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

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.

Sniffing behaviour‐related changes in cardiac and cortical activity in rats

“…; Shikano et al . , ). The electrode assembly was composed of an electrical interface board (EIB) (EIB‐36‐PTB, Neuralynx, Inc., Bozeman, MT, USA) that consisted of an outer cover and a core body, which were custom‐made with 3‐D printers (UP Plus2, Tiertime, Beijing, China; formlabs Form2, Formlabs, Somerville, MA, USA).…”

“…; Shikano et al . , ). Conventionally, the sniff frequency of rodents is quantified based on respiration‐locked intranasal pressure or the temperature of nasal air flow (Clarke et al .…”

Vagus nerve spiking activity associated with locomotion and cortical arousal states in a freely moving rat

“…An electrode assembly including recording and stimulating electrodes was prepared as described previously (Okada et al., ; Sasaki et al., ; Shikano, Sasaki, et al., ). The electrode assembly was composed of an electrical interface board (EIB) (EIB‐36‐PTB, Neuralynx, Inc., Bozeman, MT) that consisted of an outer cover and a core body, which were custom‐made by 3D printers (UP Plus2, Tiertime, Beijing, China; formlabs Form2, Formlabs, Somerville, MA).…”

“…The open ends of the VN electrode were extruded from the incision. After implantation of the VN electrode, all rats underwent surgery to implant the ECG, EMG, BR, and LFP electrodes as described previously (Okada et al., ; Sasaki et al., ; Shikano, Sasaki, et al., ). Briefly, two ECG electrodes (stainless‐steel wires; AS633, Cooner Wire Company, CA) were attached to the intercostal muscles on both sides of the chest (Figure a, ECG), and two EMG electrodes were sutured to the dorsal neck area (Figure a, EMG).…”

“…In addition, VN spikes might be associated with activity states of the central nervous systems. To examine these basic physiological dynamics of the vagus nerve in relation to the central and peripheral organs, we integrated the VN recordings into our recording technique that captures local field potentials (LFPs) from multiple brain regions together with electroencephalogram (ECG), electromyogram (EMG), and breathing (BR) electrical signals (Okada, Igata, Sakaguchi, Sasaki, & Ikegaya, ; Sasaki, Nishimura, & Ikegaya, ; Shikano, Sasaki, & Ikegaya, ). From large‐scale electrophysiological datasets, our analyses specifically addressed physiological issues of how VN spike patterns undergo acute changes in relation to (a) locomotor activity, (b) peripheral organ activity such as heartbeats and respiration, and (c) cortical arousal levels in freely moving rats.…”