Neural Noise- Peripheral and brain stimulation can be combined to restore somatosensory function.1
Weekly enrichment (2026-07-20)
- A within-participant study directly compared intracortical microstimulation (ICMS), peripheral nerve stimulation (PNS), and mechanical indentation in one man (20s, C3/C4 AIS-B sensory-incomplete, motor-complete spinal cord injury) enrolled in the Reconnecting the Hand and Arm to the Brain (ReHAB) trial (NCT03898804).2
- His implant included two 64-channel (8×8) Blackrock Neurotech microelectrode arrays in Brodmann area 1 of left primary somatosensory cortex (hand region) for ICMS, plus 16-channel composite flat interface nerve electrodes (C-FINEs) around the right median and ulnar nerves for sensory PNS.2
- Stimuli were cathodal-first, charge-balanced 50 Hz pulse trains of 1 s: ICMS used a 200 µs pulse width with amplitude swept 0–100 µA (100 µA safety limit), while PNS amplitude was fixed daily near threshold (~0.5–0.6 mA) with pulse width varied 50–250 µs, all kept under Shannon charge-safety limits.2
- Percepts were sampled at 30%, 60%, and 90% of each modality’s sensory dynamic range across 30-trial blocks (3 repetitions × 3 modalities × 3 levels plus 3 catch trials), 4–5 blocks per session; 13 trials (11 PNS, 1 mechanical, 1 ICMS) were excluded for involuntary muscle spasm.2
- Key result: ICMS evoked more localized percepts and felt qualitatively closer to natural touch, whereas PNS evoked higher-intensity, more reliable percepts; PLS-SEM modeling indicated perceived naturalness depends more on intensity and quality than on stimulation parameters, behaving as a higher-order cognitive construct.2
- Clinical implication: ICMS may better convey naturalistic/affective touch and object properties while PNS may deliver more consistent feedback during closed-loop functional tasks; PNS is also less invasive than the craniotomy ICMS requires and is a viable option for incomplete SCI, where roughly 47% of people with tetraplegia retain partial below-injury sensation.2
- Complementary 2026 work on combining brain and spinal stimulation, a “double neural bypass,” linked an intracortical BCI with patterned spinal cord stimulation and activity-informed intracortical microstimulation (“cortical mirroring”) in a C4-sensory/C5-motor complete tetraplegia participant, restoring self-feeding plus significant, persistent gains in elbow flexion and wrist tactile sensation that outlasted system use.3
- The originating ReHAB proof-of-concept implanted six 64-channel intracortical arrays and nine 16-channel peripheral nerve electrodes in a C3–C4 tetraplegia participant, demonstrating bidirectional read/write: cortical decoding of movement intent, S1 microstimulation producing repeatable finger percepts, and nerve stimulation driving functional muscle contractions under brain control.4