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Quantitative automatic analysis of motor unit potentials with a special two-channel EMG electrode
s90 D-3.08 LABIAL REFLEXES IN MAN DURING PERFORHANCE OF AN ORAL REACTION TIME TASK. M. Bratzlavsky and H. Vander Eecken (Ghent, Belgium) The experiments were designed to investigate the role of labial reflexes in the control of lip muscle activities of normal man. The human orbicularis oris reflex consists of two electromyographic components which are most adequately evoked by a short innocuous pressure stimulus applied to the lips. The location of the involved pressure-sensitive receptors (muscular versus cutaneous) and the central trigeminal pathways are still unknown. The only dissimilarities shown by the first and second lip reflex components are inherent in the different lengths of their respective loops, with the late response travelling through a much longer polysynaptic pathway. When studied throughout labial reaction time experiments, both reflex components are shown to be strongly potentiated 20 to 40 msec prior to and during voluntary lip muscle activation. Isometric orbicularis oris contraction is most efficient in this facilitation. The results indicate that in man the force-controlling properties of the lip musculature depend in pari oh segmental afferent input mediated bv lio reflex afferents. It is suagested that thiough their positive feedbackaction, the labial reflexes may regulate labial tension during mastication and sucking. C-2.02 QUANTITATIVE AUTOMATIC ANALYSIS OF MOTOR UNIT POTENTIALS WITH A SPECIAL TWO-CHANNEL EMG ELECTRODE. B. Falck. and H. Lana (Turku, Finland) A concise quantitative method for the analysis of motor unit potentials (MUPs) is described. The method is based on averaging and a special 2-channel EM6 electrode. The electrode has two separate recording surfaces, a single-fibre electrode and a conventional size electrode on the opposite side of the cannula. Both surfaces The activity of are referred to the cannula. the single-fibre electrode is used as a trigger when MUPs are recorded from the conventional size electrode. Different criteria for automatic measurement of the MUP parameters have been compared with a desk top computer. Advantages of ihe method are that (1) the identificatjon of individual MUPs is reliable and does not require separate computer programs, (2) medium and high threshold units may be analysed, since individual MUPs may be extracted, even from a complete interference pattern, by the averaging procedure, (3) subjective bias in the selection of MUPs to be analysed is avoided, (4) during the analysis information on single fibre parameters (jitter and fibre density) is acquired. Results from normal controls and various neuromuscular disorders are presented.
A-9.07 SOMATOSENSORY EVOKED POTENTIALS IN THE EVALUATION OF INFANTS AND CHILDREN WITH SPINAL DYSRAPHISM. J.B. Cracco and R.Q. Cracco (Brooklyn, NY, USA) Spinal and cerebral evoked potentials to peroneal nerve stimulation were recorded from surface electrodes over the spine and scalp of 40 infants and children with various forms of spinal dysraphism. These were compared with similar potentials in age-matched normals. In most children with meningomyelocele and a few with occult dysraphism and weakness of the legs, cerebral potentials were absent. Small potentials were recorded over the cauda equina. No responses were recorded from more rostra1 spinal leads in some of these patients; in others rostra1 leads yielded positive potentials which decreased in amplitude but did not change in latency rostrally. These positive potentials reflect volume conducted events which are consistent with physiological transection of the spinal cord ("killed-end" effect). Similar potentials have been recorded in cats folIn a lowing complete spinal cord transection. few children with clinically asymmetrical deficits, relatively normal responses were obtained with stimulation of the normal leg; stimulation of the weak leg yielded responses only over the 'cauda equina. In several children with occult dysraphism and minimal neurological findings, the complex spinal potentials which were always recorded in normals over the lower thoracic spines (Tg-T12) were recorded over lumbar spines (L2-L4), Suggesting caudal displacement of the co?d. This interpretation was confirmed by myelography. A-3.07 EFFECTS ON THE NERVOUS SYSTEM OF EXPOSURE ~0 A SINGLE SOLVENT (TOLUENE) IN INDUSTRIAL WORK - A COMPARISON WITH THE EFFECTS OF EXPOSURE TO A MIXTURE OF SOLVENTS. A. Wennberg (Stockholm, Sweden)
In a previous study on car painters it was shown that long-term exposure to organic solvents has effects on both the central and peripheral nervous systems even at low exposure levels (mean level was 30% of TLV). The effects were: psychiatric symptoms (neurasthenic syndrome), reduced capacity in performance tests, impaired nerve conduction, increased vibration sense levels. There were also some effects on EEG, VER and computed tomography, though nonconclusive. (Scandinavian Journal of Work, Environment & Health, Elofsson et al. 1980) As the exposure in all cases in that study consisted of a mixture of several (usually around 10) different solvents, it was not possible to confirm whether the effects were caused by one or several of them and whether two or more might interact in a synergistic way. It would therefore be informative to study a similar group of subjects exposed to only one of the solvents involved in the car painter
A-9.07 SOMATOSENSORY EVOKED POTENTIALS IN THE EVALUATION OF INFANTS AND CHILDREN WITH SPINAL DYSRAPHISM. J.B. Cracco and R.Q. Cracco (Brooklyn, NY, USA) Spinal and cerebral evoked potentials to peroneal nerve stimulation were recorded from surface electrodes over the spine and scalp of 40 infants and children with various forms of spinal dysraphism. These were compared with similar potentials in age-matched normals. In most children with meningomyelocele and a few with occult dysraphism and weakness of the legs, cerebral potentials were absent. Small potentials were recorded over the cauda equina. No responses were recorded from more rostra1 spinal leads in some of these patients; in others rostra1 leads yielded positive potentials which decreased in amplitude but did not change in latency rostrally. These positive potentials reflect volume conducted events which are consistent with physiological transection of the spinal cord ("killed-end" effect). Similar potentials have been recorded in cats folIn a lowing complete spinal cord transection. few children with clinically asymmetrical deficits, relatively normal responses were obtained with stimulation of the normal leg; stimulation of the weak leg yielded responses only over the 'cauda equina. In several children with occult dysraphism and minimal neurological findings, the complex spinal potentials which were always recorded in normals over the lower thoracic spines (Tg-T12) were recorded over lumbar spines (L2-L4), Suggesting caudal displacement of the co?d. This interpretation was confirmed by myelography. A-3.07 EFFECTS ON THE NERVOUS SYSTEM OF EXPOSURE ~0 A SINGLE SOLVENT (TOLUENE) IN INDUSTRIAL WORK - A COMPARISON WITH THE EFFECTS OF EXPOSURE TO A MIXTURE OF SOLVENTS. A. Wennberg (Stockholm, Sweden)
In a previous study on car painters it was shown that long-term exposure to organic solvents has effects on both the central and peripheral nervous systems even at low exposure levels (mean level was 30% of TLV). The effects were: psychiatric symptoms (neurasthenic syndrome), reduced capacity in performance tests, impaired nerve conduction, increased vibration sense levels. There were also some effects on EEG, VER and computed tomography, though nonconclusive. (Scandinavian Journal of Work, Environment & Health, Elofsson et al. 1980) As the exposure in all cases in that study consisted of a mixture of several (usually around 10) different solvents, it was not possible to confirm whether the effects were caused by one or several of them and whether two or more might interact in a synergistic way. It would therefore be informative to study a similar group of subjects exposed to only one of the solvents involved in the car painter