Production and suppression of tremor by mesencephalic tegmental lesions in monkeys

In a group of rhesus monkeys two consecutive lesions were placed in the mesencephalic tegmental region. The first lesion, for tremor production, was placed ventromedially in a region where multiunit activity was organized in rhythmic bursts of 4 to 8 cps and threshold electrical stimulation induced III nerve type of responses. The second lesion, for tremor suppression, was placed dorsolateral to the previous one, in a region where nonrhythmic multiunit activity was enhanced by peripheral nociceptive stimulus and threshold electrical stimulation produced awakening. Studying the lesions by planimetry in a quantitative manner, it was found that tremor production depended on the involvement of a critical amount of the pars compacta of the substantia nigra and the region immediately behind it, whereas tremor suppression depended on the involvement of a critical amount of the nucleus reticularis mesencephali. Involvement of other adjacent structures was not significant for either tremor production or suppression.     

Autoimmune neuromuscular disease induced by a preparation of choline acetyltransferase

An apparent fatal autoimmune disease was induced in guinea pigs by injection of a preparation of choline acetyltransferase in complete Freund's adjuvant. The animals probably died from respiratory failure based on the evidence from clinical, histological, and histochemical examination. At autopsy the pathogenic lesions were located at the neuromuscular junctions and near the nerves where choline actyltransferase was found. It is further proposed that this is a presynaptic autoimmune neuromuscular disease based on the finding of numerous target, as well as targetoid, fibers in muscle after histochemical staining. There was also denervation shown by electromyographic measurements in the form of positive sharp waves as well as fibrillation discharges.     

Morphine versus haloperidol catalepsy in the rat: An electromyographic analysis of postural support mechanisms

Electromyographic recordings from antagonistic flexor and extensor muscles in the forelegs (biceps and triceps) and hind legs (tibialis and gastrocnemius-soleus) of freely moving rats demonstrated that haloperidol (5 and 10 mg/kg, i.p.) and morphine (20 and 40 mg/kg, i.p.) produced contrasting patterns of rigidity. Haloperidol catalepsy was characterized by increases in frequency, intensity, and duration of simultaneous tonic cocontractions in antagonistic flexor and extensor muscles of the limbs. Such synergistic rigidity suggested the release of an adaptive mechanism involved in static support and the maintenance of stable static equilibrium (the positive supporting reaction of Schoen and Magnus), at the expense of locomotor mechanisms. In contrast, morphine produced antagonistic/reciprocal rigidity, which was insensitive to challenges to static equilibrium, and was compatible with locomotion. Contrary to the haloperidol-induced limb postures, which were enhanced supporting reactions, those induced by morphine were “frozen” phases of the step cycle. Haloperidol-induced synergistic rigidity and morphine-induced antagonistic/reciprocal rigidity are discussed as manifestations of contrasting movement subsystems underlying these functionally opposite immobility states. In addition, we present hypotheses concerning supraspinal and spinal mechanisms underlying cataleptic rigidity states, and their relevance as models of parkinsonian rigidity and akinesia.     

Types of gaze movement: Variable interactions of eye and head movements

The patterns of coordinated eye-head movement in gaze shift are influenced by preconditions of the experimental protocol, such as the predictability and amplitude of the stimulus and the subject's endeavor to move as instructed, either naturally or as fast as possible. Gaze-shift movements fall into four distinct types with respect to eye-head latency, each one involving particular gaze-shift errors and head acceleration trajectories.     

Microinjection of neostigmine into the pontine reticular formation of the mouse: further evaluation of a proposed REM sleep enhancement technique

Microinjections of cholinergic agonists into the pontine reticular formation (PRF) powerfully induce rapid eye movement sleep (REMS) in cats but have comparatively weaker effects in rats. Recently, the cholinomimetic neostigmine has been reported to strongly enhance REMS following microinjection into the PRF of the mouse. That study used behavioral assessments of locomotion in lieu of electrophysiological measures of muscle tone to identify REMS. We sought to confirm that the behavioral state induced in mice by PRF injections of neostigmine meets standard electroencephalogram (EEG) and electromyogram (EMG) criteria for defining REMS. Cortical EEG, nuchal muscle EMG, and PGO waves were recorded from male C57BL/6N mice with chronic indwelling cannulae for the delivery of neostigmine to the PRF. Recordings were made during midday following injections of neostigmine (8.8 mM, 50 nl), 2 h after lights on (LD 12:12). Neostigmine induced a behavioral state characterized by low amplitude, highly desynchronized cortical EEG with little theta, no PGO waves, and a sustained high muscle tone. Behavioral states meeting standard criteria for slow-wave sleep (SWS) and REMS were significantly suppressed compared to baseline recordings, and REMS onset was delayed by 3 h. Consistent with earlier reports, neostigmine did strongly suppress locomotor activity in open field tests and in the home cage. Due to the failure to meet criteria for defining REMS, we conclude that neostigmine microinjection into the PRF of the mouse induces an abnormal waking state rather than REMS.     

Tracking motor unit action potentials in the tibialis anterior during fatigue

New surface electromyogram (SEMG) techniques offer the potential to advance knowledge of healthy and diseased motor units. Conduction velocity (CV) estimates, obtained from indwelling electrodes, may provide diagnostic information, but the standard method of CV estimation from SEMG may be of only limited value. We developed a motor unit (MU) tracking algorithm to extract motor unit conduction velocity (MUCV) and motor unit action potential (MUAP) amplitude estimates from SEMG. The technique is designed to provide a noninvasive means of accessing fatigue and recruitment behavior of individual MUs. We have applied this MU tracking algorithm to SEMG data recorded during isometric fatiguing contractions of the tibialis anterior (TA) muscle in nine healthy subjects, at 30%-40% maximum voluntary contraction (MVC). The results reveal that MUCVs and MUAP amplitudes of individual MUs can be estimated and tracked across time. Time-related changes in the MU population may also be monitored. Thus, the SEMG technique employed provides insight into the behavior of the underlying muscle at the MU level by noninvasive means.     

Classification of Duane’s Retraction Syndrome: Two Additional Electromyogram Types

Background Hubers clinical and electromyographical classifications of Duanes retraction syndrome have been considered to correspond to each other. However, cases that do not correspond to these classifications have been reported recently.Cases Retrospectively, we tried to classify the clinical types and electromyogram types of 17 eyes (15 cases) with Duanes retraction syndrome according to Hubers classification.Observations Eleven eyes could not be classified into any of Hubers electromyogram types. Among these eyes, two major additional electromyogram patterns were newly classified: a center-peak type, in which the lateral rectus or medial rectus muscle showed maximum activity in the primary position; and a type with continuous lateral rectus muscle discharge. Some minor electromyogram patterns were also recorded.Conclusion The wide variation in these electromyogram patterns may be due to the diversity of the lesions in Duanes retraction syndrome, which can be the result of muscular, nuclear, internuclear, or supranuclear failure. Jpn J Ophthalmol 2004;48:148–153 © Japanese Ophthalmological Society 2004     

Human masticatory muscle activity and jaw position under experimental stress

The purpose of the present study was to determine whether stress induced a consistent pattern of increased electromyographic (EMG) activity in different masticatory muscles, and whether stress produced changes in jaw position. Thirty-five dental students at Taipei Medical College volunteered for this study. Mental arithmetic was used to create a stress condition and relaxation instruction was used to help relax the subjects. Subjects were asked to evaluate the stress they felt under each experimental condition with a visual analogue scale (VAS). Surface electrodes were used to monitor the EMG activities of the right masseter, right posterior temporalis and suprahyoid muscles. A kinesiograph was used to observe the jaw position. Data collected before mental arithmetic or relaxation monitored the baseline level. The VAS means were significantly increased during the stress condition and significantly decreased following relaxation, compared with the baseline. There was also a significant increase in EMG activity of all three muscles during mental arithmetic compared with baseline; different patterns of increased EMG activity were noticed in the three muscles under a continuous stress condition. Under stress, the incidence of tooth contact at intercuspal position was also increased.     

儿童脊肌萎缩症23例临床特点及遗传学分析

目的 探讨脊肌萎缩症的临床特点和遗传方式。方法 对23例脊肌萎缩症患儿的临床资料进行总结，并用Weiber先证法分析其发病的遗传规律。结果 临床特点为出生后双下肢呈对称性弛缓性瘫痪且进行性加重，四肢近端无力，肌张力、肌力低下；肌电图主要表现为神经原性损害。隐性遗传分离分析表明，12个家系23例患儿发病方式符合常染色体隐性遗传。结论 脊肌萎缩症的临床发病早且病死率高，在遗传咨询中注意作相关产前基因检查，可避免该类患儿的出生。     

Activity pattern of swallowing-related muscles, food properties and body position in normal humans

Summary  Activity patterns of the swallowing-related muscles were examined in normal subjects at different four body positions during swallowing of foods with different textural properties. Surface electromyograms were recorded from two muscle groups, the anterior tongue and suprahyoid muscles. The T _P technique we developed was applied to the electromyograms for quantitative analysis of the activity patterns. Three test foods were prepared by dissolving 2·0% (low), 5·7% (middle) and 9·1% (high concentration) of a thickening agent into distilled water. Each subject was delivered randomly, one of the test foods to swallow at one of the four body positions i.e. horizontal supine, 30° inclined, 60° inclined and upright. In this study, T ₅₀ values were calculated in activity data of the two muscle groups, and the T ₅₀ values were statistically examined analysis of variance with a linear model including four fixed effects of 'concentrations', 'body positions', 'subjects' and 'sessions'. Three major findings obtained were that (i) the activity pattern of the anterior tongue was altered from a decrementing discharge pattern to an incrementing discharge pattern by shifting from the upright to the horizontal supine position, (ii) the activity pattern of the suprahyoid muscles was altered from a decrementing discharge pattern to an incrementing discharge pattern by shifting from the low concentration food to the higher ones and (iii) two subgroups were detected in subjects with the significant effects of 'concentrations' and 'body positions'. These findings lead a conclusion that activity patterns of the swallowing-related muscles are affected by food properties and body positions.