How the feedback works

There are two primary approaches to restoring sensation, both now in human testing.

Intracortical microstimulation (ICMS) targets the somatosensory cortex directly. Electrode arrays in area 1 deliver precisely timed pulses that evoke tactile sensations on specific parts of the phantom hand—a fingertip, the palm, a particular digit. Sequential activation of overlapping electrode pairs can even create motion sensations, helping users sense how prosthetic fingers are moving without looking.

Peripheral nerve interfaces take a different route. Cuff electrodes on residual median and ulnar nerves activate somatotopically—stimulating specific locations produces sensation in corresponding hand regions. These systems have remained stable for over three years in amputees. Longitudinal intrafascicular electrodes (LIFE/TIME) go deeper into the nerve, providing graded touch and slip feedback that users can interpret in real time.

The functional impact

The clinical data—though from small cohorts—are striking. Users with bidirectional BCIs:

• Identify letters and shapes traced on prosthetic fingertips
• Reach and grasp at able-bodied speeds
• Handle delicate objects (cherries, grapes) without visual or audio cues
• Report enhanced prosthetic embodiment—the device feels like part of them
• Experience reduced or eliminated phantom limb pain in chronic cases

The gap

These findings come primarily from single-subject or small studies. There are no large-scale clinical trials with formal registrations (NCT numbers) yet. The technology works in principle. Whether it scales—broader electrode coverage, multicenter validation, long-term stability—is the next question.

Attribution

Research synthesis via Aubrai.