In this protocol we demonstrate how to fabricate and condition tetrodes for use with a micro-drive array, which was designed for chronic electrophysiological recordings in rats. In addition, we illustrate the final stages of micro-drive array construction, which includes installing ground wires and a protective cone.
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Method Article
Micro-drive Array for Chronic in vivo Recording: Tetrode Assembly
In This Article
Summary
Abstract
The tetrode, a bundle of four electrodes, has proven to be a valuable tool for the simultaneous recording of multiple neurons in-vivo. The differential amplitude of action potential signatures over the channels of a tetrode allows for the isolation of single-unit activity from multi-unit signals. The ability to precisely control the stereotaxic location and depth of the tetrode is critical for studying coordinated neural activity across brain regions. In combination with a micro-drive array, it is possible to achieve precise placement and stable control of many tetrodes over the course of days to weeks. In this protocol, we demonstrate how to fabricate and condition tetrodes using basic tools and materials, install the tetrodes into a multi-drive tetrode array for chronic in-vivo recording in the rat, make ground wire connections to the micro-drive array, and attach a protective cone onto the micro-drive array in order to protect the tetrodes from physical contact with the environment.
Protocol
1. Fabrication of tetrodes
- Begin the construction of one tetrode by obtaining a 50 cm long, polyimide insulated, ni-chrome wire with a 12.5 micron diameter core. Fold the wire in half. Run your fingers along the pair to make them stick together. Make sure the pair of wires have good contact throughout their entire length.
- Fold the pair again by holding the two ends together. Make sure that the loop formed on one end is not kinked. Cut the four wires on the non-looped end so that the four tips are aligned.
- For the next step, you will need a modified alligator clip, a motorized turning device, and a horizontal bar above the turning d....
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Discussion
This protocol is the second installment of a two part protocol: “Micro-drive array for chronic in-vivo recording.” The combination of the micro-drive array and tetrode is a powerful tool for obtaining simultaneous recordings of many neurons in an awake, behaving animal preparation. Hopefully, we have provided you with all the necessary information for you will need to begin or improve electrophysiological recordings in your own laboratory.
The motorized tetrode twister device wa.......
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Acknowledgements
We would like to acknowledge Jun Yamamoto for his design and construction of the automatic, motorized tetrode twister device depicted in the video. In addition, we would like to acknowledge all past and present Wilson Lab members for their contributions to micro-drive and tetrode technology development in the lab.
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Materials
| Name | Company | Catalog Number | Comments | |
|---|---|---|---|---|
| Panavise | Tool | Panavise | Model 301 | Holds either micro-drive array or serrated scissors |
| Modified Xcelite 378M Pliers | Tool | Newark Inc | 96F8903 | For inserting connector board pins. To make, remove 2mm from one tip of the pliers. |
| Slow Cure Glue | Material | Great Planes (Champaign, IL) | GPMR6015 | To glue the tetrode to the micro-drive |
| Gold Plating Solution | Material | Neuralynx Inc. | Sifco Selectron Gold NC | Contains gold particles for electroplating |
| Current Generator | Tool | World Precision Instruments, Inc. | A365D-B | A.K.A. Stimulus Isolator. Used to electroplate gold solution onto electrode tips. |
| Impedance Meter | Tool | BAK Electronics | IMP-1 / 6662 / 2788 | To check impedance of electrodes |
| Hot Air Gun | Tool | Steinel (Germany) | HG 3002 LCD | To fuse electrodes together to make tetrode |
| Accu-Tek Carbofib Tip Tweezers | Tool | Aven | 18768 (Pattern 304) | For handling tetrodes |
| Alligator Clip | Tool | Fine Science Tools | 18050-35 | A.K.A. Bulldog serrefine. To clip the tetrodes together during twisting |
| Micro Dissecting Scissors | Tool | Biomedical Research Instruments | 25-1000 | For general cutting of tetrode/electrode wire |
| Iris Toughcut Serrated Scissors | Tool | Fine Science Tools | 14058-09 | For final cut of tetrodes |
| Teflon Coated Stainless Steel Wire | Material | A-M Systems | 790500 | Ground wire |
| 12.5 micron nichrome wire | Material | Kanthal Palm Coast | Rediohm-800 1/4 HARD PAC COATING | Polyimide coated micro-wire for making tetrodes. |
| Tetrode Twister | Tool | Neuralynx Inc. | Tetrode Assembly Station | Increases the speed and consistency of tetrode fabrication. |
| Silver Paint | Material | GC International | 22-023 | For connecting the micro-electrode wires of the tetrode to the connector pins (see Discussion) |
| X-Acto Knife Handle | Material | MSC Direct | X3001 | For constructing a micro-drive holding device. |
| 26 Pin, 2 Row Connector | Material | Mill-Max | 852-10-026-30-001000 | For constructing a micro-drive holding device. |
References
- Gray, C. M., Maldonado, P. E., Wilson, M., McNaughton, B. Tetrodes markedly improve the reliability and yield of multiple single-unit isolation from multi-unit recordings in cat striate cortex. J. Neurosci. Methods. 63 (1-2), 43-54 (1995).
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