64-Channel Carbon Fiber Electrode Arrays for Chronic Electrophysiology

Grigori Guitchounts,David Cox

doi:10.1038/s41598-020-60873-y

Abstract

A chief goal in neuroscience is to understand how neuronal activity relates to behavior, perception, and cognition. However, monitoring neuronal activity over long periods of time is technically challenging, and limited, in part, by the invasive nature of recording tools. While electrodes allow for recording in freely-behaving animals, they tend to be bulky and stiff, causing damage to the tissue they are implanted in. One solution to this invasiveness problem may be probes that are small enough to fly under the immune system's radar. Carbon fiber (CF) electrodes are thinner and more flexible than typical metal or silicon electrodes, but the arrays described in previous reports had low channel counts and required time-consuming manual assembly. Here we report the design of an expanded-channel-count carbon fiber electrode array (CFEA) as well as a method for fast preparation of the recording sites using acid etching and electroplating with PEDOT-TFB, and demonstrate the ability of the 64-channel CFEA to record from rat visual cortex. We include designs for interfacing the system with micro-drives or flex-PCB cables for recording from multiple brain regions, as well as a facilitated method for coating CFs with the insulator Parylene-C. High-channel-count CFEAs may thus be an alternative to traditional microwire-based electrodes and a practical tool for exploring the neural code.

Highlights

In order to understand information processing in the brain, scientists must be able to take reliable measurements from the central nervous system (CNS)
We demonstrate the design of 64-channel carbon fiber electrode array (CFEA) and a method for bulk preparation of the recording sites
Our results show the feasibility of producing high channel-count, high-density CFEAs and using them to record evoked activity in rat visual cortex

Summary

Introduction

In order to understand information processing in the brain, scientists must be able to take reliable measurements from the central nervous system (CNS). A further limitation of electrode methods is their invasive nature: implanting large electrode arrays damages the tissue the electrodes are meant to record from[10,11], limiting the yield of recorded neurons, the longevity of the recording quality, and the ability to track the activity of individual neurons over long timescales These are pressing problems for investigations into how the neural code changes during learning, which unfolds over days, weeks or months[12,13,14,15,16,17,18]; or for the creation of practical brain-machine-interfaces (BMIs), which rely on the stability of recorded signals as well as the underlying neural code in order to decode a patient’s thoughts or intended actions[13,19]. We share designs for laser-cut cartridges that facilitate preparation of CFs for insulation with Parylene-C

Methods

Results

Conclusion