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- Beloozerova, IN, et al.
(författare)
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Postural control in the rabbit maintaining balance on the tilting platform
- 2003
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 90:6, s. 3783-3793
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Tidskriftsartikel (refereegranskat)abstract
- A deviation from the dorsal-side-up body posture in quadrupeds activates the mechanisms for postural corrections. Operation of these mechanisms was studied in the rabbit maintaining balance on a platform periodically tilted in the frontal plane. First, we characterized the kinematics and electromyographic (EMG) patterns of postural responses to tilts. It was found that a reaction to tilt includes an extension of the limbs on the side moving down and flexion on the opposite side. These limb movements are primarily due to a modulation of the activity of extensor muscles. Second, it was found that rabbits can effectively maintain the dorsal-side-up body posture when complex postural stimuli are applied, i.e., asynchronous tilts of the platforms supporting the anterior and posterior parts of the body. These data suggest that the nervous mechanisms controlling positions of these parts of the body can operate independently of each other. Third, we found that normally the somatosensory input plays a predominant role for the generation of postural responses. However, when the postural response appears insufficient to maintain balance, the vestibular input contributes considerably to activation of postural mechanisms. We also found that an asymmetry in the tonic vestibular input, caused by galvanic stimulation of the labyrinths, can affect the stabilized body orientation while the magnitude of postural responses to tilts remains unchanged. Fourth, we found that the mechanisms for postural corrections respond only to tilts that exceed a certain (threshold) value.
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- Deliagina, TG, et al.
(författare)
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Role of different sensory inputs for maintenance of body posture in sitting rat and rabbit
- 2000
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Ingår i: Motor control. - : Human Kinetics. - 1087-1640 .- 1543-2696. ; 4:4, s. 439-452
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we describe the postural activity in sitting rats and rabbits. An animal was positioned on the platform that could be tilted in the frontal plane for up to ±20-30°, and postural corrections were video recorded. We found that in both rat and rabbit, the postural reactions led to stabilization of the dorsal-side-up trunk orientation. The result of this was that the trunk tilt constituted only ~50% (rat) and 25% (rabbit) of the platform tilt. In addition, in the rabbit the head orientation was also stabilized. Trunk stabilization persisted in the animals subjected to the bilateral labyrinthectomy and blindfolding, suggesting that the somatosensory input is primarily responsible for trunk stabilization. Trunk stabilization was due to extension of the limbs on the side moving down, and flexion of the opposite limbs. EMG recordings showed that the limb extension was caused by the active contraction of extensor muscles. We argue that signals from the Golgi tendon organs of the extensor muscles may considerably contribute to elicitation of postural corrective responses to the lateral tilt.
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- PANCHIN, YV, et al.
(författare)
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Control of locomotion in marine mollusk Clione Limacina. IX. Neuronal mechanisms of spatial orientation
- 1995
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 73:5, s. 1924-1937
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Tidskriftsartikel (refereegranskat)abstract
- 1. When swimming freely, the pteropod mollusk Clione limacina actively maintains a vertical orientation, with its head up. Any deflection from the vertical position causes a correcting motor response, i.e., bending of the tail in the opposite direction, and an additional activation of the locomotor system. Clione can stabilize not only the vertical orientation with its head up, but also the posture with its head down. The latter is observed at higher water temperature, as well as at a certain stage of hunting behavior. The postural control is absent in some forms of behavior (vertical migrations, defensive reactions, "looping" when hunting). The postural reflexes are driven by input from the statocysts. After removal of the statocysts, Clione was unable to maintain any definite spatial orientation. 2. Activity of the neuronal mechanisms controlling spatial orientation of Clione was studied in in vitro experiments, with the use of a preparation consisting of the CNS and statocysts. Natural stimulation (tilt of the preparation up to 90 degrees) was used to characterize responses in the statocyst receptor cells (SRCs). It was found that the SRCs depolarized and fired (10-20 Hz) when, during a tilt, they were in a position on the bottom part of the statocyst, under the statolith. Intracellular staining has shown that the SRC axons terminate in the medial area of the cerebral ganglia. Electrical connections have been found between some of the symmetrical SRCs of the left and right statocysts. 3. Gravistatic reflexes were studied by using both natural stimulation (tilt of the preparation) and electrical stimulation of SRCs. The reflex consisted of three components: 1) activation of the locomotor rhythm generator located in the pedal ganglia; this effect of SRCs is mediated by previously identified CPA1 and CPB1 interneurons that are located in the cerebral ganglia and send axons to the pedal ganglia; 2) bending the tail evoked by differential excitation and inhibition of different groups of tail muscle motor neurons; this effect is mediated by CPB3 interneurons; and 3) modification of wing movements by differential excitation and inhibition of different groups of wing motor neurons; this effect is mediated by CPB2 interneurons. 4. Gravistatic reflexes in the tail motor neurons were inhibited or reversed at a higher water temperature. 5. The SRCs are not "pure" gravitation sensory organs because they are subjected to strong influences from the CNS. In particular, CPC1 interneurons, participating in coordination of different aspects of the hunting behavior, exert an excitatory action on some of the SRCs, and inhibitory actions on others.(ABSTRACT TRUNCATED AT 400 WORDS)
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- PANCHIN, YV, et al.
(författare)
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Control of locomotion in marine mollusk Clione limacina. VIII. Cerebropedal neurons
- 1995
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 73:5, s. 1912-1923
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Tidskriftsartikel (refereegranskat)abstract
- 1. The pteropod mollusk Clione limacina swims by rhythmical oscillations of two wings, and its spatial orientation during locomotion is determined by tail movements. The majority of neurons responsible for generation of the wing and tail movements are located in the pedal ganglia. On the other hand, the majority of sensory inputs that affect wing and tail movements project to the cerebral ganglia. The goal of the present study was to identify and characterize cerebropedal neurons involved in the control of the swimming central generator or motor neurons of wing and tail muscles. Cerebropedal neurons affecting locomotion-controlling mechanisms are located in the rostromedial (CPA neurons), caudomedial (CPB neurons), and central (CPC neurons) zones of the cerebral ganglia. According to their morphology and effects on pedal mechanisms, 10 groups of the cerebropedal neurons can be distinguished. 2. CPA1 neurons project through the ipsilateral cerebropedal connective to both pedal ganglia. Activation of a CPA1 by current injection resulted in speeding up of the locomotor rhythm and intensification of the firing of the locomotor motor neurons. 3. CPA2 neurons send numerous thin fibers into the ipsi- and contralateral pedal and pleural ganglia through the cerebropedal and cerebropleural connectives. They strongly inhibit the wing muscle motor neurons and, to a lesser extent, slow down the locomotor rhythm. 4. CPB1 neurons project through the contralateral cerebropedal connective to both pedal ganglia. They activate the locomotor generator. 5. CPB2 neurons also project, through the contralateral cerebropedal connective, to both pedal ganglia. They affect wing muscle motor neurons. 6. CPB3 neurons have diverse morphology: they project to the pedal ganglia either through the ipsilateral cerebropedal connective, or through the contralateral one, or through both of them. They affect putative motor neurons of the tail muscles. 7. CPC1, CPC2, and CPC3 neurons project through the ipsilateral cerebropedal connective to both pedal ganglia. They activate the locomotor generator. 8. CPC4 and CPC5 neurons project through the contralateral cerebropedal connective to the contralateral pedal ganglia. They activate the locomotor generator. 9. Serotonergic neurons were mapped in the CNS of Clione by immunohistochemical methods. Location and size of cells in two groups of serotonin-immunoreactive neurons in the cerebral ganglia appeared to be similar to those of CPA1 and CPB1 neurons. This finding suggests a possible mechanism for serotonin's ability to exert a strong excitatory action on the locomotor generator of Clione. 10. The role of different groups of cerebropedal neurons is discussed in relation to different forms of Clione's behavior in which locomotor activity is involved.
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- Pavlova, EL, et al.
(författare)
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Vestibular compensation in lampreys: restoration of symmetry in reticulospinal commands
- 2004
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Ingår i: The Journal of experimental biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 207:26Pt 26, s. 4595-4603
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Tidskriftsartikel (refereegranskat)abstract
- Removal of a vestibular organ (unilateral labyrinthectomy, UL) in the lamprey results in a loss of equilibrium, so that the animal rolls (rotates around its longitudinal axis) when swimming. Owing to vestibular compensation,UL animals gradually restore postural equilibrium and, in a few weeks, swim without rolling. Important elements of the postural network in the lamprey are the reticulospinal (RS) neurons, which are driven by vestibular input and transmit commands for postural corrections to the spinal cord. As shown previously, a loss of equilibrium after UL is associated with disappearance of vestibular responses in the contralateral group of RS neurons. Are these responses restored in animals after compensation? To answer this question, we recorded vestibular responses in RS neurons (elicited by rotation of the compensated animal in the roll plane) by means of chronically implanted electrodes. We found that the responses re-appeared in the compensated animals. This result supports the hypothesis that the loss of equilibrium after UL was caused by asymmetry in supraspinal motor commands, and the recovery of postural control in compensated animals was due to a restoration of symmetry.
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