Devices

A biologically integrated intracortical electrode (hollow cone with microwires) designed to encourage neurite ingrowth for long-term single-unit recording in humans.

Device — Intracortical

Neurotrophic Electrode (Kennedy cone electrode)

Official site →

BCI · intracortical · single-unit · neurotrophic · cone electrode · Kennedy · cortex · recording · regenerative · array

Neurotrophic Electrode (Kennedy cone electrode)

One-line verdict: A biologically integrated intracortical electrode that encourages neurite ingrowth for long-term single-unit recording, trading channel count and scalability for potential stability.

Quick tags: Recording · Intracortical · Neurotrophic · Species: Human · First implanted: 1990s (reported)

Overview

What it is: The Neurotrophic Electrode (NTE), also known as the cone electrode, is an intracortical neural interface designed to promote neurite growth into a hollow cone containing recording microwires. Rather than relying purely on mechanical compliance or coatings to reduce tissue response, it aims for biological integration (ingrowth) to stabilize the recording interface.

Why it matters: The NTE represents a distinct philosophy from many modern intracortical arrays: invite neurons in rather than repeatedly penetrating tissue with many shanks. It contributed early demonstrations of long-term human single-unit recording and BCI control using very low channel counts.

Most comparable devices: early microwire approaches (signal class), Utah array (contrast in scaling/channel count), regenerative PNI interfaces (conceptual similarity: ingrowth/integration).

Spec Card Grid

Identity

  • Device name: Neurotrophic Electrode (NTE)
  • Canonical ID: BTSD-IMBCI-0009
  • Inventor / key authors: Philip R. Kennedy; Roy A. E. Bakay
  • Org / manufacturer: academic / historical research program
  • First demonstrated (year): ~1990 (reported)
  • First implanted (year): 1990s (reported)
  • Species: human
  • Regulatory / trial status: human research (historical)
  • Primary use: recording
  • Primary target: motor cortex (reported; motor and speech motor areas appear in literature)

Geometry & Architecture

  • Interface type: intracortical neurotrophic (ingrowth)
  • Penetrating?: yes
  • Form factor: hollow cone with internal microwires
  • Array layout: single cone per implant site (very low channel count)
  • Footprint (mm): sub-mm cone tip (typical)
  • Insertion depth (mm): intracortical (depth varies by implant)
  • Shank / lead dimensions: cone-shaped; wire leads exit posteriorly
  • Site spacing (µm): N/A (single site)
  • Tip geometry: hollow cone opening
  • Insertion method: surgical cortical insertion
  • Anchoring method: biological integration via neurite ingrowth
  • Packaging location: historically percutaneous connector/tether (program-dependent)

Electrode & Channel Physics

  • Channel count: ~1–2 channels per electrode (typical)
  • Active sites used (vs total): all
  • Electrode material: glass cone + metal microwires (reported)
  • Site area (µm²): very small (single-unit regime)
  • Impedance @ 1 kHz: high (single-unit recording regime; exact varies)
  • Noise floor / SNR: potentially high SNR when stable units are present
  • Recording modality: spikes (primary), LFP (secondary)
  • Stimulation capability: no (recording-focused)
  • Charge injection limit / safe stim range: N/A

Tissue Interface & Bioresponse

  • Target tissue: cortical neurons
  • BBB disruption: moderate–high (penetrating)
  • Vascular disruption risk: moderate (implant-dependent)
  • Micromotion sensitivity: reduced after successful ingrowth (hypothesis/goal)
  • Gliosis / encapsulation: reported as different from typical rigid arrays; varies with biological response
  • Neuron loss (if reported): not clearly quantified in a single canonical source
  • Foreign-body response mitigation: neurotrophic/ingrowth concept
  • Typical failure mode: unsuccessful/limited ingrowth, loss of viable units, infection risk from percutaneous components

System Architecture

  • Onboard electronics: none (historical configurations)
  • Data path: percutaneous wired tether (historical)
  • Telemetry bandwidth: low (few channels)
  • Sampling rate: spike-capable (kHz range; system-dependent)
  • Power: external
  • Thermal management: N/A
  • Hermeticity: none (percutaneous systems)
  • MRI compatibility: generally no (system-dependent)
  • Surgical complexity: moderate; biologically delicate placement

Performance Envelope

  • Typical yield (acute): low–moderate (very few channels)
  • Typical yield (chronic): variable; can be stable for long durations when integration succeeds
  • Stability over time: high when stable units persist (reported in case-series)
  • Longevity (median / max): multi-year recordings reported
  • Revision / explant: difficult
  • Adverse events (high-level): infection risk from percutaneous leads/connectors
  • Notable demos / tasks: early BCI control and communication demonstrations using low channel count

Clinical / Preclinical Evidence

  • N implanted subjects: very small (case reports / small series)
  • Follow-up duration: months to years
  • Indications: paralysis / locked-in syndrome (experimental)
  • Trial registry: not applicable (pre-modern registry era)
  • Primary outcomes: feasibility of long-term single-unit human recording and control
  • Key limitations of evidence: extremely low channel count; surgical/biological variability; heterogeneous reporting

Engineering Verdict

Strengths:

  • conceptually “regenerative” intracortical interface (biological integration)
  • potential for long-term single-unit stability when successful

Limitations / failure modes:

  • very low information bandwidth (few channels)
  • percutaneous infection risk in historical implementations
  • integration/ingrowth success may be variable

Scaling constraints:

  • scaling channel count is non-trivial
  • surgical complexity and device routing scale poorly

What newer designs try to fix:

  • combine regeneration concepts with higher channel counts
  • fully implantable packaging
  • improve reliability of tissue–electrode coupling without sacrificing density

References

  • Kennedy PR, Bakay RAE. Restoration of neural output from a paralyzed patient by a direct brain connection. NeuroReport. 1998;9(8):1707–1711. doi: 10.1097/00001756-199806010-00007. PubMed: https://pubmed.ncbi.nlm.nih.gov/9665587/
  • Bartels J, Andreasen D, Ehirim P, et al. Neurotrophic electrode: method of assembly and implantation into human motor speech cortex. J Neurosci Methods. 2008. PubMed: https://pubmed.ncbi.nlm.nih.gov/18672003/
  • Kennedy PR, et al. Histological confirmation of myelinated neural filaments within the tip of the neurotrophic electrode after a decade of neural recordings. Front Hum Neurosci. 2020;14:111. doi: 10.3389/fnhum.2020.00111. (Open access copies vary.)