Emg100c

ECG and EMG were recorded both during rests and visual tasks, the signals being amplified, band-pass filtered (ECG: 0.05–35 Hz, EMG: 10–500 Hz) and sampled at 2000 Hz (EMG100C, BIOPAC Systems, Inc., Santa Barbara, CA, USA). ECG was used to assess the heart rate variability (HRV) as an indicator of autonomic reactivity (e.g., due to stress) during the experiments. The variation in the length of intervals between consecutive heartbeats can be utilised to quantify autonomic heart regulation, as well as balance between sympathetic and parasympathetic activation [32 (link)]. The standard deviation in the length of the periods between R peaks (SDNN) was used here to quantify HRV. The individual means in HRV for the various viewing conditions were calculated for statistical analysis.
The raw EMG signals were first filtered to eliminate disturbance from heart signals [20 (link),33 ], then converted by the root-mean-square (RMS) procedure, normalised to submaximal reference contractions, and expressed as %RVE (reference voluntary electrical activity) [24 (link)]. The 10^th percentile of the normalised RMS-values was utilised as an indicator of static muscular activity [19 ,34 (link),35 (link)]. For statistical analyses, the individual differences (in %RVE) between rest and the various viewing conditions were calculated.

Prior to the sacrifice on day 21 posttreatment, stimulating hooked platinum electrodes were placed around the sciatic nerve 5 mm proximal to the crushed site under general anesthesia by sodium thiopental (50 mg/kg—IP—n = 30). The electrical current application started with a monophasic, single, square pulse with a duration of 1 ms and an intensity of 10 μA produced by an electric stimulator (EMG100C, Biopac Systems, Inc., USA). The intensity was gradually increased until the supramaximal stimulation that ensured maximal amplitude was reached (1 mA). After that, the recorded signals were digitally converted, with an MP 150 Biopac System, into data. The recording electrodes were placed in the medial gastrocnemius muscle through a percutaneous puncture, ipsilaterally to the surgical procedure. The positive electrode was applied in the muscle origin, the negative electrode in the muscle insertion (back of the knee), and the ground electrode in the rat's tail. The amplitude was calculated from the baseline to the maximal peak [19 (link)].