Suppression of enhanced physiological tremor via stochastic noise: initial observations.

Enhanced physiological tremor is a disabling condition that arises because of unstable interactions between central tremor generators and the biomechanics of the spinal stretch reflex. Previous work has shown that peripheral input may push the tremor-related spinal and cortical systems closer to anti-phase firing, potentially leading to a reduction in tremor through phase cancellation. The aim of the present study was to investigate whether peripherally applied mechanical stochastic noise can attenuate enhanced physiological tremor and improve motor performance.

Enhanced corticomuscular coherence by external stochastic noise.

Noise can have beneficial effects as shown by the stochastic resonance (SR) phenomenon which is characterized by performance improvement when an optimal noise is added. Modern attempts to improve human performance utilize this phenomenon. The purpose of the present study was to investigate whether performance improvement by addition of optimum noise (ON) is related to increased cortical motor spectral power (SP) and increased corticomuscular coherence.

Broad-band Gaussian noise is most effective in improving motor performance and is most pleasant.

Modern attempts to improve human performance focus on stochastic resonance (SR). SR is a phenomenon in non-linear systems characterized by a response increase of the system induced by a particular level of input noise. Recently, we reported that an optimum level of 0-15 Hz Gaussian noise applied to the human index finger improved static isometric force compensation.

A battery-driven, low-field NMR unit for thermally and hyperpolarized samples.

Object: The design of a multinuclear low-field NMR unit with variable field strength <6 mT providing accurate spin manipulations and sufficient sensitivity for direct detection of samples in thermal equilibrium to aid parahydrogen-based hyperpolarization experiments.

Materials And Methods: An optimized, resistive magnet connected to a battery or wall-power driven current source was constructed to provide a magnetic field <6 mT. A digital device connected to a saddle-shaped transmit- and solenoid receive-coil enabled MR signal excitation and detection with up to 10(6) samples/s, controlled by a flexible pulse-programming software.

The strength of the corticospinal coherence depends on the predictability of modulated isometric forces.

Isometric compensation of predictably frequency-modulated low forces is associated with corticomuscular coherence (CMC) in beta and low gamma range. It remains unclear how the CMC is influenced by unpredictably modulated forces, which create a mismatch between expected and actual sensory feedback. We recorded electroencephalography from the contralateral hand motor area, electromyography (EMG), and the motor performance of 16 subjects during a visuomotor task in which they had to isometrically compensate target forces at 8% of the maximum voluntary contraction with their right index finger.

Improved sensorimotor performance via stochastic resonance.

Several studies about noise-enhanced balance control in humans support the hypothesis that stochastic resonance can enhance the detection and transmission in sensorimotor system during a motor task. The purpose of the present study was to extend these findings in a simpler and controlled task. We explored whether a particular level of a mechanical Gaussian noise (0-15 Hz) applied on the index finger can improve the performance during compensation for a static force generated by a manipulandum.

Corticomuscular coherence reflects interindividual differences in the state of the corticomuscular network during low-level static and dynamic forces.

In the investigation of corticomuscular coherence (CMC), it remained unclear why some subjects do not present significant CMC. We predicted that such subjects will develop CMC as a result of learning as indexed by improved performance during a visuomotor task. We investigated CMC, cortical motor spectral power (SP), and performance in 14 subjects during isometric compensation of a static force or dynamic force (DF) with their right index finger.

Corticospinal interaction during isometric compensation for modulated forces with different frequencies.

Background: During isometric compensation of modulated low-level forces corticomuscular coherence (CMC) has been shown to occur in high-beta or gamma-range. The influence of the frequency of force modulation on CMC has up to now remained unexplored. We addressed this question by investigating CMC, motor performance, and cortical spectral power during a visuomotor task in which subjects had to compensate a modulated force of 8% of the maximum voluntary contraction exerted on their right index finger.

Role of proprioception and vision in handwriting.

The objective of this study is to better understand the role of proprioception in handwriting and test earlier conclusions stating that the automated shaping of letters was not impaired by the removal of visual control in deafferentation. To this aim we compared the performance of the deafferented patient GL, who suffers from a complete loss of cutaneous and proprioceptive sensation, with that of eight healthy age- and sex-matched subjects. The word "Parallele", written within a short sentence with and without visual control, was quantified using a digital writing tablet.

Beta-range EEG-EMG coherence with isometric compensation for increasing modulated low-level forces.

Corticomuscular synchronization has been shown to occur in beta (15-30 Hz) and gamma range (30-45 Hz) during isometric compensation of static and dynamic (periodically modulated) low-level forces, respectively. However, it is still unknown to what extent these synchronization processes in beta and gamma range are modified with increasing modulated force. We addressed this question by investigating the corticomuscular coherence (CMC) between the electroencephalogram (EEG) and electromyogram (EMG) from the first dorsal interosseus muscle (FDI) as well as the cortical and muscular spectral power during a visuomotor task where different levels of a dynamic (modulated) force were used.

Dopamine release in human neocortical slices: characterization of inhibitory autoreceptors and of nicotinic acetylcholine receptor-evoked release.

The autoinhibitory control of electrically evoked release of [3H]-dopamine and the properties of that induced by nicotinic receptor (nAChR) stimulation were studied in slices of the human neocortex. In both models [3H]-dopamine release was action potential-induced and exocytotic. The selective dopamine D2 receptor agonist (-)-quinpirole reduced electrically evoked release of [3H]-dopamine, yielding IC50 and I(max) values of 23 nM and 76%, respectively.