scholarly journals Functional Principles of Pattern Generation for Walking Movements of Stick Insect Forelegs: The Role of the Femoral Chordotonal Organ Afferences

1988 ◽  
Vol 136 (1) ◽  
pp. 125-147 ◽  
Author(s):  
ULRICH BÄSSLER
Keyword(s):  
Pattern Generator ◽  
Stick Insect ◽  
Pattern Generation ◽  
Chordotonal Organ ◽  
Step Cycle ◽  
Strongly Coupled ◽  
Loosely Coupled ◽  
Active Reaction ◽  
Motor Neurones ◽  
High Stimulus

A rampwise stretch of the femoral chordotonal organ is known often to elicit a response in the active decerebrate stick insect that is termed an ‘active reaction’, and which can be considered to represent part of the step cycle. During the first part of the response, the flexor motor neurones are excited and the excitatory extensor motor neurones are inhibited, forming a positive feedback loop. When the chordotonal organ reaches a position corresponding to a flexed femur-tibia joint, the flexor motor neurones are inhibited and the extensor motor neurones are excited. In this study, extracellular and intracellular recordings showed that, during an active reaction, the excitation of the retractor unguis motor neurones usually paralleled that of the flexor motor neurones, whereas the protractor coxae motor neurones were less strongly coupled to this system. The first part of the active reaction occurred only at low stimulus velocities. At high stimulus velocities negative feedback was present. The first part therefore represents some kind of velocity-control-system for active flexions. Electrical stimulation of the nerve containing the axons of trochanteral campaniform sensilla and of the hairfield trHP decreased the likelihood that concurrent chordotonal organ stimulation would elicit an active reaction. Furthermore, most of the active reactions that occurred under these stimulus conditions involved only the flexor tibiae muscle. The results indicate that: the walking pattern generator is composed of subunits that are only loosely coupled centrally; it probably does not include a central pattern generator; and generation of an active reaction is a two-step process.

scholarly journals The Inherent Walking Direction Differs for the Prothoracic and Metathoracic Legs of Stick Insects

1985 ◽  
Vol 116 (1) ◽  
pp. 301-311 ◽  
Author(s):  
ULRICH BÄSSLER ◽  
EVA FOTH ◽  
GERHARD BREUTEL
Keyword(s):  
Positive Feedback ◽  
Stick Insect ◽  
Chordotonal Organ ◽  
Suboesophageal Ganglion ◽  
Stick Insects ◽  
Motor Neurones ◽  
Direction Of Movement ◽  
Slippery Surface

On a slippery surface the forelegs of a decapitated stick insect walk forwards and the hindlegs, backwards. Animals with only forelegs but that are otherwise intact walk forwards, whereas animals with only hindlegs walk mostly backwards. Usually when intact animals start to walk, their hindlegs exert a rearwards thrust on the substrate, but occasionally the starting forces are directed forwards. A rampwise extension of the femoral chordotonal organ in the fixed foreleg of a walking animal first excites the flexor tibiae muscle (positive feedback). Towards the end of the ramp stimulus the activity of the flexor decreases, and the extensor tibiae motor neurones become strongly active. All experiments indicated that the inherent direction of movement of the metathorax is rearwards. In intact animals there must be a coordinating pathway from the prothorax to the metathorax that, together with the suboesophageal ganglion, induces the hindlegs to walk forwards.

scholarly journals Motor Output of the Denervated Thoracic Ventral Nerve Cord in the Stick Insect Carausius Morosus

1983 ◽  
Vol 105 (1) ◽  
pp. 127-145 ◽  
Author(s):  
ULRICH BÄSSLER ◽  
U. T. A. WEGNER
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Intact Animal ◽  
Stick Insect ◽  
Motor Output ◽  
The Other ◽  
Chordotonal Organ ◽  
Motor Neurones ◽  
Leg Movements ◽  
Stimulation Of

The denervated thoracic ventral nerve cord produces a motor output which is similar to that observed in the intact animal during irregular leg movements (seeking movements) or rocking, but not walking. When the nerves to some legs are left intact, and the animal walks on a wheel, the motor output in the protractor and retractor motor neurones of the denervated legs is modulated by the stepping frequency of the walking legs. The modulation is similar to that observed in the motor output to a not actually stepping leg of an intact walking animal. When only the crural nerve of one leg is left intact, stimulation of the trochanteral campaniform sensilli induces protractor and retractor motor output to that leg and the leg behind it. In this case the motor output to the ipsilateral leg is in phase. Stimulation of the femoral chordotonal organ influences activity in motor neurones of the extensor tibiae (FETi and SETi) but not those of the protractor and retractor coxae muscles. In a restrained leg of an intact animal stretching of the femoral chordotonal organ excites FETi and SETi as long as the other legs walk (as in a walking leg) and inhibits FETi and SETi (as in a seeking leg) when the other legs are unable to walk.

scholarly journals Swimming in the Pteropod Mollusc, Clione Limacina: II. Physiology

1985 ◽  
Vol 116 (1) ◽  
pp. 205-222 ◽  
Author(s):  
RICHARD A. SATTERLIE ◽  
ANDREW N. SPENCER
Keyword(s):  
Electrical Coupling ◽  
Pattern Generator ◽  
Pattern Generation ◽  
Motor Neurone ◽  
Pedal Ganglion ◽  
Complex Activity ◽  
Firing Patterns ◽  
Friday Harbor ◽  
Tightly Coupled ◽  
Motor Neurones

The central pattern generator (CPG) for swimming inClione limacina was localized in cutting experiments. A separate pattern generator for each wing islocated in the ipsilateral pedal ganglion. The CPGs are tightly coupled butcan be isolated by severing the pedal commissure. Removal of the cerebralganglia results in a decrease in swim frequency and regularity suggesting descending modulation of the CPGs. Two classes of pedal neurones display firing patterns in phase with swimming movements. One class, swim motor neurones, are further divided intodepressor and elevator groups. Motor neurone recordings show complex subthreshold activity consisting of alternate depolarizations and hyperpolarizations. The complex activity is in antiphase in antagonistic motorneurones. Significant motor neurone-motor neurone interactions do notoccur centrally as neither electrical coupling nor chemical synaptic interactionscould be demonstrated. Injected currents do not alter the motorneurone firing rhythm or the swimming rhythm. Motor neurone cell bodies are located in the lateral region of the ipsilateralpedal ganglion, near the emergence of the wing nerve. Each motor neuroneprovides a single axon to the wing nerve which branches repeatedly in thewing. Each motor neurone has an extremely large innervation field, somecovering up to half of the wing area. The second class of pedal neurones that display firing patterns in phasewith either wing upswing or downswing are pedal-pedal inter neurones. Eachswim interneurone provides axon branches in both pedal ganglia and the axonruns in the pedal commissure. Interneurone axon branches occur in thelateral neuropile of each pedal ganglion, in the region of motor neurone branching.The swim interneurones presumably play a major role in bilateralcoordination of the wings and are involved in pattern generation since injectedcurrents were found to accelerate or slow the firing rhythms of interneuronesand motor neurones, and wing movements. Note: A significant portion of this work was conducted at Friday Harbor Laboratories, Friday Harbor, Washington, U.S.A.

Peripheral control of the gain of a central synaptic connection between antagonistic motor neurones in the locust

1996 ◽  
Vol 199 (3) ◽  
pp. 613-625
Author(s):  
T Jellema ◽  
W Heitler
Keyword(s):  
Muscle Contraction ◽  
Sensory Input ◽  
Sense Organ ◽  
Gain Control ◽  
Motor Neurone ◽  
Extensor Muscle ◽  
Chordotonal Organ ◽  
Excitatory Postsynaptic Potential ◽  
Motor Neurones ◽  
Peripheral Sensory

The metathoracic fast extensor tibiae (FETi) motor neurone of locusts is unusual amongst insect motor neurones because it makes output connections within the central nervous system as well as in the periphery. It makes excitatory chemical synaptic connections to most if not all of the antagonist flexor tibiae motor neurones. The gain of the FETi-flexor connection is dependent on the peripheral conditions at the time of the FETi spike. This dependency has two aspects. First, sensory input resulting from the extensor muscle contraction can sum with the central excitatory postsynaptic potential (EPSP) to augment its falling phase if the tibia is restrained in the flexed position (initiating a tension-dependent reflex) or is free to extend (initiating a movement-dependent resistance reflex). This effect is thus due to simple postsynaptic summation of the central EPSP with peripheral sensory input. Second, the static tibial position at the time of the FETi spike can change the amplitude of the central EPSP, in the absence of any extensor muscle contraction. The EPSP can be up to 30 % greater in amplitude if FETi spikes with the tibia held flexed rather than extended. The primary sense organ mediating this effect is the femoral chordotonal organ. Evidence is presented suggesting that the mechanism underlying this change in gain may be specifically localised to the FETi-flexor connection, rather than being due to general position-dependent sensory feedback summing with the EPSP. The change in the amplitude of the central EPSP is probably not caused by general postsynaptic summation with tonic sensory input, since a diminution in the amplitude of the central EPSP caused by tibial extension is often accompanied by overall tonic excitation of the flexor motor neurone. Small but significant changes in the peak amplitude of the FETi spike have a positive correlation with changes in the EPSP amplitude, suggesting a likely presynaptic component to the mechanism of gain control. The change in amplitude of the EPSP can alter its effectiveness in producing flexor motor output and, thus, has functional significance. The change serves to augment the effectiveness of the FETi-flexor connection when the tibia is fully flexed, and thus to increase its adaptive advantage during the co-contraction preceding a jump or kick, and to reduce the effectiveness of the connection when the tibia is partially or fully extended, and thus to reduce its potentially maladaptive consequences during voluntary extension movements such as thrusting.

Intersegmental Coordination of Walking Movements in Stick Insects

2005 ◽  
Vol 93 (3) ◽  
pp. 1255-1265 ◽  
Author(s):  
Björn Ch. Ludwar ◽  
Marie L. Göritz ◽  
Joachim Schmidt
Keyword(s):  
Motor Pattern ◽  
Central Pattern Generators ◽  
Stick Insect ◽  
Neural Mechanisms ◽  
Chordotonal Organ ◽  
Adjacent Segment ◽  
Body Segments ◽  
Stick Insects ◽  
Pattern Generators ◽  
Leg Movements

Locomotion requires the coordination of movements across body segments, which in walking animals is expressed as gaits. We studied the underlying neural mechanisms of this coordination in a semi-intact walking preparation of the stick insect Carausius morosus. During walking of a single front leg on a treadmill, leg motoneuron (MN) activity tonically increased and became rhythmically modulated in the ipsilateral deafferented and deefferented mesothoracic (middle leg) ganglion. The pattern of modulation was correlated with the front leg cycle and specific for a given MN pool, although it was not consistent with functional leg movements for all MN pools. In an isolated preparation of a pair of ganglia, where one ganglion was made rhythmically active by application of pilocarpine, we found no evidence for coupling between segmental central pattern generators (CPGs) that could account for the modulation of MN activity observed in the semi-intact walking preparation. However, a third preparation provided evidence that signals from the front leg's femoral chordotonal organ (fCO) influenced activity of ipsilateral MNs in the adjacent mesothoracic ganglion. These intersegmental signals could be partially responsible for the observed MN activity modulation during front leg walking. While afferent signals from a single walking front leg modulate the activity of MNs in the adjacent segment, additional afferent signals, local or from contralateral or posterior legs, might be necessary to produce the functional motor pattern observed in freely walking animals.

Stimulation of the Parapyramidal Region of the Neonatal Rat Brain Stem Produces Locomotor-Like Activity Involving Spinal 5-HT7 and 5-HT2A Receptors

2005 ◽  
Vol 94 (2) ◽  
pp. 1392-1404 ◽  
Author(s):  
Jun Liu ◽  
Larry M. Jordan
Keyword(s):  
Brain Stem ◽  
Pattern Generator ◽  
Neonatal Rat ◽  
Cycle Duration ◽  
Receptor Antagonists ◽  
Step Cycle ◽  
Output Stage ◽  
Discrete Population ◽  
First Time ◽  
Neonatal Rat Brain

Locomotion can be induced in rodents by direct application 5-hydroxytryptamine (5-HT) onto the spinal cord. Previous studies suggest important roles for 5-HT7 and 5-HT2A receptors in the locomotor effects of 5-HT. Here we show for the first time that activation of a discrete population of 5-HT neurons in the rodent brain stem produces locomotion and that the evoked locomotion requires 5-HT7 and 5-HT2A receptors. Cells localized in the parapyramidal region (PPR) of the mid-medulla produced locomotor-like activity as a result of either electrical or chemical stimulation, and PPR-evoked locomotor-like activity was blocked by antagonists to 5-HT2A and 5-HT7 receptors located on separate populations of neurons concentrated in different rostro-caudal regions. 5-HT7 receptor antagonists blocked locomotor-like activity when applied above the L3 segment; 5-HT2A receptor antagonists blocked locomotor-like activity only when applied below the L2 segment. 5-HT7 receptor antagonists decreased step cycle duration, consistent with an action on neurons involved in the rhythm-generating function of the central pattern generator (CPG) for locomotion. 5-HT2A antagonists reduced the amplitude of ventral root activity with only small effects on step cycle duration, suggesting an action directly on cells involved in the output stage of the pattern generator for locomotion, including motoneurons and premotor cells. Experiments with selective antagonists show that dopaminergic (D1, D2) and noradrenergic (α1, α2) receptors are not critical for PPR-evoked locomotor-like activity.

Intra- and intersegmental pathways active during walking in the locust

1983 ◽  
Vol 218 (1212) ◽  
pp. 287-308 ◽  
Keyword(s):  
Pattern Generator ◽  
Short Latency ◽  
Chordotonal Organ ◽  
Campaniform Sensilla ◽  
Flexor Muscle ◽  
Walking Pattern ◽  
Excitatory Pathways ◽  
Motor Information ◽  
Antagonist Group ◽  
Stimulation Of

Electrical stimulation of femoral chordotonal organs, trochanteral campaniform sensilla, trochanteral hairplates and tibial muscles was used to reveal neuronal pathways active in the standing and walking locust. Responses evoked by campaniform sensilla stimulation were also recorded intracellularly from flexor motoneurons in fixed animals. The trochanteral campaniform sensilla have a direct short-latency connection to tibial extensor motoneurons and more labile, longer-latency, excitatory and inhibitory connections to the tibial flexors of the same leg. Trains of stimuli to the trochanteral campaniform sensilla initiated an early swing only if the stimulation was timed to occur during late stance. The importance of this type of load afference in step-timing was demonstrated by amputating the mesothoracic leg: the stump oscillated at a higher than normal frequency. Addition of a prosthetic leg restored normal stepping. Stimulation of the femoral chordotonal organ revealed short latency, excitatory pathways to both extensor and flexor motoneurons of the same leg. Trains of stimuli to the organ initiated early swing of this leg if applied late in stance. Stimulation of either the flexor or the extensor muscle evoked a response in the antagonist group of the same leg which was abolished by amputation distal to the muscles. The flexor-evoked response functioned only in the presence of load afference. The same was found for the pathway to the walking-pattern generator activated by stimulating the flexor muscle. Stimulation of the posterior trochanteral hairplates often evoked a swing but the latency could be several hundred milliseconds. Deafferentation showed that sensory input is critical for interganglionic coordination. There are labile polysynaptic excitatory and inhibitory pathways from the trochanteral campaniform senilla to the flexor motoneurons of the adjacent leg. Trains could evoke an early swing in the adjacent leg if time to occur during late stance and if the homonymous leg itself was not in late stance. Stimulation of the chordotonal organ revealedfast-conducting stable pathways to the flexors and extensors of all the ipsilateral legs. Trains could induce an early swing if timed late in the stance of the adjacent leg and if the homonymous leg itself was not in late stance. Amputation of the adjacent leg had no effect on the direct evoked responses but swing could not be evoked unless a prosthesis was added. Load afference is necessary for the effectiveness of the intersegmental chordotonal input to the walkingpattern generator. Stimulation of the trochanteral hairplate revealed no intersegmental pathway. The intra- and intersegmental pathways revealed by our experiments are summarized diagrammatically. The results suggest that an important function of load afference is to modulate the flow of proprioceptive and motor information within the walking-pattern generator.

INTEGRATION OF POSITIVE AND NEGATIVE FEEDBACK LOOPS IN A CRAYFISH MUSCLE

1994 ◽  
Vol 187 (1) ◽  
pp. 305-313
Author(s):  
P Skorupski ◽  
P Vescovi ◽  
B Bush
Keyword(s):  
Negative Feedback ◽  
Positive Feedback ◽  
Motor Neurone ◽  
Chordotonal Organ ◽  
Negative Feedback Loops ◽  
Reflex Pathways ◽  
Motor Neurones ◽  
Receptor Organ ◽  
Group 2

It is now well established that in arthropods movement-related feedback may produce positive, as well as negative, feedback reflexes (Bassler, 1976; DiCaprio and Clarac, 1981; Skorupski and Sillar, 1986; Skorupski et al. 1992; Vedel, 1980; Zill, 1985). Usually the same motor neurones are involved in both negative feedback (resistance) reflex responses and positive feedback reflexes. Reflex reversal involves a shift in the pattern of central inputs to a motor neurone, for example from excitation to inhibition. In the crayfish, central modulation of reflexes has been described in some detail for two basal limb proprioceptors, the thoracocoxal muscle receptor organ (TCMRO) and the thoracocoxal chordotonal organ (TCCO) (Skorupski et al. 1992; Skorupski and Bush, 1992). Leg promotor motor neurones are excited by stretch of the TCMRO (which, in vivo, occurs on leg remotion) in a negative feedback reflex, but when this reflex reverses they are inhibited by the same stimulus. Release of the TCCO (which corresponds to leg promotion) excites some, but not all, promotor motor neurones in a positive feedback reflex. There are at least two ways in which the reflex control of a muscle may be modulated in this system. Firstly, inputs to motor neurones may be routed via alternative reflex pathways to produce different reflex outputs. Secondly, the pattern of inputs to a motor pool may be inhomogeneous, so that activation of different subgroups of the motor pool causes different outputs. Different crayfish promotor motor neurones are involved in different reflexes. On this basis, the motor neurones may be classified into at least two subgroups: those that are excited by the TCCO in a positive feedback reflex (group 1) and those that are not (group 2). Do these motor neurone subgroups have different effects on the promotor muscle, or is the output of the two promotor subgroups summed at the neuromuscular level? To address this question we recorded from the promotor nerve and muscle in a semi-intact preparation of the crayfish, Pacifastacus leniusculus. Adult male and female crayfish, 8-11 cm rostrum to tail, were decapitated and the tail, carapace and viscera removed. The sternal artery was cannulated and perfused with oxygenated crayfish saline, as described previously (Sillar and Skorupski, 1986).

Octopamine modulates the responses and presynaptic inhibition of proprioceptive sensory neurones in the locust Schistocerca gregaria

1997 ◽  
Vol 200 (9) ◽  
pp. 1317-1325 ◽  
Author(s):  
T Matheson
Keyword(s):  
Presynaptic Inhibition ◽  
Schistocerca Gregaria ◽  
Chordotonal Organ ◽  
Mechanical Stimuli ◽  
Sensory Neurone ◽  
Tonic Component ◽  
Sensory Neurones ◽  
Phasic Component ◽  
Bath Application ◽  
Motor Neurones

A multineuronal proprioceptor, the femoral chordotonal organ (feCO), monitors the position and movements of the tibia of an insect leg. Superfusing the locust metathoracic feCO with the neuromodulator octopamine, or the octopamine agonist synephrine, affects the position (tonic) component of the organ's response, but not the movement (phasic) component. Both octopamine and synephrine act with the same threshold (10(-6) mol l-1). Individual sensory neurones that respond tonically at flexed tibial angles show increased tonic spike activity following application of octopamine, but those that respond at extended angles do not. Tonic spiking of phaso-tonic flexion-sensitive neurones is enhanced but their phasic spiking is unaffected. Bath application of octopamine to the feCO increases the tonic component of presynaptic inhibition recorded in the sensory terminals, but not the phasic component. This inhibition should at least partially counteract the increased sensory spiking and reduce its effect on postsynaptic targets such as motor neurones. Furthermore, some phasic sensory neurones whose spiking is not affected by octopamine nevertheless show enhanced tonic synaptic inputs. The chordotonal organ is not known to be under direct efferent control, but its output is modified by octopamine acting on its sensory neurones to alter their responsiveness to mechanical stimuli and by presynaptic inhibition acting on their central branches. The effects of this neuromodulator acting peripherally on sensory neurones are therefore further complicated by indirect interactions between the sensory neurones within the central nervous system. Increases of sensory neurone spiking caused by neuromodulators may not necessarily lead to parallel increases in the responses of postsynaptic target neurones.

Sign in / Sign up

Export Citation Format

Share Document