Sensory and motor impairment in the nerve compression block

Recently nerve compression block as a method of investigating movement control without kinaesthetic feedback has been questioned on the grounds that motor impairment (as measured by nerve conduction parameters) is a confounding factor. In order to clarify the relationship between sensory and motor function, behavioural data was obtained on both at systematic time intervals throughout the duration of the block. The findings indicated that significant decrements in tapping measures occurred somewhat earlier in the time course of the block than decreases in kinaesthetic discrimination. Also, contrary to assumption, the majority of subjects ceased to perform prior to total kinaesthetic loss. The data suggest that motor impairment is a “crucial” issue (Laszlo, 1966) in the use of this technique, and provide further behavioural support for the neurological findings of Kelso, Stelmach and Wanamaker (1974).     

What Does Computer-Mediated Control of a Thermal-Hydraulic System Have to Do With Moving Your Jaw to Speak? Evidence for Synergies in Process Control

Coordination phenomena can take many diverse forms, but ecological psychologists have focused primarily on understanding human motor control. In this article we report an experiment on human-machine coordination that was designed to replicate and extend an early experiment on human jaw movement during speech production that provided initial evidence of synergies. Participants controlled a thermal-hydraulic process simulation for about 1 hr per weekday for approximately 1 month. Half of the participants used a human-computer interface that presented predominantly lower level physical (P) information, whereas the other half used an interface that presented higher level functional (P+F) information as well. During the last block of trials, local perturbations were introduced by increasing the time constant of a particular component per trial by a factor of 20. The component perturbations had less impact on the performance of the P+F participants than the P, and this effect was mostly localized to components that had alternative degrees of freedom for control. Most important, the P+F participants exhibited more evidence of higher level control than the P, providing some initial evidence for synergies in process control. These findings suggest that it may be possible to develop a general unified theory of coordination that subsumes motor control and human-machine interaction as special cases.     

Psychology has to deal with efferences too

The authors argue that F. Mechsner's (2004) perceptual-cognitive approach is an important contribution to the current discussion of motor control. Mechsner presents convincing evidence against direct motor control. Nevertheless, the mechanisms by which perceptual-cognitive representations determine efferent commands must still be clarified.     

Agency in the face of error

Experiencing oneself as the cause of an action is a fundamental building block for a sense of self. A recent study by Sato and Yasuda provides evidence that motor prediction contributes to the experience of agency. Their findings demonstrate that agency is experienced not only for intended, but also for erroneous, unintended actions. This extends our knowledge on the phenomenology of action, and raises questions about the relation between explicit reports and agency-related changes in sensation and perception.     

Accurate reaching after active but not passive movements of the hand: evidence for forward modeling

Converging behavioral findings support recent models of motor control suggesting that estimates of the future positions of a limb as well as the expected sensory consequences of a planned movement may be derived, in part, from efference copies of motor commands. These estimates are referred to as forward models. However, relatively little behavioral evidence has been obtained for proposed forward models that provide on-line estimates of current position. We report data from a patient (JD) who reached accurately to visualized targets with and without vision of her hand despite substantial proprioceptive loss. Additionally, we administered a double-start reaching test to examine the possibility that efference copy information could be used to estimate current limb position. JD reached accurately, without vision, to a final target after actively reaching to a landmark, but exhibited severely impaired reaching after passive movements to the landmark. This finding suggests that forward modeling of efference copy signals may provide relatively accurate estimates of current limb position for the purpose of motor planning. The possibility that such estimates may also contribute to the awareness of body position and to self-recognition is discussed.     

Psychology Has to Deal with Efferences Too

The authors argue that F. Mechsner's (2004) perceptual-cognitive approach is an important contribution to the current discussion of motor control. Mechsner presents convincing evidence against direct motor control. Nevertheless, the mechanisms by which perceptual-cognitive representations determine efferent commands must still be clarified.     

Timing of in situ visual information pick-up that differentiates expert and near-expert anticipation in a complex motor skill

The timing of visual information pick-up for visual anticipation was examined by comparing the capability of multiple skill groups, expert and near-expert karate athletes and novices, to block attacks using an in situ temporal occlusion paradigm. Participants stood facing a karate opponent and then attempted to block attacks (kicks and punches), whilst their vision of attacks was occluded: (a) prior to onset of opponent motion (O1), (b) after preparatory head movement (O2), and (c) after initiation of the attacking motion (O3). A no occlusion control condition provided complete vision of attacks (O4). Results revealed that expert anticipation was not significantly different to that of near-experts at O1, but was significantly different to the other group across O2–O4. Expert anticipation, however, was significantly above chance across all occlusion conditions, but near-experts performed above chance at O3 and O4, whilst novices were better than chance at O4. Unexpectedly, unique evidence was found that expert anticipation could be differentiated from near-expert anticipation in the earliest occlusion condition, where it was found that only experts were capable of using visual information from a static opponent to anticipate and block attacks above chance. The findings further understanding of expert visual anticipation to guide motor skills beyond existing expert–novice comparisons.     

Understanding of action-related and abstract verbs in comparison: a behavioral and TMS study

Does the comprehension of both action-related and abstract verbs rely on motor simulation? In a behavioral experiment, in which a semantic task was used, response times to hand-action-related verbs were briefer than those to abstract verbs and both decreased with repetition of presentation. In a transcranial magnetic stimulation (TMS) experiment, single-pulse stimulation was randomly delivered over hand motor area of the left primary motor cortex to measure cortical-spinal excitability at 300 or 500 ms after verb presentation. Two blocks of trials were run. In each block, the same verbs were randomly presented. In the first block, stimulation induced an increase in motor evoked potentials only when TMS was applied 300 ms after action-related verb presentation. In the second block, no modulation of motor cortex was found according to type of verb and stimulation-delay. These results confirm that motor simulation can be used to understand action rather than abstract verbs. Moreover, they suggest that with repetition, the semantic processing for action verbs does not require activation of primary motor cortex anymore.     

Effects of physical fatigue and cognitive challenges on the potential for low back injury

There is no question that the motor control system will adapt under fatiguing conditions; however, there is documented evidence showing that when fatigued or challenged, the motor control system will, on occasion, perform inappropriate muscle sequencing, increasing the risk of injury, or directly causing injury. Knowing that inappropriate muscle activations can lead to injury, the purpose of this study was to investigate motor patterns during cognitive and physical challenges. Rather than ensure change with severe challenges, milder challenges were purposefully chosen. Eight male subjects performed a low external load task performed near end ROM while in an unchallenged state, and while in three challenged states: passive tissue creep, muscle fatigue and cognitive distraction. Data were collected using EMG of the trunk muscles and angular displacement of the lumbar spine. Comparison of motor control patterns between the unchallenged state and each of the three challenged conditions showed no systematic differences. However, several random anomalies were observed. A case study of a single subject was chosen to show inappropriate motor control during one trial under the cognitive distraction conditions. The response of the motor control system is very individualized and does on occasion produce inappropriate motor patterns. This supports the notion that injury may also occur as the result of random motor control errors as well as predictable, systematic changes.     

Introversion-extraversion: the Bell-Magendie law revisited

Evidence from several sources, including psychophysical, electrodermal and evoked potential measures, indicates that introverts display an enhanced response to sensory stimulation. There is also evidence, primarily from psychophysical studies, which suggests that extraverts may be disposed to emit short, strong bursts of motor activity which facilitate performance on tasks that involve gross motor activity but which impede performance on tasks which require refined motor control. The present paper develops an argument in which the differences between introverts and extraverts in the response to sensory stimulation and in the expression of motor activity may be referred to differences at the level of the sensory and motor nerve.     

Higher Levels of Psychopathy Predict Poorer Motor Control: Implications for Understanding the Psychopathy Construct

A review of the literature suggests that higher levels of psychopathy may be linked to less effective behavioral control. However, several commentators have urged caution in making statements of this type in the absence of direct evidence. In two studies (total N?=?142), moment-to-moment accuracy in a motor control task was examined as a function of dimensional variations in psychopathy in an undergraduate population. As hypothesized, motor control was distinctively worse at higher levels of psychopathy relative to lower levels, both as a function of primary and secondary psychopathy and particularly their shared variance. These novel findings provide support for the idea that motor control systematically varies by psychopathy, in a basic manner, consistent with views of psychopathy emphasizing lesser control.     

What do fully paralyzed awake humans feel when they attempt to move?

Subjects are able to judge the strength of muscle contraction. In theory, the force of muscular exertion could be perceived either from mechanoreceptor afferents or from knowledge of central motor command (corollary discharge). Sensations of great effort or exerted force have been described by subjects when their limbs were weakened by fatigue or partial paralysis. This has been taken as evidence that effort sensations arise from central motor commands rather than from mechanoreceptor afferent signals produced by muscle contraction. To differentiate between these possibilities, we used neuromuscular block to completely paralyze four waking subjects and required them to attempt maximal contraction of inspiratory muscles and of hand muscles. They were questioned after recovery about what their sensations were when attempting these contractions. None described the sensations of exerted force, great effort, or heaviness, which would have been expected if motor commands alone were the source of these sensations. The contradiction between our findings and those previously reported suggests that the specific neural mechanisms for effort sensations must be reexamined.     

Laterality differences for speed but not for control in sequential finger tapping

Multiple or sequential finger tapping is preferential to the dominant right hand with respect to speed. However, in more complex movement, variables other than speed become important. The present investigation uses a sequential finger-tapping task which permits assessment of between-hands differences with respect to rate and control of movement, with and without vision. 36 right-handed normal adults rapidly tapped their fingers in sequential order on a block (2.54 cm. sq.), trying not to move the block. Analyses of variance (mode x hand) performed for taps and shift of the block show the right hand to be faster than the left hand with and without vision, adding further to the notion that the left hemisphere predominates in increases in rapid movement and in sequencing aspects of motor activity. However, while both hands were steadier with vision than without, there were no between-hand differences with regard to control, suggesting equivalency of cerebral function for factors of manual sequencing other than speed.     

The cerebellum and the timing of coordinated eye and hand tracking.

The cerebellum is known to have important functions in motor control, coordination, motor learning, and timing. It may have other "higher" functions as well, up to and including cognitive processing independent of motor behavior. In this article, we will review some of the evidence from functional imaging, lesion studies, electrophysiological recordings, and anatomy which support the theory that the cerebellum provides a "forward model" of the motor system. This forward model would be used for control of movement; it could also underlie a cerebellar role in coordination. In this role, the forward model would generate time-specific signals predicting the motion of each motor effector, essential for predictive control of, for example, eye and hand movements. Data are presented from human eye and hand tracking that support this. Tracking performance is better if eye and hand follow the same spatial trajectory, but better still if the eye leads the hand by about 75 to 100 ms. This suggests that information from the ocular control system feeds into the manual control system to assist its tracking.     

Internal models in the cerebellum

This review will focus on the possibility that the cerebellum contains an internal model or models of the motor apparatus. Inverse internal models can provide the neural command necessary to achieve some desired trajectory. First, we review the necessity of such a model and the evidence, based on the ocular following response, that inverse models are found within the cerebellar circuitry. Forward internal models predict the consequences of actions and can be used to overcome time delays associated with feedback control. Secondly, we review the evidence that the cerebellum generates predictions using such a forward model. Finally, we review a computational model that includes multiple paired forward and inverse models and show how such an arrangement can be advantageous for motor learning and control.     

A cortical circuit for voluntary laryngeal control: Implications for the evolution language

The development of voluntary laryngeal control has been argued to be a key innovation in the evolution of language. Part of the evidence for this hypothesis comes from neuroscience. For example, comparative research has shown that humans have direct cortical innervation of motor neurons controlling the larynx, whereas nonhuman primates do not. Research on cortical motor control circuits has shown that the frontal lobe cortical motor system does not work alone; it is dependent on sensory feedback control circuits. Thus, the human brain must have evolved not only the required efferent motor pathway but also the cortical circuit for controlling those efferent signals. To fill this gap, I propose a link between the evolution of laryngeal control and neuroscience research on the human dorsal auditory-motor speech stream. Specifically, I argue that the dorsal stream Spt (Sylvian parietal-temporal) circuit evolved in step with the direct cortico-laryngeal control pathway and together represented a key advance in the evolution of speech. I suggest that a cortical laryngeal control circuit may play an important role in language by providing a prosodic frame for speech planning.     

不同浓度罗哌卡因复合利多卡因行骶管阻滞应用于痔上黏膜环切术的效果比较

本文通过将120位择期行痔上黏膜环切术的患者随即分为三组,仔细地比较了不同浓度的罗哌卡因复合利多卡因骶管阻滞在痔上黏膜环切术中的镇痛效果和运动阻滞程度,结果发现了0.2%罗哌卡因＋1%利多卡因骶管阻滞最适用于痔上黏膜环切术,它不但可以取得理想的镇痛效果,而且无明显的运动神经阻滞作用。     

Control theories in motor behavior

The goal of contemporary motor control theorist is the delineation of the “language” of movements. That is, in what unambiguous code are the parameters of movement specified, given the composition of the human body? In this pursuit not only are the elements of the language of movement sought, but the rules of combination or syntax of movement are also to be derived. This paper compares a number of motor control theories according to the form of control they exhibit and according to their ability to address issues in the area. Recurring theoretical trends in motor control are examined and the evidence for each is reviewed, emphasizing their explanatory power in the classical problems of control: motor equivalence (Hebb 1949), complexity (Bernstein 1967), and variability (Glencross 1980; Schmidt 1975, 1976).     

Minimizing motor mimicry by myself: Self-focus enhances online action-control mechanisms during motor contagion

Ideomotor theory of human action control proposes that activation of a motor representation can occur either through internally-intended or externally-perceived actions. Critically, sometimes these alternatives of eliciting a motor response may be conflicting, for example, when intending one action and perceiving another, necessitating the recruitment of enhanced action-control to avoid motor mimicry. Based on previous neuroimaging evidence, suggesting that reduced mimicry is associated with self-related processing, we aimed to experimentally enhance these action-control mechanisms during motor contagion by inducing self-focus. In two within-subjects experiments, participants had to enforce their action intention against an external motor contagion tendency under heightened and normal self-focus. During high self-focus participants showed reduced motor mimicry, induced either by mirror self-observation or self-referential judgments. This indicates that a self-focus provoking situation can enhance online action-control mechanisms, needed to resist unintentional motor contagion tendencies and thereby enables a modulation of automatic mirroring responses.     

The physiology of motor delusions in anosognosia for hemiplegia: Implications for current models of motor awareness

Right brain damaged patients sometimes deny that their left arm is paralysed or even claim to have just moved it. This condition is known as anosognosia for hemiplegia (AHP). Here, we used fMRI to study patients with and without AHP during the execution of a motor task. We found that the delusional belief of having moved was preceded by brain activation of the cortical regions that are implicated in motor control in the left intact hemisphere and in the spared motor regions of the right hemisphere; patients without anosognosia did not present with the same degree of activation. We conclude that the false belief of movement is associated with a combination of strategically placed brain lesions and the preceding residual neural activity of the fronto-parietal motor network. These findings provide evidence that the activity of motor cortices contributes to our beliefs about the state of our motor system.