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  • 1
    Electronic Resource
    Electronic Resource
    Control of feeding movements in the freshwater snail Planorbis corneus (1988)
    Springer
    Experimental brain research 70 (1988), S. 310-322 
    Details
    ISSN: 1432-1106
    Keywords: Mollusc ; Feeding ; Buccal ganglia ; Central pattern generator ; Rhythmic neurons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary (1) The buccal mass of the freshwater snail Planorbis corneus, dissected together with the buccal ganglia, performs rhythmic feeding movements. Radula movements and the electrical activity in various nerves of buccal ganglia were recorded in such a preparation. The cycle of radula movements consisted of three phases: quiescence (Q), protraction (P) and retraction (R). The activity in the radular nerve was observed mainly in the P-phase and that in the dorsobuccal nerve, largely in the R-phase. (2) Isolated buccal ganglia were capable of generating a feeding rhythm, the activity in buccal nerves being similar to that observed in the buccal mass-buccal ganglion preparation, i.e., a burst in the radular nerve preceded a burst in the dorsobuccal nerve. The activity of neurons in isolated buccal ganglia during generation of the feeding rhythm has been studied with intracellular microelectrodes. About 10% of ganglion neurons exhibited periodic activity related to the feeding rhythm (“rhythmic” neurons). (3) Rhythmic neurons have been divided into 7 groups according to the phase of their activity and to the characteristics of slow oscillations of the membrane potential during the feeding cycle. Group 1 neurons revealed a gradual increase of depolarization during the Q- and P-phases. In subgroup le neurons, spike discharges began in the Q-phase, while in subgroup 1d neurons activity started in the P-phase. During the R-phase, group 1 neurons were strongly hyperpolarized, and their discharges terminated. In group 2 neurons, small depolarization gradually increased during the Q- and P-phases. Then, in the R-phase, a large (20–50 mV) rectangular wave of depolarization arose with superimposed high-frequency oscillations. Group 3 neurons exhibited an excitatory postsynaptic potential (EPSP) in the P-phase and inhibitory postsynaptic potential (IPSP) in the R-phase. The neurons of group 4 revealed two EPSPs: a small one in the P-phase and a larger one in the R-phase. Group 5 neurons exhibited an EPSP in the P-phase, those of group 7 — an IPSP in the R-phase, and those of group 9 — IPSPs in the P- and R-phases. Neurons within each of the groups 1, 2 and 4 were electrically coupled, and in addition, there were also electrical connections between neurons of groups 2 and 4. (4) Data are presented showing that neurons of groups 1 and 2 are the main source of postsynaptic potentials in rhythmic neurons in the P-phase and in the R-phase of the cycle, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248356
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  • 2
    Electronic Resource
    Electronic Resource
    Control of feeding movements in the freshwater snail Planorbis corneus (1988)
    Springer
    Experimental brain research 70 (1988), S. 332-341 
    Details
    ISSN: 1432-1106
    Keywords: Mollusc ; Feeding ; Buccal ganglia ; Central pattern generator ; Neuron polarization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary (1) Neurons of different groups (for group classification, see Arshavsky et al. 1988a) have been polarized through an intracellular recording microelectrode in Planorbis corneus buccal ganglia during feeding rhythm generation. Group 1 neurons, active in the quiescence (Q) and in the protractor (P) phases of the cycle, and also group 2 and 4 neurons, active in the retractor (R) phase, have proved to be “influential”, i.e., altering the rhythm generator operation. (2) Injection of a depolarizing current into group 1 neurons caused an increase of the rate of depolarization that neurons of this group exhibit in the Q- and P-phases of the feeding cycle. As a result, Q-phase shortened, the P-phase became longer, and the feeding rhythm accelerated. Opposite effects occured when a hyperpolarizing current was injected into group 1 neurons. In some of the experiments, the hyperpolarization of group 1 neurons resulted in cessation of both their activity and the activity of all other protractor neurons. As a result, the P-phase of the cycle disappeared, i.e., the rhythm generator transited from A mode of operation to B mode. (3) With hyperpolarization of individual group 2 or 4 neurons, excitation of the R-phase neurons was delayed and the feeding rhythm phase shifted. This delay was accompanied by the enhanced activity of protractor neurons. (4) A generator model is considered in which two groups (1 and 2) of endogeneously active neurons are coordinated by the excitatory effect of group 1 on group 2 and the inhibitory action of group 2 on group 1. (5) Evidence is given that the different modes of rhythm generator operation (A, B and C, see Arshavsky et al. 1988a) are determined by different tonic inflow to group 1 neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248358
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  • 3
    Electronic Resource
    Electronic Resource
    Control of locomotion in marine mollusc — Clione limacina. V. Photoinactivation of efferent neurons (1985)
    Springer
    Experimental brain research 59 (1985), S. 203-205 
    Details
    ISSN: 1432-1106
    Keywords: Pteropodial mollusc ; Pedal ganglia ; Locomotion ; Lucifer yellow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Efferent neurons in isolated pedal ganglia of the pteropodial mollusc Clione limacina were filled with Lucifer Yellow through the wing nerves. Then the ganglia were illuminated with intense blue light which resulted in the complete inactivation of these neurons. After inactivation of efferent neurons, interneurons of the pedal ganglia continued to generate the locomotor rhythm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237680
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  • 4
    Electronic Resource
    Electronic Resource
    Control of feeding movements in the freshwater snail Planorbis corneus (1988)
    Springer
    Experimental brain research 70 (1988), S. 323-331 
    Details
    ISSN: 1432-1106
    Keywords: Mollusc ; Buccal ganglia ; Feeding rhythm generation ; Endogenous activity ; Isolated neurons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Isolated buccal ganglia of Planorbis corneus are capable of generating a feeding rhythm. In the present work, “rhythmic” neurons of different groups (see Arshavsky et al. 1988a) have been extracted, by means of an intracellular microelectrode, from the buccal ganglia. (1) After extraction, efferent neurons of groups 3, 5, 7, 9 and most group 4 neurons generated repeated spikes at a frequency controlled by a polarizing current. Any periodic oscillations, similar to those during feeding rhythm generation, were absent in these isolated neurons. It is concluded, therefore, that these neurons are “followers”, that is, their rhythmic activity before extraction is determined by synaptic inputs from other neurons of the ganglia. (2) Isolated interneurons of groups 1 and 2 generated slow periodic oscillations similar to those observed in these neurons before their extraction. Subgroup 1e neurons generated smoothly growing depolarization accompanied by increasing spike activity; this depolarization was periodically interrupted by abrupt hyperpolarization, after which a new cycle started. Subgroup 1d neurons periodically generated short series of spikes. Group 2 neurons periodically generated a rectangular wave of depolarization with spike-like oscillations on its top. These results suggest that feeding rhythm generation in Planorbis is based on the endogenous rhythmic activity of group 1 and 2 neurons. (3) A pulse of hyperpolarizing current injected into an isolated neuron of subgroup 1e stopped the growth of depolarization in the neuron and reinitiated the process. This property as well as the character of the synaptic interactions of the interneurons (group 1 neurons excite those of group 2, while those of group 2 inhibit group 1 neurons; Arshavsky et al. 1988b) determine the alternating activity of groups 1 and 2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248357
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  • 5
    Electronic Resource
    Electronic Resource
    Vestibular control of swimming in lamprey (1992)
    Springer
    Experimental brain research 90 (1992), S. 479-488 
    Details
    ISSN: 1432-1106
    Keywords: Reticulospinal neurons ; Vestibular reactions ; Locomotion ; Lamprey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A method has been developed for recording the response of single neurons in the lamprey brainstem in vitro to natural stimulation of vestibular receptors. The brainstem dissected together with the intact vestibular apparatus could be rotated in space, in two perpendicular planes (transverse, the roll tilt, and sagittal, the pitch tilt), in one of them up to 360°, and in the other one up to ± 30°. The responses of single reticulospinal (RS) neurons, in all four reticular nuclei of the brainstem, to roll and pitch were recorded extracellularly and, with small inclinations (up to ±45°) also intracellularly. Two types of preparations were used, with and without the rostral part of the spinal cord. In the brainstem preparations, most RS neurons responded both to a definite brain orientation in space and to a change of the orientation (static and dynamic reactions). Responses to roll tilt were similar in all reticular nuclei: all cells were excited with roll tilt towards the contralateral side, this reaction was qualitatively preserved when the roll was performed in combination with different pitch inclinations. Responses to pitch tilt were less clearcut; some neurons were activated with noseup deflection while others responded to nose-down tilt. In preparations including the spinal cord, responses of RS neurons to roll and pitch tilt differed from those in the isolated brainstem in that they were much less specific and sfable. Roll and pitch tilts could trigger the spinal locomotor CPG, which, by sending “efference copy” signals back to the brainstem, produced modulation of RS neurons in relation to the locomotor rhythm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230930
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  • 6
    Electronic Resource
    Electronic Resource
    Visual input affects the response to roll in reticulospinal neurons of the lamprey (1993)
    Springer
    Experimental brain research 95 (1993), S. 421-428 
    Details
    ISSN: 1432-1106
    Keywords: Reticulospinal neurons ; Visual input ; Vestibular reactions ; Visuo-vestibular interaction ; Lamprey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A body orientation with the dorsal side up is usually maintained by lampreys during locomotion. Of crucial importance for this is the vestibular-driven control system. A visual input can affect the body orientation: illumination of one eye during swimming evokes roll tilt towards the source of light. The aim of the present study was to investigate the interaction of visual and vestibular inputs in reticulospinal (RS) neurons of the brainstem. The RS system is the main descending system transmitting information from the brainstem to the spinal cord. The response of neurons in the middle rhombencephalic reticular nucleus to a unilateral nonpatterned optic input was investigated, as well as the influence of this input on the response of RS neurons to vestibular stimulation (roll tilt). Experiments were carried out on a brainstem preparation with intact labyrinths and, in some cases, intact eyes. Illumination of one eye or electrical stimulation of the optic nerve (10 Hz) resulted in an activation of RS neurons preferentially on the ipsilateral side of the brainstem. The same result was obtained after ablation of the optic tectum, demonstrating that there are asymmetrical visual projections to the lower brainstem which do not involve the tectum. Stimulation of the optic nerve strongly affected the vestibular response in RS neurons. As a rule RS neurons are silent at the normal (dorsal-side-up) orientation of the brainstem and become active with contralateral roll tilt. During continuous optic nerve stimulation, however, the RS neurons on the side of stimulation fire during normal orientation of the brainstem, and the response to contralateral roll tilt increases considerably in many neurons. The effects of the optic input in contralateral RS neurons were less consistent. Any asymmetry in the signals transmitted to the spinal cord by the two (left and right) sub-populations of RS neurons can be expected to evoke a correcting motor response aimed at turning the body around its longitudinal axis to a position at which the symmetry between left and right RS neurons is restored. Normally, the symmetry will occur when the dorsal side is upwards, but with a unilateral visual input it will occur instead at some degree of ipsilateral roll.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227134
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  • 7
    Electronic Resource
    Electronic Resource
    Control of locomotion in marine mollusc Clione limacina IV. Role of type 12 interneurons (1985)
    Springer
    Experimental brain research 58 (1985), S. 285-293 
    Details
    ISSN: 1432-1106
    Keywords: Pteropodial mollusc ; Pedal ganglia ; Locomotion ; Central pattern generator ; Plateau potentials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Type 12 interneurons in pedal ganglia of Clione limacina exerted a strong influence upon the locomotor generator during “intense” swimming. These neurons generated “plateau” potentials, i.e. their membrane potential had two stable states: the “upper” one when a neuron was depolarized, and the “down” one, separated by 30–40 mV. The interneurons could remain in each state for a long time. Short depolarizing and hyperpolarizing current pulses, as well as excitatory and inhibitory postsynaptic potentials, could transfer the interneurons from one state to another. 2. When the pedal ganglia generated the locomotory rhythm, type 12 neurons received an EPSP and passed to the “upper” state in the V2-phase of a locomotor cycle. They remained at this state until the beginning of the D1-phase when they received an IPSP and passed to the “down” state. The EPSP in type 12 neurons was produced by type 8d neurons, and the IPSP by type 7 neurons. 3. Type 12 neurons exerted inhibitory influences upon many neurons active in the V1 and V2 phases, and excitatory influences upon the D-phase interneurons (type 7). 4. The functional role of type 12 neurons was to limit the activity of neurons discharging in the V-phase of a locomotory cycle. In addition, they enhanced the excitation of the D-phase neurons and promoted, thus, the transition from the V-phase to the D-phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235310
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  • 8
    Electronic Resource
    Electronic Resource
    Control of feeding movements in the pteropod mollusc, Clione limacina (1989)
    Springer
    Experimental brain research 78 (1989), S. 387-397 
    Details
    ISSN: 1432-1106
    Keywords: Mollusc ; Buccal ganglia ; Feeding rhythm generation ; Rhythmic neurons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary (1) The buccal apparatus of the pteropod marine mollusc Clione limacina, isolated together with buccal ganglia, could perform rhythmic feeding movements. Movements of the radula and the hooks (which the Clione inserts into the body of its prey) as well as the electroneurogram of the radular nerve were recorded. Usually one could observe rhythmic radula movements alone, while the hooks were motionless. But sometimes the hooks also performed rhythmic movements which were more or less synchronous with those of the radula. The radula movement cycle consisted of the protraction and the retraction phases, which were occasionally followed by a quiescent phase. Corresponding to each radula movement was a burst of activity in the radular nerve, consisting of the protractor and the retractor components. (2) Isolated buccal ganglia were capable of feeding rhythm generation. Most of the buccal neurons exhibited rhythmic activity correlating with the activity in the radular nerve. According to the phase of activity in the feeding cycle, rhythmic neurons were divided into two groups — the protractor and the retractor ones. The neurons within each of the groups were electrically coupled with each other. The protractor and retractor neurons inhibited each other. (3) Protractor and retractor neurons were extracted from buccal ganglia by means of a microelectrode. Many isolated cells generated slow oscillations of membrane potential and bursts of spikes, the pattern of this activity being similar to that before isolation. (4) A model of the feeding rhythm generator is discussed. It consists of two (protractor and retractor) groups of neurons with mutual inhibitory connections, neurons of each group being endogenous bursters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228911
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  • 9
    Electronic Resource
    Electronic Resource
    Control of locomotion in marine mollusc Clione limacina (1989)
    Springer
    Experimental brain research 78 (1989), S. 398-406 
    Details
    ISSN: 1432-1106
    Keywords: Pteropod mollusc ; Locomotion ; Central pattern generator ; Interneurons ; Plateau potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In previous work carried out on the isolated pedal ganglia of the pteropod mollusc Clione limacina we described the activity of a neuronal element (type 12 neuron) and looked into its role in the locomotor rhythm generation (Arshavasky et al. 1985d). As we learned subsequently, the activity was recorded from the neuron axon passing in the pedal ganglia, while the neuron soma was located in the pleural ganglia and consequently was cut off in the course of pedal ganglia isolation. It thus became necessary to reinvestigate the properties of this neuron and its role in locomotory rhythm generation by using less reduced preparation of the central nervous system. The following results were obtained. (1) Each pleural ganglion contains only one neuron of this type, this cell is thus to be considered as the identified neuron. The neuron's axon reaches into the pedal ganglion via the pleuro-pedal connective. Then the axon divides into two branches terminating in the lateral regions of both pedal ganglia. The neurons 12 from the left and right pleural ganglia have no direct connections with one another; their synchronous operation in the locomotor cycle is determined by common inputs. (2) The electrical properties of an intact neuron 12 and one without a soma are about the same. In either case the neuron generates “plateau” potentials, i.e., it may persist for a long time in the depolarized state. Plateau potentials can be induced by a depolarizing current pulse or by an EPSP, and terminated by hyperpolarizing current or by an IPSP. The neuron input resistance drops about twofold during generation of the plateau potential. (3) Recording of the neuron 12 in the pleural ganglia showed that its activity during “fictive swimming” does not differ from that of somadeprived axon recorded in the isolated pedal ganglia. The neuron generates a plateau potential in the V-phase of the locomotor cycle (definitions for the phases of the cycle were given in Arshavsky et al. 1985b). This potential is triggered by an EPSP evoked by subgroup 8d pedal neurons. The plateau potential terminates in the D-phase under the influence of an IPSP evoked by group 7 neurons. The effects of the neuron 12 on other neuronal elements of the locomotor generator in pedal ganglia do not depend on the presence of the cell soma either. (4) The pedal ganglia locomotor generator sometimes generates an “anomalous rhythm” when normal cycles alternate with reduced ones in which the activity of some groups of neurons is inhibited. Simultaneous recording from two neurons 12 demonstrated that the alternating rhythm generation was caused by the anomalous behaviour of one of the neurons 12: the neuron persisted in the depolarized state for one cycle and a half and not for half a cycle, as during the normal operation of the locomotor generator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228912
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  • 10
    Electronic Resource
    Electronic Resource
    Vestibular control of swimming in lamprey (1992)
    Springer
    Experimental brain research 90 (1992), S. 499-507 
    Details
    ISSN: 1432-1106
    Keywords: Vestibular afferents ; Reticulospinal neurons ; Vestibular reactions ; Lamprey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experiments were carried out on the in vitro preparation of the lamprey brainstem isolated together with the labyrinths. The brain orientation in space could be changed in steps of 45° by rotation (360°) around the longitudinal axis (roll) or the transverse axis (pitch). Vestibular afferents in the VIII nerve, or reticulospinal (RS) neurons, were recorded extracellularly during roll and pitch. Two main types of afferents could be distinguished. Presumed otolith afferents responded both to a change of position and to a maintained new position. These afferents were classified in several groups according to the position of their zone of sensitivity. For roll, the largest group had their maximal sensitivity around 90° tilt to the ipsilateral side, the next group in size responded at 180°, and only a few afferents were activated by contralateral roll. For pitch, there are groups responding with maximal sensitivity at 90° nose-up, 90° nose-down and at 180°. A minority of afferents were active when the brainstem was in a normal position, i.e. horizontal, with the dorsal side up. Another type of afferent responded only by a high-frequency burst to a change of brain orientation. They were classified as canal afferents in analogy with other species. All tested canal afferents responded to rotation towards ipsi-side down. Pitch tilt revealed two groups that responded to rotation towards either nose-up or nosedown. RS neurons from the anterior and middle rhombencephalic nuclei (ARRN and MRRN) were recorded before and after unilateral transection of the VIII nerve. For ARRN neurons, the inputs from the ipsi- and contralateral labyrinths were found to be almost equivalent, while for MRRN neurons these inputs contributed differently to the cells' response to tilt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230932
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