An interventional study of Microneurography and Intraneural Microstimulation in Upper Limb Amputation and Healthy Subjects, sponsored by Azienda Ospedaliero, Universitaria Pisana. Recruiting at 1 site in Italy. Open to participants aged 18 Years to 60 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-09.
Sponsored by Azienda Ospedaliero, Universitaria Pisana · Not applicable, Interventional, and Basic science
The goal of this experimental study is to investigate the somatosensory system through intraneural recording and stimulation of the median nerve in healthy volunteers and participants with upper-limb amputation. The main questions it aims to answer are:
Participants will undergo median nerve recordings using microneurography during controlled mechanical tactile stimulation, as well as intraneural microstimulation with specific patterns to evoke near-natural tactile sensations. They will perform perceptual reporting tasks related to stimulus type, intensity, and localization, as well as psychophysical tests under different stimulation conditions. When possible, they will also undergo non-invasive recordings of brain activity using electroencephalography during sensory stimulation.
Participants will attend the laboratory where the entire research protocol will be conducted in a single visit lasting up to 4 hours.
Medical history and a physical examination will be collected. In participants with amputation, additional clinical information from previous neurological assessments will be reviewed (including medical records, nerve conduction velocity data, and ultrasound or MRI examinations required to verify inclusion/exclusion criteria). Psychometric tests will also be administered to assess language abilities, visuospatial skills, and general intelligence, ensuring that participants are able to understand and perform the experimental tasks. If inclusion and exclusion criteria are met, participants will undergo microneurography and/or intraneural microstimulation procedures. Participants will be seated comfortably, with the dominant arm (healthy volunteers) or the residual limb (participants with amputation) supported. A trained medical operator will identify the median nerve using external stimulation and/or ultrasound guidance to assist electrode insertion. The active electrode will be inserted into the nerve, while a reference electrode will be placed in the subcutaneous tissue a few centimeters away. Correct electrode placement will then be refined using intraneural stimulation. Once the nerve fascicle is reached, tactile stimulation of the hand will be used to identify single mechanoreceptive units. Final electrode placement will be confirmed by visual and auditory inspection of the neural signal. The median nerve activity must be clearly distinguishable from background activity when mechanical stimuli are applied to the skin. During electrode insertion, participants will be instructed to remain still until the procedure is completed. The intraneural microstimulation session, performed in both healthy volunteers and participants with upper-limb amputation, is preceded by peripheral neural recordings using microneurography during the presentation of tactile stimuli (e.g., Von Frey filaments). This step is used for accurate nerve localization and preliminary assessment of the receptors and their receptive fields. Once the neural target is identified, participants undergo intraneural stimulation involving the perception and recognition of artificially generated tactile stimuli. These stimuli are delivered via intraneural microstimulation and are derived from mechanoneural transduction, using a sensorized artificial finger interacting with different surfaces to encode surface-dependent tactile information. Participants will be asked to recognize different properties of the presented stimuli. During the tests, electroencephalographic (EEG) activity may be recorded using a 128-channel EEG system, synchronized with the onset of stimulation.
Azienda Ospedaliero, Universitaria Pisana is the lead sponsor of 57 studies on the registry; 10 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Healthy participants
Amputee participants
Exclusion Criteria:
Healthy participants
Amputee participants
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
During MNG session, microneurographic signals are recorded while mechanical tactile stimuli (e.g., Von Frey filaments) are applied. This recording-only task is used to characterize the mechanoreceptor properties, including receptive field mapping, response type, and firing behavior.
Procedure: Microneurography
During INMS session, intraneural microstimulation is delivered via the microelectrode to evoke tactile sensations. Stimulation patterns are generated from sensor-based interactions with different surfaces and are used to assess tactile perception, including stimulus recognition, intensity, and localization in both healthy and amputee participants.
Procedure: Intraneural Microstimulation
Microneurography is a minimally invasive neurophysiological technique that allows direct recording of the electrical activity of single peripheral nerve fibers using specific microelectrodes inserted into the nerve.
Intraneural microstimulation is a minimally invasive neurophysiological technique in which small electrical currents are delivered through a microelectrode inserted into a peripheral nerve to selectively activate nerve fibers and evoke sensory perceptions.
Mechanoreceptor identification success rate
The proportion of experimental sessions in which a single mechanoreceptive afferent is successfully isolated and identified using MNG during controlled mechanical tactile stimulation, expressed as the percentage of successful recordings (%).
Time frame: During the experimental protocol (up to 3 hours)
Mechanoreceptor classification accuracy
The accuracy of mechanoreceptor type classification (e.g., SA1, SA2, RA, PC) based on MNG recordings during mechanical tactile stimulation, expressed as the percentage of correctly classified receptors (%).
Time frame: During the experimental session (up to 3 hours)
Peripheral afferent firing rate during tactile stimulation
The mean firing rate (spikes/s) of mechanoreceptive afferents recorded by MNG during controlled mechanical tactile stimulation.
Time frame: During the experimental session (up to 3 hours)
Tactile mechanical detection threshold
The minimum stimulus intensity (expressed in grams of calibrated Von Frey Hairs) required to evoke a consistent neural response during mechanical tactile stimulation.
Time frame: During the experimental session (up to 3 hours)
Receptive field size of mechanoreceptive afferents
The spatial extent of skin area (mm²) eliciting neural responses during mechanical tactile stimulation mapped via MNG.
Time frame: During the experimental session (up to 3 hours)
Perceived sensory perception during intraneural microstimulation
Participant-reported sensory percepts will be classified into predefined categories (e.g., pressure, vibration, tingling, tapping) and summarized as the frequency and percentage of each sensory class across stimulation conditions.
Time frame: During the experimental protocol (up to 3 hours)
Perceived intensity of tactile sensations elicited during intraneural microstimulation
Participants will rate the perceived intensity of each evoked sensation using a numerical rating scale from 0 (no sensation) to 10 (maximum imaginable intensity). Mean and standard deviation (or median and interquartile range) will be reported for each stimulation condition.
Time frame: During the experimental protocol (up to 3 hours)
Perceived location of tactile sensations elicited during intraneural microstimulation
Participants will indicate the anatomical location of each evoked sensation on a standardized hand map. Responses will be summarized as frequencies and percentages for each anatomical region.
Time frame: During the experimental protocol (up to 3 hours)
Tactile discrimination performance
Discrimination performance will be assessed using a two-alternative forced-choice (2AFC) psychophysical paradigm during intraneural microstimulation. Performance will be quantified using the Elo rating system, a continuous score derived from pairwise stimulus comparisons. The Elo rating has no predefined minimum or maximum value. Higher Elo scores indicate greater discrimination performance.
Time frame: During the experimental session (up to 3 hours)
Event-related potential amplitude during intraneural microstimulation
Event-related potentials (ERPs) elicited by intraneural microstimulation and recorded using 128-channel EEG will be quantified by peak amplitude (µV) of stimulus-locked cortical responses.
Time frame: During the experimental protocol (up to 3 hours)
Event-related potential latency during intraneural microstimulation
Event-related potentials (ERPs) elicited by intraneural microstimulation and recorded using 128-channel EEG will be quantified by peak latency (ms) of stimulus-locked cortical responses.
Time frame: During the experimental protocol (up to 3 hours)
EEG spectral power modulation during intraneural microstimulation
Changes in EEG spectral power recorded using 128-channel EEG during intraneural microstimulation expressed as spectral power (µV²) or percentage change from baseline (%)
Time frame: During the experimental session (up to 3 hours)
Decoding accuracy of tactile stimulation conditions from EEG signals
Machine learning-based classification of tactile stimulation conditions using EEG-derived features (classification accuracy %)
Time frame: During the experimental session (up to 3 hours)
Plan to share: Yes — Upon publication of results, anonymized data and analysis code will be shared to ensure reproducibility.
Supporting information: Study protocol, Analytic code
Time frame: Upon publication of results
Access criteria: Data and code will be available for research purposes upon request to authors.
Started Mar 2024 (actual). Primary completion is estimated for Dec 2026, 33 months after the start.
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Azienda Ospedaliero, Universitaria Pisana