Showing papers on "Motor neuron published in 1977"

The imaginal ecdysis of the cricket ( Teleogryllus oceanicus )

Abstract: 1. The activities of individual motor neurons have been recorded by electromyography from the muscles of unrestrained, successfully ecdysing crickets. 2. As the behavior progresses, each muscle becomes involved in stereotyped patterns of contractions corresponding to a sequence ofmotor programs (Carlson, 1977). For example, muscle 71d participates in 3 programs: (1) Pushups (A1, Fig. 3), (2) Proximal Leg-segment Extrication (B7, Fig. 3), and (3) Distal Leg-segment Extrication (B11, Fig. 3). These motor programs are recruited in tandem, and involve 3 different modes of coordination (Figs. 5A, 7C, 8-bout 55). 3. In this study, 3 motor programs were selected for intensive analysis: (1) Pushups — bilaterally symmetric contractions of front leg muscles; (2) Abdominal Peristalsis (B1, Fig. 3) — longitudinally sequential contractions of abdominal intersegmental muscles; and (3) Proximal Legsegment Extrication — bilaterally alternating contractions of the leg muscles. 4. The entire 4 h period of ecdysis can be recorded bilaterally from right and left muscles 71d, and the motor output underlying all 3 motor programs in which they participate is interrupted by regular interbout intervals (Figs. 4A, 7A, 8, 9). 5. Abdominal peristaltic waves (Fig. 6A, E) occur between bouts of rhythmical contractions by thoracic motor programs (Fig. 9C2), and thus occur at the bout frequency of other programs. 6. During Leg Extrication, the strengths of successive contractions by muscles 71d vary in register with each bout cycle. The strongest contractions occur near the centers of bouts, and are produced by longer bursts of higher frequency impulses (Fig. 7C). Additional motor neurons may be recruited during strong contractions, subject to the “size principle” (see Henneman, 1965). 7. While motor neuron activation varies sinusoidally within each bout cycle, the period of successive burst changes only vary gradually (Fig. 7B, C, 8). This fact implies that the bout generating oscillator does not influence the contraction generating oscillator as it modulates motor neuron activity. The motor neurons must therefore be independent of the oscillator which drives the alternating contractions that extricate the legs. 8. An hypothesis is presented in which “non-spiking interneurons”, are the major components of central oscillators underlying rhythmical contractions, and a series of these, located in each of the segmental ganglia, generate bouts of activity. 9. During a major peak in the intensity of the behavior, which occurs during the Ecdysial Phase, concurrent peaks in bout, burst, and intraburst impulse frequencies of the neurons involved in Proximal Leg-segment Extrication occur (Fig. 10). As interbout intervals shrink, and the burst frequency increases, additional bursts are recruited during each bout, and a second motor neuron is recruited (Fig. 8). 10. Since sensory feedback from areas of newly exposed cuticle are known to accelerate the bout oscillator (Carlson, 1977), it is hypothesized that acceleration of the burst frequency and concurrent increases in average firing rates for motor neurons, which accompany the major intensity peak of the Ecdysial Phase result from sensory feedback. 11. Sensory feedback provides immediate control of the strength of contractions by individual muscles during Pushups (Figs. 5C, 9B1, 9C1), and prolongs motor programs (compare Fig. 9A2 with 9B2, 9C2), without disrupting coordination. 12. It is concluded that a multilayered system of central control which includes more than 48 motor programs, a temporal bout structure, and 4 functionally distinct behavioral phases, cooperates with sensory feedback mechanisms to permit the successful completion of the nearly 4 h of stereotyped behavior which results in the ecdysis of the cricket.

Neuronal organization of escape swimming inTritonia

Abstract: 1 Escape swimming behavior inTritonia diomedea consists of two major components: an initial reflexive withdrawal followed by a series of alternating ventral and dorsal flexions The basic mechanism of generating motor neuron activity, therefore, switches from reflexive to centrally programmed 2 Three classes of cerebral interneurons and some of their synaptic connections have been identified 3 Reflexive withdrawal interneurons (RWI) receive direct input from sensory afferents and synapse with motoneurons in the pedal ganglion (DFN, VFN) This class of interneuron is excited during reflexive withdrawals and inhibited during the swim phase 4 Swim interneurons (SI) are excited during reflexive withdrawals and burst during the swim phase 5 The third set of interneurons (C2) are shown to be necessary for the normal initiation and maintenance of the cyclical swim phase Activity in C2 neurons appears to retrigger the swim oscillator network cycle-by-cycle 6 C2 neurons inhibit the RWI neurons during swimming thus freeing motoneurons to respond predominantly to inputs from the SI and C2 neurons The switch from reflexive to programmed motor output is, therefore, mediated centrally by two identified C2 neurons

Organization of Invertebrate Motor Systems

Abstract: The sections in this article are: 1 Properties of Muscle 11 Anatomic Organization 12 Contraction Speed 13 Strength and Extent of Contraction 14 Thresholds for Excitation-Contraction Coupling 15 Correlations with Innervation 16 Dependence of Tension on Recent History 2 Motor Neurons and the Motor Unit 21 Motor Neuron Morphology 22 Correlations Between Motor Neuron Morphology and Function 23 Neuromuscular Transmission 24 Excitation-Contraction Coupling 25 Peripheral Motor Unit Organization 26 Matching of Central and Peripheral Properties 27 Ontogeny and Regeneration 3 Reflex Organization 31 Proprioceptive Reflexes 32 Exteroreceptive Reflexes 33 Righting Reflexes 34 Optomotor Reflexes 35 Control of Reflex Excitability 4 Central Organization of Motor Systems 41 Structure of Motor Programs 42 Storage of Motor Programs 43 Release of Motor Programs by Command Elements 44 Central Versus Peripheral Control of Motor Output 45 Development of Pattern-Generating Networks 46 Complex Behavioral Phenomena 5 Conclusion

Localization of motor neuron pools supplying identified muscles in normal and supernumerary legs of chick embryo

Abstract: Neuromuscular specificity has been investigated in chick embryos with a grafted supernumerary leg. The nerves of the lumbar plexus are divided between the two legs so that rostral nerves innervate the grafted leg and the caudal nerves supply the host9s original leg. The basic topographic organization of the histologically definable motor neuron clusters of the lateral motor columns remains unchanged by the addition of a supernumerary leg. Intramuscular injections of identified leg muscles have been used to map the intraspinal location of specific motor pools in stage 38 (12-day) embryos. In the normal embryo, the gastrocnemius muscle is innervated by neurons in a central dorsal cluster of motor neurons in segments 26-29. In six experimental cases, the motor neurons supplying the gastrocnemius muscle of a rostrally placed grafted leg were consistently located in a specific medial cluster of neurons in segments 23-25. Motor neurons in this location never normally innervate a gastrocnemius muscle, even in the very young embryos during the period of naturally occurring cell death. This observation of a systematic mismatch between a particular motor cluster and an abnormally innervated muscle indicates the operation of a selective developmental process. A hierarchy of selective chemoaffinities may best explain our experimental results.

Regeneration of synaptic connections by sensory neurons in leech ganglia maintained in culture.

Abstract: Leech ganglia maintained in organ culture were used to follow regeneration and the formation of synaptic connections by individual neurons. From earlier physiological studies on operated animals it is known that the c.n.s. of the leech is able to regenerate and that specific connections can be reformed. The present experiments show that specific regeneration also occurs in vitro but that axons do not simply grow directly back to their targets. (1) Axons were severed by crushing the connectives linking pairs of ganglia at the time of removal from the animal. Light and electron microscopy indicated that the procedure of crushing severed all the axons within the connectives. For several days after the lesion had been made, conduction of impulses from one ganglion to the next was abolished. (2) After 5-10 days in culture, stimulation of the connectives with external electrodes gave rise to impulses that were once again conducted beyond the site of the lesion. Characteristic excitatory and inhibitory synaptic potentials were evoked in identified sensory and motor cells in both ganglia by this indiscriminate stimulation of axons. Electron micrographs of the crushed region showed not only regenerated axons traversing the site of the lesion but also synaptic profiles similar to those seen in the neuropile of normal ganglia. Thus, pre- and post-synaptic specializations had been formed during regeneration in a part of the c.n.s. where they are not normally present. (3) Individual sensory neurons were injected with horseradish peroxidase to reveal the course taken by their regenerating axons. At the site of the crush profuse branching occurred/by 7 days. The arborization of a single axon was highly complex, with many varicosities present on fine branches. After two weeks in culture, one or more of the processes had usually grown beyond the crush and in certain instances had reached the next ganglion. Other branches ran back towards the ganglion in which the cell body was situated. During the period of the experiments (up to 45 days) no retraction of the sprouted fibres or of the arborization at the crush was observed. In addition to sprouting at the site of the lesion considerable sprouting also occurred within the ganglion, close to the cell body. (4) Individual mechanosensory neurons regenerated and would once again evoke synaptic potentials in their original targets after two weeks in culture. Thus, intracellular stimulation of single sensory cells in one ganglion gave rise to synaptic potentials in the appropriate motor neuron of the neighbouring ganglion. Injection of such sensory cells with horse-radish peroxidase showed that their axons had extended beyond the lesion and ramified in the neuropile of the next ganglion. (5) It is concluded that neurons in leech ganglia are able to regenerate and reform appropriate synaptic connections in culture. The degree of precision is hard to assess because of novel synaptic interactions and numerous additional sprouts that develop during regeneration.

Facilitation at Neuromuscular Junctions: Contribution to Habituation and Dishabituation of the Aplysia Gill Withdrawal Reflex

Abstract: The gill withdrawal reflex of Aplysia has been used as a model for studying the neuronal mechanisms of habituation, a behavioral plasticity. We have assessed the contribution of neuromuscular facilitation, an elementary synaptic plasticity, during habituation of the reflex by recording gill muscle potentials, which we show are caused by excitatory junctional potentials. These potentials show systematic frequency-dependent changes in amplitude. The gill withdrawal evoked by central motor neuron firing during each habituation trial is determined by facilitation of the excitatory junctional potentials during the trial and the facilitated state of the initial excitatory junctional potential in a trial, determined by neuron activity prior to the trial. The neuromuscular junctions, therefore, act like a frequency-dependent amplifier of central motor activity. They are fully responsive to the dynamic changes of motor neuron firing that occurs during habituation and especially after dishabituation.

The anatomy and motor nerve distribution of the eye muscles in the crayfish

Abstract: The gross anatomy of the muscles in the crayfish compound eye and the distribution of brain oculomotor neurons were studied by a variety of anatomical and physiological techniques. There are 11 major muscles in each eye. These vary considerably in size and influence upon eye movements and in their source of motor innervation. Muscles that cause defensive eyestalk withdrawal are controlled by axons of a giant motor neuron cluster. Muscles that move the eyecup in vertical planes are innervated by cells of an anterior motor cluster, as well as by cells in the medulla terminalis. Muscles which move the eyecup horizontally are supplied by neurons of the lateral motor cluster. The separation of the oculomotor system into different neuronal groups that supply different sets of muscles thus reflects functional specializations of the component divisions.

Macroglobulinemia waldenström and motor neuron syndrome

Abstract: One patient suffering from macroglobulinemia Waldenstrom developed a neurological disease which may be a previously unrecognized para-malignant phenomenon in this disorder. The clinical symptoms and signs indicated a motor neuron syndrome and autopsy revealed degeneration of ventral and lateral funicles in the spinal cord, loss of ventral motor neurons, degeneration of ventral nerve roots and muscular atrophy. The rather low incidence of macroglobulinemia and motor neuron disease suggests some casual relationship rather than a sporadic occurrence of two disorders in the same patient.

Functional properties of interganglionic motor neurons in the stomatogastric nervous system of the rock lobster

Abstract: 1. In the decapod crustacea the stomatogastric nervous system, which involves the oesophageal (OG) and the stomatogastric (STGG) ganglia, commands the movements of the four successive parts of the foregut: oesophagus, cardiac sac, gastric mill and pylorus. The limited number of neurons (42) contained in the two ganglia are organized in several small networks producing various motor activities that are entirely centrally patterned. 2. In the rock lobster,Palinurus vulgaris, the motricity of the cardiac sac is ensured by three motor neurons. Two of them, CD1 and CD2, innervate all the extrinsic dilator muscles (7 paired muscles). 3. The CD1 cell body is located in theOG, and one of its axon branches reaches theSTGG. The CD2 cell body has been identified in theSTGG and its axon is connected to theOG region by the Stomatogastric nerve (stgn). 4. For the CD2, two sites of spike initiation (one in theOG and the other in theSTGG) produce two different activities (bursting and tonic discharges) and induce spikes travelling in opposite directions (orthodromic and antidromic) in itsstgn axon branch. In the CD2 cell body the intracellular potentials correlated in time to orthodromic and antidromic spikes have different waveforms. 5. The possibility of CD2 excitation from two functionally different ganglia suggests that this motor neuron a. might be involved in various motor programs, b. could be considered as a “two-way coordinating system” 6. The physiological properties of CD1 and CD2 are discussed in comparison with data on the stomatogastric nervous system of other rock lobster species.

Sensory-motor interactions in antennal reflexes of the American lobster

Abstract: 1. The behavior, proprioceptors, musculature, and innervation of the distal three segments of the antenna of the American lobster,Homarus americanus, were studied. 2. The unrestrained lobster moves the two distal joints of the antenna in two ways: 1) simultaneous extension or flexion at both joints, or 2) movement of the distal segment by itself. 3. Sensory information about the movements at the two joints is provided mainly by two proprioceptors, the MCF chordotonal organ spanning both joints and the CF myochordotonal organ spanning the most distal joint. 4. The MCF chordotonal organ is an unusual proprioceptor in that some of its units respond similarly to movement at either joint. 5. Movement at the two distal joints is controlled by four muscles, one pair of flexors and one pair of extensors. 6. The innervation pattern involves seven excitatory motor neurons: one independent motor neuron to each of the four muscles, one common motor neuron to the flexor muscles, and two common motor neurons to the extensor muscles. 7. Induced joint movements generate resistance-reflex responses: flexion drives the two independent extensor motor neurons E4 and E5 and one of the two common extensor motor neurons EC1; extension drives the independent motor neurons F4 and F5. The response is the same to movement at either joint. 8. Direct mechanical stimulation of the MCF chordotonal organ also generates resistance reflexes: stretch drives the flexor motor neurons F4 and F5; relaxation drives extensor motor neurons E4, E5, and EC1. These responses are similar to those produced by induced joint movement. 9. The functional significance of the relationship between the common proprioceptor and the motor neurons is discussed.

Penis-retractor muscle of Aplysia: excitatory motor neurons.

Abstract: Cobalt axonal iontophoresis and intracellular recordings were used to identify a cluster of several motor neurons innervating the penis-retractor muscle of Aplysia. Intracellularly recorded motor neuron action potentials elicited direct, one-for-one, constant latency excitatory junctional potentials (ejps) in individual muscle fibers. The axons of motor neurons could be recorded extracellularly in the penis-retractor nerve and stimulation of the nerve backfired the motor neurons. Perfusion of the ganglion, the muscle, or both with solutions of either increased Mg++/decreased Ca++ or increased Ca++ sea water indicated that the presumed motor neuron impaled was not a sensory cell and that interneurons were not intercalated in the pathway. Innervation of muscle fibers was found to be functionally polyneuronal and diffuse. The ejps were found to undergo marked facilitation with repetitive motor-neuron stimulation. The motor neurons were isolated in a distinct cluster in the right pedal ganglion. Their electrical activity was characterized by spontaneous irregular action potentials and a moderate input of postsynaptic potentials.

Excitation of the common inhibitory motor neuron: A possible role in the startle reflex of the cockroach, Periplaneta americana

Abstract: The responses of the widespread common inhibitory motor neuron (CI) to tactile stimulation of the cercus and the abdomen and electrical stimulation of the cercal nerve and the abdominal connectives are investigated. Tactile stimulation produces high frequency (greater than 500 impulses/s) spike discharge in CI with the onset of CI activity preceding the discharge of the excitatory motor neurons. Electrical stimulation of the connectives demonstrates a monosynaptic connection between at least one intermediate sized fiber (conduction velocity =3.7 m/s) in the abdominal connective and the ipsilateral CIs in the meso-and metathoracic ganglia. Electrical stimulation of the cercal nerve suggests a disynaptic path from cercal nerve to CI. Arguments are presented for a cercal afferent-to-CI reflex and the possible functional role of early excitation of CI is discussed.

Electrodiagnostic investigation of the motor neuron and spinal reflex arch (H-reflex) in spinal cord injury

Abstract: Twenty patients with spinal cord injury underwent serial electromyographic examinations Fibrillation potentials and positive waves were noted in six patients in the spinal shock phase In another subject, these potentials were found 27 months after injury Our finding of significant slowing in the NCV of both nerves, indicates that lower motor neurons are indeed affected by upper motor neuron lesions The H-reflex studies showed an increase in the mean H/M ratio This may indicate an increase of reflex motor neuron excitability No clear correlation was found between this increase and the degree of clinical spasticity With repeat investigations, after a period of physical activity, a trend to reduction of the H/M ratio was noted with no clinical confirmation of reduction in spasticity These findings emphasise the need for not assigning diagnostic terms to EMC abnormalities, but rather identifying them as neurophysiological changes which must be interpreted in the light of the clinical picture

Ventral motor neuron alterations in rat spinal cord after chronic exercise.

Abstract: The observed differences in the soma and nuclear diameters reflect chronic changes specific to each exercise regimen used.

Dominantly Inherited Amyotrophic Lateral Sclerosis (Motor Neuron Disease)

Abstract: This is paper #46 from the Department of Human Genetics of the Medical College of Virginia and was supported in part by Grant #C-187 from the National Foundation-March of Dimes. Correspondence and reprint requests to Lpuise E. Wilki!)s, Box 33, Medical College of Virginia, Richmond, Virginia 23298. sensory impairment.1 Later, th~ syndromes of progressive bulbar palsy (PBP) and progressive muscular atrophy (PMA) were recognized to be variations of the same pathological process, and ALS was used as an inclusive term to refer to these syndromes as well. Although some authors reserve the term ALS for the specific syndrome of mixed upper. and lower motor neuron lesions and use the term "motor neuron disease" to refer to the constellation of syndromes, most

An autoradiographic study of muscular dystrophy, motor neuron disease and Charcot-Marie-Tooth disease.

Abstract: The autoradiographic findings using tritiated leucine are described in muscle biopsy material from five patients with progressive muscular dystrophy (P.M.D.), three with motor neuron disease (M.N.D.) and four with Charcot-Marie-Tooth disease (C.M.T.). In progressive muscular dystrophy there is a marked increase in uptake of leucine into cytoplasmic proteins and precursors, and reduced incorporation into structural protein. In Charcot-Marie Tooth disease muscle there is a significantly increased uptake into cytoplasmic elements and a normal uptake into structural protein. In motor neuron disease the uptake into cytoplasmic elements appears normal but is reduced into structural proteins. The abnormal uptake in C.M.T. could be explained as a product of regenerative efforts associated with reinnervation. However, the abnormal uptake may represent the primary effects of gene action in the muscle, as seems probable in progressive muscular dystrophy.