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  • 1
    Electronic Resource
    Electronic Resource
    The Concerted Activity in Parallel Proprioceptive Pathways Controls the Initiation of Co-activation in the Locust Kick Motor Programme (1997)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 9 (1997), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: To jump and kick the locust uses a catapult mechanism implemented by a three-stage motor programme: initial flexion of the hind tibiae, co-activation of the antagonist flexor and extensor tibiae motor neurons and trigger inhibition of the flexor motorneurons. The transition from stage 1 to stage 2 thus involves a switch from the normal alternate activation to co-activation of the antagonist tibiae motorneurons. However, co-activation has never been observed when the central nervous system has been isolated from the leg. This led us to investigate the possibility that the transition from stage 1 to stage 2 is controlled by a proprioceptive signal. In the first set of experiments intracellular recordings were made in the flexor and extensor motorneurons while the position of the tendon of the femoral chordotonal organ (FCO), which signals tibial position and movement, was experimentally controlled. In these heavily dissected preparations, stretch of the FCO tendon (signalling tibial flexion) was a necessary condition for co-activation. However, in minimally dissected preparations (in which merely EMG recordings were made), we found that co-activation occurred even when the FCO was signalling tibial extension, suggesting the involvement of other proprioceptors. A series of experiments were then conducted on minimally dissected preparations to determine the relative contributions of each of the three main hind leg proprioceptors which might signal tibial flexion: the FCO, the lump receptor and Brünners organ. When all three proprioceptors were intact the chance of evoking co-activation was largest, when all three were eliminated co-activation could no longer be evoked, irrespective of the level of arousal. Various combinations of partial de-afferentation showed that the FCO plays the major role, with the lump receptor and Brünners organ playing significant, but progressively less important, roles. We conclude that the three receptors act together as a permissive proprioceptive gate for the kick and jump motor programme, but with a hierarchy of the strengths of their effectiveness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1997.tb01353.x
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  • 2
    Electronic Resource
    Electronic Resource
    Quasi-reversible Photo-axotomy Used to Investigate the Role of Extensor Muscle Tension in Controlling the Kick Motor Programme of Grasshoppers (1995)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 7 (1995), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The jump and kick of the grasshopper are behaviours which are potentially critical for the survival of the animal, and whose maximal Performance depends upon optimizing the rate and level of tension development in the extensor tibiae muscle of the hind legs. In experimental conditions extensor tension control can be reduced to a single motoneuron, the fast extensor tibiae (FETi). The axon of FETi can be cut using dye-mediated laser photo- axotomy without damaging the central or peripheral portions of that neuron or any other neuron innervating the leg. The axotomy can be functionally reversed (i.e. the cut axon repaired) by an electronic axonal bypass which detects FETi spikes on the proximal side of the cut and stimulates the axon on the distal side of the cut. In this way motor spikes can either be allowed to reach the muscle or prevented from doing so (by switching the bypass on or off), and the motor programmes produced with and without extensor tension can be compared. The jump and kick are normally produced by a three-stage motor programme: (i) initial flexion brings the tibia into the fully flexed position; (ii) coactivation of extensor and flexor muscles allows the extensor muscle to develop maximal tension almost isometrically, while the simultaneous contraction of the flexor muscle holds the tibia flexed; (iii) sudden trigger inhibition of the flexor system (motoneurons and muscle) releases the tibia and allows the behaviour to be expressed. The grasshopper can produce fictive kicks with motor programmes which show each of these three major structural features of a normal kick, but without any extensor tension whatsoever. There is no significant difference in the frequency of FETi spikes, the duration of coactivation or the maximum depolarization of the flexor motoneurons between fictive and quasi-normal (i.e. reversed axotomy) kicks. The trigger inhibition of flexor motoneurons is shallower in fictive than in quasi-normal kicks. The significance of this is discussed in relation to the activity of the interneuron M, which is known to mediate trigger inhibition onto FlTi motoneurons. There are two main conclusions from this study. First, the CNS does not need feedback from ETi muscle tension in order to produce the three-stage motor programme of the kick (and, by implication, the jump). Second, the CNS does not adjust the frequency or duration of FETi activity in response to unexpected changes in ETi tension. ETi tension appears to be under open-loop control in the kick motor programme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1995.tb01086.x
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  • 3
    Electronic Resource
    Electronic Resource
    Adaptive reconfiguration of a reflex circuit during different motor programmes in the locust (1997)
    Springer
    Journal of comparative physiology 180 (1997), S. 659-669 
    Details
    ISSN: 1432-1351
    Keywords: Key words Grasshopper  ;  Schistocerca gregaria  ;   Campaniform sensilla  ;  Proprioceptor  ;  Kicking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The cuticle strain which develops in the hindleg tibiae when a locust prepares to kick, or when the tibia thrusts against an obstacle, is detected by two campaniform sensilla, which reflexly excite the fast extensor tibiae motoneuron, some of the flexor tibiae motoneurons and nonspiking interneurons. The reflex excitation is adaptive for the extensor motoneuron during both co-activation and thrusting, but is only adaptive for the flexor motoneurons during co-activation, and is maladaptive during thrusting. We show that the femoral chordotonal organ, which monitors tibial position, controls the efficacy of the strain feedback. The campaniform sensilla-induced depolarization in the extensor motoneuron is about twice as large when the tendon is in mid position (reflecting a tibial-femoral angle of 90°) than when fully stretched (reflecting tibial flexion), while in the flexors the reverse is true. The amplitudes of excitatory postsynaptic potentials evoked by single campaniform sensilla spikes, are, however, not affected. Our data suggests that the chordotonal organ modulates the gain of the strain feedback onto the motoneurons by exciting interneuronal circuits whose output sums with the former. Thrusting typically occurs with the tibia partially extended, therefore the actions of the chordotonal organ support the production of a maximal thrusting force.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050081
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  • 4
    Electronic Resource
    Electronic Resource
    The locust jump (1974)
    Springer
    Journal of comparative physiology 89 (1974), S. 93-104 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The locust jumps by a rapid extension of its metathoracic tibiae. The comparatively slow rate of rise of tension of the extensor tibia muscle means that if it is to shorten rapidly, it must develop tension isometrically prior to the jump by co-contracting with the flexor muscle. The extensor muscle is far stronger than the flexor and thus there has to be considerable structural specialisation of the joint to enable the flexor to prevent the tibia moving under the extensor tension. The geometry of the joint gives the flexor muscle a very large mechanical advantage over the extensor in the fully flexed position. This mechanical advantage decreases rapidly as the joint extends so that the residual flexor tension does not slow down the movement (Fig. 4). There is also a locking device associated with the flexor tendon which is engaged when the tibia is fully flexed and which holds it in this position against the developing extensor force (Fig. 5).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00696166
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  • 5
    Electronic Resource
    Electronic Resource
    The effects of temperature on the threshold of identified neurons in the locust (1977)
    Springer
    Journal of comparative physiology 117 (1977), S. 163-182 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. At the preferred body temperature of the locust (30 °C and above), the metathoracic fast extensor of the tibia (FETi) motorneuron will sometimes spike in response to synaptic input from the descending movement detector (DMD) visual interneurons. This does not occur at lower temperatures (Fig. 1). The mechanism of the change in excitability is investigated in FETi and other identified motorneurons over the range 18–35 °C. 2. Action potentials show a reversible decrease in amplitude and duration on heating (Fig. 2). 3. EPSP amplitudes are relatively unchanged by temperature, but their duration decreases slightly on heating (Fig. 3). 4. Membrane potential hyperpolarises on heating and depolarises on cooling (Fig. 4). 5. Membrane resistance shows a transient increase on cooling, and a transient decrease on heating (Fig. 10), but there is usually little steady-state change in resistance with temperature (Fig. 5). 6. Spike threshold shows a transient increase followed by a steady-state decrease on heating, and the opposite on cooling (Fig. 10). This can be demonstrated with injected current (Fig. 6), membrane depolarisation (Fig. 7), spontaneous spike frequency (Fig. 9), and naturally occurring EPSPs (Fig. 8). This change in spike threshold is regarded as the major neural correlate of the change in excitability with temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00612785
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  • 6
    Electronic Resource
    Electronic Resource
    Different types of rectification at electrical synapses made by a single crayfish neurone investigated experimentally and by computer simulation (1991)
    Springer
    Journal of comparative physiology 169 (1991), S. 707-718 
    Details
    ISSN: 1432-1351
    Keywords: Crayfish ; Electrical synapse ; Rectification ; Computer simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The rectification properties of electrical synapses made by the segmental giant (SG) neurone of crayfish (Pacifastacus leniusculus) were investigated. The SG acts as an interneurone, transmitting information from the giant command fibres (GFs) to the abdominal fast flexor (FF) motoneurones. The GF-SG (input) synapses are inwardly-rectifying electrical synapses, while the SG-FF (output) synapses are outwardly rectifying electrical synapses. This implies that a single neurone can make gap junction hemichannels with different rectification properties. The coupling coefficient of these synapses is dependent upon transjunctional potential. There is a standing gradient in resting potential between the GFs, SG and FFs, with the GFs the most hyperpolarized, and the FFs the most depolarized. The gradient thus biases each synapse into the low-conductance state under resting conditions. There is functional double rectification between the bilateral pairs of SGs within a single segment, such that depolarizing membrane potential changes of either SG pass to the other SG with less attenuation than do hyperpolarizing potential changes. Computer simulation suggests that this may result from coupling through the intermediary FF neurones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194899
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  • 7
    Electronic Resource
    Electronic Resource
    Isogenic locusts and genetic variability in the effects of temperature on neuronal threshold (1977)
    Springer
    Journal of comparative physiology 117 (1977), S. 183-207 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Physiological variability was previously encountered while studying the effects of temperature on identified motorneurons. Of 22 locusts examined from within the breeding colony, 3 deviant animals were found in which the current threshold of the fast extensor tibiae (FETi) motorneuron did not decrease as was expected with increasing temperature (Fig. 1). We have used clones of isogenic locusts to study the genetic basis, physiological extent, and behavioral effects of a similar abnormal threshold response of FETi to increases in temperature. Over 30 clones, raised by parthenogenetic breeding, were used to isolate naturally-occurring genotypic variability. In this study we have focused our attention on the behaviorally abnormal clone 7 animals that have a low probability of jumping which is not altered by heating; and the behaviorally normal clone 8 animals that have a higher probability of jumping which increases with increasing temperature (Table 1). In clone 8 animals, the physiological properties of FETi show the normal steady-state responses to increases in temperature: the current threshold decreases (Fig. 1), the voltage threshold decreases, and the membrane resistance remains relatively unchanged. In clone 7 animals, the physiological properties of FETi show abnormal steady-state responses to increases in temperature: the current threshold increases (Fig. 1), the voltage threshold remains relatively unchanged (Fig. 2), and the membrane resistance decreases (Fig. 3), all of which are similar to the abnormal responses observed occasionally from the heterogenic breeding colony. These abnormalities in FETi of clone 7 animals are regarded as a neurophysiological correlate of the absence of an increase in jumpiness with increasing temperature. An abnormal response to heating in clone 7 animals is also found in AAdC (Fig. 6), ASFlTi, and the first basalar motorneuron. A normal response to heating in clone 7 animals is found in the spiracle closer motorneurons (Fig. 7), the DUM neurons, and the CI neuron.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00612786
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  • 8
    Electronic Resource
    Electronic Resource
    Coupled motoneurones are part of the crayfish swimmeret central oscillator (1978)
    [s.l.] : Nature Publishing Group
    Nature 275 (1978), S. 231-234 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Experiments were performed on the 4th abdominal ganglion of Pacifastacus leniusculus, which was attached to the rest of the abdominal CNS, but isolated from the peripheral and rostral nervous system. Intracellular recordings were made with microelectrodes penetrating neuropilar regions of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/275231a0
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  • 9
    Electronic Resource
    Electronic Resource
    Coupling of flight initiation to the jump in locusts (1986)
    Springer
    Journal of comparative physiology 158 (1986), S. 81-89 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. In adult locusts' wing opening for flight occurs soon after a jump is triggered. Previous studies have shown that the interval between the triggering of a jump and the initial wing movement (or the start of elevator muscle activity) is often too short for either the loss of tarsal contact with the ground or the self-generated air stream on the head to be responsible for the onset of wing opening. Thus it has been postulated that the system generating the motor program for the jump is directly linked to the system generating flight motor activity. To investigate this proposal we have recorded activity in flight motoneurons and interneurons during bilateral kicks of the hindlegs. 2. The preparation was arranged to allow intracellular recording from flight motoneurons and interneurons during hindleg kicks. Kicks were readily evoked by mechanical stimulation of the abdomen, and the motor activity associated with the kicks was similar to that for a jump in unrestrained animals. 3. Short sequences of flight activity were often associated with hindleg kicks. The time of onset of flight activity relative to the time kicks were triggered was variable, and often flight activity commencedbefore the kicks were triggered. The probability of flight activity being initiated increased throughout the co-contraction phase with the peak probability being close to the time kicks were triggered. Thus it appears that the flight system receives a progressively increasing excitatory input during the co-contraction phase of the kick, and that the onset of flight activity isnot tightly linked to the system triggering the kick. 4. Intracellular recordings from flight motoneurons showed that wing elevator motoneurons often received an excitatory input during the co-contraction phase, whereas wing depressor motoneurons either showed no change in membrane potential or were slightly hyperpolarized during co-contraction. These recordings failed to reveal any significant input to flight motoneurons at the time a kick was triggered. 5. The lack of any influence of the trigger system on the flight system was also apparent in recordings from identified flight interneurons. None consistently showed a synaptic response timelocked to triggering but many received synaptic input during the co-contraction phase. Those receiving excitatory input were also those excited by wind on the head, while those receiving inhibitory input were hyperpolarized by wind on the head. 6. We conclude that the flight system receives an excitatory input during the co-contraction phase of the kick, and that this input produces many of the same changes in membrane potential in interneurons and motoneurons as does a wind stream to the head (a stimulus known to readily evoke flight activity). None of our data indicates that the system triggering the kick is responsible for exciting the flight system. We propose that in an intact animal the initiation of flight activity following a jump is facilitated by an excitatory input to the flight system during the co-contraction phase of the jump. The origin of this input has not been determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614522
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  • 10
    Electronic Resource
    Electronic Resource
    Thoracic output of crayfish giant fibres (1989)
    Springer
    Journal of comparative physiology 166 (1989), S. 117-124 
    Details
    ISSN: 1432-1351
    Keywords: Crayfish ; Promotor motor neurone ; Medial giant fibre ; Thoracic ganglia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A crayfish (Pacifastacus leniusculus) thoracic pereiopod promotor motor neurone (PMM) receives direct input from the ipsilateral medial giant fibre (MG) via a 1∶1 rectifying electrical synapse. The evidence for this is as follows. (1) PMM spikes follow MG spikes at very short latency. (2) Negative current injected into the PMM propagates antidromically to the MG. (3) Positive voltage perturbations in the PMM (antidromic spikes) fail to propagate to the MG. (4) There is very close anatomical apposition between the PMM and MG as observed in wholemount preparations following staining with Lucifer Yellow. (5) Dye coupling between the MG and a neurone with anatomy similar to the PMM has been observed in very young crayfish, although not in adults. The electrical input from MG to PMM can be gated by depolarizing IPSPs impinging on the latter. The PMM produces EJPs in the leg promotor muscle which show initial massive antifacilitation, followed by slow facilitation. Homologous neurones occur in each of the 5 thoracic ganglia innervating the legs and claws.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190216
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