Speech motor control

The development of new measurement techniques and improved models of the larynx and the vocal tract have significantly advanced our understanding of speech motor control. Recently, several groups have been using electromagnetic transduction techniques to record tongue movements. The laryngeal vibrations have been modeled and studied using techniques from non-linear dynamics. Computational models of supraglottal movements have been proposed and tested. A connectionist model that synthesizes the results obtained from observing the effects of variations in rate, stress, and phonetic context on speech kinematics has recently been proposed.     

Bacterial flagellar motor

The bacterial flagellar motor is a reversible rotary nano-machine, about 45 nm in diameter, embedded in the bacterial cell envelope. It is powered by the flux of H+ or Na+ ions across the cytoplasmic membrane driven by an electrochemical gradient, the proton-motive force or the sodium-motive force. Each motor rotates a helical filament at several hundreds of revolutions per second (hertz). In many species, the motor switches direction stochastically, with the switching rates controlled by a network of sensory and signalling proteins. The bacterial flagellar motor was confirmed as a rotary motor in the early 1970s, the first direct observation of the function of a single molecular motor. However, because of the large size and complexity of the motor, much remains to be discovered, in particular, the structural details of the torque-generating mechanism. This review outlines what has been learned about the structure and function of the motor using a combination of genetics, single-molecule and biophysical techniques, with a focus on recent results and single-molecule techniques.     

Yeast motor proteins

Yeast accomplish a variety of intracellular motile events with the aid of mechanochemical enzymes known as motor proteins. This review covers the current state of knowledge on myosins, kinesins, dyneins, dynamins and SMC proteins present in yeast cells, and the most important developments in the study of yeast mitosis. Both topics have seen rapid progress over the past few years. Dedicated to Professor O. Nečas on the occasion of his 70th birthday     

The polymerization motor

Polymerization and depolymerization of actin filaments and microtubules are thought to generate force for movement in various kinds of cell motility, ranging from lamellipodial protrusion to chromosome segregation. This article reviews the thermodynamic and physical theories of how a nonequilibrium polymerization reaction can be used to transduce chemical energy into mechanical energy, and summarizes the evidence suggesting that actin polymerization produces motile force in several biological systems.     

Myosins motor Miranda

New evidence shows that myosin motors drive the spatial segregation of cell fate determinants during asymmetric cell division. How they do so remains a mystery.     

Neuronal correlates of the motor function of the cerebral motor cortex

Modern ideas about the motor cortex neuronal mechanisms ensuring the initiation and correction of the instrumental manipulational movements in mammals have been analysed. A close correlation has been established to exist between the neuronal activity and various characteristics of movement including those that are not induced by muscle force. The role of somatic afferentation in the formation and realization of the movement programme is analysed as well as in motor output modulation by means of fast feedback.     

Aluminum hydroxide injections lead to motor deficits and motor neuron degeneration

Gulf War Syndrome is a multi-system disorder afflicting many veterans of Western armies in the 1990–1991 Gulf War. A number of those afflicted may show neurological deficits including various cognitive dysfunctions and motor neuron disease, the latter expression virtually indistinguishable from classical amyotrophic lateral sclerosis (ALS) except for the age of onset. This ALS “cluster” represents the second such ALS cluster described in the literature to date. Possible causes of GWS include several of the adjuvants in the anthrax vaccine and others. The most likely culprit appears to be aluminum hydroxide. In an initial series of experiments, we examined the potential toxicity of aluminum hydroxide in male, outbred CD-1 mice injected subcutaneously in two equivalent-to-human doses. After sacrifice, spinal cord and motor cortex samples were examined by immunohistochemistry. Aluminum-treated mice showed significantly increased apoptosis of motor neurons and increases in reactive astrocytes and microglial proliferation within the spinal cord and cortex. Morin stain detected the presence of aluminum in the cytoplasm of motor neurons with some neurons also testing positive for the presence of hyper-phosphorylated tau protein, a pathological hallmark of various neurological diseases, including Alzheimer’s disease and frontotemporal dementia. A second series of experiments was conducted on mice injected with six doses of aluminum hydroxide. Behavioural analyses in these mice revealed significant impairments in a number of motor functions as well as diminished spatial memory capacity. The demonstrated neurotoxicity of aluminum hydroxide and its relative ubiquity as an adjuvant suggest that greater scrutiny by the scientific community is warranted.     

The assessment of preschool children's motor skills after familiarization with motor tests

This research study was conducted to establish the influence of familiarization on the information component of movement in a motor task for the assessment of preschool children's motor skills. The sample included 50 children whose mean age was 5.9 years (71.5 months). The experimental group consisted of 27 children who were 5.9 years (71.5 months) old, and the control group consisted of 23 children who were 5.9 years (71.5 months) old. The examinees performed 2 motor tasks, standing long jump (SJ, explosive strength) and standing on 1 leg on a beam "flamingo test" (FT, balance). The experimental group underwent a period of familiarization with the motor task in 3 sessions with 5 trials every 3 days. The results indicate statistically significant differences in the final testing between both groups of examinees; the experimental group mean was 112.73 cm, and the control group mean was 100.62 in the SJ test (p = 0.00), and the experimental group mean was 27.10 seconds and the control group mean was 15.01 seconds in the FT (for balance) (p = 0.00). The results obtained in this research indicate that children significantly improved the results in the motor test of strength and balance, being influenced by familiarization. It was confirmed that it was necessary for preschool children to be familiar with the test and it is not justified to use testing and assessment protocols and standards for adults. Physical educators and coaches, when testing preschool children, should introduce children to tests to obtain the best result.     

Analysis of motor unit firing characteristics in patients with motor neuron diseases

This study was designed to evaluate firing rate variability in patients with upper/lower motor neuron disorders. Twenty healthy subjects and 19 patients with motor neuron disorders participated in the study. Consecutive motor unit action potential pairs from extensor digitorum communis (EDC) muscle were recorded from each subject with trigger-delay line mode. Patients with motor neuron disorders (17.7?±?10.8?ms) showed significantly higher mean time variability of interpotential interval value than healthy volunteers (10.3?±?0.1?ms) (p?相似文献   

Central motor conduction studies in motor neurone disease using magnetic brain stimulation

Central motor conduction (CMC) to abductor digiti minimi (ADM) was evaluated in 22 patients with motor neurone disease (MND) using magnetic stimulation of the motor cortex and electrical stimulation at the C7/T1 interspace. CMC was abnormal in 14 patients; prolonged CMC time and absence of response to brain stimulation were more frequent abnormalities than low amplitude responses without prolonged CMC time. The technique can reveal subclinical upper motor neurone involvement and document central motor pathway dysfunction in MND. The patterns of abnormality are not specific to MND; all may occur in other neurological disorders including multiple sclerosis.