Surgical Guide -- Silicon probes, chronic neural recording/stimulation

Technical Note

Document Title: Surgical Guide -- Silicon probes, chronic neural recording/stimulation

Document Number: NN-TN-2025-002

Version: 1.0

Date: March 16, 2025

Author: NeuroNexus Technical Support Team

Revision History: N/A (Initial Release)

Status: Approved for Publication

Intended Audience: Researchers conducting chronic neural recordings with NeuroNexus silicon probes

Application Area: Electrophysiology techniques, electrodes, micro-scale neural interfaces, brain-computer interfaces

Associated Resources:

• pdf version of this technical note
• NeuroNexus website

1. Introduction

This technical note provides an overview of general principles for the chronic implantation of NeuroNexus silicon probes. Chronic experiments involve long-term implantation of probes for data collection over extended periods, allowing for longitudinal studies of neural activity.

Detailed surgical procedures vary by laboratory based on experimental design, species, and institutional protocols. This document outlines a general approach to illustrate proper probe handling and configuration within the basic procedural framework. Researchers should adapt these recommendations to their specific methodologies while complying with all applicable ethical and regulatory guidelines.

2. Pre-Surgical Preparations

a. Subject Preparation

• Anesthesia and Analgesia: Follow institutional guidelines for administering anesthesia and analgesia appropriate for the species and study requirements.
• Aseptic Technique: Ensure all surgical instruments and the surgical environment are sterile to prevent infection.
• Stabilization: Secure the subject in a stereotaxic frame to maintain proper positioning during surgery.

b. Surgical Instruments and Materials

• Essential Tools:
  • Fine forceps, scissors, hemostats, scalpels, needle holders
  • High-speed drill with appropriate burrs
  • Micropipette or blunt needle for saline application
• Sterilization Supplies:
  • 70% ethanol, iodine-based solutions (e.g., Betadine)
  • Autoclaved or disinfected instruments
• Grounding and Reference Materials:
  • Stainless steel or Ag/AgCl wires for ground/reference
  • Bone screws for anchoring wires if required

c. Equipment Setup

• Stereotaxic Frame: Ensure a stable setup with auxiliary ear bars and a micromanipulator for controlled probe insertion.
• Microscopy: A dissecting microscope with a cold light source enhances visibility.

3. Surgical Procedure (General Framework)

a. Preparing the Surgical Site

• Positioning: Secure the subject in the stereotaxic frame.
• Scalp Incision: Make an incision to expose the skull.
• Cleaning: Remove the periosteum with a cotton swab and rinse with saline.

b. Craniotomy and Electrode Placement

• Marking and Drilling:
  • Outline the craniotomy location and bone screw positions.
  • Carefully drill the craniotomy, ensuring it is appropriately sized for the probe.
• Screw Placement (if used):
  • Secure bone screws for ground/reference connections, avoiding dural penetration.
• Dura Removal (if required):
  • In some protocols, dura removal facilitates probe insertion.
  • This step may not be necessary for all subjects.
• Probe Insertion:
  • Attach the probe to the micromanipulator.
  • Lower it slowly to minimize tissue dimpling and damage.

c. Securing the Probe

• Stabilization:
  • Once the probe is in place, secure it using dental cement or an appropriate adhesive to prevent movement during the chronic implantation period.
• Connector Placement:
  • Position the connector in a location that minimizes stress on the probe and allows for easy access during recording sessions.

d. Wiring Configuration

• 16-Channel Probes:
  • If using a separate reference electrode, insert a reference wire into a saline-filled craniotomy (contralateral or ipsilateral).
  • If using no separate reference, connect the probe reference input to a bone screw near the site.
• 32-Channel Probes:
  • If using an internal reference, connect the designated reference wire to a bone screw.
  • If disabling the internal reference, modify the connector and follow external referencing steps.
• 64-Channel Probes:
  • Similar to 32-channel probes, with additional considerations for multiple reference wires. Refer to specific wiring configurations provided by NeuroNexus. citeturn0search1

4. Post-Surgical Considerations

a. Immediate Post-Operative Care

• Analgesia: Administer appropriate analgesics as per institutional guidelines.
• Monitoring: Observe the subject during recovery, ensuring normal behavior and absence of distress.
• Housing: Individually house subjects with nesting material to prevent damage to the implant.

b. Data Acquisition

• Impedance Check: Verify proper probe function before recording.
• Signal Quality: Connect the probe to the acquisition system and confirm expected activity.

c. Long-Term Maintenance

• Connector Care: Keep the connector clean and protected when not in use.
• Regular Monitoring: Periodically check the implant site for signs of infection or mechanical issues.