EDDS Microdrive System

EDDS Microdrive System

Introduction

The EDDS Microdrive System is a mechanical guide for chronically implantable Microelectrode Arrays.

It allows precise movement, simplifies the implantation procedure and increases the flexibility and quiality of chronic recording.

The EDDS Microdrive System provides a mechanical positioning system for chronically implanted 1D, 2D and 3D arrays. Both Microelectrode Arrays (MEA) and Linear Microelectrode Array (LMA) are available for use with it.

Compared to fixed implants the EDDS Microdrive allows precise repositioning of the electrodes in depth, which increases the yield and flexibility during chronic recordings.

Description
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Metal Type

W
Tungsten
Pt/Ir
Platinum
Iridium
Ir
Pure Iridium
TEFLON SHUTTLE

The lexan cap allows visibility without removal and protects the drive from debris, when the animal is placed in its cage.

PROTECTIVE CAP

The recording array is fixed to a teflon shuttle which fits precisely into the case, hence, avoiding any sideways tilt and smooth positioning of the array. Depth is controlled by a single screw. One turn of the screw provides 282µm of travel.

CONNECTOR

The connector is typically mounted near the base of the case allowing for easy implantation. Other connector mounting schemes are possible at the request of the researcher.

CASE

The case houses the mechanics and provides a precise guide for the array. Since it is transparent the electrodes can be visualized to some degree. The base of the case is covered with a transparent, thin sheet of silicone which seals and protects the drive against leakage up the electrodes.

Specifications

Key Design

Key Design
Item Value
Material Lexan/Stainless Steel/Silicone
Weight 1.4g (without cap), 1.8g (with cap)
Footprint 11.5x10mm
Max. footprint of the array 4x3mm (ext. to 5x4mm if neccesary)
Height 15.5mm
Maximal travel ~7.5mm
Depth travel per turn 282μm

Advantages

  • Allows many channels to be implanted in small species.
  • Allows for arrays to be repositioned precisely in depth.
Results and Data

The following information was provided by University of Maryland at College Park.

Data from 1st Implant (Dual Screw)
Number of electrodes 32
Recording duration ~2 months
Movement range ~4mm
Number of neurons ~135
Neurons per electrode ~4.2 (over whole depth)
Neurons per working channel ~4.8 (over whole depth)
Signal-To-Noise Ratios Ø7.2 Range (2.2, 25.9)
Data from 2nd Implant (Dual Screw)
Number of electrodes 32
Recording duration ~2 months
Movement range ~6.3mm
Number of neurons ~114
Neurons per electrode ~3.6 (over whole depth)
Neurons per working channel ~5.2 (over whole depth)
Signal-To-Noise Ratios Ø7.6 Range (3.1, 34.2)
Data from 3rd Implant (Single Screw)
Number of electrodes 64
Recording duration ~3 weeks (ongoing)
Movement range ~7.5mm
Coverage of the array >2/3 channels with signals
Neurons per electrode ~3.6 (over whole depth)
[Analisis ongoing]

Cortical Depth Estimulation

Cortical depth is estimated using a combination of techniques. The electrode tip position is known exactly. The depth of the cortical surface is estimated during surgery. A CSD estimate is computed from neural recordings.

Implant Location

Implant location on skull and craniotomy positioned on the ectosylvian gyrus (AI & AFF).

Illustration of Spike Distribution

Visualization of a subset of the recorded depths for the first implant. Largest number of simultaneous cells (30) at time was obtained a few hundred microns deeper.

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