Different oscillators control the circadian rhythm of eclosion and activity inDrosophila

Summary Anatomical studies on the 6 posterior cirri of the barnacle,Balanus hameri, have revealed the presence of a number of bipolar and multipolar sensory neurons in the coxopodite-basipodite-ramal (CBR) region which appear to function as proprioceptors. The cells are associated with two simple strands which terminate on the surface of the flexor muscles or on the hypodermis.Electrophysiological results suggest that the units show uni-directional responses to movements of the limb segments. No position receptors were identified. The difference in receptor activity to imposed and endogenously generated limb movements suggest that many units normally function as muscle tension receptors.     

Fine structure of a mandibular stretch receptor in Thrips physapus L. (Thysanoptera,Insecta)

Summary Only one non-ciliary proprioceptor is developed on the mandible of Thrips. It consists of two bipolar, multiterminal sense cells, the dendrites of which form a strand extended between the tentorium and the back mandibular margin. The dendritic terminals are embedded in an electron-dense, homogeneous matrix, which obviously represents the stimulus transmitting structure. The strand is stretched, if the mandible is moved forwards and upwards. In Thrips, the system of proprioceptors monitoring the mandibular movement is reduced extensively compared with other pterygote insects. This is linked up with the far-reaching reduction of the mobility of the mandible itself.This study is dedicated to Mrs. Signe Ulmer, in memory of her winning nature, her invaluable assistance, and her disciplineSupported by a grant from the Deutsche Forschungsgemeinschaft (Ho 826/2-2)     

Further studies on Mouthpart Receptors in decapoda crustacea

Summary In the lobster Homarus gammarus (L.) (=Homarus vulgaris M. Ed.) three bilateral groups of proprioceptors are arranged around the mouth. These strand receptor organs, termed Mouthpart Receptors (MPRs) 1, 2 and 3, were described previously and their physiological responses, mainly to mandibular movements, were characterised (Laverack and Dando, 1968).The receptor organs are described here for Panulirus argus Latr., Nephrops norvegicus L. and Astacus leptodactylus Esch.. Because of the anatomical differences between the receptors in Panulirus and Homarus the physiological work on Panulirus was designed to characterise the responses of the receptor neurones in some detail. The input from the receptors studied was similar to that of the Homarus receptors. In Nephrops and Astacus where the anatomy is similar to that of Homarus we have demonstrated that these receptors form a non-specialised system which responds to many of the movements associated with the act of ingestion of food.It is suggested that with other work now in progress, particularly on the innervation of the mandible (Wales and Laverack, 1970), a reasonably complete summary of the proprioceptive input associated directly with food ingestion is now possible. The relevance of this work to studies on the stomatogastric ganglia is discussed, and finally an attempt is made to compare the crustacean information with that for several insect species where the anatomy of the receptors in the mouth region is known but physiological experiments are much more difficult.This work was supported partly by the Centre National de la Recherche Scientifique (Equipe de Recherche Associée No. 231).This represents contribution No. 487 from the Bermuda Biological Station. Work carried out in Bermuda was supported by the Science Research Council (B/SR/4866).     

The structure and properties of an abdominal chordotonal organ in Carausius morosus and Blaberus discoidalis

Each side of the abdominal segments of the stick insect Carausius morosus contains a chordotonal organ lying longitudinally in a ventro-lateral position. These ventro-lateral chordotonal organs each possess two nerve cell bodies and two scolopales. There is a single attachment strand to the cuticle.Electrical recordings from the receptors show that they respond in a highly phasic manner to both stretching and subsequent relaxation of the attachment strand. They are sensitive to substrate vibration but are activated by ventilatory movements. The effects of ramp and square wave stimulation are examined. The rôle of the ventro-lateral chordotonal organs as ventilatory receptors is discussed and abdominal chordotonal organs of insects in general are reviewed.The ‘ventral phasic receptors’ of the cockroach are re-examined and shown to be chordotonal organs. They are re-named ‘mid-ventral’ chordotonal organs.     

A strand receptor with a central cell body synapses upon spiking local interneurones in the locust

Summary Movements of the femoro-tibial joint of a locust hind leg are monitored by three classes of proprioceptors; a chordotonal organ (Usherwood et al. 1968), multipolar joint receptors (Coillot and Boistel 1968) and a strand receptor innervated by a single afferent with a central cell body (Bräunig 1985). All three classes are excited by imposed or voluntary extension of the tibia. The strand receptor (fe-tiSR) spikes tonically and at a frequency dependent upon the position of the joint whilst the multipolar joint receptors give overlapping information but for a more restricted range. The afferent from the strand receptor makes an excitatory connection with a spiking local interneurone in the midline group of the metathoracic ganglion. The central latency and consistency with which the EPSP follows each sensory spike suggests that the connection is direct. This interneurone also receives convergent inputs from neurones in the chordotonal organ, but not from multipolar joint receptors. Neither the strand receptor nor the multipolar joint receptors apparently synapse upon leg motor neurones that we have tested, in contrast to receptors in the chordotonal organ.     

Range fractionation in the locust metathoracic femoral chordotonal organ

Summary Insect femoral chordotonal organs are internal proprioceptors which monitor the position and movements of the femur-tibia joint of the leg. The locust (Locusta migratoria) metathoracic femoral chordotonal organ is composed of approximately 100 neurones with a variety of response properties. In this study intracellular recordings were used to examine the range fractionation of phasic and tonic responses to tibial movements. Some neurones responded across the full range of leg angles, while others had restricted response ranges, and could therefore act as labeled lines. Neurones with maximal firing at mid-angles are described for the first time in a locust femoral chordotonal organ. Responses are discussed in terms of underlying structural constraints on signal transduction.Abbreviation (mt) FCO (metathoracic) femoral chordotonal organ     

Responses of midbrain lateral line units of the goldfish, Carassius auratus, to constant-amplitude and amplitude-modulated water wave stimuli

 Responses of mechanosensory lateral line units to constant-amplitude hydrodynamic stimuli and to sinusoidally amplitude-modulated water movements were recorded from the goldfish (Carassius auratus) torus semicircularis. Responses were classified by the number of spikes evoked in the unit's dynamic range and by the degree of phase locking to the carrier- and amplitude-modulation frequency of the stimulus. Most midbrain units showed phasic responses to constant-amplitude hydrodynamic stimuli. For different units peri-stimulus time histograms varied widely. Based on iso-displacement curves, midbrain units prefered either low frequencies (≤33 Hz), mid frequencies (50–100 Hz), or high frequencies (≥200 Hz). The distribution of the coefficient of synchronization to constant-amplitude stimuli showed that most units were only weakly phase locked. Midbrain units of the goldfish responded to amplitude-modulated water motions in a phasic/tonic or tonic fashion. Units highly phase locked to the amplitude modulation frequency, provided that modulation depth was at least 36%. Units tuned to one particular amplitude modulation frequency were not found. Accepted: 10 July 1999     

The mandibular common inhibitor system

Summary The mandibular common inhibitor neurones ofHomarus gammarus receive sensory input from a wide receptive field (Table 1, Figs. 2, 3) and from their symmetrical homologue (Ferrero and Wales, 1976).The CI system receives excitatory input from mandibular proprioceptors, with the notable exception of the mandibular muscle receptor organ, and its activity increases, during mandible opening and closing, towards the extremes of movement (Fig. 1). The output of CI neurones is usually coupled except during some high frequency bursts. Unilateral sensory input usually produces a coupled output. Electrical stimulation of a wide range of mandibular nerves (Table 2) has a similar effect and entrains the CI output at lower frequencies (Figs. 4, 5).Antidromic stimulation of a CI neurone causes excitation of its homologue but to a lower level of activity and without enhanced coupling. Even when the excitatory state is raised, by concurrent stimulation of a sensory nerve, the pathway activated by antidromic stimuli does not produce coupled activity at frequencies above 20 Hz (Fig. 8).Stimulation with single pulses will frequently produce short trains of impulses from the CI neurones (Figs. 6, 7) suggesting reciprocal excitation between the neurones.A model of the system based on current knowledge is presented.     

Response characteristics of single trochanteral campaniform sensilla in the stick insect, Cuniculina impigra

ABSTRACT. The campaniform sensilla on the trochanter of the stick insect, Cuniculina impigra Redtenbacher, were stimulated by slightly bending the leg in the horizontal plane. Single sensory units in the nerve were recorded using glass microelectrodes. These units can be classified into tonic and phasic-tonic receptors. In both cases there were units which increased their discharge frequency during forward movement of the femur, and units which responded to backward movement. No purely phasic receptors were found.     

Coding proprioceptive information to control movement to a target: Simulation with a simple neural network

When the stick insect walks, the middle and rear legs step to positions immediately behind the tarsus of the adjacent rostral leg. Previous reports have described this movement to a target as a relationship between the tarsus positions of the two legs in a Cartesian coordinate system. However, leg proprioceptors measure the position of the target leg in terms of joint angles and leg muscles bring the tarsus of the moving leg to the proper end-point by establishing appropriate angles at the joints. Representation of this task in Cartesian coordinates requires non-linear coordinate transformations; realizing such a transformation in the nervous system appears to require many neurons. The present simulation using the back-propagation algorithm shows that a simple network of only nine units — 3 sensory input units, 3 motor output units, and 3 hidden units — suffices. The simulation also shows that an analytic coordinate transformation can be replaced by a direct association of joint configurations in the moving leg with those in the target leg.     

The peripheral and central nervous organization of the locust coxo–trochanteral joint

The micromorphology of the locust coxo–trochanteral joint was examined in cobalt-stained material. Peripheral nervous system, musculature, and internal proprioceptors—two strand receptors and a muscle receptor organ—of the metathoracic coxa are compared with those of the pro- and mesothoracic legs. The number and position of trochanter levator and depressor motoneurons as well as the central projections of coxal sense organs are described. Evidence for a femoro–tibial strand receptor was obtained by tracing the path of a particular nerve branch.     

The oscillatory system responsible for the oculomotor activity during the bursts of REM.

1. In precollicular decerebrate cats the electrical activity of single pontine neurons was recorded before, during and after the episodes of postural atonia produced by i.v. injection of 0.03-0.1 mg/kg of eserine sulphate. These episodes were characterized by the regular occurrence of horizontal conjugate eye movements, which were mainly grouped in bursts of REM; moreover, a burst of REM in one direction was generally followed by a burst of REM in the opposite direction. 2. Among the recorded units, 32 showed an increase in their discharge rate during these cataplectic episodes. However, while these units fired at regular frequency when postural rigidity was present, they showed periodic changes in their discharge rate as soon as the bursts of REM appeared in the electrooculogram. In particular a nearly sinusoidal increase in the discharge rate was related to the appearance of an ocular burst in one direction, while a decrease in the unit discharge occurred during an ocular burst in the opposite direction. In some instances neighbouring pontine units located within each side of the brain stem showed reciprocal rate profiles during REM bursts oriented in a given direction, making it likely that the cyclic alternation of their activity depended upon their reciprocal interaction. 3. The alternative hypothesis, i.e., that these periodic changes in unit discharge depend upon the proprioceptive feedback due to the eye movements was excluded by the fact that these changes started before the occurrence of the bursts of REM and began to decline before the end of the burst. Moreover no variation in their firing rate was observed during the positional nystagmus induced by tilting the animal in the control period, i.e., when postural rigidity had reappeared following the end of the cataplectic episode. 4. Most of the neurons showing periodic changes in their discharge frequency during the bursts of REM were located in the pontine reticular formation. Scattered units were also found within the region of the locus coeruleus and the raphe system, close to the surrounding reticular structures. 5. In addition to these neurons, 60 pontine units were recorded, which did not show any changes in their discharge rate during transition from the control period to the cataplectic episode. However, phsiic increases or phasic decreases in their discharge rate appeared synchronously with the individual eye movements. Since in most instances these phasic changes in unit activity coincided with the appearance of the individual monophasic potentials recorded from the ascending MLB, which immediately preceded the rapid eye movements, these units could be attributed either to the premotor neurons responsible for these REM or to the closely related structures which generate their rhythmic discharge. In only a few instances did the discharge of these units not precede but follow the individual eye movements, indicating that they resulted from a proprioceptive feedback originating during the eye movements. 6...     

The control of mandible movements in the ant Odontomachus

Ants use their mandibles to manipulate many different objects including food, brood and nestmates. Different tasks require the modification of mandibular force and speed. Besides normal mandible movements the trap-jaw ant Odontomachus features a particularly fast mandible reflex during which both mandibles close synchronously within 3 ms. The mandibular muscles that govern mandible performance are controlled by four opener and eight closer motor neurons. During slow mandible movements different motor units can be activated successively, and fine tuning is assisted by co-activation of the antagonistic muscles. Fast and powerful movements are generated by the additional activation of two particular motor units which also contribute to the mandible strike. The trap-jaw reflex is triggered by a fast trigger muscle which is derived from the mandible closer. Intracellular recording reveals that trigger motor neurons can generate regular as well as particularly large postsynaptic potentials, which might be passively propagated over the short distance to the trigger muscle. The trigger motor neurons are dye-coupled and receive input from both sides of the body without delay, which ensures the synchronous release of both mandibles.     

A push-pull set of elastic strand stretch receptor neurons for the swimmeret in an isopod Bathynomus doederleini

There coexist two types of neuronal terminal processes attaching to elastic strands at the socket of the swimmeret in Bathynomus doederleini. One of the processes, stretch receptor I is derived from the 1st nerve root of the abdominal ganglion. The other, stretch receptor II is derived from the 2nd nerve root of the ganglion. Both axons of stretch receptors are very thick (30-60 micro m) at sites before the terminal arborization. Cell bodies of the stretch receptors are located in the ganglion of their own segments. The neuronal cell body of the stretch receptor I is located at the anterior half of the hemiganglion ipsilateral to the periphery, and the neuronal cell body of the stretch receptor II at the posterior half of the hemiganglion contralateral to the periphery. Their signaling modalities in response to swimmeret movements were analyzed from intracellular recordings from the cell bodies. Stretch receptor I produced a sustained hyperpolarizing potential in response to protraction of the swimmeret. Stretch receptor II produced a sustained depolarizing potential in response to the protraction, and moreover, generated spike potentials on the rising phase of the depolarizing potential according to its height and steepness. Both the stretch receptors are a push-pull set of elastic strand stretch receptors for the angular position and velocity of swimmeret movements.     

A simple and inexpensive system for monitoring jaw movements in ambulatory humans

A simple and inexpensive method for recording vertical movements of the human mandible relative to the maxilla is presented. Measurements are made from accelerometers and a Hall-effect device temporarily glued to the upper and lower anterior teeth. The accelerometer signals are integrated once to give velocity and a second time to give position. Movements of the mandible relative to the maxilla are obtained by integrating the difference between the two accelerometer signals. The (relative) velocity and position records derived in this way are linear, but subject to drift when the jaw is stationary. Steady mandibular position is obtained from the Hall-effect system, but this signal must be corrected for its inherent non-linearity. This device can record rapid movements of the mandible even when the head is unrestrained, and interferes minimally with normal jaw movements.     

Wing receptors of the American cockroach Periplaneta americana]

Wing receptors of the cockroach have been studied using staining technique with methylene blue in living animals. Five types of the receptors were found: trychoid hairs, bristles, complaniform sensillae, chordotonal organs and multiterminal neurons. The majority of the receptors is located at the lower surface of the wing, especially along its ribs. Together with primitive features in the structure (polyneuronal origin of hairs and bristles, poor content of chordotonal organs, absence of distinct groups of companiform sensillae), some specialization of wing receptors with respect to flight function is noted (concentration of proprioceptors along the main mechanical axis of the wing and formation of distinct rows by the companiform sensillae).     

Biplanar X-ray motion analysis of the lower jaw movement during incisor interaction and mastication in the beaver (Castor fiber L. 1758)

The first biplanar X-ray motion analysis of mastication and food processing for Castor fiber is presented. While particles are chipped off interaction of incisors involves variable movements of the lower mandible and thus incisors. After jaw opening the tip of the lower incisors can reach different positions anteriorly of the upper incisors. Then the mandible moves upwards and backwards and brings the tips of the incisors into contact. The lower incisors slide along the wear facet of the upper to the ledge when the cheek teeth occlude. The glenoid fossa and lower jaw condyle are in close contact during incisor contact and no transverse movements are observed. Mastication involves interaction of the cheek teeth with no contact of the incisors. When the cheek teeth are in occlusal contact the mandible is moved forward and transverse, or mediolateral. In consecutive power strokes the jaw is moved alternately to the right and left side. When the jaw opens it is brought into a more central but not totally centred position. During mastication the condyles are positioned posteriorly to the glenoid allowing lateral movement of the mandible. The lateral movement is particularly noticeable in the anterior part of the mandible. With the lateral movements of the incisors one glenoid has to move posteriorly, the other anteriorly.     

Cerebellar cortical activity during stretch of antagonist muscles

Single unit activity was recorded from the anterior lobe of the cerebellum during ramp and hold stretches of limb muscles in chloralose anesthetized cats. The activity of 95 "phasic" units showed a transient response during dynamic stretch of at least one muscle usually lasting for less than 350 ms following the stimulus onset. The activity of 59 phasic-tonic units was modified not only during dynamic stretch but also during the 1 s of maintained muscle length. All Purkinje cells, identified by their complex spikes, that responded to muscle stretch demonstrated exclusively phasic changes in discharge. Fourteen of 25 Purkinje cells (56%) responded to stretch of both antagonist muscles and these responses were always similar rather than reciprocal. From the 129 units without complex spikes, 70 demonstrated phasic discharge patterns whereas 59 had tonic responses. Seventy-five (59%) of these unidentified units revealed convergent responses to stretch of both antagonists, compared with 54 which responded to stretch of one muscle only. Of the unidentified units receiving convergent afferents from antagonist muscles, 62 (83%) had similar responses and only 13 (17%) had reciprocal reactions. There appeared to be no evidence that muscle afferents alone can induce reciprocal discharge patterns in Purkinje neurons of the cerebellar cortex. The firing frequency of some phasic-tonic units was correlated with both the velocity and amplitude of muscle stretch. No Purkinje cells were found with activity related to either velocity or amplitude of muscle stretch. One phasic and seven phasic-tonic unidentified units were activated at fixed latencies following trains of electrical stimulation applied to the thoracic spinal cord at frequencies exceeding 200 Hz, implying they were terminal portions of mossy fibers originating from direct spinocerebellar tracts. A few recordings of compound potentials were presumed to arise from the cerebellar glomeruli. The changing form of one of these potentials suggested that the glomerulus might be a site at which somatosensory peripheral information is modified by the cerebellar cortex.     

Effect of movement and illusion of movement on human vestibulomotor response

Lateral stabilographic response to galvanic labyrinth stimulation was investigated in healthy subjects in the standing position. Vestibulomotor response increased during forwards volitional body tilt as well as involuntary tilt occurring in response to stimulating (by vibration) the proprioceptors of the anterior tibial muscles. An illusion of the forward body tilt induced by stimulating (vibrating) the proprioceptors of the triceps surae muscles with the trunk fastened in a fixed position was accompanied by practically the same intensification of vestibulomotor response as during actual body movement. It was concluded that reinforcement of vestibulomotor response during volitional movements is brought about by the spatial perception system.Institute for Research into Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 20, No. 2, pp. 250–255, March–April, 1988.     

Ultrastructure de l'équipement sensoriel de la mandibule chez la larve duSpeophyes lucidulus Delar. (Coléoptère cavernicole de la sous-famille desBathysciinae)

Summary The sensorial organization of the mandible of theSpeophyes lucidulus larva is studied by means of electron microscopy.This sensorial apparatus is remarkably homogeneous, i.e. it includes only mechanoreceptors: — tactile receptors such as trichoide sensillae in the external edge of the mandible, — proprioceptors such as campaniform sensillae and scolopidia which are the more numerous.The latter, end in the zone of the mandible which are widely concerned with strains and deformations during mandibular movements.Furthermore, these receptors present certain original morphological features which are described below.Résumé L'organisation sensorielle de la mandibule de la larve duSpeophyes lucidulus est étudiée au microscope électronique. L'équipement sensoriel est remarquablement homogène puisqu'il ne comprend que des mécanorécepteurs: — récepteurs tactiles, comme les sensilles trichoïdes du bord externe de la mandibule, — propriocepteurs, comme les sensilles campaniformes d'une part et les récepteurs scolopidiaux d'autre part, qui sont les plus abondants.Ceux-ci se terminent dans les zones de la mandibule qui sont le plus fortement soumises à des tensions et des déformations lors des mouvements mandibulaires. Ces récepteurs présentent en outre certaines caractéristiques morphologiques originales que nous décrivons.