Simultaneous Recordings of Cortical Local Field Potentials, Electrocardiogram, Electromyogram, and Breathing Rhythm from a Freely Moving Rat

Summary

This study introduces a method for the simultaneous recording of local field potentials in the brain, electrocardiograms, electromyograms, and breathing signals of a freely moving rat. This technique, which reduces experimental costs and simplifies data analysis, will contribute to the understanding of the interactions between the brain and peripheral organs.

Abstract

Monitoring the physiological dynamics of the brain and peripheral tissues is necessary for addressing a number of questions about how the brain controls body functions and internal organ rhythms when animals are exposed to emotional challenges and changes in their living environments. In general experiments, signals from different organs, such as the brain and the heart, are recorded by independent recording systems that require multiple recording devices and different procedures for processing the data files. This study describes a new method that can simultaneously monitor electrical biosignals, including tens of local field potentials in multiple brain regions, electrocardiograms that represent the cardiac rhythm, electromyograms that represent awake/sleep-related muscle contraction, and breathing signals, in a freely moving rat. The recording configuration of this method is based on a conventional micro-drive array for cortical local field potential recordings in which tens of electrodes are accommodated, and the signals obtained from these electrodes are integrated into a single electrical board mounted on the animal's head. Here, this recording system was improved so that signals from the peripheral organs are also transferred to an electrical interface board. In a single surgery, electrodes are first separately implanted into the appropriate body parts and the target brain areas. The open ends of all of these electrodes are then soldered to individual channels of the electrical board above the animal's head so that all of the signals can be integrated into the single electrical board. Connecting this board to a recording device allows for the collection of all of the signals into a single device, which reduces experimental costs and simplifies data processing, because all data can be handled in the same data file. This technique will aid the understanding of the neurophysiological correlates of the associations between central and peripheral organs.

Introduction

The central nervous system controls body states in response to various environmental changes, and this control is typically represented as changes in heart rate, breathing rate, and muscle contractions. However, few studies have tested how such peripheral physiological factors are associated with cortical activity. To address this issue, a large-scale recording method for monitoring electrical biosignals from both central and peripheral tissues is necessary. In the cerebral cortex, local field potential (LFP) signals are extracellularly recorded by electrodes that are inserted into the cortical tissues^1,2....

Protocol

All of the procedures involving animal subjects were performed according to the NIH guidelines for the care and use of animals.

1. Preparation of the Integrative Micro-Drive Array

1. Create a micro-drive array for cortical LFP recordings as described elsewhere^1,2,3. Leave at least 6 metal holes open on an electrode interface board (EIB) for use as ECG/EMG/BR channels that are connected to bioflex wires as described in 1.2.
2. Cut a bioflex wire into 6 pieces with lengths of 5.0 cm. Peel off the polytetrafluoroethylene (PTFE) coating....

Results

This method can simultaneously capture bioelectrical signals from multiple organs that represent the neuronal activity of the brain, heart rate, breathing rhythm, and skeletal muscle contractions (Figure 1). Figure 4 provides representative recording data from a freely moving rat that was freely foraging in a rectangular box (25 × 40 cm²). The example dataset includes typical behavioral transitions bet.......

Discussion

For understanding how the brain modulates peripheral activity levels, and vice versa, large-scale recording methods to simultaneously capture electrical biosignals from multiple body areas are necessary. This study described a surgical procedure, and a recording system for monitoring cerebral local field potentials, heart rates, the magnitude of muscle construction and respiratory rates, which have been improved on a recording system that is used for extracellular recordings in brain tissue. This system collects electric.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
FEP Hookup Wire Stranded Stainless Steel	Cooner Wire Company, Chatsworth, CA	AS 633	Bioflex wire
EIB-36-PTB	Neuralynx, Inc., Bozeman, MT	EIB-36-PTB	EIB
Cereplex  M	Blackrock  Microsystems, Salt Lake City, UT		Digital headstage
Cereplex Direct	Blackrock  Microsystems, Salt Lake City, UT		Data acquisition system
UEW polyurethane magnet wire	Oyaide.com, Tokyo, Japan	UEW 0.14mm 20m	Enamel wire
SD-102	Narishige, Tokyo, Japan	SD-102	High-speed drill
Minimo ONE SERIES ver.2	Minitor Co.,Ltd, Tokyo, Japan	C2012	High-peed drill Power Supply
Provinice 250 mL	Shofu Inc., Kyoto, Japan	213620136	Dental cement
Small Animal Anesthetizer	Biomachinery, Chiba, Japan	TK-7	Anesthetizer
Buprenorphine hydrochloride	Sigma-Aldrich, St. Louis, MO	B7536-1ML	Analgesic
Isoflurane	DS Pharma Animal Health, Osaka, Japan	Isoflu 250mL
Vaseline, White	Wako Pure Chemical Industries, Ltd., Osaka, Japan	224-00165	Vet ointment
Sodium alginate	Nacalai tesque, Kyoto, Japan	31131-85
Calcium Chloride Dihydrate	Wako Pure Chemical Industries, Ltd., Osaka, Japan	031-00435
Stainless steel screw M1.0×4.0	MonotaRO, Hyogo, Japan	42617504	Stainless steel screw for BR electrodes
Stainless steel screw M1.4×3.0	MonotaRO, Hyogo, Japan	42617687	Stainless steel screw for g/r electrodes and anchors