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Journal of Neurophysiology Apr 2012We compared the activity profiles and synergies of spinal motoneurons recorded during fictive locomotion evoked in immobilized decerebrate cat preparations by midbrain... (Comparative Study)
Comparative Study
We compared the activity profiles and synergies of spinal motoneurons recorded during fictive locomotion evoked in immobilized decerebrate cat preparations by midbrain stimulation to the activity profiles and synergies of the corresponding hindlimb muscles obtained during forward level walking in cats. The fictive locomotion data were collected in the Spinal Cord Research Centre, University of Manitoba, and provided by Dr. David McCrea; the real locomotion data were obtained in the laboratories of M. A. Lemay and B. I. Prilutsky. Scatterplot representation and minimum spanning tree clustering algorithm were used to identify the possible motoneuronal and muscle synergies operating during both fictive and real locomotion. We found a close similarity between the activity profiles and synergies of motoneurons innervating one-joint muscles during fictive locomotion and the profiles and synergies of the corresponding muscles during real locomotion. However, the activity patterns of proximal nerves controlling two-joint muscles, such as posterior biceps and semitendinosus (PBSt) and rectus femoris (RF), were not uniform in fictive locomotion preparations and differed from the activity profiles of the corresponding two-joint muscles recorded during forward level walking. Moreover, the activity profiles of these nerves and the corresponding muscles were unique and could not be included in the synergies identified in fictive and real locomotion. We suggest that afferent feedback is involved in the regulation of locomotion via motoneuronal synergies controlled by the spinal central pattern generator (CPG) but may also directly affect the activity of motoneuronal pools serving two-joint muscles (e.g., PBSt and RF). These findings provide important insights into the organization of the spinal CPG in mammals, the motoneuronal and muscle synergies engaged during locomotion, and their afferent control.
Topics: Animals; Cats; Decerebrate State; Hindlimb; Locomotion; Motor Neurons; Muscle, Skeletal
PubMed: 22190626
DOI: 10.1152/jn.00865.2011 -
Journal of Neurophysiology Oct 2011Spinal reflexes are modified by spinal cord injury (SCI) due the loss of excitatory inputs from supraspinal structures and changes within the spinal cord. The stretch... (Comparative Study)
Comparative Study
Spinal reflexes are modified by spinal cord injury (SCI) due the loss of excitatory inputs from supraspinal structures and changes within the spinal cord. The stretch reflex is one of the simplest pathways of the central nervous system and was used presently to evaluate how inputs from primary and secondary muscle spindles interact with spinal circuits before and after spinal transection (i.e., spinalization) in 12 adult decerebrate cats. Seven cats were spinalized and allowed to recover for 1 mo (i.e., chronic spinal state), whereas 5 cats were evaluated before (i.e., intact state) and after acute spinalization (i.e., acute spinal state). Stretch reflexes were evoked by stretching the left triceps surae (TS) muscles. The force evoked by TS muscles was recorded along with the activity of several hindlimb muscles. Stretch reflexes were abolished in the acute spinal state due to an inability to activate TS muscles, such as soleus (Sol) and lateral gastrocnemius (LG). In chronic spinal cats, reflex force had partly recovered but Sol and LG activity remained considerably depressed, despite the fact that injecting clonidine could recruit these muscles during locomotor-like activity. In contrast, other muscles not recruited in the intact state, most notably semitendinosus and sartorius, were strongly activated by stretching TS muscles in chronic spinal cats. Therefore, stretch reflex pathways from TS muscles to multiple hindlimb muscles undergo functional reorganization following spinalization, both acute and chronic. Altered activation patterns by stretch reflex pathways could explain some sensorimotor deficits observed during locomotion and postural corrections after SCI.
Topics: Acute Disease; Animals; Biomechanical Phenomena; Cats; Chronic Disease; Cordotomy; Decerebrate State; Electromyography; Reflex, Stretch; Spinal Cord Injuries
PubMed: 21734111
DOI: 10.1152/jn.00504.2011 -
Journal of Neurophysiology Mar 2000In precollicular decerebrate and paralyzed cats, respiratory nerve activities were recorded during fictive vocalization (FV), which consisted of a distinctive pattern of...
In precollicular decerebrate and paralyzed cats, respiratory nerve activities were recorded during fictive vocalization (FV), which consisted of a distinctive pattern of 1) decreased inspiratory (I) and expiratory (E) phase durations, 2) marked increase of phrenic activity and moderate changes of recurrent laryngeal (RL) and superior laryngeal (SL) I activities, and 3) massive recruitment of laryngeal and abdominal (ABD; lumbar) E activities. FV was produced by electrical stimulation (100 Hz) in the midbrain periaqueductal gray (PAG) or its putative descending pathways in the ventrolateral pons (VLP). Spectral and correlation analyses revealed three types of effect on fast rhythms during FV. 1) I activities: the coherent high-frequency oscillations in I (I-HFO, 60-90 Hz) present in phrenic and RL discharges during the control state did not change qualitatively, but there was an increase of power and a moderate increase (4-10 Hz) of frequency. Sometimes a distinct relatively weak stimulus-locked rhythm appeared. 2) RL and SL activities during E: in recruited discharges, a prominent intrinsic rhythm (coherent E-HFOs at 50-70 Hz) appeared; sometimes a distinct relatively strong stimulus-locked rhythm appeared. 3) ABD activities during E: this recruited activity had no intrinsic rhythm but had an evoked oscillation locked to the stimulus frequency. Thus FV is characterized by 1) appearance of prominent coherent intrinsic rhythms in RL and SL E discharges, which presumably arise as a result of excitation and increased interactions in laryngeal networks; 2) modification of intrinsic rhythmic interactions in inspiratory networks; and 3) evoked rhythms in augmenting-E neuron networks without occurrence of intrinsic rhythms.
Topics: Anesthesia; Animals; Cats; Decerebrate State; Electrophysiology; Laryngeal Muscles; Nerve Net; Phrenic Nerve; Recruitment, Neurophysiological; Recurrent Laryngeal Nerve; Respiratory Mechanics; Vocalization, Animal
PubMed: 10712468
DOI: 10.1152/jn.2000.83.3.1415 -
The Journal of Physiology Dec 19711. Micro-electrode recordings were made from ascending axons of the spinocervical tract in unanaesthetized decerebrate cats before, during and after reversible cold...
1. Micro-electrode recordings were made from ascending axons of the spinocervical tract in unanaesthetized decerebrate cats before, during and after reversible cold block of impulse conduction in the spinal cord rostral to the recording site.2. Most units (forty-one of forty-four) fell into one of four categories as defined by their evoked responses to mechanical stimulation of identified cutaneous receptors. These categories were; Type I excited by movement of tylotrichs (hairs) in the decerebrate preparation but by movement of all types of hairs after block of descending impulses; Type II excited by movement of guard hairs and usually weakly by pressure in the decerebrate state but by movement of all types of hairs and by pressure in the spinal state; Type III excited by movement of all types of hairs and often by pressure in the decerebrate animal but by movement of all types of hairs and always by pressure in the spinal animal; Type IV weakly excited by heavy pressure or with no receptive field in the decerebrate state but excited by pressure in the spinal state.3. The descending influences depressed the spontaneous activity and the evoked responses to harmful stimuli.4. The descending influences depressed inhibitory inputs from segmental levels.5. The functional significance of the descending control is discussed.
Topics: Action Potentials; Animals; Axons; Cats; Cold Temperature; Decerebrate State; Evoked Potentials; Hair; Hindlimb; Mechanoreceptors; Neural Conduction; Neural Inhibition; Spinal Cord; Synaptic Transmission
PubMed: 4333861
DOI: 10.1113/jphysiol.1971.sp009652 -
The Yale Journal of Biology and Medicine 1987Studies of the stretch reflex in decerebrate cats indicate a phase advance of peak sinusoidal tension in steady-state cycles between 0.1 and 10 Hz. This phase advance is...
Studies of the stretch reflex in decerebrate cats indicate a phase advance of peak sinusoidal tension in steady-state cycles between 0.1 and 10 Hz. This phase advance is reduced in acute and chronic cerebellectomy, as shown in previous investigations. Also, the augmentation of muscle peak tension in initial sinusoidal stretch cycles at 0.5-5 Hz has been found to be reduced during the time of reflex and motor instability in the several months following cerebellar ablation. This report shows the increased amplitude and phase lead of integrated electromyographic activity in initiating sinusoidal stretch cycles in the decerebrate cat. These reflex aspects are demonstrated in relation to the discharge of neurons in the dorsal spinocerebellar tract and of cerebellar cortical Purkinje cells in initial sinusoidal cycles. The intensity and phase advance of the discharge in dorsal spinocerebellar tract neurons is altered little, but these features are usually increased in Purkinje cells during initial stretches compared to continuous cycling. In terms of overall motor control, these findings are compatible with concepts of movement control, modulated by the cerebellum, in which the discharge of antagonist motor neurons is regulated in concert with that of agonist muscles upon initiation and termination of movement.
Topics: Action Potentials; Animals; Cerebellum; Decerebrate State; Movement; Muscles; Periodicity; Reflex, Stretch
PubMed: 3577209
DOI: No ID Found -
American Journal of Physiology. Heart... Jun 2003I investigated whether muscular contraction evokes cardiorespiratory increases (exercise pressor reflex) in alpha-chloralose- and chloral hydrate-anesthetized and...
I investigated whether muscular contraction evokes cardiorespiratory increases (exercise pressor reflex) in alpha-chloralose- and chloral hydrate-anesthetized and precollicular, midcollicular, and postcollicular decerebrated rats. Mean arterial pressure (MAP), heart rate (HR), and minute ventilation (Ve) were recorded before and during 1-min sciatic nerve stimulation, which induced static contraction of the triceps surae muscles, and during 1-min stretch of the calcaneal tendon, which selectively stimulated mechanosensitive receptors in the muscles. Anesthetized rats showed various patterns of MAP response to both stimuli, i.e., biphasic, depressor, pressor, and no response. Sciatic nerve stimulation to muscle in precollicular decerebrated rats always evoked spontaneous running, so the exercise pressor reflex was not determined from these preparations. None of the postcollicular decerebrated rats showed a MAP response or spontaneous running. Midcollicular decerebrated rats consistently showed biphasic blood pressure response to both stimulations. The increases in MAP, HR, and Ve were related to the tension developed. The static contractions in midcollicular decerebrated rats (381 +/- 65 g developed tension) significantly increased MAP, HR, and Ve from 103 +/- 12 to 119 +/- 24 mmHg, from 386 +/- 30 to 406 +/- 83 beats/min, and from 122 +/- 7 to 133 +/- 25 ml/min, respectively. After paralysis, sciatic nerve stimulation had no effect on MAP, HR, or Ve. These results indicate that the midcollicular decerebrated rat can be a model for the study of the exercise pressor reflex.
Topics: Anesthetics; Anesthetics, Intravenous; Animals; Blood Pressure; Carbon Dioxide; Chloral Hydrate; Chloralose; Decerebrate State; Female; Forelimb; Hindlimb; Hydrogen-Ion Concentration; Male; Oxygen; Physical Exertion; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Respiratory Mechanics; Sciatic Nerve
PubMed: 12543631
DOI: 10.1152/ajpheart.00400.2002 -
ENeuro 2019There is evidence that a variety of central and afferent stimuli, including swallowing, can produce phase resetting in the respiratory rhythmicity. Also, there are...
There is evidence that a variety of central and afferent stimuli, including swallowing, can produce phase resetting in the respiratory rhythmicity. Also, there are reports about the intrinsic linkage between locomotion and respiration. However, little is known about the interaction between the central pattern generators (CPGs) for scratching and respiration. The present study aims to examine whether the activation of scratching CPG produces phase resetting of the respiratory rhythm. We employed decerebrate cats to apply brief tactile stimuli to the pinna during the inspiratory-expiratory transition. We observed that those stimuli to the pinna not eliciting fictive scratching did not reset the respiratory rhythm. However, when the pinna stimuli elicited fictive scratching, then the respiratory rhythm exhibited a significant phase resetting. We also found interneurons in the medulla oblongata exhibiting phase resetting related to scratching-CPG episodes. This second finding suggests that this type of resetting involves brainstem components of the respiratory CPG. These results shed new light on the resetting action from a spinal CPG on the respiratory rhythm.
Topics: Animals; Cats; Central Pattern Generators; Decerebrate State; Female; Interneurons; Male; Medulla Oblongata; Periodicity; Reflex; Respiratory Rate; Spinal Cord; Touch Perception
PubMed: 31043462
DOI: 10.1523/ENEURO.0116-19.2019 -
Journal of Vestibular Research :... 2009Inputs from the skin and muscles of the limbs and trunk as well as the viscera are relayed to the medial, inferior, and lateral vestibular nuclei. Vestibular nucleus... (Review)
Review
Inputs from the skin and muscles of the limbs and trunk as well as the viscera are relayed to the medial, inferior, and lateral vestibular nuclei. Vestibular nucleus neurons very quickly regain spontaneous activity following a bilateral vestibular neurectomy, presumably due to the presence of such nonlabyrinthine inputs. The firing of a small fraction of vestibular nucleus neurons in animals lacking labyrinthine inputs can be modulated by whole-body tilts; these responses are eliminated by a spinal transection, showing that they are predominantly elicited by inputs from the trunk and limbs. The ability to adjust blood distribution in the body and maintain stable blood pressure during movement is diminished following a bilateral vestibular neurectomy, but compensation occurs within a week. However, bilateral lesions of the caudal portions of the vestibular nuclei produce severe and long-lasting cardiovascular disturbances during postural alterations, suggesting that the presence of nonlabyrinthine signals to the vestibular nuclei is essential for compensation of posturally-related autonomic responses to occur. Despite these observations, the functional significance of nonlabyrinthine inputs to the central vestibular system remains unclear, either in modulating the processing of vestibular inputs or compensating for their loss.
Topics: Afferent Pathways; Animals; Autonomic Nervous System; Cerebellum; Decerebrate State; Ear, Inner; Forelimb; Hindlimb; Neurons; Posture; Recovery of Function; Vestibular Nuclei; Vestibule, Labyrinth
PubMed: 20495235
DOI: 10.3233/VES-2009-0337 -
Journal of Neurophysiology Oct 2008Current models propose that a neuronal network in the ventrolateral medulla generates the basic respiratory rhythm and that this ventrolateral respiratory column (VRC)...
Current models propose that a neuronal network in the ventrolateral medulla generates the basic respiratory rhythm and that this ventrolateral respiratory column (VRC) is profoundly influenced by the neurons of the pontine respiratory group (PRG). However, functional connectivity among PRG and VRC neurons is poorly understood. This study addressed four model-based hypotheses: 1) the respiratory modulation of PRG neuron populations reflects paucisynaptic actions of multiple VRC populations; 2) functional connections among PRG neurons shape and coordinate their respiratory-modulated activities; 3) the PRG acts on multiple VRC populations, contributing to phase-switching; and 4) neurons with no respiratory modulation located in close proximity to the VRC and PRG have widely distributed actions on respiratory-modulated cells. Two arrays of microelectrodes with individual depth adjustment were used to record sets of spike trains from a total of 145 PRG and 282 VRC neurons in 10 decerebrate, vagotomized, neuromuscularly blocked, ventilated cats. Data were evaluated for respiratory modulation with respect to efferent phrenic motoneuron activity and short-timescale correlations indicative of paucisynaptic functional connectivity using cross-correlation analysis and the "gravity" method. Correlogram features were found for 109 (3%) of the 3,218 pairs composed of a PRG and a VRC neuron, 126 (12%) of the 1,043 PRG-PRG pairs, and 319 (7%) of the 4,340 VRC-VRC neuron pairs evaluated. Correlation linkage maps generated for the data support our four motivating hypotheses and suggest network mechanisms for proposed modulatory functions of the PRG.
Topics: Animals; Cats; Computer Simulation; Data Interpretation, Statistical; Decerebrate State; Electrophysiology; Humans; Medulla Oblongata; Models, Statistical; Nerve Endings; Neural Pathways; Neurons; Patch-Clamp Techniques; Pons; Respiratory System
PubMed: 18632881
DOI: 10.1152/jn.90414.2008 -
American Journal of Physiology.... Nov 2019The exercise pressor reflex is initiated by the contraction-induced activation of group III and IV muscle afferents. The reflex is manifested by increases in arterial...
The exercise pressor reflex is initiated by the contraction-induced activation of group III and IV muscle afferents. The reflex is manifested by increases in arterial blood pressure and cardiac output, which, in turn, are generated by increases in the sympathetic outflow to the heart and vasculature and decreases in the vagal outflow to the heart. In previous experiments, we used a pharmacological approach to assess the role played by the acid-sensing ion channel 3 (ASIC3) on group III and IV afferents in evoking the exercise pressor reflex. In the present experiments, we used an alternative approach, namely functional knockout (KO) of the ASIC3 gene, to confirm and extend our previous finding that pharmacological blockade of the ASIC3 had only a small impact on the expression of the exercise pressor reflex when the arterial supply to the contracting hindlimb muscles of rats was patent. Using this alternative approach, we compared the magnitude of the exercise pressor reflex evoked in ASIC3 KO rats with that evoked in their wild-type (WT) counterparts. We found both WT and ASIC3 KO rats displayed similar pressor responses to static contraction (WT, = 10, +12 ± 2 mmHg; KO, = 9, +11 ± 2 mmHg) and calcaneal tendon stretch (WT, = 9, +13 ± 2 mmHg; KO, = 7, +11 ± 2 mmHg). Likewise, both WT and ASIC3 KO displayed similar pressor responses to intra-arterial injection of 12 mM lactic acid (WT, = 9, +14 ± 3 mmHg; KO, = 8, +18 ± 5 mmHg), 24 mM lactic acid (WT, = 9,+24 ± 2 mmHg; KO, = 8, +20 ± 5 mmHg), capsaicin (WT, = 9,+27 ± 5 mmHg; KO, = 10, +29 ± 5 mmHg), and diprotonated phosphate ([Formula: see text]; WT, = 6,+22 ± 3 mmHg; KO, = 6, +32 ± 6 mmHg). We conclude that redundant receptors are responsible for evoking the pressor reflexes arising from group III and IV afferents.
Topics: Acid Sensing Ion Channels; Animals; Decerebrate State; Lower Extremity; Muscle Contraction; Muscle, Skeletal; Physical Conditioning, Animal; Physical Exertion; Rats; Rats, Sprague-Dawley; Reflex
PubMed: 31347922
DOI: 10.1152/ajpregu.00148.2019