Different phases of motor skill learning appear to involve different physiological processes, with long-term potentiation (LTP) occurring at existing synapses in early and cortical reorganization involving synaptogenesis in later phases. Here, we test the evolution of skill learning-dependent changes in motor plasticity and excitability in six subjects trained to perform rapid thumb abductions over 5 d. Plasticity was examined using paired-associative stimulation (PAS) of the median nerve and motor cortex to induce LTP-like [PAS given with an interstimulus interval of 25 ms (PAS25)] or long-term depression (LTD)-like [PAS given with an interstimulus interval of 10 ms (PAS10)] plasticity. Excitability was tested by measuring recruitment of motor-evoked-potentials [input-output (IO) curve] and of short-latency intracortical inhibition (SICI curve), and sensorimotor organization (SMO). Task performance improved continuously over 5 d. After practice on day 1, the PAS25 effect reversed from facilitation to inhibition whereas the slope of the IO curve increased and the level of SICI decreased. These effects on IO curve and SICI were still present or even enhanced before the last practice on day 5, and were not changed by it. The effect of proprioceptive input from the trained muscle on SMO was also strengthened before practice on day 5. In contrast, PAS-induced plasticity was not influenced by motor practice on day 5, and had returned to prepractice values. The interference with PAS-induced plasticity suggests that the initial performance improvement relies on increasing the efficacy of existing synaptic connections. However, the long-lasting changes in the IO curve, SICI curve, and SMO suggest that continued practice enhances performance by changing Motor cortical organization. We hypothesize that new synaptic connections might have formed that allow LTP/LTD-susceptibility to be restored without reducing synaptic strength and performance skill.

Musicians not only have extraordinary motor and sensory skills, but they also have an increased ability to learn new tasks compared with non-musicians. We examined how these features are expressed in neurophysiological parameters of excitability and plasticity in the motor system by comparing the results of 11 professional musicians and 8 age-matched non-musicians. Parameters of motor excitability were assessed using transcranial magnetic stimulation (TMS) to measure motor-evoked potentials (MEPs) together with recruitment of corticospinal projections [input-output curve (IOcurve)] and of short-latency intracortical inhibition (SICIcurve). Plasticity, here defined as change of synaptic effectiveness, was tested by measuring MEPs and IOcurves after paired associative stimulation (PAS), which consists of an electric median nerve stimulus repeatedly paired (200 times at 0.25Hz) with a TMS pulse over the hand motor area. ). Additionally, PAS25 increased and PAS10 decreased the MEP amplitudes and the slope of the IOcurves significantly more in musicians than in non-musicians. This is consistent with a wider modification range of synaptic plasticity in musicians. Together with the steeper recruitment of corticospinal excitatory and intracortical inhibitory projections, this suggests that they regulate plasticity and excitability with a higher gain than normal. Because some of these changes depend on age at which instrumental playing commenced and on practice intensity, they may reflect an increase in number and modifiability of synapses within the motor area caused by long-term musical practice. Using an interstimulus interval of 25 ms (PAS25) or 10 ms (PAS10), this leads to long-term potentiation-or long-term depression-like plasticity, respectively. Musicians showed steeper recruitment of MEPs and SICI (IOcurve and SICIcurve

Low amplitude muscle vibration (0.5 ms; 80 Hz; duration 1.5 s) was applied in turn to each of three different intrinsic hand muscles (first dorsal interosseus, FDI; abductor pollicis brevis, APB; and abductor digiti minimi, ADM) in order to test its effect on the EMG responses evoked by transcranial magnetic stimulation (TMS). Recordings were also taken from flexor and extensor carpi radialis (FCR and ECR, respectively). We evaluated the amplitude of motor evoked potentials (MEPs) produced by a single TMS pulse, short interval intracortical inhibition and facilitation (SICI and ICF) and long interval intracortical inhibition (LICI). TMS pulses were applied 1 s after the start of vibration with subjects relaxed throughout. Vibration increased the amplitude of MEPs evoked in the vibrated muscle (162 ± 6 % of MEP with no vibration; mean ± S.E.M.), but suppressed MEPs in the two non-vibrated hand muscles (72 ± 9 %). Compared with no vibration (test response reduced to 51 ± 5 % of control), there was less SICI in the vibrated muscle (test response reduced to 92 ± 28 % of control) and more in the non-vibrated hand muscles (test response reduced to 27 ± 5 % of control). The opposite occurred for LICI: compared with the no vibration condition (test response reduced to 33 ± 6 % control), there was more LICI in the vibrated muscle (test response reduced to 17 ± 3 % control) than in the non-vibrated hand muscles (test response reduced to 80 ± 11 % control) even when the intensity of the test stimulus was adjusted to compensate for the changes in baseline MEP. There was no effect on ICF. Cutaneous stimulation of the index finger (80 Hz, 1.5 s duration, twice sensory threshold) had no consistent differential effect on any of the parameters. We conclude that vibratory input from muscle can differentially modulate excitability in motor cortical circuits.

HADES is a versatile magnetic spectrometer aimed at studying dielectron production in pion, proton and heavy-ion induced collisions. Its main features include a ring imaging gas Cherenkov detector for electron-hadron discrimination, a tracking system consisting of a set of 6 superconducting coils producing a toroidal field and drift chambers and a multiplicity and electron trigger array for additional electron-hadron discrimination and event characterization. A two-stage trigger system enhances events containing electrons. The physics program is focused on the investigation of hadron properties in nuclei and in the hot and dense hadronic matter. The detector system is characterized by an 85 % azimuthal coverage over a polar angle interval from 18• to 85• , a single electron efficiency of 50 % and a vector meson mass resolution of 2.5 %. Identification of pions, kaons and protons is achieved combining time-of-flight and energy loss measurements over a large momentum range. This paper describes the main features and the performance of the detector system.

The integration of brain monitoring based on electroencephalography (EEG) into everyday life has been hindered by the limited portability and long setup time of current wearable systems as well as by the invasiveness of implanted systems (e.g. intracranial EEG). We explore the potential to record EEG in the ear canal, leading to a discreet, unobtrusive, and user-centered approach to brain monitoring. The in-the-ear EEG (Ear-EEG) recording concept is tested using several standard EEG paradigms, benchmarked against standard onscalp EEG, and its feasibility proven. Such a system promises a number of advantages, including fixed electrode positions, user comfort, robustness to electromagnetic interference, feedback to the user, and ease of use. The Ear-EEG platform could also support additional biosensors, extending its reach beyond EEG to provide a powerful health-monitoring system for those applications that require long recording periods in a natural environment.