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 and amplitude, as well as temporal resolution using a gap-in-noise detection task. Task accuracy and reaction time will also be evaluated. In selected experimental conditions, electroencephalography (EEG) will be recorded non-invasively from the scalp during electrotactile stimulation to investigate neural responses associated with electrotactile sensory processing.
The results are expected to provide foundational data for sensory assessment, electrotactile feedback design, and sensory-based rehabilitation technologies for older adults and patients with stroke.
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.
Age 55 to 70 years.
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.
Parallel
Electrotactile Sensory Discrimination Tasks
BehavioralParticipants will receive non-invasive electrotactile stimulation through surface electrodes attached to the upper limb, such as the fingertip, palm, elbow, or shoulder, depending on the stimulation condition. Participants will perform sensory discrimination tasks to assess their ability to discriminate changes in stimulation frequency, stimulation amplitude, and temporal gaps in stimulation. Stimulation intensity will be individualized based on each participant's perception threshold and discomfort threshold and will remain below the discomfort threshold throughout the experiment. Task performance, including just noticeable difference, task accuracy, and reaction time, will be recorded.
Just Noticeable Difference for Electrotactile Sensory Discrimination
The just noticeable difference (JND) will be calculated as the minimum detectable difference for electrotactile stimulation frequency and amplitude, and as the threshold for detecting temporal gaps in stimulation during the electrotactile sensory discrimination tasks.
Reaction Time During Electrotactile Sensory Discrimination Tasks
Reaction time will be measured as the time interval between stimulus presentation or response cue and the participant's behavioral response during the electrotactile sensory discrimination tasks.
Effect of Cognitive Load on Electrotactile Sensory Discrimination Performance
In young and older adult participants, electrotactile sensory discrimination performance under the focused condition will be compared with performance under the cognitive load condition.
Accuracy in Electrotactile Sensory Discrimination Tasks
Accuracy will be calculated as the percentage of trials in which participants correctly discriminate electrotactile stimulation frequency, amplitude, or temporal gaps. Accuracy will be compared among young adults, older adults, and participants with stroke.
EEG Evoked Responses to Electrotactile Stimulation
Electroencephalography (EEG) will be recorded during electrotactile stimulation to evaluate stimulus-evoked cortical responses. Event-related EEG components, including N50 and P100, will be analyzed based on their amplitude and latency to characterize neural responses to electrotactile sensory stimulation.
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