Regaining Motor Control in Musician's Dystonia by Restoring Sensorimotor Organization

Professional musicians are an excellent human model of long term effects of skilled motor training on the structure and function of the motor system. However, such effects are accompanied by an increased risk of developing motor abnormalities, in particular musician's dystonia. Previously we found that there was an expanded spatial integration of proprioceptive input into the hand area of motor cortex (sensorimotor organisation, SMO) in healthy musicians as tested with a transcranial magnetic stimulation (TMS) paradigm. In musician's dystonia, this expansion was even larger, resulting in a complete lack of somatotopic organisation. We hypothesised that the disordered motor control in musician's dystonia is a consequence of the disordered SMO. In the present paper we test this idea by giving pianists with musician's dystonia 15 min experience of a modified proprioceptive training task. This restored SMO towards that seen in healthy pianists. Crucially, motor control of the affected task improved significantly and objectively as measured with a MIDI piano, and the amount of behavioural improvement was significantly correlated to the degree of sensorimotor re-organisation. In healthy pianists and non-musicians, the SMO and motor performance remained essentially unchanged. These findings suggest a link between the differentiation of SMO in the hand motor cortex and the degree of motor control of intensively practiced tasks in highly skilled individuals

Vibrotactile-auditory interactions are post-perceptual

Vibrotactile stimuli can elicit compelling auditory sensations, even when sound energy levels are minimal and undetectable. It has previously been shown that subjects judge auditory tones embedded in white noise to be louder when they are accompanied by a vibrotactile stimulus of the same frequency. A first experiment replicated this result at four different levels of auditory stimulation (no tone, tone at detection threshold, tone at 5 dB above threshold, and tone at 10 dB above threshold). The presence of a vibrotactile stimulus induced an increase in the perceived loudness of auditory tones at three of the four values in this range. In two further experiments, a 2-interval forced-choice procedure was used to assess the nature of this cross-modal interaction. Subjects were biased when vibrotaction was applied in one interval, but applying vibrotaction in both intervals produced performance comparable to conditions without vibrotactile stimuli. This demonstrates that vibrotaction is sometimes ignored when judging the presence of an auditory tone. Hence the interaction between vibrotaction and audition does not appear to occur at an early perceptual level

A simulation model of time-dependent plasma-spacecraft interactions

A plasma simulation code is presented that models the time-dependent plasma properties in the vicinity of a spherical, charged spacecraft. After showing agreement with analytic, steady-state theories and ATS-6 satellite data, the following three problems are treated: (1) transient pulses from photoemission at various emission temperatures and ambient plasma conditions, (2) spacecharge limited emission, and (3) simulated plasma oscillations in the long wavelength limit

Tremor in motor neuron disease may be central rather than peripheral in origin

BACKGROUND AND PURPOSE: Motor neuron disease (MND) refers to a spectrum of degenerative diseases affecting motor neurons. Recent clinical and post-mortem observations have revealed considerable variability in the phenotype. Rhythmic involuntary oscillations of the hands during action, resembling tremor, can occur in MND, but their pathophysiology has not yet been investigated. METHODS: A total of 120 consecutive patients with MND were screened for tremor. Twelve patients with action tremor and no other movement disorders were found. Ten took part in the study. Tremor was recorded bilaterally using surface electromyography (EMG) and triaxial accelerometer, with and without a variable weight load. Power spectra of rectified EMG and accelerometric signal were calculated. To investigate a possible cerebellar involvement, eyeblink classic conditioning was performed in five patients. RESULTS: Action tremor was present in about 10% of our population. All patients showed distal postural tremor of low amplitude and constant frequency, bilateral with a small degree of asymmetry. Two also showed simple kinetic tremor. A peak at the EMG and accelerometric recordings ranging from 4 to 12 Hz was found in all patients. Loading did not change peak frequency in either the electromyographic or accelerometric power spectra. Compared with healthy volunteers, patients had a smaller number of conditioned responses during eyeblink classic conditioning. CONCLUSIONS: Our data suggest that patients with MND can present with action tremor of a central origin, possibly due to a cerebellar dysfunction. This evidence supports the novel idea of MND as a multisystem neurodegenerative disease and that action tremor can be part of this condition

Cooperatively breeding cottontop tamarins (Saguinus oedipus) do not donate rewards to their long-term mates

This study tested the hypothesis that cooperative breeding facilitates the emergence of prosocial behavior by presenting cottontop tamarins (Saguinus oedipus) with the option to provide food rewards to pair-bonded mates. In Experiment 1, tamarins could provide rewards to mates at no additional cost while obtaining rewards for themselves. Contrary to the hypothesis, tamarins did not demonstrate a preference to donate rewards, behaving similar to chimpanzees in previous studies. In Experiment 2, the authors eliminated rewards for the donor for a stricter test of prosocial behavior, while reducing separation distress and food preoccupation. Again, the authors found no evidence for a donation preference. Furthermore, tamarins were significantly less likely to deliver rewards to mates when the mate displayed interest in the reward. The results of this study contrast with those recently reported for cooperatively breeding common marmosets, and indicate that prosocial preferences in a food donation task do not emerge in all cooperative breeders. In previous studies, cottontop tamarins have cooperated and reciprocated to obtain food rewards; the current findings sharpen understanding of the boundaries of cottontop tamarins’ food-provisioning behavior