Differential Effects of the Reticulospinal System on Locomotion in Lamprey

1998 ◽  
Vol 80 (1) ◽  
pp. 103-112 ◽  
Author(s):  
T. Wannier ◽  
T. G. Deliagina ◽  
G. N. Orlovsky ◽  
S. Grillner
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Reticular Formation ◽  
Reticular Nucleus ◽  
Caudal Part ◽  
Ventral Roots ◽  
Reticular Nuclei ◽  
The Brain ◽  
Rostral Part ◽  
Different Parts

Wannier, T., T. G. Deliagina, G. N. Orlovsky, and S. Grillner. Differential effects of the reticulospinal system on locomotion in lamprey. J. Neurophysiol. 80: 103–112, 1998. Specific effects of stimulating different parts of the reticulospinal (RS) system on the spinal locomotor pattern are described in lamprey. In the in vitro brain stem and spinal cord preparation, microstimulation in different areas of the reticular formation was performed by ejecting a small amount of d-glutamate from a micropipette. These areas were distributed over the four reticular nuclei of the brain stem: the mesencephalic reticular nucleus (MRN) and the anterior, middle and posterior rhombencephalic reticular nuclei (ARRN, MRRN, and PRRN, respectively). To prevent synaptic spread of excitation within the brain stem, the synaptic transmission was blocked by using a low Ca2+, high Mn2+ physiological saline in the brain stem pool. “Fictive” locomotion was evoked by applying N-methyl-d-aspartate (NMDA) to the spinal cord. Rhythmical discharges of motoneurons were recorded bilaterally in the midbody area, from the ventral roots that had been subdivided in dorsal and ventral branches, supplying the dorsal and ventral part of the myotome, respectively. Two major effects of brain stem stimulation were elicited: a change in the frequency of the locomotory rhythm and an induction of asymmetry (left/right, dorsal/ventral) in the segmental motor output. Approximately 50% of the stimulated sites evoked a change in locomotor frequency. In the PRRN almost all effective sites evoked an increase in frequency (10–50%). In the other nuclei, increase and decrease (10–30%) were observed equally frequently. Most of the stimulated sites (50–80%) in any reticular nucleus evoked asymmetry in the segmental motor output. Distortion of the segmental output symmetry was classified into eight categories by comparing the intensity of locomotor bursts in the dorsal and ventral branches of the two ventral roots, ipsilateral and contralateral to the stimulated side. These categories differed in the direction of the body flexion, which would be evoked during normal swimming: ipsilateral (I), contralateral (C), dorsal (D), ventral (V), ipsilateral and dorsal (ID), ipsilateral and ventral (IV), contralateral and dorsal (CD), and contralateral and ventral (CV). The different categories were not equally represented in each nucleus and across the nuclei. The most pronounced categories for each nucleus were as follow. In MRN: I (33%); ARRN: C (44%); MRRN: rostral part, I (36%) and caudal part, CV (42%); and PRRN: rostral part, I (40%) and caudal part, IV (35%). Other categories were also present but less common in each nucleus. To examine if the effects of brain stem stimulation were uniform along the spinal cord, recordings were performed from distal parts of the cord. Stimulation of a given point in the brain stem produced similar pattern of effects in 59% of cases and different patterns in 41% of cases. The main conclusion of the present study is that the proportion of RS neurons with different influences on the spinal locomotor network differs significantly among different parts of the reticular formation of the lamprey. The specificity of RS influences may represent a basis for modifications of the segmental locomotor output necessary for the control of equilibrium and steering during locomotion.

Anatomy and physiology of saccadic long-lead burst neurons recorded in the alert squirrel monkey. I. Descending projections from the mesencephalon

1996 ◽  
Vol 76 (1) ◽  
pp. 332-352 ◽  
Author(s):  
C. A. Scudder ◽  
A. K. Moschovakis ◽  
A. B. Karabelas ◽  
S. M. Highstein
Keyword(s):  
Superior Colliculus ◽  
Brain Stem ◽  
Reticular Formation ◽  
Discharge Pattern ◽  
Reticular Nucleus ◽  
Medullary Reticular Formation ◽  
Burst Neurons ◽  
Nucleus Reticularis ◽  
Efferent Neurons ◽  
The Brain

1. The intra-axonal recording and horseradish peroxidase injection technique together with spontaneous eye movement monitoring has been employed in alert behaving monkeys to study the discharge pattern and axonal projections of mesencephalic saccade-related long-lead burst neurons (LLBNs). 2. Most of the recovered axons (N = 21) belonged to two classes of neurons. The majority (N = 13) were identified as efferents of the superior colliculus and had circumscribed movement fields typical of collicular saccade-related burst neurons. This discharge pattern, their responses to electrical stimulation of one or both superior colliculi, and their morphological appearance identified them as members of the T class of tectal efferent neurons. 3. Axons of these T cells deployed terminal fields within several saccade-related brain stem areas including the nucleus reticularis tegmenti pontis, which projects to the cerebellum; the nucleus reticularis pontis oralis and caudalis, which contains excitatory premotor burst neurons; the nucleus raphe interpositus, which contains omnipause neurons; the nucleus paragigantocellularis, which contains inhibitory premotor burst neurons, as well as other less differentiated parts of the brain stem reticular formation. 4. The other class of LLBNs (N = 4) had their somata in the medullary reticular formation just lateral to the interstitial nucleus of Cajal. They projected primarily to the raphe nuclei, the medullary reticular formation, and the paramedian reticular nucleus. Discharges were of the directional type with up ON directions (N = 3) and down ON directions (N = 1). 5. Other fibers, which project to pontine and medullary oculomotor structures but whose somata were not recovered (N = 4), illustrate that there are also other types of LLBNs that contribute to the generation and control of saccadic eye movements. 6. Our findings complement previous data about the axonal trajectories of T-type superior colliculus efferents. They also demonstrate the existence of LLBNs located in the mesencephalic reticular formation and their target areas in the brain stem. Implications of these findings for current concepts of oculomotor control are discussed.

Development and characterization of pathways descending to the spinal cord in the embryonic chick

1995 ◽  
Vol 73 (3) ◽  
pp. 1223-1233 ◽  
Author(s):  
G. N. Sholomenko ◽  
M. J. O'Donovan
Keyword(s):  
Spinal Cord ◽  
Electrical Stimulation ◽  
Motor Activity ◽  
Brain Stem ◽  
Reticular Formation ◽  
Cervical Spinal Cord ◽  
Embryonic Chick ◽  
Medullary Reticular Formation ◽  
Lumbosacral Spinal Cord ◽  
The Brain

1. We used an isolated preparation of the embryonic chick brain stem and spinal cord to examine the origin, trajectory, and effects of descending supraspinal pathways on lumbosacral motor activity. The in vitro preparation remained viable for < or 24 h and was sufficiently stable for electrophysiological, pharmacological, and neuroanatomic examination. In this preparation, as in the isolated spinal cord, spontaneous episodes of both forelimb and hindlimb motor activity occur in the absence of phasic afferent input. Motor activity can also be evoked by brain stem electrical stimulation or modulated by the introduction of neurochemicals to the independently perfused brain stem. 2. At embryonic day (E)6, lumbosacral motor activity could be evoked by brain stem electrical stimulation. At E5, neither brain stem nor spinal cord stimulation evoked activity in the lumbosacral spinal cord, although motoneurons did express spontaneous activity. 3. Lesion and electrophysiological studies indicated that axons traveling in the ventral cord mediated the activation of lumbosacral networks by brain stem stimulation. 4. Partition of the preparation into three separately perfused baths, using a zero-Ca2+ middle bath that encompassed the cervical spinal cord, demonstrated that the brain stem activation of spinal networks could be mediated by long-axoned pathways connecting the brain stem and lumbosacral spinal cord. 5. Using retrograde tracing from the spinal cord combined with brain stem stimulation, we found that the brain stem regions from which spinal activity could be evoked lie in the embryonic reticular formation close to neurons that send long descending axons to the lumbosacral spinal cord. The cells giving rise to these descending pathways are found in the ventral pontine and medullary reticular formation, a region that is the source of reticulospinal neurons important for motor activity in adult vertebrates. 6. Electrical recordings from this region revealed that the activity of some brain stem neurons was synchronized with the electrical activity of lumbosacral motoneurons during evoked or spontaneous episodes of rhythmic motor activity. 7. Both brain stem and spinal cord activity could be modulated by selective application of the glutamate agonist N-methyl-D-aspartate to the brain stem, supporting the existence of functionally active descending projections from the brain stem to the spinal cord. It is not yet clear what role the brain stem activity carried by these pathways has in the genesis and development of spinal cord motor activity.

Connections of midbrain periaqueductal gray in the monkey. II. Descending efferent projections

1983 ◽  
Vol 49 (3) ◽  
pp. 582-594 ◽  
Author(s):  
P. W. Mantyh
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Reticular Formation ◽  
Cervical Spinal Cord ◽  
Great Majority ◽  
Periaqueductal Gray ◽  
Locus Ceruleus ◽  
Contralateral Projection ◽  
Efferent Projections ◽  
The Brain

1. We have defined the descending efferent projections of the midbrain periaqueductal gray (PAG) by injecting small amounts of [3H]leucine into the various regions of the squirrel monkey PAG. 2. Despite the fact that different regions of the PAG were injected in separate animals, the majority of the brain stem areas labeled remained constant. 3. The PAG exhibited a dense projection to the superior colliculus, the nucleus cuneiformis, and the locus ceruleus. Parts of the reticular formation (nucleus reticularis: pontis oralis, pontis caudalis, gigantocellularis, magnocellularis, and ventralis) received a projection from the PAG, as did the nucleus parabrachial pars lateralis, ambiguous, the nucleus raphe magnus, and raphe pallidus. 4. In contrast to the brain stem, the deep laminae of the nucleus caudalis and the deep laminae of the cervical spinal cord were labeled only after injections of the lateral aspect of the PAG. 5. The main route for the PAG leads to brain stem projections is through the lateral edge of the paramedian reticular formation. The great majority of the anterograde labeling was ipsilateral to the injection although a small contralateral projection was present. 6. These results indicate that the PAG projects to the brain stem and spinal cord in the monkey. Many of the brain stem areas that the PAG projects to are known to project to the spinal cord. These secondary spinal projections coupled with the direct PAG leads to spinal projection provide a wide variety of routes through which the PAG may influence spinal cord activity.

scholarly journals Bing. Compendium of topical brain and spinal cord diagnostics. 5th ed. Berlin. 1922. 242+VІII pp., 102 fig.

1923 ◽  
Vol 19 (6) ◽  
pp. 106-106
Author(s):  
I. Rusetsky
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Skull Base ◽  
Topical Diagnosis ◽  
Brain And Spinal Cord ◽  
The Brain ◽  
Different Parts

The fifth edition of the Bing Compendium is considerably more extensive than previous editions. Of the additions, the following are noteworthy. A general diagram of lesions of the skull base and a table of symptoms observed in these lesions are included in the chapter on the topical diagnosis of the brain stem. Further, there is a diagram of anesthesia sites in lesions of different parts of substantiae gelatinosae Rolandi.

Regional blood flow in the brain and spinal cord of hypothermic rats

1989 ◽  
Vol 257 (3) ◽  
pp. H785-H790
Author(s):  
T. Sakamoto ◽  
W. W. Monafo
Keyword(s):  
Spinal Cord ◽  
Blood Flow ◽  
Brain Stem ◽  
Regional Blood Flow ◽  
Experimental Conditions ◽  
Pentobarbital Sodium ◽  
Arterial Blood ◽  
Group A ◽  
Group B ◽  
The Brain

[14C]butanol tissue uptake was used to measure simultaneously regional blood flow in three regions of the brain (cerebral and cerebellar hemispheres and brain stem) and in five levels of the spinal cord in 10 normothermic rats (group A) and in 10 rats in which rectal temperature had been lowered to 27.7 +/- 0.3 degrees C by applying ice to the torso (group B). Pentobarbital sodium anesthesia was used. Mean arterial blood pressure varied minimally between groups as did arterial pH, PO2, and PCO2. In group A, regional spinal cord blood flow (rSCBF) varied from 49.7 +/- 1.6 to 62.6 +/- 2.1 ml.min-1.100 g-1; in brain, regional blood flow (rBBF) averaged 74.4 +/- 2.3 ml.min-1.100 g-1 in the whole brain and was highest in the brain stem. rSCBF in group B was elevated in all levels of the cord by 21-34% (P less than 0.05). rBBF, however, was lowered by 21% in the cerebral hemispheres (P less than 0.001) and by 14% in the brain as a whole (P less than 0.05). The changes in calculated vascular resistance tended to be inversely related to blood flow in all tissues. We conclude that rBBF is depressed in acutely hypothermic pentobarbital sodium-anesthetized rats, as has been noted before, but that rSCBF rises under these experimental conditions. The elevation of rSCBF in hypothermic rats confirms our previous observations.

scholarly journals Fictive Rhythmic Motor Patterns Induced by NMDA in an In Vitro Brain Stem–Spinal Cord Preparation From an Adult Urodele

1999 ◽  
Vol 82 (2) ◽  
pp. 1074-1077 ◽  
Author(s):  
Isabelle Delvolvé ◽  
Pascal Branchereau ◽  
Réjean Dubuc ◽  
Jean-Marie Cabelguen
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Rhythm Generation ◽  
Motor Patterns ◽  
Rhythmic Motor ◽  
Bath Application ◽  
The Neural Networks ◽  
Ventral Roots ◽  
Pleurodeles Waltl

An in vitro brain stem–spinal cord preparation from an adult urodele ( Pleurodeles waltl) was developed in which two fictive rhythmic motor patterns were evoked by bath application of N-methyl-d-aspartate (NMDA; 2.5–10 μM) with d-serine (10 μM). Both motor patterns displayed left-right alternation. The first pattern was characterized by cycle periods ranging between 2.4 and 9.0 s (4.9 ± 1.2 s, mean ± SD) and a rostrocaudal propagation of the activity in consecutive ventral roots. The second pattern displayed longer cycle periods (8.1–28.3 s; 14.2 ± 3.6 s) with a caudorostral propagation. The two patterns were inducible after a spinal transection at the first segment. Preliminary experiments on small pieces of spinal cord further suggested that the ability for rhythm generation is distributed along the spinal cord of this preparation. This study shows that the in vitro brain stem–spinal cord preparation from Pleurodeles waltl may be a useful model to study the mechanisms underlying the different axial motor patterns and the flexibility of the neural networks involved.

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