The
EMG raw signals were amplified (1000 ×) and band-pass filtered (20 Hz–2 kHz) by a Digitimer D360 amplifier (Digitimer, Welwyn Garden City, Hertfordshire, UK), digitized at a sampling rate of 4 kHz by an analogue-to-digital interface (Micro 1401; Cambridge Electronic Design, UK) and stored on a laboratory computer for off-line analyses. The EMG traces were analysed using customized Signal® version 4.00 (Cambridge Electronic Design, UK) and matlab® version 7.1 (The MathWorks, Natick, USA) selleck screening library software. Participants were comfortably seated in a chair with the arms slightly abducted from the trunk (~45–50 °), the elbow flexed (~90 °) and both forearms in prone position. The right forearm and wrist were tightly attached on the armrest with straps. The right wrist was kept in a neutral position. The right BIBW2992 nmr thumb was slightly abducted, and fingers 2–5 adducted extended at the inter-phalangeal and flexed at the metacarpo-phalangeal joints (~70–80 °). The motor training
task was adopted from previous studies (Agostino et al., 2007, 2008). Participants were first asked to keep their dominant index finger extended and in line with the forearm. Participants were then instructed to produce ballistic finger abductions of their dominant index finger, so as to achieve the highest initial acceleration possible, in response (but not to react immediately) to a ‘go’ signal, given randomly at ~0.2 Hz, and to return to the neutral position. While performing fast abductions with their dominant index finger, participants were instructed to pinch with the 1st and 2nd finger a cylindrical body in order to isometrically recruit at ~5–10% of the maximal voluntary contraction in the contralateral FDIMIRROR (Fig. 2A; Giovannelli et al., 2006; Hübers et al., 2008).
The maintenance of a constant level of isometric contraction in the FDIMIRROR was monitored online by displaying the continuous EMG activity on a PC Hydroxychloroquine clinical trial screen in front of the participants. In each training session 100 movements were collected; 10 consecutive movements were considered as a trial and averaged (Fig. 2A). A rest interval of 10 s was left between trials to avoid fatigue (Fig. 2A). Before starting the motor training, one practice trial was permitted for the participants to become familiar with the experimental setup. In the present study we adopted a simple ballistic motor task with no real requirements for accuracy, just acceleration, as it fitted in well with the possibility to explore the effects of motor practice on the EMG mirroring activity related to fast finger movements. Moreover, although the after-effect of a simple ballistic motor task has been clearly described in terms of changes of corticospinal excitability, i.e. cortical plasticity (Classen et al., 1998; Muellbacher et al., 2001, 2002; Agostino et al.