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The balance of muscle activation in a fast limb movement
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C-3.03 VALUE OF ELECTROMYOGRAPHY IN THE THORAG A. Vila, A.M. Ouvrard, F. IC OUTLET SYNDROME. (Grenoble, Reymond, A. Franc0 and C. Quesada France) EMG studies were conducted in 53 patients with the thoracic outlet syndrome, together with the motor nerve conduction velocity in the median and cubital nerves, between Erb's point and axDistal sensory illa, and in the upper limb. nerve conduction velocity was measured in 19 cases. Proximal nerve compression was confirmed in 29% of cases, with associated carpal canal compression in 22%. The proximal nerve conduction velocities of the median and cubital in the neurological forms, and of the median in the neurovascular forms, were significantly different from normal values in 18 control subjects, but were not so in the vascular forms. Though EMG examination cannot confirm the need for surgery it can supply supportive No correlation between the clinical evidence. course and the proximal nerve conduction velocity was found in the 18 patients seen after treatment (surgery in 13 cases). B-3.04 RECIPROCAL INHIBITION IN THE HUMAN FOREARM. J. Rothwell. B. Dav and J. Obeso (London, G.B.) ”
With care, H reflexes may be obtained in human subjects at rest in the flexor muscles of the forearm by stimulating the median nerve at the Using this techelbow with submaximal shocks. nique we have demonstrated Ia reciprocal inhibition of forearm flexor motoneurones by showing that a willed wrist and finger extension depresses the H reflex in flexor muscles. Such reciprocal inhibition may be due, in part, to peripheral input for application of an appropriately timed shock below or at motor threshold to the radial nerve of the relaxed subject The reduces the size of the flexor H reflex. time course of this inhibition was very abrupt in onset and short in duration (5 msec); recovery was followed by a second period of inhibition lasting 0.5 to 2 sec. Anaesthetizing the radial nerve at the elbow to produce complete paralysis of the forearm extensor muscles appeared to facilitate H reflexes in the flexor muscles. However , if the paralysed subject attempted to extend the fingers and wrist, the H reflex was reduced in size even though no Reciprocal inhibition theremovement occurred. fore may be also produced in conscious man by The efa descending voluntary command alone. fect of a single stimulus applied to the radial nerve proximal to the block in an anaesthetized subject during willed wrist extension caused an even greater diminution of the flexor H reflex. The peripheral and central mechanisms responsible for reciprocal inhibition therefore appear to summate.
B-3.05 THE BALANCE OF MUSCLE ACTIVATION IN A J. Rothwell, J. Obeso and FAST LIMB MOVEMENT. C.D. Marsden (London, G.B;)
In the triphasic pattern of EMG activity in agonist and antagonist muscles which accompanies fast limb movements in man, the first agonist burst provides the impulsive force for the movement, while the antagonist burst, together with the viscoelastic properties of the limb, proMovements may be vide the decelerative force. made at different velocities by changing the size of the first burst of agonist activity. In the elbow and thumb we have found that movements made at different speeds over the same distance preserve a linear relationship between the size of the first agonist and the antagonist bursts of activity since a larger impulsive force, producing a faster movement, requires more antagonist action to halt it. However, movements made over different distances had various relationships between agonist and antagonist bursts of activitv because of the different amounts of passive decelerative force offered by the limb at different joint angles. Thus, movements made over short distances required more antagonist activity to halt them than movements made at the same speed over longer disWe suggest that learning a new relatances. tionship between the amount of agonist and antagonist activity for movements executed over different distances underlies the observation that it is much more difficult to move a limb accurately to different positions than it is to move through the same distance at various speeds. D-19.08 DETECTION OF EEG CHANGES DURING CAROTID ARTERY SURGERY. J.S. Barlow (Boston, Mass, USA) EEG recording during carotid artery surgery is a widely used technique to monitor the functiorr al state of the brain during this procedure, and various types of on-line computer processing of the EEG are used to supplement visual inspection of the ink-written record by the technologist on the site in the operating room. In the present retrospective study, three different methods for detecting a change in the EEG subsequent to clamping of an internal carotid artery are compared: (1) a relatively simple procedure based on determinations of envelope and baseline crossings, respectively, of the EEG (EEG Handbook 8B-46); (2) a particular form of inverse filtering (EEGJ 48: 246) and (3) a method of adaptive segmentation of.clinical EEGs (EEG J 46: 232: EEGJ in Dress). For this study, existing pen-and-ink monitoring records were reconverted to electrical form by means of a multichannel photo-optical scanner (EEGJ 23: 371; IEEE BioMed Trans 15: 46), and recorded on an EEG cassette tape recorder system (EEGJ 43: Each EEG was then analysed by the three 569). methods.
C-3.03 VALUE OF ELECTROMYOGRAPHY IN THE THORAG A. Vila, A.M. Ouvrard, F. IC OUTLET SYNDROME. (Grenoble, Reymond, A. Franc0 and C. Quesada France) EMG studies were conducted in 53 patients with the thoracic outlet syndrome, together with the motor nerve conduction velocity in the median and cubital nerves, between Erb's point and axDistal sensory illa, and in the upper limb. nerve conduction velocity was measured in 19 cases. Proximal nerve compression was confirmed in 29% of cases, with associated carpal canal compression in 22%. The proximal nerve conduction velocities of the median and cubital in the neurological forms, and of the median in the neurovascular forms, were significantly different from normal values in 18 control subjects, but were not so in the vascular forms. Though EMG examination cannot confirm the need for surgery it can supply supportive No correlation between the clinical evidence. course and the proximal nerve conduction velocity was found in the 18 patients seen after treatment (surgery in 13 cases). B-3.04 RECIPROCAL INHIBITION IN THE HUMAN FOREARM. J. Rothwell. B. Dav and J. Obeso (London, G.B.) ”
With care, H reflexes may be obtained in human subjects at rest in the flexor muscles of the forearm by stimulating the median nerve at the Using this techelbow with submaximal shocks. nique we have demonstrated Ia reciprocal inhibition of forearm flexor motoneurones by showing that a willed wrist and finger extension depresses the H reflex in flexor muscles. Such reciprocal inhibition may be due, in part, to peripheral input for application of an appropriately timed shock below or at motor threshold to the radial nerve of the relaxed subject The reduces the size of the flexor H reflex. time course of this inhibition was very abrupt in onset and short in duration (5 msec); recovery was followed by a second period of inhibition lasting 0.5 to 2 sec. Anaesthetizing the radial nerve at the elbow to produce complete paralysis of the forearm extensor muscles appeared to facilitate H reflexes in the flexor muscles. However , if the paralysed subject attempted to extend the fingers and wrist, the H reflex was reduced in size even though no Reciprocal inhibition theremovement occurred. fore may be also produced in conscious man by The efa descending voluntary command alone. fect of a single stimulus applied to the radial nerve proximal to the block in an anaesthetized subject during willed wrist extension caused an even greater diminution of the flexor H reflex. The peripheral and central mechanisms responsible for reciprocal inhibition therefore appear to summate.
B-3.05 THE BALANCE OF MUSCLE ACTIVATION IN A J. Rothwell, J. Obeso and FAST LIMB MOVEMENT. C.D. Marsden (London, G.B;)
In the triphasic pattern of EMG activity in agonist and antagonist muscles which accompanies fast limb movements in man, the first agonist burst provides the impulsive force for the movement, while the antagonist burst, together with the viscoelastic properties of the limb, proMovements may be vide the decelerative force. made at different velocities by changing the size of the first burst of agonist activity. In the elbow and thumb we have found that movements made at different speeds over the same distance preserve a linear relationship between the size of the first agonist and the antagonist bursts of activity since a larger impulsive force, producing a faster movement, requires more antagonist action to halt it. However, movements made over different distances had various relationships between agonist and antagonist bursts of activitv because of the different amounts of passive decelerative force offered by the limb at different joint angles. Thus, movements made over short distances required more antagonist activity to halt them than movements made at the same speed over longer disWe suggest that learning a new relatances. tionship between the amount of agonist and antagonist activity for movements executed over different distances underlies the observation that it is much more difficult to move a limb accurately to different positions than it is to move through the same distance at various speeds. D-19.08 DETECTION OF EEG CHANGES DURING CAROTID ARTERY SURGERY. J.S. Barlow (Boston, Mass, USA) EEG recording during carotid artery surgery is a widely used technique to monitor the functiorr al state of the brain during this procedure, and various types of on-line computer processing of the EEG are used to supplement visual inspection of the ink-written record by the technologist on the site in the operating room. In the present retrospective study, three different methods for detecting a change in the EEG subsequent to clamping of an internal carotid artery are compared: (1) a relatively simple procedure based on determinations of envelope and baseline crossings, respectively, of the EEG (EEG Handbook 8B-46); (2) a particular form of inverse filtering (EEGJ 48: 246) and (3) a method of adaptive segmentation of.clinical EEGs (EEG J 46: 232: EEGJ in Dress). For this study, existing pen-and-ink monitoring records were reconverted to electrical form by means of a multichannel photo-optical scanner (EEGJ 23: 371; IEEE BioMed Trans 15: 46), and recorded on an EEG cassette tape recorder system (EEGJ 43: Each EEG was then analysed by the three 569). methods.