Mechanical implications of paired motor unit discharges in pathological and voluntary tremor

Elek, J.; Dengler, Reinhard; Konstanzer, A.; Hesse, Stefan; Wolf, W.

doi:10.1016/0168-5597(91)90014-o

Cited by 32 publications

(25 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As explained in , the previously used indices (e.g. Dengler et al 1989; Elek et al 1991) for single MUs, or small groups of MUs, were non‐representative.…”

Section: Discussionmentioning

confidence: 98%

“…Secondly, we examined the impact of the spike doublets and triplets on the FT amplitude. Notably, a coexistence of doublets and overt FT has previously been noticed and examined (Dengler et al 1986, 1989; Elek et al 1991). However, the demonstration of a quantitative relationship between the two phenomena has been complicated by difficulties relating to representative measures of doublet incidence in individual MUs and, more so, in the population of active MUs (see and ).…”

Section: Introductionmentioning

confidence: 85%

“…The FT‐related firing behaviours of MUs in PD have been examined in relatively few early studies, later tremor research having predominantly focused on cerebral activities. These early studies have described abnormal firing patterns exhibiting rhythmical pairs of spikes separated by 20–80 ms in individual MUs, and considered the impact of these spike doublets on the tremor (Das Gupta, 1963; Dietz et al 1974; Dengler et al 1986, 1989; Elek et al 1991); they have also examined the short‐term correlation between MUs (Baker et al 1992). The employed analyses in these pioneering studies have provided a first description of MU firing behaviours and their consequences for the parkinsonian FT.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Tremor‐related motor unit firing in Parkinson's disease: implications for tremor genesis

Christakos

Erimaki

Anagnostou

et al. 2009

The Journal of Physiology

View full text Add to dashboard Cite

Muscle tremors reflect rhythmical motor unit (MU) activities. Therefore, the MU firing patterns and synchrony determine the properties of the parkinsonian force tremor (FT) and the neurogenic components of associated limb tremors. They may also be indicative of the neural mechanisms of tremor genesis which to date remain uncertain. We examined these MU behaviours during isometric contractions of a finger muscle in 19 parkinsonian subjects. Our results reveal that the parkinsonian FT is abnormally large. Like the physiological FT, it is accompanied by in-phase rhythms in all MU activities. However, there exist two important differences. Firstly, the synchrony during the parkinsonian FT is stronger than the normal one and therefore contributes to the FT enhancement. Secondly, the synchronous MU components partly represent rhythmical sequences of spike doublets and triplets whose incidences directly reflect the differences of the MU firing rates to the FT frequency. According to our analyses, the latter frequency coincides with the MU recruitment rate. Consequently, the numerous mediumand small-sized active MUs contribute rhythmical twitch doublets and triplets, i.e. large force pulses, to the parkinsonian FT. The impact of this effect on the FT amplitude is found to predominate over the impact of the augmented synchrony. Importantly, apart from the rule governing the occurrence of doublets/triplets, the mean interspike intervals within such spike events are fairly fixed around 50 ms. Such regularities in MU activities may reflect properties of the neural input underlying the FT, and thus represent a basis for more focused studies of the generator(s) of parkinsonian tremors.

show abstract

“…As explained in , the previously used indices (e.g. Dengler et al 1989; Elek et al 1991) for single MUs, or small groups of MUs, were non‐representative.…”

Section: Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Tremor‐related motor unit firing in Parkinson's disease: implications for tremor genesis

Christakos

Erimaki

Anagnostou

et al. 2009

The Journal of Physiology

View full text Add to dashboard Cite

show abstract

“…The temporal characteristics included the variability in the interval between subsequent tremor bursts (inter-burst interval) and the width of the tremor burst. This was done considering single motor unit spike trains (accounting for the commonly observed behavior of doublet and triplet discharges [21,22,37]) as well as approximations of the compound output of the entire motor unit population (neural drive to the muscle). In this part and throughout the manuscript we define the ratio 7/2/7/1 as the power of the second harmonic of the oscillatory component of the neural drive to muscles in tremor relative to that of the first harmonics.…”

Section: Resultsmentioning

confidence: 99%

“…Next, we consider the more realistic case of tremorogenic oscillations of the neural drive determined by trains of action potentials that present multiple activations for each tremor burst, as is often observed in experimental conditions [21,22]. Here we consider the cases of two and three discharges per burst, henceforth termed doublets and triplets, respectively.…”

Section: >(F)mentioning

confidence: 99%

One central oscillatory drive is compatible with experimental motor unit behaviour in essential and Parkinsonian tremor

et al. 2015

View full text Add to dashboard Cite

Objective. Pathological tremors are symptomatic to several neurological disorders that are difficult to differentiate and the way by which central oscillatory networks entrain tremorogenic contractions is unknown. We considered the alternative hypotheses that tremor arises from one oscillator (at the tremor frequency) or, as suggested by recent findings from the superimposition of two separate inputs (at the tremor frequency and twice that frequency). Approach. Assuming one central oscillatory network we estimated analytically the relative amplitude of the harmonics of the tremor frequency in the motor neuron output for different temporal behaviors of the oscillator. Next, we analyzed the bias in the relative harmonics amplitude introduced by superimposing oscillations at twice the tremor frequency. These findings were validated using experimental measurements of wrist angular velocity and surface electromyography (EMG) from 22 patients (11 essential tremor, 11 Parkinson's disease). The ensemble motor unit action potential trains identified from the EMG represented the neural drive to the muscles. Main results. The analytical results showed that the relative power of the tremor harmonics in the analytical models of the neural drive was determined by the variability and duration of the tremor bursts and the presence of the second oscillator biased this power towards higher values. The experimental findings accurately matched the analytical model assuming one oscillator, indicating a negligible functional role of secondary oscillatory inputs. Furthermore, a significant difference in the relative power of harmonics in the neural drive was found across the patient groups, suggesting a diagnostic value of this measure (classification accuracy: 86%). This diagnostic power decreased substantially when estimated from limb acceleration or the EMG. Signficance. The results indicate that the neural drive in pathological tremor is compatible with one central network providing neural oscillations at the tremor frequency. Moreover, the regularity of this neural oscillation varies across tremor pathologies, making the relative amplitude of tremor harmonics a potential biomarker for diagnostic use.

show abstract

Consensus Statement of the Movement Disorder Society on Tremor

2008

View full text Add to dashboard Cite

Summary: This is a proposal of the Movement Disorder Society for a clinical classification of tremors. The classification is based on the distinction between rest, postural, simple kinetic, and intention tremor (tremor during target-directed movements). Additional data from a medical history and the results of a neurologic examination can be combined into one of the following clinical syndromes defined in this statement: enhanced physiologic tremor, classical essential tremor (ET), primary orthostatic tremor, task-and position-specific tremors, dystonic tremor, tremor in Parkinson's disease (PD), cerebellar tremor, Holmes' tremor, palatal tremor, drug-induced and toxic tremor, tremor in peripheral neuropathies, or psychogenic tremor. Conditions such as asterixis. epilepsia partialis continua, clonus, and rhythmic myoclonus can be misinterpreted as tremor. The features distinguishing these conditions from tremor are described. Controversial issues are outlined in a comment section for each item and thus reflect the open questions that at present cannot be answered on a scientific basis. We hope that this statement provides a basis for better communication among clinicians working in the field and siimulates tremor research. Key Words: Tremor-ClassificationClinical assessment.The present effort has been undertaken to create a common terminology for tremor disorders within the Movement Disorder Society (MDS). The article was discussed during the symposium on tremor in Kiel, Germany, subsequently distributed within the Scientific Issues Committee of the MDS, and finally approved by the EXCO of the MDS. One goal of the MDS is to foster such consensus statements. We hope that this article will be the first of several to be published on different issues.Authorities in the field of tremor differ in their views of tremors because similar observations are interpreted differently. It cannot be the intent of this article to solve all of these controversies because scientific data are lacking for many of them. However, it is our goal to summarize the minimal consensus, to address the controversial issues, and to provide a framework in which unresolved questions can be addressed. Tremor can be classified in different ways. Because of the numerous etiologies for tremor. a practical etiologic classification or a valid physiologic classification is not available. Therefore, the gold standard for tremor research remains clinical classification. We propose to classify tremors according to the traditional approach of clinical neurology. Based on their specific clinical features, tremors are grouped into syndromes that can be separated on the basis of clinical observations alone. This article is based on the assumption that different components of tremor can be separated by clinical observation and need to be described with a common terminology (see 1.1, Definitions of the Phenomenology of Tremor). To achieve this objective, the meaning and interpretation of some tremor-related tests must be defined (see 1.2, 2

show abstract

Mechanical implications of paired motor unit discharges in pathological and voluntary tremor

Cited by 32 publications

References 17 publications

Tremor‐related motor unit firing in Parkinson's disease: implications for tremor genesis

Tremor‐related motor unit firing in Parkinson's disease: implications for tremor genesis

One central oscillatory drive is compatible with experimental motor unit behaviour in essential and Parkinsonian tremor

Consensus Statement of the Movement Disorder Society on Tremor

Contact Info

Product

Resources

About