Motor System Function Research Articles

Reorganization of the Executive Motor System after Stroke

We wished to characterize changes in function of the executive motor system individually and to correlate these with the degree of recovery from motor disability following stroke. Six male stroke patients underwent perfusion positron emission tomography scanning while undertaking a repetitive, graded force exertion task with the hand affected by stroke, and at rest. We correlated regional cerebral blood flow (rCBF) and force exerted, and compared the distribution of blood flow in all active states with that at rest. The statistical parametric maps of task-related flow changes that were generated were coregistered with anatomical magnetic resonance imaging scans. A comparison of force exertion with rest (categorical comparison) in the group as a whole showed fewer activations than found in normal subjects in both the infarcted and unaffected hemispheres, indicating disruption of the entire motor network. We found a polynomial correlation between synaptic activity (as indexed by blood flow change) and force exerted in 3 patients in the contralateral primary sensorimotor cortex, distinctly different from the logarithmic curve in normal volunteers. For the group there was an initial steep rise of relative rCBF at lower exerted forces, a plateau, and then a second steep rCBF increase at a force of approximately 50% of maximal voluntary contraction (MVC). The ipsilateral ventral posterior supplementary motor area (pSMA) and parietal areas showed correlated activity with force exerted that was not found in normal subjects. Coregistered functional and anatomical images in individuals indicated considerable intersubject variability in the patterns of activation of the contralateral primary motor cortex, pSMA, anterior cingulate cortex, dorsolateral prefrontal cortex, anterior opercular cortex, and parietal cortex. Compensatory actuation of cortical areas that comprise components of the sensorimotor system not normally activated by the task used favours the concept that recruitment of preexisting corticocortical and possibly parallel corticospinal pathways plays a prominent role in functional reorganization. Ipsilateral force-correlated rCBF changes were sometimes present in dorsolateral premotor, insular and parietal cortex consistent with bilateral representation of movements in these motor-associated areas. Quantitative analysis of the rCBF-force relationship provides clearer evidence for large-scale functional reorganization than simple task-control comparisons. The binominal relationship between rCBF and force suggests increased synaptic activity at approximately 50% MVC, a level at which many stroke patients experience an increased sense of effort.

Parasite infection alters schooling behaviour: deviant positioning of helminth-infected minnows in conspecific groups

The formation of polarized swimming groups is a successful antipredator adaptation of many fish species because the confusion created by multiple synchronously moving targets reduces the attack success of predators. However, maintaining synchrony and spatial position within such groups requires the functioning of complex sensory and motor systems, so the ability to school effectively could be sensitive to disease or infection with debilitating parasites. As many predators overcome this confusion by attacking visually distinct individuals in groups, infection-associated traits that impair schooling ability might increase predation on parasitized school members, with consequences for the survival of both host and parasite. We report here on a study designed to investigate the effects of parasite infection on the schooling behaviour of European minnows, Phoxinus phoxinus. Over a series of trials done in a flow-pool, minnows infected with plerocercoid larvae of the cestode Ligula intestinalis consistently exhibited increased nearest neighbour distances when compared with uninfected conspecifics in the same school, suggesting that infected fish may be unable to maintain close spatial positions within schools. Positive relations were found between the area covered by a school and both the nearest neighbour differences of uninfected and infected fish in the school, but these relations differed with infected fish exhibiting increasingly larger nearest neighbour differences than uninfected fish as schools became more dispersed. Infected fish also occupied peripheral positions more often than would have been expected if individuals assorted randomly within schools. Our results indicate that infected fish in schools exhibit positioning behaviour that deviates from that of uninfected conspecifics. As schooling is known to be a primary antipredator response of minnows, the altered behaviour of parasitized individuals within polarized groups could increase their susceptibility to certain predators, with potential consequences for parasite transmission.

Analyzing ocular-motor control dysfunction: insights into disease processes and normal function

The author examines several ways in which the application of engineering analysis tools have contributed to one's understanding of both dysfunction (e.g., eye movements provoked by disease) and normal function of the ocular motor system. In the past 30 years, beginning with the work of Gerald Westheimer, Larry Stark, Laurence Young and David Robinson, there have been scores of studies of ocular motility that were firmly based on engineering principles and carried out using a classic control-systems approach. The author limits the discussion to concentrating on only a few such studies that have eliminated from the author's own laboratory. Specifically, the author focuses on studies into two eye-movement disorders: gaze-evoked nystagmus and congenital nystagmus. These studies were conducted on humans with one or the other of these conditions and had the dual aims of: 1) understanding the mechanisms underlying the pathological eye movements; and 2) using the findings to infer how the normal ocular motor system is organized. >

Physiological effects produced by botulinum toxin treatment of upper limb dystonia. Changes in reciprocal inhibition between forearm muscles.

Patients with upper limb dystonia have abnormal reciprocal inhibition between flexor and extensor forearm muscles. To see whether botulinum toxin treatment alters segmental motor system function, we studied reciprocal inhibition between forearm flexor and extensor muscles, before and after botulinum toxin injection in forearm muscles in 12 patients with upper limb dystonia. Reciprocal inhibition was studied by conditioning the H reflex in forearm flexors with a radial nerve stimulus delivered at a range of time intervals. Botulinum toxin injection improved upper limb dystonia. Before botulinum toxin injection, the dystonic patients had a decreased second phase of reciprocal inhibition. After botulinum toxin injections this second abnormal phase of reciprocal inhibition increased. Botulinum toxin did not change the first phase of reciprocal inhibition. Botulinum toxin treatment also reduced the M wave and the H reflex by a similar amount but left the Hmax:Mmax ratio unchanged. Ample evidence has shown that the therapeutic effects of botulinum toxin in dystonia depend mainly on its neuromuscular junction blocking action. Our data now suggest a concurrent indirect effect on spinal cord circuitry, probably through the action of botulinum toxin on the intrafusal neuromuscular junction.

Individualized Developmental Care for the Very Low-Birth-Weight Preterm Infant

To investigate the effectiveness of individualized developmental care in reducing medical and neurodevelopmental sequelae for very low-birth-weight infants. Randomized controlled trial. Newborn intensive care unit. Thirty-eight singleton preterm infants, free of known congenital abnormalities, weighing less than 1250 g, born before 30 weeks' gestation, mechanically ventilated within 3 hours of delivery and for more than 24 hours in the first 48 hours, randomly assigned to a control or an experimental group. Caregiving by nurses specifically trained in individualized developmental care; observation and documentation of the infants' behavior within 12 hours of admission, and subsequently every 10th day; developmental care recommendations and ongoing clinical support for the nurses and parents based on regular observation of the infant by developmental specialists; and the availability of special caregiving accessories. Medical outcome, including average daily weight gain; number of days the infant required mechanical ventilation, oxygen, gavage tube feeding, and hospitalization; severity of retinopathy of prematurity, bronchopulmonary dysplasia, pneumothorax, and intraventricular hemorrhage; pediatric complications; age at discharge; and hospital charges. Neurodevelopmental outcome, including Assessment of Preterm Infants' Behavior scale and quantified electroencephalography (2 weeks after due date); and Bayley Scales of Infant Development and Kangaroo Box Paradigm (9 months after due date). The infants in the experimental group had a significantly shorter duration of mechanical ventilation and supplemental oxygen support; earlier oral feeding; reduced incidence of intraventricular hemorrhage, pneumothorax, and severe bronchopulmonary dysplasia; improved daily weight gain; shorter hospital stays; younger ages at hospital discharge; and reduced hospital charges compared with the infants in the control group. At 2 weeks after their due dates, these infants also showed improved autonomic regulation, motor system functioning, self-regulatory abilities, and visual evoked potential measures; and at 9 months, they had improved Bayley Mental and Psychomotor Developmental Index scores, as well as Kangaroo Box Paradigm scores. Very low-birth-weight preterm infants may benefit from individualized developmental care in the neonatal intensive care unit in terms of medical and neurodevelopmental outcome.

Individualized developmental care for the very low-birth-weight preterm infant. Medical and neurofunctional effects

<h3>Objective.</h3> —To investigate the effectiveness of individualized developmental care in reducing medical and neurodevelopmental sequelae for very low-birth-weight infants. <h3>Design.</h3> —Randomized controlled trial. <h3>Setting.</h3> —Newborn intensive care unit. <h3>Patients.</h3> —Thirty-eight singleton preterm infants, free of known congenital abnormalities, weighing less than 1250 g, born before 30 weeks' gestation, mechanically ventilated within 3 hours of delivery and for more than 24 hours in the first 48 hours, randomly assigned to a control or an experimental group. <h3>Intervention.</h3> —Caregiving by nurses specifically trained in individualized developmental care; observation and documentation of the infants' behavior within 12 hours of admission, and subsequently every 10th day; developmental care recommendations and ongoing clinical support for the nurses and parents based on regular observation of the infant by developmental specialists; and the availability of special caregiving accessories. <h3>Main Outcome Measures.</h3> —Medical outcome, including average daily weight gain; number of days the infant required mechanical ventilation, oxygen, gavage tube feeding, and hospitalization; severity of retinopathy of prematurity, bronchopulmonary dysplasia, pneumothorax, and intraventricular hemorrhage; pediatric complications; age at discharge; and hospital charges. Neurodevelopmental outcome, including Assessment of Preterm Infants' Behavior scale and quantified electroencephalography (2 weeks after due date); and Bayley Scales of Infant Development and Kangaroo Box Paradigm (9 months after due date). <h3>Results.</h3> —The infants in the experimental group had a significantly shorter duration of mechanical ventilation and supplemental oxygen support; earlier oral feeding; reduced incidence of intraventricular hemorrhage, pneumothorax, and severe bronchopulmonary dysplasia; improved daily weight gain; shorter hospital stays; younger ages at hospital discharge; and reduced hospital charges compared with the infants in the control group. At 2 weeks after their due dates, these infants also showed improved autonomic regulation, motor system functioning, self-regulatory abilities, and visual evoked potential measures; and at 9 months, they had improved Bayley Mental and Psychomotor Developmental Index scores, as well as Kangaroo Box Paradigm scores. <h3>Conclusion.</h3> —Very low-birth-weight preterm infants may benefit from individualized developmental care in the neonatal intensive care unit in terms of medical and neurodevelopmental outcome. (<i>JAMA</i>. 1994;272:853-858)

Microglial infection by a neurovirulent murine retrovirus results in defective processing of envelope protein and intracellular budding of virus particles.

The observation of murine retrovirus infection of microglial cells in brain regions expressing spongiform neurodegenerative changes suggests that these cells may play an important role in pathogenesis. To evaluate this potential in vitro, murine microglial cells were infected in mixed glial cultures with the highly neurovirulent murine retrovirus, FrCasE. The microglia were then isolated from the mixed cultures on the basis of their differential adherence and shown to be approximately 98% pure. The infected microglia expressed viral envelope protein at the plasma membrane, while viral budding was primarily intracellular. Evaluation of the viral envelope protein by immunoblotting indicated that the immunoreactive species produced was exclusively a 90-kDa precursor protein. Very little of the envelope protein was associated with particles released from these cells, and viral titers in the culture supernatant were low. Interestingly, these cells were still capable of infecting permissive target cells when seeded as infectious centers. This partially defective infection of microglial cells suggests a potential cellular means by which a neurovirulent retrovirus could disrupt normal microglia and in turn central nervous system motor system functioning.

Ontogenetic studies of flight initiation in Locusta: Wind response of an identified interneurone (TCG)

The tritocerebral commissure giant (TCG) wind-sensitive interneurone is involved in initiation and maintenance of flight in adult locusts. In this paper we study this interneurone in the imago and non-flying larval instars. Cobalt fills show that the TCG establishes its adult morphology by the first larval instar. An accompanying axon, apparently representing the peculiar tritocerebral commissure “dwarf” (TCD) is present, too, at least for the last preimaginal instars. Physiological tests show similar responses of the TCG to wind stimuli in the 4th, 5th instar and adult stages. Spike activity, however, is usually higher in adult compared to larval instars. It is possible that all interneurones, involved in adult-specific motor patterns (such as flight), are present in preimaginal stages and can be activated independently of the function of the final motor system.

Insomnia in neurological diseases

Sleep disturbance, common in many neurological diseases, can be caused by underlying CNS pathology, altered motor system function, associated cognitive and psychiatric disorders, secondary effects of the disease such as pain and immobility, and medication effects. Nocturnal behavioral disturbances are a major contributor to institutionalization of such patients, and respiratory abnormalities of sleep can be life-threatening. Rational approach to diagnosis and treatment can lead to significant improvements in many such patients.

Werner's Syndrome: A Libyan Family with Nine Affected Members

Werner's Syndrome: A Libyan Family with Nine Affected Members

Isoflurane-induced attenuation of motor evoked potentials caused by electrical motor cortex stimulation during surgery

Dysfunction of spinal motor conduction during surgical procedures may not be reflected by changes in somatosensory evoked potential waveforms. A method of monitoring that allows direct and continuous assessment of motor function within the central nervous system during surgery would be useful. This paper describes one such method utilizing noninvasive electric cortical stimulation to evoke muscle activity (the motor evoked potential, or MEP) during surgery. The effect of isoflurane (superimposed on a baseline of N2O/narcotic anesthesia) on MEP's in response to cortical stimulation is specifically examined. Eight patients undergoing elective neurosurgical operations were included in the study. All patients received a background of general anesthesia and partial nondepolarizing neuromuscular blockade. The motor cortex was stimulated electrically via self-adhesive scalp electrodes. Electromyographic responses from multiple muscles were measured with subdermal electroencephalograph-type needle electrodes. Motor responses to stimulation were continually recorded on magnetic tape for off-line analysis. Once closing of the surgical incision was begun, a series of four to five stimuli of constant magnitude were applied to obtain "baseline" MEP responses. Patients were then ventilated with isoflurane for up to 8 minutes, during which time stimuli were continued every 15 to 20 seconds. Comparison was made of MEP responses for trials before, 1 minute after, and 5 minutes after the addition of isoflurane. All patients demonstrated reproducible motor responses to cortical stimulation during surgery. Addition of isoflurane [isoflurane)exp, less than or equal to 0.5%) to pre-existing anesthesia caused marked attenuation of MEP amplitudes in all patients within 5 minutes of its application, without affecting neuromuscular transmission as judged by direct peripheral nerve stimulation. It is concluded that: 1) monitoring motor system integrity and function with electric transcranial cortical stimulation during surgery is feasible when utilizing an N2O/narcotic anesthetic protocol; and 2) the quality of data obtained will likely suffer with the addition of isoflurane.

The effects of dopamine-depleting brain lesions on the electrophysiological activity of rat substantia nigra dopamine neurons

Extensive damage to the nigrostriatal dopamine (DA) system initiates a number of compensatory changes that may be involvei in counterbalancing the effects of the lesion. In this study, we examined whether changes in the electrophysiological activity of the remaining DA cells play a role in compensating for 6-hydroxydopamine (6-OHDA)-induced depletions of striatal DA. DA cell activity in lesioned rats was assessed along three dimensions: (1) the relative proportion of the remaining DA neurons firing spontaneously, (2) their firing rate, and (3) their firing pattern. Histofluorescence studies revealed a sparing of DA neurons in the midbrain of 6-OHDA-lesioned rats relative to the levels of DA remaining in the striatu. With respect to DA cell activity, depletions of up to 96% of striatal DA did not result in substantial alterations in the proportion of DA neurons active, their mean firing rate, or their firing pattern. Increases in these parameters only occurred when striatal DA depletions exceeded 96%. These results suggest that the biochemical and receptor compensations produced in the DA system in response to injury are of sufficient magnitude to allow the DA cells to maintain baseline levels of activity. In this way, the remaining DA neurons would maintain the wide dynamic range of electrophysiological responsivity that may be necessary for the normal function of the extrapyramidal motor system.

Electrical Activity of Corpus Cavernosum During Flaccidity and Erection of the Human Penis: A New Diagnostic Method?

We investigated 7 normal men and 1 diabetic patient with erectile dysfunction. Electromyography electrodes were placed in the corpus cavernosum of the penis and electrical activity was recorded during flaccidity. With sexual arousal the activity decreased and tumescence was initiated. During tumescence and full erection the electrical activity of the corpus cavernosum almost ceased but in the diabetic patient (neurogenic impotence) an increase was observed. This discoordination might be the cause of the erectile dysfunction.Recording the electrical activity of the corpus cavernosum in patients with suspected neurogenic erectile dysfunction could become clinically valuable, since this is the first test possible to study the function of the autonomic motor system that normally regulates penile function.

The computer-vibromyography as a biometric progress in studying muscle function.

Muscular vibrations were recorded from different relaxed and contracted skeletal muscles in human subjects, with the use of a piezo-electric device. Simultaneous wire-EMG recordings were performed. Spectral analysis of the acceleration curves (vibromyograms) disclosed muscle and function dependent compound frequency patterns. We suggest that the activity of motor units including the action of central reflex loops and oscillatory driving is mainly responsible for the muscular vibrations. Other sources are discussed. Computer-Vibromyography as a mechanical ensemble measurement supplements bioelectric EMG techniques and classical tremor analysis and provides further insights into the function of muscle and motor-system.

Central nervous system toxicity following the treatment of pediatric patients with ifosfamide/mesna.

Ifosfamide/mesna treatment of 50 patients with pediatric malignant solid tumors was associated with the development of neurotoxic signs and symptoms in 11 of these individuals who received 29 courses of treatment. Neurologic toxicity included changes in mental status, cerebellar function, cranial nerve, and cerebellar and motor system function, including seizures. All symptoms, signs, and EEG abnormalities were transient. Some of the affected individuals failed to develop acute neurotoxic signs of symptoms when retreated with ifosfamide. A grading system for scoring these neurologic abnormalities is presented for comparison of acute neurotoxic effects of other agents. Recommendations are made regarding early termination or delay of ifosfamide/mesna treatments in the presence of significant neurotoxicity.

Motor disorder and the timing of repetitive movements.

This paper is concerned with the timing of regular repetitive movements. The two-process model of Wing and Kristofferson attributes variability in self-paced interresponse intervals to imprecision in a timekeeper and to temporal noise in the execution of motor responses triggered by the timekeeper. Assuming independence of timekeeper intervals and motor delays, the variance of each may be estimated from interresponse-interval statistics. Comparison of changes in timing performance associated with alterations in motor-system functioning offer the possibility of a new approach to investigation of this model. Illustrative data are presented from a case study of a patient with Parkinson's disease whose lesions affecting the dopaminergic pathways of the basal ganglia have given rise to asymmetric symptoms, including differences in timing performance of the two hands. Analysis of interresponse-interval variability according to the two-process model indicates that the elevated variability of the side more greatly affected by parkinsonism is attributable to the timekeeper intervals rather than the motor delays.

Effects of TRH-T and DN-1417 on the central nervous system: an electrophysiological study of arousal reaction and evoked muscular discharges.

For the purpose of elucidating the effects of TRH and DN-1417 on the CNS, electrophysiological experiments were performed and the following observed. 1. TRH and DN-1417 exerted threshold-decreasing action not only on the threshold for arousal reaction but also on the threshold for evoked muscular discharges, which occur on stimulation of the brainstem reticular formation. 2. The threshold decreasing effect of DN-1417 was stronger than that of TRH, not only for the arousal reaction but also for the evoked muscular discharges. 3. Both TRH and DN-1417, with facilitating effects on the brainstem reticular formation, increased the number of spontaneous unit discharges. DN-1417 increased the number of reticular units, to the same degree as TRH with a smaller dose. These results indicate that both TRH and DN-1417 act on the nerve cells in the brainstem reticular formation, awaken consciousness and facilitate the function of the motor system.

Dopamine excretion and vulnerability to drug-induced Parkinsonism. Schizophrenic patients.

Before and during a standardized course of trifluoperazine therapy, 18 schizophrenic patients underwent repeated examinations for extrapyramidal motor signs, clinical psychopathology, and urinary excretion of free and conjugated forms of dopamine and its metabolites. Patients excreting more free dopamine and metabolites, or showing less complete conjugation, before drug treatment, were much less likely than others to develop parkinsonian akinesia and rigidity during drug treatment. Neither catatonic rigidity nor akinesia before treatment was predictive of a parkinsonian response to trifluoperazine, but pretreatment tremor may have been. The severity of schizophrenic psychopathology was unrelated to dopamine excretion. This study of schizophrenic patients, and our previous research in Parkinson's disease, suggest that urinary dopamine excretion may reflect dopaminergic function of the extrapyramidal motor system in both conditions.