disorder, schizophrenia, bipolar disorder, or dementia. * Implanted pacemaker.