Functional organization within the medullary reticular formation of intact unanesthetized cat. I. Movements evoked by microstimulation

1990 ◽  
Vol 64 (3) ◽  
pp. 767-781 ◽  
Author(s):  
T. Drew ◽  
S. Rossignol
Keyword(s):  
Brain Stem ◽  
Reticular Formation ◽  
Functional Organization ◽  
The Body ◽  
Large Area ◽  
Medullary Reticular Formation ◽  
Discrete Movements ◽  
The Brain ◽  
Flexion And Extension ◽  
Made In

1. The present article described the various patterns of movement evoked in the limbs and neck by microstimulation (33-ms trains, 330 Hz, 0.2-ms pulses at less than or equal to 35 microA) of the medullary reticular formation (MRF) of seven chronically implanted, unanesthetized, intact cats. Altogether 878 loci were stimulated in 83 penetrations. However, as stimulation in the more lateral regions of the MRF was less effective, the results are based on stimulation in 592 loci made in 56 penetrations at distances of between 0.5 and 2.5 mm lateral to the midline. 2. Of these 592 loci, movement of one or more parts of the body was evoked from a total of 539 (91%) sites. Most of these movements were compound in nature, involving movement of one or more limbs as well as the head. Discrete movements were observed only with respect to the head; limb movements were always accompanied by head movement. In addition, hindlimb movements were always accompanied by forelimb movements, although the inverse was generally not true. 3. The most common effects of the stimulation were as follows: a turning of the head to the ipsilateral side (79% of stimulated sites); flexion of the ipsilateral elbow (41%); and extension of the contralateral elbow (45%). Effects in the hindlimbs were more variable and less frequent, with the majority of the effective loci causing flexion of the ipsilateral knee (9%) together with extension of the contralateral knee (8%). In total, including both flexion and extension, 18% of the stimulated sites caused movement of the ipsilateral hindlimb and 11% of the contralateral hindlimb. 4. Although movements of the head were obtained from the whole extent of the brain stem, movements of the forelimbs showed a dorsoventral organization with flexion of the ipsilateral elbow being evoked from the more dorsal regions of the brain stem, whereas contralateral elbow extension was evoked more frequently from the ventral regions. There was a large area of overlap from which movements of both limbs could be obtained simultaneously. Movements of the hindlimbs were more frequently evoked from central and ventral areas of the brain stem and from the most rostral aspect of the explored region. 5. In examining the combinations of movements evoked by the MRF stimulation, it was found that the most commonly evoked pattern was movement of the head to the stimulated side together with flexion of the ipsilateral forelimb and extension of the contralateral forelimb (26.5% of sites).(ABSTRACT TRUNCATED AT 400 WORDS)

Functional organization within the medullary reticular formation of intact unanesthetized cat. II. Electromyographic activity evoked by microstimulation

1990 ◽  
Vol 64 (3) ◽  
pp. 782-795 ◽  
Author(s):  
T. Drew ◽  
S. Rossignol
Keyword(s):  
Brain Stem ◽  
Reticular Formation ◽  
Functional Organization ◽  
Large Degree ◽  
Neck Muscles ◽  
Electromyographic Activity ◽  
Medullary Reticular Formation ◽  
Preceding Article ◽  
Excitatory Responses ◽  
Antagonistic Muscles

1. The present study has examined the detailed organization of the medullary reticular formation (MRF) as revealed by microstimulation (33-ms trains of 0.2-ms duration pulses at 330 Hz and 35 microA or less) in the intact, chronically implanted, unanesthetized cat. Stimulus-locked electromyographic (EMG) responses were recorded from flexors and extensors of each of the four limbs, as well as bilaterally from muscles of the neck and back, during stimulation of the same 592 loci that formed the basis of the preceding article. 2. The thresholds of the responses were different for each group of muscles, with, on the average, the neck muscles being activated at the lowest range of currents, 13.8-16.5 microA; forelimb muscles at 16.9-17.9 microA; back muscles at 25.4-25.7 microA; and hindlimb muscles at 21.1-25.7 microA. 3. Whereas stimulation within the MRF evoked movement of the head only to the stimulated side (preceding article), analysis of the EMG responses showed there was frequently bilateral activation of the neck muscles. Similarly, even though stimulation produced predominantly ipsilateral elbow flexion and contralateral elbow extension, most loci caused cocontraction of antagonistic muscles at these joints. Cocontraction was also frequently observed for the hindlimbs. Reciprocal activation of antagonistic muscles was less frequent but was observed in the ipsilateral forelimb as well as in both hindlimbs; it was never observed in the contralateral forelimb. 4. Although excitatory responses were observed from widespread regions for all of the muscles under study, those regions of the MRF that evoked the strongest responses in each muscle showed a large degree of segregation. Muscles of the ipsilateral forelimb were most strongly activated from the rostrodorsal MRF, whereas muscles of the contralateral forelimb were most strongly effected by stimulation caudoventrally. Muscles of the hindlimbs were more strongly activated from the rostral brain stem, although with some exceptions. Responses in axial muscles were evoked from widespread regions of the brain stem but were concentrated further caudally than were the limb muscles. 5. Excitatory responses were much more prevalent than inhibitory responses and were evoked from all regions of the MRF, including the most caudal and ventral areas. The shortest latency responses in each track were, on the average, as follows: 6.6-8.8 ms for the neck; 11.2-13.4 ms for the forelimbs; 13.8-14.2 ms for the back; and 15.9-17.2 ms for the hindlimbs. Inhibitory responses were also evoked from widely distributed regions, which were intermingled with those loci evoking excitatory responses.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Functional Organization of the Brain Stem Reticular Formation and Sensory Input

Science ◽  
1962 ◽  
Vol 138 (3544) ◽  
pp. 973-975 ◽  
Author(s):  
J. Courville ◽  
J. Walsh ◽  
J. P. Cordeau
Keyword(s):  
Brain Stem ◽  
Reticular Formation ◽  
Sensory Input ◽  
Functional Organization ◽  
The Brain

scholarly journals Atonia-Related Regions in the Rodent Pons and Medulla

2000 ◽  
Vol 84 (4) ◽  
pp. 1942-1948 ◽  
Author(s):  
T. Hajnik ◽  
Y. Y. Lai ◽  
J. M. Siegel
Keyword(s):  
Electrical Stimulation ◽  
Brain Stem ◽  
Reticular Formation ◽  
Muscle Tone ◽  
Neck Muscle ◽  
Medullary Reticular Formation ◽  
Anatomical Distribution ◽  
Hindlimb Muscles ◽  
The Brain ◽  
Stimulation Of

Electrical stimulation of circumscribed areas of the pontine and medullary reticular formation inhibits muscle tone in cats. In this report, we present an analysis of the anatomical distribution of atonia-inducing stimulation sites in the brain stem of the rat. Muscle atonia could be elicited by electrical stimulation of the nuclei reticularis pontis oralis and caudalis in the pons as well as the nuclei gigantocellularis, gigantocellularis alpha, gigantocellularis ventralis, and paragigantocellularis dorsalis in the medulla of decerebrate rats. This inhibitory effect on muscle tone was a function of the intensity and frequency of the electrical stimulation. Average latencies of muscle-tone suppressions elicited by electrical stimulation of the pontine reticular formation were 11.02 ± 2.54 and 20.49 ± 3.39 (SD) ms in the neck and in the hindlimb muscles, respectively. Following medullary stimulation, these latencies were 11.29 ± 2.44 ms in the neck and 18.87 ± 2.64 ms in the hindlimb muscles. Microinjection of N-methyl-d-aspartate (NMDA, 7 mM/0.1 μl) agonists into the pontine and medullary inhibitory sites produced muscle-tone facilitation, whereas quisqualate (10 mM/0.1 μl) injection induced an inhibition of muscle tone. NMDA-induced muscle tone change had a latency of 31.8 ± 35.3 s from the pons and 10.5 ± 0.7 s from the medulla and a duration of 146.7 ± 95.2 s from the pons and 55.5 ± 40.4 s from the medulla. The latency of quisqualate (QU)-induced reduction of neck muscle tone was 30.1 ± 37.9 s after pontine and 39.5 ± 21.8 s after medullary injection. The duration of muscle-tone suppression induced by QU injection into the pons and medulla was 111.5 ± 119.2 and 169.2 ± 145.3 s. Smaller rats (8 wk old) had a higher percentage of sites producing muscle-tone inhibition than larger rats (16 wk old), indicating an age-related change in the function of brain stem inhibitory systems. The anatomical distribution of atonia-related sites in the rat has both similarities and differences with the distribution found in the cat, which can be explained by the distinct anatomical organization of the brain stem in these two species.

Convergence of heterotopic nociceptive information onto neurons of caudal medullary reticular formation in monkey (Macaca fascicularis)

1990 ◽  
Vol 63 (5) ◽  
pp. 1118-1127 ◽  
Author(s):  
L. Villanueva ◽  
K. D. Cliffer ◽  
L. S. Sorkin ◽  
D. Le Bars ◽  
W. D. Willis
Keyword(s):  
Electrical Stimulation ◽  
Reticular Formation ◽  
Mechanical Stimulation ◽  
Background Activity ◽  
The Body ◽  
Thermal Stimulation ◽  
Medullary Reticular Formation ◽  
Nociceptive Information ◽  
Noxious Mechanical Stimulation ◽  
Stimulation Of

1. Recordings were made in anesthetized monkeys from neurons in the medullary reticular formation (MRF) caudal to the obex. Responses of 19 MRF neurons to mechanical, thermal, and/or electrical stimulation were examined. MRF neurons exhibited convergence of nociceptive cutaneous inputs from widespread areas of the body and face. 2. MRF neurons exhibited low levels of background activity. Background activity increased after periods of intense cutaneous mechanical or thermal stimulation. Nearly all MRF neurons tested failed to respond to heterosensory stimuli (flashes, whistle sounds), and none responded to joint movements. 3. MRF neurons were excited by and encoded the intensity of noxious mechanical stimulation. Responses to stimuli on contralateral limbs were greater than those to stimuli on ipsilateral limbs. Responses were greater to stimuli on the forelimbs than to stimuli on the hindlimbs. 4. MRF neurons responded to noxious thermal stimulation (51 degrees C) of widespread areas of the body. Mean responses from stimulation at different locations were generally parallel to those for noxious mechanical stimulation. Responses increased with intensity of noxious thermal stimulation (45-50 degrees C). 5. MRF neurons responded with one or two peaks of activation to percutaneous electrical stimulation applied to the limbs, the face, or the tail. The differences in latency of responses to stimulating two locations along the tail suggested that activity was elicited by activation of peripheral fibers with a mean conduction velocity in the A delta range. Stimulation of the contralateral hindlimb elicited greater responses, with lower thresholds and shorter latencies, than did stimulation of the ipsilateral hindlimb. 6. Electrophysiological properties of monkey MRF neurons resembled those of neurons in the medullary subnucleus reticularis dorsalis (SRD) in the rat. Neurons in the caudal medullary reticular formation could play a role in processing nociceptive information. Convergence of nociceptive cutaneous input from widespread areas of the body suggests that MRF neurons may contribute to autonomic, affective, attentional, and/or sensory-motor processes related to pain.

scholarly journals Electrophysiological Studies on the Effect of Rhythmical Sound on the Threshold of the Brain Stem Reticular Formation

1985 ◽  
Vol 37 (4) ◽  
pp. 511-521
Author(s):  
Hiroe Naito ◽  
Kyoko Takemura ◽  
Hiroshi Ikeda ◽  
Yoshiteru Shiba ◽  
Mineo Okamoto ◽  
...  
Keyword(s):  
Brain Stem ◽  
Reticular Formation ◽  
Electrophysiological Studies ◽  
The Brain
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