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:
* How does median nerve activity encode tactile perception during different types of mechanical tactile stimulation in healthy subjects?
* How can tactile information be artificially encoded and restored through intraneural microstimulation in both healthy subjects and upper-limb amputee participants? How rich and functionally meaningful is the restored sensory information?
* What are the neurophysiological mechanisms underlying tactile stimulus processing and the associated patterns of brain activation during tactile stimulation?
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.