Stimulus–response relationships during locomotion

1981 ◽  
Vol 59 (7) ◽  
pp. 667-674 ◽  
Author(s):  
S. Rossignol ◽  
C. Julien ◽  
L. Gauthier
Keyword(s):  
Hind Limb ◽  
Stance Phase ◽  
Fictive Locomotion ◽  
Superficial Peroneal Nerve ◽  
Similar Stimulus ◽  
Stimulus Response ◽  
Stimulus Train ◽  
Flexion Response ◽  
Decerebrate Cats ◽  
Stimulation Of

Crossed hind limb responses to high intensity stimulation of the superficial peroneal nerve in the cat were studied under various conditions. In precollicularly decerebrate cats walking on a treadmill, the same stimulus train evokes a crossed extension response during the contralateral stance phase and a crossed flexion response during the contralateral swing phase. In acute spinal cats (Th13) injected with clonidine, a similar stimulus train can evoke a crossed extension response when the limb is manually placed in flexion and a crossed flexion response when the limb is positioned in extension. During "fictive" locomotion, induced in spinal paralyzed cats by nialamide and L-DOPA, the same stimulus may increase the amplitude and (or) the duration of crossed flexor or crossed extensor activity (in-phase responses). In some instances in these preparations, the crossed responses may be out-of-phase with the central rhythm. It is concluded that crossed hind limb responses during locomotion are selected by both central and peripheral mechanisms.

Stumbling Corrective Reaction During Fictive Locomotion in the Cat

2005 ◽  
Vol 94 (3) ◽  
pp. 2045-2052 ◽  
Author(s):  
Jorge Quevedo ◽  
Katinka Stecina ◽  
Simon Gosgnach ◽  
David A. McCrea
Keyword(s):  
Dorsal Surface ◽  
Fictive Locomotion ◽  
Step Cycle ◽  
Stimulus Train ◽  
Subsequent Step ◽  
Extensor Motoneuron ◽  
Motoneuron Activity ◽  
Hind Foot ◽  
Hip Flexor ◽  
Decerebrate Cats

An obstacle contacting the dorsal surface of a cat’s hind foot during the swing phase of locomotion evokes a reflex (the stumbling corrective reaction) that lifts the foot and extends the ankle to avoid falling. We show that the same sequence of ipsilateral hindlimb motoneuron activity can be evoked in decerebrate cats during fictive locomotion. As recorded in the peripheral nerves, twice threshold intensity stimulation of the cutaneous superficial peroneal (SP) nerve during the flexion phase produced a very brief excitation of ankle flexors (e.g., tibialis anterior and peroneus longus) that was followed by an inhibition for the duration of the stimulus train (10–25 shocks, 200 Hz). Extensor digitorum longus was always, and hip flexor (sartorius) activity was sometimes, inhibited during SP stimulation. At the same time, knee flexor and the normally quiescent ankle extensor motoneurons were recruited (mean latencies 4 and 16 ms) with SP stimulation during fictive stumbling correction. After the stimulus train, ankle extensor activity fell silent, and there was an excitation of hip, knee, and ankle flexors. The ongoing flexion phase was often prolonged. Hip extensors were also recruited in some fictive stumbling trials. Only the SP nerve was effective in evoking stumbling correction. Delivered during extension, SP stimulus trains increased ongoing extensor motoneuron activity as well as increasing ipsilateral hip, knee, and ankle hindlimb flexor activity in the subsequent step cycle. The fictive stumbling corrective reflex seems functionally similar to that evoked in intact, awake animals and involves a fixed pattern of short-latency reflexes as well as actions evoked through the lumbar circuitry responsible for the generation of rhythmic alternating locomotion.

Mechanism for Activation of Locomotor Centers in the Spinal Cord by Stimulation of the Mesencephalic Locomotor Region

2003 ◽  
Vol 90 (3) ◽  
pp. 1464-1478 ◽  
Author(s):  
Brian R. Noga ◽  
Dean J. Kriellaars ◽  
Robert M. Brownstone ◽  
Larry M. Jordan
Keyword(s):  
Spinal Cord ◽  
Electrical Stimulation ◽  
Fictive Locomotion ◽  
Mesencephalic Locomotor Region ◽  
Spinal Interneurons ◽  
Inhibitory Postsynaptic Potentials ◽  
Conduction Velocities ◽  
Decerebrate Cats ◽  
Ventral Funiculus ◽  
Stimulation Of

The synaptic pathways of mesencephalic locomotor region (MLR)-evoked excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs) recorded from lumbar motoneurons of unanesthetized decerebrate cats during fictive locomotion were analyzed prior to, during, and after cold block of the medial reticular formation (MedRF) or the low thoracic ventral funiculus (VF). As others have shown, electrical stimulation of the MLR typically evoked short-latency excitatory or mixed excitatory/inhibitory PSPs in flexor and extensor motoneurons. The bulbospinal conduction velocities averaged ∼88 m/s (range: 62–145 m/s) and segmental latencies for EPSPs ranged from 1.2 to 10.9 ms. The histogram of segmental latencies showed three peaks, suggesting di-, tri-, and polysynaptic linkages. Segmental latencies for IPSPs suggested trisynaptic or polysynaptic transmission. Most EPSPs (69/77) were significantly larger during the depolarized phase of the intracellular locomotor drive potential (LDP), and most IPSPs (35/46) were larger during the corresponding hyperpolarized phase. Bilateral cooling of the MedRF reversibly abolished locomotion of both hindlimbs as measured from the electroneurogram (ENG) activity of muscle nerves and simultaneously abolished or diminished the motoneuron PSPs and LDPs. Unilateral cooling of the VF blocked locomotion ipsilaterally and diminished it contralaterally with concomitant loss or decrease the motoneuron PSPs and LDPs. Relative to the side of motoneuron recording, cooling of the ipsilateral VF sometimes uncovered longer-latency EPSPs, whereas cooling of the contralateral VF abolished longer-latency EPSPs. It is concluded that MLR stimulation activates a pathway that relays in the MedRF and descends bilaterally in the VF to contact spinal interneurons that project to motoneurons. Local segmental pathways that activate or inhibit motoneurons during MLR-evoked fictive locomotion appear to be both ipsilateral and contralateral.

Motoneuron input-resistance changes during fictive locomotion produced by stimulation of the mesencephalic locomotor region

1985 ◽  
Vol 54 (5) ◽  
pp. 1101-1108 ◽  
Author(s):  
S. J. Shefchyk ◽  
L. M. Jordan
Keyword(s):  
Input Resistance ◽  
Inhibitory Input ◽  
Fictive Locomotion ◽  
Step Cycle ◽  
Potential Oscillations ◽  
Mesencephalic Locomotor Region ◽  
Excitatory Synaptic Input ◽  
Decerebrate Cats ◽  
Membrane Potential Oscillations ◽  
Stimulation Of

Input-resistance changes during fictive locomotion were monitored in a variety of extensor and flexor hindlimb alpha-motoneurons in precollicular, postmammillary decerebrate cats induced to "walk" by electrical stimulation of the mesencephalic locomotor region (MLR). Using intracellular recording techniques and injected hyperpolarizing current pulses, the changes in the motoneuron input resistance recorded at the motoneuron soma were examined during nonlocomoting control periods as well as during the depolarized and hyperpolarized phases of the membrane potential oscillations (locomotor drive potentials, or LDPs) of fictive locomotion. In 28 of the 52 motoneurons examined, no change in the input resistance between the control and locomotor periods was observed. The remainder of the cells displayed a decrease (less than 20%) in input resistance when fictive stepping commenced. Over 80% of all the motoneurons depolarized (mean depolarization 4 mV), whereas only one LG motoneuron hyperpolarized (2 mV) with the onset of stimulation of the MLR. The remaining motoneurons did not display such changes. In 43 out of 52 motoneurons examined, no significant change in the input resistance could be observed between the depolarized and hyperpolarized phases of the step cycle. A decrease in the input resistance during the depolarized phase of the LDP was observed in four LG motoneurons, whereas five other motoneurons (2 LG, 1 TA, 1 PB, and 1 ST) displayed an increased input resistance during the depolarized phase compared with the hyperpolarized phase of locomotion. The data are consistent with the presence of an excitatory synaptic input alternating with an inhibitory input to the motoneuron during the fictive step cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracellular Analysis of Reflex Pathways Underlying the Stumbling Corrective Reaction During Fictive Locomotion in the Cat

2005 ◽  
Vol 94 (3) ◽  
pp. 2053-2062 ◽  
Author(s):  
Jorge Quevedo ◽  
Katinka Stecina ◽  
David A. McCrea
Keyword(s):  
Short Latency ◽  
Excitatory Postsynaptic Potential ◽  
Fictive Locomotion ◽  
Epsp Amplitude ◽  
Knee Flexor ◽  
Reflex Pathways ◽  
Inhibitory Postsynaptic Potentials ◽  
Postsynaptic Potential ◽  
Stimulus Train ◽  
Decerebrate Cats

In cat and humans, contact between an obstacle and the dorsum of the foot evokes the stumbling corrective reaction (reflex) that lifts the foot to avoid falling. This reflex can also be evoked by short trains of stimuli to the cutaneous superficial peroneal (SP) nerve in decerebrate cats during the flexion phase of fictive locomotion. Here we examine intracellular events in hindlimb motoneurons accompanying stumbling correction. SP stimulation delivered during the flexion phase excites knee flexor motoneurons at short latency [minimum excitatory postsynaptic potential (EPSP) latency 1.8 ms; mean 2.7 ms]. Although a similar short latency excitation occurs in ankle extensors (mean latency, 2.8 ms), recruitment is delayed until successive shocks in the stimulus train overcome the locomotor-related hyperpolarization of ankle extensors. In ankle flexor motoneurons, SP stimulation evokes an inhibition (mean latency, 2.7 ms) that briefly reduces or stops their firing during the flexion phase. There is a phase-dependent modulation of SP-evoked EPSP amplitude as well as latency during locomotion. However, the more obvious change in SP reflex pathways with the onset of fictive locomotion is the reduced inhibition of ankle extensor motoneurons and the increased inhibition of ankle flexors. These results show that the characteristic pattern of hindlimb motoneuron activation during SP nerve–evoked stumbling correction results from 1) di- and trisynaptic excitation of knee flexor and ankle extensor motoneurons; 2) increased inhibitory postsynaptic potentials in ankle flexors and a suppression of inhibition in extensors, 3) sculpting of the short-latency SP postsynaptic effects by motoneuron membrane potential, and 4) longer latency excitatory effects that are likely evoked by lumbar interneurons involved in the generation of fictive locomotion.

Central connections of sensory neurones from a hair plate proprioceptor in the thoraco-coxal joint of the locust.

1995 ◽  
Vol 198 (7) ◽  
pp. 1589-1601 ◽  
Author(s):  
F Kuenzi ◽  
M Burrows
Keyword(s):  
Stance Phase ◽  
Swing Phase ◽  
Motor Neurone ◽  
Sensory Neurone ◽  
Sensory Neurones ◽  
Selective Stimulation ◽  
Basal Joint ◽  
Motor Neurones ◽  
Individual Motor ◽  
Stimulation Of

The hair plate proprioceptors at the thoraco-coxal joint of insect limbs provide information about the movements of the most basal joint of the legs. The ventral coxal hair plate of a middle leg consists of group of 10-15 long hairs (70 microns) and 20-30 short hairs (30 microns). The long hairs are deflected by the trochantin as the leg is swung forward during the swing phase of walking, and their sensory neurones respond phasically during an imposed deflection and tonically if the deflection is maintained. Selective stimulation of the long hairs elicits a resistance reflex that rotates the coxa posteriorly and is similar to that occurring at the transition from the swing to the stance phase of walking. The motor neurones innervating the posterior rotator and adductor coxae muscles are excited, and those to the antagonistic anterior rotator muscle are inhibited. By contrast, selective stimulation of the short hairs leads only to a weak inhibition of the anterior rotator. The excitatory effects of the long hairs are mediated, in part, by direct connections between their sensory neurones and particular motor neurones. A spike in a sensory neurone elicits a short-latency depolarising postsynaptic potential (PSP) in posterior rotator and adductor motor neurones whose amplitude is enhanced by hyperpolarising current injected into the motor neurone. When the calcium in the saline is replaced with magnesium, the amplitude of the PSP is reduced gradually, and not abruptly as would be expected if an interneurone were interposed in the pathway. Several sensory neurones from long hairs converge to excite an individual motor neurone, evoking spikes in some motor neurones. The projections of the sensory neurones overlap with some of the branches of the motor neurones in the lateral association centre of the neuropile. It is suggested that these pathways would limit the extent of the swing phase of walking and contribute to the switch to the stance phase in a negative feedback loop that relieves the excitation of the hairs by rotating the coxa backwards.

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