Repeatability and validity of an upper limb and neck discomfort questionnaire: the utility of the standardized Nordic questionnaire.
(33/2578)The repeatability and validity of a questionnaire for upper limb and neck complaints were assessed in a population of 105 hospital outpatients with a range of upper limb and neck disorders (including cervical spondylosis, adhesive capsulitis, lateral epicondylitis, carpal tunnel syndrome and Raynaud's phenomenon). Subjects were asked to complete a modified Nordic-style upper limb and neck discomfort questionnaire on two occasions closely spaced in time. The repeatability of their responses was assessed by calculating a kappa coefficient (kappa), and the sensitivity and specificity of component items in the questionnaire were determined for specific diagnostic categories of upper limb and neck disorder. Symptom reports for pain in the upper limb and neck, pain interfering with physical activities, neurological symptoms and blanching were all found to be highly repeatable (kappa = 0.63-0.90). A number of regional pain reports proved to be very sensitive in relation to specific upper limb disorders, but, with the exception of reported finger blanching in patients with Raynaud's phenomenon, none proved to have a good specificity (range = 0.33-0.38). We conclude that a modified Nordic-style questionnaire is repeatable and sensitive, and is likely to have a high utility in screening and surveillance. However a complementary examination schedule of adequate specificity and repeatability is essential to establish a clinical diagnosis. (+info)
A neural model of cerebellar learning for arm movement control: cortico-spino-cerebellar dynamics.
(34/2578)A neural network model of opponent cerebellar learning for arm movement control is proposed. The model illustrates how a central pattern generator in cortex and basal ganglia, a neuromuscular force controller in spinal cord, and an adaptive cerebellum cooperate to reduce motor variability during multijoint arm movements using mono- and bi-articular muscles. Cerebellar learning modifies velocity commands to produce phasic antagonist bursts at interpositus nucleus cells whose feed-forward action overcomes inherent limitations of spinal feedback control of tracking. Excitation of alpha motoneuron pools, combined with inhibition of their Renshaw cells by the cerebellum, facilitate movement initiation and optimal execution. Transcerebellar pathways are opened by learning through long-term depression (LTD) of parallel fiber-Purkinje cell synapses in response to conjunctive stimulation of parallel fibers and climbing fiber discharges that signal muscle stretch errors. The cerebellar circuitry also learns to control opponent muscles pairs, allowing cocontraction and reciprocal inhibition of muscles. Learning is stable, exhibits load compensation properties, and generalizes better across movement speeds if motoneuron pools obey the size principle. The intermittency of climbing fiber discharges maintains stable learning. Long-term potentiation (LTP) in response to uncorrelated parallel fiber signals enables previously weakened synapses to recover. Loss of climbing fibers, in the presence of LTP, can erode normal opponent signal processing. Simulated lesions of the cerebellar network reproduce symptoms of cerebellar disease, including sluggish movement onsets, poor execution of multijoint plans, and abnormally prolonged endpoint oscillations. (+info)
Reorganization in primary motor cortex of primates with long-standing therapeutic amputations.
(35/2578)Intracortical microstimulation was used to investigate the organization of primate primary motor cortex (M1) in three squirrel monkeys and two galagos years after the therapeutic amputation of an injured forelimb or hindlimb. In two squirrel monkeys with forelimb amputation, physiological results were correlated with the distribution of corticospinal neurons after injections of tracers into the lower cervical segments of the spinal cord. Distributions of labeled corticospinal neurons helped identify the locations of the former forelimb cortex in M1. Evoked movements from M1 ipsilateral to the missing limb were not obviously different from M1 of normal controls. Stimulation in the deefferented part of M1 contralateral to the missing limb elicited movements of the remaining proximal muscles as well as movements from adjacent body representations in all cases. Stimulation in the deefferented forelimb cortex evoked shoulder stump, trunk, and orofacial movements, whereas stimulation in the deefferented hindlimb cortex evoked hip stump, trunk, and tail movements. Movements were evoked from all sites in the deprived cortex, so that there were no unresponsive zones. Minimal levels of current necessary to evoke these movements varied from those in the normal range to those of much higher levels, with the average threshold higher than normal. Finally, multiunit recording from the two galagos revealed that the deprived portions of S1 were responsive to touch or taps on the stump and neighboring body parts. (+info)
Magnetoencephalography in the study of human somatosensory cortical processing.
(36/2578)Magnetoencephalography (MEG) is a totally non-invasive research method which provides information about cortical dynamics on a millisecond time-scale. Whole-scalp magnetic field patterns following stimulation of different peripheral nerves indicate activation of an extensive cortical network. At the SI cortex, the responses reflect mainly the activity of area 3b, with clearly somatotopical representations of different body parts. The SII cortex is activated bilaterally and it also receives, besides tactile input, nociceptive afference. Somatically evoked MEG signals may also be detected from the posterior parietal cortex, central mesial cortex and the frontal lobe. The serial versus parallel processing in the cortical somatosensory network is still under debate. (+info)
Where is my arm? The relative role of vision and proprioception in the neuronal representation of limb position.
(37/2578)A central problem in motor control, in the representation of space, and in the perception of body schema is how the brain encodes the relative positions of body parts. According to psychophysical studies, this sense of limb position depends heavily on vision. However, almost nothing is currently known about how the brain uses vision to determine or represent the location of the arm or any other body part. The present experiment shows that the position of the arm is represented in the premotor cortex of the monkey (Macaca fascicularis) brain by means of a convergence of visual cues and proprioceptive cues onto the same neurons. These neurons respond to the felt position of the arm when the arm is covered from view. They also respond in a similar fashion to the seen position of a false arm. (+info)
Do repetitive tasks give rise to musculoskeletal disorders?
(38/2578)Repetitive tasks can undoubtedly cause discomfort and pain, but whether they cause or worsen the pathology causing the pain is most uncertain. Research in this area is difficult as the 'work-related upper limb disorders' do not occur exclusively in workers and because there is no simple, reliable and reproducible test for most 'work-related upper limb disorders'. Furthermore many studies are difficult to interpret as they detect disease by the presence of symptoms: one would expect manual workers to complain of more symptoms than sedentary workers and symptom aggravation does not tell one anything about the causation of the underlying pathology. (+info)
Neuronal interactions improve cortical population coding of movement direction.
(39/2578)Interactions among groups of neurons in primary motor cortex (MI) may convey information about motor behavior. We investigated the information carried by interactions in MI of macaque monkeys using a novel multielectrode array to record simultaneously from 12-16 neurons during an arm-reaching task. Pairs of simultaneously recorded cells revealed significant correlations in their trial-to-trial firing rate variation when estimated over broad (600 msec) time intervals. This covariation was only weakly related to the preferred directions of the individual MI neurons estimated from the firing rate and did not vary significantly with interelectrode distance. Most significantly, in a portion of cell pairs, correlation strength varied with the direction of the arm movement. We evaluated to what extent correlated activity provided additional information about movement direction beyond that available in single neuron firing rate. A multivariate statistical model successfully classified direction from single trials of neural data. However, classification was consistently better when correlations were incorporated into the model as compared to one in which neurons were treated as independent encoders. Information-theoretic analysis demonstrated that interactions caused by correlated activity carry additional information about movement direction beyond that based on the firing rates of independently acting neurons. These results also show that cortical representations incorporating higher order features of population activity would be richer than codes based solely on firing rate, if such information can exploited by the nervous system. (+info)
An application of upper-extremity constraint-induced movement therapy in a patient with subacute stroke.
(40/2578)BACKGROUND AND PURPOSE: The purpose of this case report is to demonstrate the application of constraint-induced movement therapy with an individual with upper-extremity hemiparesis within 4 months after sustaining a cerebrovascular accident (stroke). Such patients often fail to develop full potential use of their affected upper extremity, perhaps due to a "learned nonuse phenomenon." CASE DESCRIPTION: The patient was a 61-year-old woman with right-sided hemiparesis resulting from an ischemic lacunar infarct in the posterior limb of the left internal capsule. The patient's less-involved hand was constrained in a mitten so that she could not use the hand during waking hours, except for bathing and toileting. On each weekday of the 14-day intervention period, the patient spent 6 hours being supervised while performing tasks using the paretic upper extremity. Pretreatment, posttreatment, and 3-month follow-up outcome measures included the Wolf Motor Function Test and the Motor Activity Log (MAL). OUTCOMES: For the Wolf Motor Function Test, both the mean and median times to complete 16 tasks improved from pretreatment to posttreatment and from posttreatment to follow-up. Results of the MAL indicated an improved self-report of both "how well" and "how much" the patient used her affected limb in 30 specified daily tasks. These improvements persisted to the follow-up. DISCUSSION: Two weeks of constraining the unaffected limb, coupled with practice of functional movements of the impaired limb, may be an effective method for restoring motor function within a few months after cerebral insult. Encouraging improvements such as these strongly suggest the need for a group design that would explore this type of intervention in more detail. (+info)