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.     

The motor of leukocytes

The movements of leukocytes involve extension, flow, and contraction of a margin of organelle-excluding cytoplasm. Actin is the principal structural component of this region. This paper reviews evidence that the expansion of cortical cytoplasm can result from the growth of actin polymers into an orthogonal network in which actin fibers branch perpendicularly under the influence of actin-binding protein. Flow occurs when actin filaments are disassembled and severed. The assembly and fragmentation of actin are regulated by actin-modulating proteins such as profilin, which sequesters actin monomers, acumentin, which binds to the slow-growing end of actin fibers, and gelsolin, a calcium-regulated protein that binds to the fast-growing end of actin polymers and severs actin filaments. Contraction of the actin network is caused by myosin, the assembly and activity of which are regulated by its state of phosphorylation, which is in turn controlled by phosphorylating and dephosphorylating enzymes and by calmodulin and calcium. Present information leads to the prediction that intracellular calcium gradients guide cytoplasmic movement and that the direction of actin assembly and therefore of cytoplasmic extension is toward regions of low cytoplasmic free calcium.     

Regulation of motor behaviour

The review is devoted to analysis of the basic links of motor behavior control systems: sensorimotor cortex, cerebellum, a red nucleus and striatum. The organization and communications of these structures and their participation in learning and memory processes are described. The synaptic neurotransmitter and nonsynaptic neuromodulatory systems innervating these structures are also described. Hierarchical synaptic networks are formed by GABA and glutamatergic systems. The nonsynaptic dopaminergic system innervates both of these structures, but carries out a modulatory function. The mesocorticolimbic dopaminergic system induces an emotional and motivational state - processes of reinforcement, and participates in realization of purposeful behavior. The nigrostriatal dopaminergic system, through triggering an endocellular signal and the processes ofphosphorylation and dephosphorylation modulates activity ofGABA and glutamatergic receptors ofdorsal striatum spiny neurons and adapted thalamocortical networks.     

Development of motor behaviour

The development of motor behaviour depends on the differentiation of underlying circuitry. Recent work with the zebrafish brings the simple swimming behaviour of lower vertebrates and their embryos into focus as a suitable model to study the development of motor circuitry and its genetic control. Changes in connectivity and excitability contribute to the development of swimming in this simple system. In the chick embryo, limb motor circuitry is spontaneously active before motor axons reach their muscle targets, and it has properties in common with the spontaneously active networks in the retina. The early rhythmic activity responsible for embryonic movement is probably a generalised property of developing spinal networks that precedes, and may be required for, the completion of functional locomotor circuitry.     

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   

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     

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.     

Neuronal correlates of motor performance and motor learning in the primary motor cortex of monkeys adapting to an external force field

The primary motor cortex (M1) is known to control motor performance. Recent findings have also implicated M1 in motor learning, as neurons in this area show learning-related plasticity. In the present study, we analyzed the neuronal activity recorded in M1 in a force field adaptation task. Our goal was to investigate the neuronal reorganization across behavioral epochs (before, during, and after adaptation). Here we report two main findings. First, memory cells were present in two classes. With respect to the changes of preferred direction (Pd), these two classes complemented each other after readaptation. Second, for the entire neuronal population, the shift of Pd matched the shift observed for muscles. These results provide a framework whereby the activity of distinct neuronal subpopulations combines to subserve both functions of motor performance and motor learning.     

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.