Ced power 1401

Throughout the experiment, subjects were seated comfortably in a non-reclining chair, with their right hand rested on a cushion. Electromyographic (EMG) activity was recorded from the right first dorsal interosseous (FDI) muscle using Ag/AgCl cup electrodes arranged in a belly-tendon montage. The raw signals were amplified and a bandpass filter was also applied. (20 Hz to 2 kHz (Digitimer, Welwyn Garden City, UK)) Signals were digitised at 5 kHz (CED Power 1401; Cambridge Electronic Design, Cambridge, United Kingdom) and data were stored on a computer for offline analysis (Signal Version 5.10, Cambridge Electronic Design, UK was used).

Bipolar surface EMG was recorded over the TA using electrodes (22 mm diameter, model; Kendall, Tyco Healthcare Group, Mansfield, MA) spaced 2 cm apart. The reference electrode was placed over the medial malleolus, whilst the TA electrodes were placed at one‐third distance of the line between the tip of the fibula and the tip of the medial malleolus (Hermens et al. 2000). All sites were shaved, abraded, and then wiped clean with an alcohol swab prior to electrode placement. The EMG was amplified (×1000), band pass filtered (10–1000 Hz), and sampled at 5 kHz (CED Power 1401, Cambridge Electronic Design, Cambridge, UK). M‐waves were recorded during a 500 msec window, starting 50 msec before anatomical zero. Once M_MAX stimulator was established, all further analyses were performed off‐line.

Participants were comfortably seated in front of a desk. Their right forearm rested on the desk in a neutral position with a slight shoulder abduction and about 60° elbow flexion. The palm and the forearm of the participants were strapped to a custom-made wooden structure which only allowed movement of the thumb. There was a computer monitor placed about 70 cm in front of the participant.
Surface electromyography (BagnoliTM, Delsys, USA) was recorded from the right first dorsal interosseus (FDI), abductor pollicis brevis (APB), abductor digiti minimi (ADM) and extensor pollicis longus (EPL). EMG data were sampled at 5000 Hz (CED Power 1401, Cambridge Electronic Design, UK), amplified, band pass filtered (5–1000 Hz), and stored on a PC for off-line analysis.

The birds were anesthetized with pentobarbital (6.48 mg/ml; 60 μl/10 g body weight) by intraperitoneal injection, and their heads were fixed in a stereotaxic apparatus with ear bars and a beak holder. Then, recording electrodes (Platinum-Iridium wires coated with Teflon with bare tips, 0.127 mm diameter, impedance 5 MΩ) of a wireless dual-channel transmitter (weight: 2.3 g, EPOCH-T2; Biopac Systems Inc., Goleta, CA, United States) were stereotactically implanted into bilateral NCM. The birds were allowed to recover for at least 3 days after surgery before the first recordings. We recorded LFP in freely behaving birds. Each channel of LFP signals was amplified 800-fold, sampled at 100 Hz (voltage range: ± 2.5 mV) with the transmitter, sent to a receiver (EPOCH-RAT-EEG-SYS; Biopac Systems Inc.), and stored on a PC using an acquisition unit (CED Power 1401) and software (Power 1401 and Spike2; Cambridge Electronic Design Ltd., Cambridge, United Kingdom). Figure 1C shows the ERPs elicited by each of the different frequencies in the randomized standard sequence. After all of the experiments, the birds were deeply anesthetized by an overdose of pentobarbital and perfused with 1 × PBS and then 4% paraformaldehyde/1 × PBS. Sagittal sections, 40 μm thick, were cut on a freezing microtome and stained with cresyl violet to verify the electrode position (Figure 1D).

Surface electromyographic (EMG) recordings in a belly-to-tendon montage were made from the APB and the first dorsal interosseus (FDI) muscles of the dominant hand. The raw signal was amplified and filtered with a bandpass filter of 30 Hz to 1 kHz (Digitimer D360; Welwyn Garden City, UK). Signals were digitized at 2 kHz (CED Power1401, Cambridge Electronic Design, UK) and stored on a laboratory computer for offline analysis. Online EMG was used to control for muscle relaxation during data recording and trials showing voluntary muscle activation were discarded from the analysis (<1% of trials). The recordings of the FDI were only displayed on screen during the experiments in order to support the experimenter in holding the coil in a constant position and were not analyzed further.

Evoked muscle responses were assessed by stimulating at threshold intensity and at 1.5 times the threshold intensity. To achieve this, animals were connected to a recording acquisition system (Neuralynx; CED), and to an isolated stimulation unit (A‐M Systems). The threshold value in milliamps (mA) was defined as the minimal amount of current needed to produce an evoked overt bicep contraction. The muscle activity evoked by the cortical epidural electrical stimulation was recorded and 30 triggers at a sampling rate of 20 kHz were acquired (100–300 kHz bandwidth) using Signal software from a commercial system (CED Power 1401, SIGNAL; Cambridge Electronic Design Ltd). Muscle activity was recorded from the biceps muscle group. Similar to the 3‐h stimulation period, during MEP recordings animals were also awake, unrestrained and able to freely move in the chamber. There were three aspects that helped reduce signal noise and variability due to movement artifacts: (i) by using differential recording electrodes, (ii) by recording 60 triggers and then manually selecting 20, enabling the selection of triggers with minimal spontaneous EMG activity (more details in Analysis of electrophysiological recordings section) and (iii) by averaging these 20 selected triggers, which enables a robust response by canceling spontaneous EMG activity from movements.

EMG responses were recorded with Ag-AgCl surface cup electrodes positioned in a tendon-belly configuration over the bulk of the FDI muscle and the first metacarpal-phalangeal joint from the bilateral FDI. The signal was amplified (D360 8-channel amplifier; Digitimer, Welwyn Garden City, Herfordshire, UK) and band-pass filtered (bandwidth, 20–2000 Hz). The signal was then digitized at a frequency of 2000 Hz (CED Power1401; Cambridge Electronic Design, Cambridge, UK), fed to a data acquisition system (Signal version 4.11 for Windows, Cambridge Electronic Design) and stored on a personal computer for off-line analysis. During the experiment, the EMG was monitored on a computer screen and trials with background EMG activity were discarded from further analysis.