Surgical Guide -- Thin-film grids, ECoG neural recording

Technical Note

Document Title: Surgical Guide – Thin-Film Grids for ECoG Neural Recording

Document Number: NN-TN-2025-003

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 electrocorticography (ECoG) neural recordings using NeuroNexus thin-film grids

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

Associated Resources:

• surgical guide as a pdf document
• NeuroNexus website

1. Introduction

This technical note provides an overview of general principles for the implantation of NeuroNexus thin-film grids designed for electrocorticography (ECoG) neural recordings. ECoG involves placing electrode arrays on the cortical surface to monitor neural activity, offering high spatial resolution and temporal fidelity.

Detailed surgical procedures vary by laboratory based on experimental design, species, and institutional protocols. This document outlines a general approach to illustrate proper grid 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: Administer anesthesia and analgesia following institutional guidelines 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 grid placement.
• 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 Grid Placement

• Marking and Drilling:
  • Outline the craniotomy location and bone screw positions.
  • Carefully drill the craniotomy, ensuring it is appropriately sized for the grid.
• Screw Placement (if used):
  • Secure bone screws for ground/reference connections, avoiding dural penetration.
• Dura Preservation:
  • Preserve the dura mater to protect the cortical surface during grid placement.
• Grid Placement:
  • Gently place the thin-film grid onto the cortical surface, ensuring optimal contact without causing tissue damage.

c. Securing the Grid

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

d. Wiring Configuration

• 16-Channel Grids:
  • 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 grid reference input to a bone screw near the site.
• 32-Channel Grids:
  • 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 Grids:
  • Similar to 32-channel grids, 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 grid function before recording.
• Signal Quality: Connect the grid 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.