Labview 2016

LFP, electromyogram (EMG), and accelerometer (ACC) signals and video were monitored continuously from video-EEG device for offline processing. Intracranial electrode signals were fed through a high input impedance, DC-cut at 1 Hz, gain of 1000, 16-channel amplifier and digitized at 20 kHz (Xcell, Dipsi, Cancale, France) for half of the recordings and through a Blackrock Cereplex System using the Cereplex Direct Software Suite (version 7.0.6.0) developed by Blackrock Microsystems (Salt Lake City, UT, USA) for the second half, together with a synchronization signal from the ultrasound scanner. LFP signals were pre-amplified and digitized onto the animal’s head which prevent artifacts originating from cable movement. Custom-made software based on LabVIEW 2016 (National Instruments, Austin, TX, USA) simultaneously acquired video from a camera pointed at the recording stage. A regular amplifier was used, and no additional electronic circuit for artifact suppression was necessary. A large bandwidth amplifier was used, which can record local field potentials in all physiological bands (LFP, 0.1–2 kHz). The spatial resolution of LFPs ranges from 250 µm to a few mm radius.

External kinetics were recorded on a bespoke instrumented ergometer with load cells at the handle, seat, and footplates and a rotary encoder on the flywheel (Murphy 2009 ; Buckeridge et al. 2012 (link)). Kinematic data was simultaneously recorded with a ten-camera optical motion tracking system, operating at 100 Hz (‘MX T-series’, Vicon, Oxford, Uk), and a four receiver ‘extended range’ EM tracking system operating at 75 Hz (‘Flock of Birds’, Ascension Technologies, VT, USA). The lab was arranged for a large capture volume (36 m³). The EM system transmitter was located 1 m to the right of the ergometer slide rail and 1.25 m above the floor on a wooden tower (Figure 1). OMC data was streamed to Vicon Nexus 1.8.5 software, while ergometer outputs and EM data were streamed to a custom data acquisition program (LabView 2016, National Instruments, TX, USA). Real-time feedback was displayed to athletes and researchers during testing (McGregor et al. 2016 (link)).Figure 1.

Diagram of OMC marker and EM receiver layout during rowing trials. Top-down view of sensors affixed to the instrumented ergometer (left). Anterior and posterior views of sensors as applied to subject anatomical landmarks (right). Relative position of key stroke occurrences (catch, mid-slide, release) is indicated to the left of the slide rail

During each ingestive session, the drinkometer recorded the change of the meal volume on the scale of time, using the LabVIEW 2016 software (National Instruments). At the end of the study, all recordings were pooled and processed into an in-house–built algorithm (44 (link)) in Matlab R2016b software (MathWorks) for noise filtering and identification of sucks, bursts (i.e., group of sucks), and intervals separating them (ISI and IBI). First, the optimal burst PC was visualized and identified by PDF and Gaussian mixture models fitted to the frequency histograms log_e transformed ISI (49 (link)). Second, the identified PC was used to compute the microstructure of meal intake. Sucks can be visualized as complex waveforms representing the rate of fluid delivery into the mouth from the reservoir. Characteristics of the entire meal, as well as the number, size, duration, and rate of sucks, are PC independent, whereas the number, size, duration, rate of sucking bursts, and the lengths of within-meal pauses (ISI and IBI) are PC dependent.

Ultrasound data is observed in real time and recorded on the EPIQ 7C Ultrasound System (Philips; Amsterdam, Netherlands). Force data is observed in real time and recorded with LabVIEW 2016 software (National Instruments; Austin, Texas, United States). Given a new orthostatic position of the subject, the orthogonal incidence angle of the force-coupled ultrasound probe with the long axis of the IJV is noted on the LabVIEW interface in terms of yaw and pitch. This angle of incidence is to be maintained throughout each compression in the given orthostatic position. When recording, three quick compressions are applied to IJV. Then, the user slowly and linearly ramps up force to slightly more than what is necessary for complete occlusion of the IJV. Then, one quick compression is applied. These steps are taken to provide recognizable artifacts in the ultrasound images and the force signal for synchronization later. When the Valsalva maneuver is performed by the subject, the only difference is that the subject does it during only the force sweep using the CR410 digital manometer (EHDIS Car Accessory Co. Ltd.; Guangdong, China) to read the airway pressure applied during the Valsalva.

A black Plexiglas elevated cross-maze (79 cm from the floor, 58 × 5.5 cm maze arms) contained a 3D printed food well connected via tubing to a computer-controlled pellet delivery apparatus (Lafayette Instruments, Lafayette, IN, USA) which provided sucrose rewards (one 45 mg sucrose pellet; TestDiet, Richmond, IN, USA) at the ends of the two goal arms. The maze was controlled remotely with LabVIEW 2016 software (National Instruments, Austin, TX, USA). Each maze arm was hinged such that its proximal end (i.e., the segment closest to the maze center) could be raised and lowered by computer control. During the choice epoch, both goal arms were available; during the return epoch, only one start arm was available to guide the rat back to the start arm. A black curtain with visual cues attached surrounded the maze.