Long latency EMG responses in hand and leg muscles: cerebellar disorders.

Friedemann, H.-H.; Noth, Johannes; Diener, Hans-Christoph; Bacher, M.

doi:10.1136/jnnp.50.1.71

Cited by 53 publications

(20 citation statements)

References 15 publications

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“…Latencies for long-latency postural EMG responses following perturbation on platform tilt have been reported by several groups (e.g. [6,26]. For the TA, values of 120 ms [19], 80-120 ms [22], 73-110 ms [13] and 119.2 ms [5] have been reported.…”

Section: Ur Onset Latenciesmentioning

confidence: 73%

Classical conditioning of postural reflexes

Kolb

Lachauer

Maschke

et al. 2002

Pfl�gers Archiv European Journal of Physiology

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Unexpected external perturbations of body equilibrium elicit compensatory postural reflexes. The reflex patterns change only minimally, even after repetitive perturbations. This study addressed the question of whether classical conditioning can alter the reflex patterns. In the first session 27 healthy subjects were tested when standing on an unexpectedly tilting platform. Electromyographic (EMG) activity from different leg muscles and the vertical ground forces, from which the centre of vertical pressure (CVP) was computed, were recorded. In a subsequent session subjects were tested using the classical conditioning paradigm with the tilting platform as the unconditioned stimulus (US) and a prior auditory signal as the conditioning stimulus (CS). The decay of the unconditioned response (UR) observed in the first session was similar and small in all subjects. During conditioning, 22% of the subjects established conditioned responses (CR) in all muscles recorded (strategy 1). UR amplitudes of the anterior tibialis (TA) decayed more than in the first session. The resulting CVP excursions were similar to those observed in US-alone trials. The remaining subjects exhibited CR only in the gastrocnemius muscle but developed a substantial decay of UR, resulting in very small CVP excursions (strategy 2). Our data suggest that processing of US-preceding conditioning stimulus leads to different strategies in the control of postural adjustment with assumed underlying associative and non-associative plastic processes.

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Section: Ur Onset Latenciesmentioning

confidence: 73%

Classical conditioning of postural reflexes

Kolb

Lachauer

Maschke

et al. 2002

Pfl�gers Archiv European Journal of Physiology

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“…A likely explanation was that individual EMG traces were analyzed rather than average responses as in most previous studies on stretch evoked response 59 19 Therefore, parameters (200 ms fixed EMG integral, time to peak and peak amplitude) were quantified for the entire early agonist burst.…”

Section: Resultsmentioning

confidence: 99%

Predictive control of muscle responses to arm perturbations in cerebellar patients

Timmann

2000

Journal of Neurology, Neurosurgery &Amp; Psychiatry

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Objectives-To examine changes in predictive control of early antagonist responses to limb perturbations in patients with defined lesions of the cerebellum. Methods-Eight cerebellar patients and eight sex and age matched control subjects participated. Subjects held a handle that was rotated around the elbow joint. They were instructed to hold the forearm at 90°fl exion against a mechanical perturbation. Extensor torque (5 Nm) was applied for 140 ms (pulse), or for 1400 ms (step) through an external motor. Motor responses were tested under two diVerent conditions of anticipatory information. In the expected condition, subjects anticipated and received a pulse. Under the unexpected condition, subjects expected steps, but received unexpected pulses. Biceps and triceps EMG as well as angular kinematics were compared between expected and unexpected pulse perturbations to quantify possible eVects of prediction. Results-In all healthy subjects, the degree of overshoot in the return flexion movement was significantly less in expected pulse perturbations compared with unexpected trials. The degree of amplitude reduction was significantly smaller in the patient group than in the control group (22.8% v 40.0%). During the expected trials, latency of peak triceps activity was on average 20% shorter in the control group, but 4% larger in the cerebellar patients. Conclusions-In the expected condition, controls achieved a significant reduction in angular amplitude by generating triceps activity earlier, whereas the ability to use prediction for adjusting early antagonist responses after limb perturbation was impaired in cerebellar patients. (J Neurol Neurosurg Psychiatry 2000;69:345-352)

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“…Indeed, several studies are suggesting that longlatency reflexes are enhanced in cerebellar disease. [91][92][93] Although this mechanism seems to be the most important mechanism, some arguments do also advocate an additional central oscillator mechanism for cerebellar tremor.…”

Section: Cerebellar Tremor Cerebellar (Intention) Tremor Is Diagnosedmentioning

confidence: 99%

Pathophysiology of nonparkinsonian tremors

2002

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Patients with nonparkinsonian tremors are the second largest group treated with functional neurosurgery. We summarize the present pathophysiological knowledge of these conditions. Essential tremor (ET) may be due to oscillations within the olivocerebellar circuit. There is experimental evidence from animal models for such a mechanism, and clinical data indicate an abnormal function of the cerebellum in ET. Cerebellar tremor may be closely related to the tremor seen in advanced ET. The malfunction of the cerebellum causes a pathological feed-forward control. Additionally an oscillator within the cerebellum or its input/output pathways may cause cerebellar tremor. Almost nothing is known about the pathophysiology of dystonic tremor. Holmes tremor is based on a nigral and a cerebellar malfunction and presents clinically as the combination of tremor in Parkinson's disease and cerebellar tremor. Neuropathic tremor can be extremely disabling and is thought to be due to an abnormal interaction of the disturbances within the periphery and abnormal cerebellar feedback. Unlike the case of Parkinson's disease, functional neurosurgery of nonparkinsonian tremors is not yet based on a solid pathophysiological background.

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Long latency EMG responses in hand and leg muscles: cerebellar disorders.

Cited by 53 publications

References 15 publications

Classical conditioning of postural reflexes

Classical conditioning of postural reflexes

Predictive control of muscle responses to arm perturbations in cerebellar patients

Pathophysiology of nonparkinsonian tremors

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