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Wrist Flexors (wrist + flexor)

Distribution by Scientific Domains

Medical Sciences	50%
Life Sciences	50%

Selected Abstracts

Computerized Tremor Analysis of Valproate-induced Tremor: A Comparative Study of Controlled-release versus Conventional Valproate

EPILEPSIA, Issue 2 2005
Martina Rinnerthaler
Summary:,Purpose: Valproate (VPA) induces postural tremor in 6,45% of patients. The characteristics of VPA-induced tremor have not yet been quantitatively assessed, and it is not known whether tremor prevalence or severity is affected by VPA formulation (controlled-release CR-VPA vs. conventional VPA). The aim of this study was quantitatively to assess tremor in epilepsy patients receiving VPA and to compare the effects of two VPA formulations (CR-VPA vs. VPA) on tremor severity. Methods: In a prospective study, 18 consecutive patients with newly diagnosed focal or generalized epilepsy were assigned to receive alternately either VPA (n = 10) or CR-VPA (n = 8) monotherapy. Computerized tremor analysis was performed at baseline 1 day before initiating VPA treatment and repeated after a seizure-free period of ,8 weeks, during which VPA doses had remained stable. Rest and postural tremor were recorded by accelerometry, and surface electromyograms (EMGs) were recorded from the wrist flexors and extensors. Results: At baseline, the two groups had similar postural tremor amplitudes. At follow-up, the CR-VPA group had remained at the same level, whereas VPA subjects exhibited a significant increase in tremor amplitudes (p < 0.05) despite comparable VPA doses and comparable plasma VPA concentrations at the time of tremor testing. Conclusions: This is the first study to assess quantitatively VPA-induced tremor by standardized tremor analysis. These results suggest that CR-VPA may cause less tremorigenic activity as compared with standard VPA. The mechanisms underlying this difference are unclear but may include greater peak,trough variation with VPA than with CR-VPA. [source]

Improving functional magnetic resonance imaging motor studies through simultaneous electromyography recordings

HUMAN BRAIN MAPPING, Issue 9 2007
Bradley J. MacIntosh
Abstract Specially designed optoelectronic and data postprocessing methods are described that permit electromyography (EMG) of muscle activity simultaneous with functional MRI (fMRI). Hardware characterization and validation included simultaneous EMG and event-related fMRI in 17 healthy participants during either ankle (n = 12), index finger (n = 3), or wrist (n = 2) contractions cued by visual stimuli. Principal component analysis (PCA) and independent component analysis (ICA) were evaluated for their ability to remove residual fMRI gradient-induced signal contamination in EMG data. Contractions of ankle tibialis anterior and index finger abductor were clearly distinguishable, although observing contractions from the wrist flexors proved more challenging. To demonstrate the potential utility of simultaneous EMG and fMRI, data from the ankle experiments were analyzed using two approaches: 1) assuming contractions coincided precisely with visual cues, and 2) using EMG to time the onset and offset of muscle contraction precisely for each participant. Both methods produced complementary activation maps, although the EMG-guided approach recovered more active brain voxels and revealed activity better in the basal ganglia and cerebellum. Furthermore, numerical simulations confirmed that precise knowledge of behavioral responses, such as those provided by EMG, are much more important for event-related experimental designs compared to block designs. This simultaneous EMG and fMRI methodology has important applications where the amplitude or timing of motor output is impaired, such as after stroke. Hum Brain Mapp 2006. © 2006 Wiley-Liss, Inc. [source]

Motor unit recruitment during lengthening contractions of human wrist flexors

MUSCLE AND NERVE, Issue 11 2001
Paula J. Stotz MSc
Abstract The purpose of this study was to revisit the question of recruitment of motor units during lengthening contractions because of conflicting views in the literature on this subject. Motor unit activity was recorded from the flexor carpi radialis muscle of four human subjects to compare the patterns of recruitment during lengthening and isometric contractions. Lengthening contractions were produced either when the subject voluntarily stopped opposing a background load or when an additional load was imposed on the already contracting muscle. In both cases, lengthening of the active muscle was produced at a variety of speeds, from quite slow to "as fast as possible." No differences in recruitment order were observed between isometric and lengthening contractions at any speed of lengthening contraction. It is concluded that all contractions in normal humans recruit motor units in an orderly fashion from small to large, according to the size principle of motor unit recruitment. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1535,1541, 2001 [source]

Time-varying changes in corticospinal excitability accompanying the triphasic EMG pattern in humans

THE JOURNAL OF PHYSIOLOGY, Issue 3 2000
Colum D. MacKinnon
1Nine healthy subjects performed single rapid wrist movements from neutral to targets at 20 deg of flexion or extension in response to an auditory cue. Surface EMG was recorded from the wrist flexors and extensors together with wrist position. Movements in both directions were characterised by the usual triphasic pattern of EMG activity in agonist (AG1), antagonist (ANTAG) and again in agonist (AG2) muscles. 2Single pulses of transcranial magnetic stimulation (TMS) were applied over the motor cortex at an intensity of 80 % of resting threshold at random times between 80 and 380 ms after the cue. We measured the peak-to-peak amplitude of the evoked motor potential (MEP) and the integrated EMG (IEMG) activity that preceded the MEP. In a separate set of experiments H reflexes were elicited in the wrist flexors instead of MEPs. 3MEP amplitudes in the agonist muscle increased by an average of 10 ± 8 ms (range ,1 to 23 ms) prior to the onset of the AG1 burst and were associated with an increase of over sevenfold in the MEP:IEMG ratio, irrespective of movement direction. Agonist H reflex amplitudes were linearly related to, and increased at the same time as, changes in agonist IEMG. 4The principal ANTAG burst was not preceded by an increase in the antagonist muscle MEP:IEMG ratio. No relationship was found between the amplitude of the antagonist H reflexes and the preceding antagonist IEMG. 5Five subjects showed an increase in the MEP:IEMG ratio preceding and during the initial part of the AG2 burst. 6Our method of analysis shows that changes in motor cortical excitability mediating the initiation of movement occur much closer to the onset of EMG activity (less than 23 ms) than the 80,100 ms lead time previously reported. The lack of such changes before the onset of the ANTAG burst suggests that this may be initiated by a different, perhaps subcortical, mechanism. [source]