Neuronal control of swimming locomotion: analysis of the pteropod mollusc Clione and embryos of the amphibian Xenopus.

It is rare to be able to explain the behaviour of a whole animal at the level of the properties and connections of characterized CNS neurones. In a marine mollusc, Clione, and a lower vertebrate embryo, Xenopus, it is possible to make intracellular recordings during fictive swimming behaviour. This has allowed us to analyse the operation of two central pattern generators (CPGs) at the cellular level.

Control of locomotion in marine mollusc Clione limacina. VII Reexamination of type 12 interneurons.

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.

Control of feeding movements in the pteropod mollusc, Clione limacina.

(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.

Control of feeding movements in the freshwater snail Planorbis corneus. III. Organization of the feeding rhythm generator.

(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.

Control of feeding movements in the freshwater snail Planorbis corneus. II. Activity of isolated neurons of buccal ganglia.

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.

Control of feeding movements in the freshwater snail Planorbis corneus. I. Rhythmical neurons of buccal ganglia.

(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).

Control of locomotion in marine mollusc Clione limacina. VI. Activity of isolated neurons of pedal ganglia.

In the pteropodial mollusc Clione limacina, the rhythmic locomotor wing movements are controlled by the pedal ganglia. The locomotor rhythm is generated by two groups of interneurons (groups 7 and 8) which drive efferent neurons. In the present paper, the activity of isolated neurons, which were extracted from the pedal ganglia by means of an intracellular electrode, is described.

Effects of stimulation of midline inhibitory area within the pontine tegmentum on scratch reflex.

Effects of stimulation of the midline inhibitory area of the dorsal tegmental field (DTF) in the pons on the fictive scratch reflex were studied in decerebrate immobilized cats. The fictive scratch reflex was evoked by tactile stimulation of the pinna. DTF stimulation suppressed both the scratch-related rhythmical activities of the nerves (ENGs) supplying m.

Control of locomotion in marine mollusc Clione limacina. I. Efferent activity during actual and fictitious swimming.

The marine mollusc Clione limacina swims by making rhythmic movements (with a frequency of 1-5 Hz) of its two wings. Filming demonstrated that the wings perform oscillatory movements in the frontal plane of the animal. During both the upward and downward movements of the wing, its posterior edge lagged behind the anterior one, i.

Control of locomotion in marine mollusc--Clione limacina. V. Photoinactivation of efferent neurons.

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.

Control of locomotion in marine mollusc Clione limacina. IV. Role of type 12 interneurons.

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.

Control of locomotion in marine mollusc Clione limacina. II. Rhythmic neurons of pedal ganglia.

Activity from neurons in isolated pedal ganglia of Clione limacina was recorded intracellularly during generation of rhythmic swimming. To map the distribution of cells in a ganglion, one of two microelectrodes was used to monitor activity of the identified neuron (1A or 2A), while the second electrode was used to penetrate successively all the visible neurons within a definite area of the ganglion. In addition, pairs of neurons of various types were recorded in different combinations with each other.

Control of locomotion in marine mollusc Clione limacina. III. On the origin of locomotory rhythm.

Neurons from the isolated pedal ganglia of the marine mollusc Clione limacina were recorded from intracellularly during generation of the locomotory rhythm. Polarization of single type 7 or type 8 interneurons (which discharge in the D- and V-phases of a swim cycle, respectively) strongly affected activity of the rhythm generator. Injection of depolarizing and hyperpolarizing current usually resulted in shortening and lengthening of a swim cycle, respectively.

Activity of cerebellar Purkinje cells during fictitious scratch reflex in the cat.

The activity of Purkinje cells (PCs) was recorded in the anterior lobe (the vermis and pars intermedia) and in the paramedian lobule of the cerebellum during the fictitious scratch reflex in thalamic cats immobilized with Flaxedil. In the anterior lobe, the activity of many PCs was rhythmically modulated in relation to the scratch cycle: they generated bursts of impulses separated by periods of silence. Different PCs were active in different phases of the scratch cycle.

Origin of signals conveyed by the ventral spino-cerebellar tract and spino-reticulo-cerebellar pathway.

The "fictitious" scratch reflex was evoked in decerebrate curarized cats by pinna stimulation. Activity of neurons of the ventral spino-cerebellar tract ( VSCT ) from the L4 and L5 segments of the spinal cord as well as of neurons of the spino-reticulo-cerebellar pathway ( SRCP ) from the lateral reticular nucleus of the medulla oblongata was recorded. Cooling and destruction of different parts of the lumbo-sacral enlargement of the spinal cord were performed.