Synaptic specificity: development of locomotor rhythmicity

Sillar, Keith T.

doi:10.1016/0959-4388(94)90038-8

Cited by 26 publications

(9 citation statements)

References 34 publications

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“…Indeed, the circuitry for controlling stepping is assembled very early in embryonic life. Many vertebrates including tadpoles (Stehouwer & Farel, 1985), chicks (Narayana & Hamburger, 1971; O'Donovan, Sernagor, Sholomenko, Ho, Antal & Yee, 1992), rats (Kudo, Ozaki & Yamada, 1991; Greer, Smith & Feldman, 1992; Robinson & Smotherman, 1992) and cats (Graham Brown, 1915; Windle & Griffen, 1931) show spontaneous or induced stepping movements with clear alternating flexor and extensor activity early in embryonic life (reviewed in Sillar, 1994). The ability to locomote soon after birth must have been an important evolutionary advantage in many animals.…”

Section: Discussionmentioning

confidence: 99%

Infant stepping: a method to study the sensory control of human walking

Yang

Stephens

Vishram

1998

The Journal of Physiology

129

116

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Stepping responses were studied in infants between the ages of 10 days and 10 months while they were supported to step on a slowly moving treadmill belt. Surface electromyography (EMG) from muscles in the lower limb, force exerted by the feet on the treadmill belt, and the motion of the lower limbs were recorded. Two groups of infants were studied, those who had a small amount of daily practice in stepping and those who did not. Practice resulted in a dramatic increase in the incidence of stepping recorded in the laboratory, particularly for the periods between 1 and 6 months of age. The majority of infants showed clear alternation between the flexor and extensor muscles during walking, regardless of age. Co‐contraction between flexors and extensors, estimated by the overlap in area between rectified and smoothed EMG from a muscle pair, was greater for some muscle groups in the infant compared with the adult. Practice resulted in a significantly lower co‐contraction index for the tibialis anterior‐ quadriceps muscle pair. Practice did not affect the mean step cycle duration. Infants of all ages could step at a range of treadmill speeds by adjusting their step cycle duration. The relationship between the treadmill speed and cycle duration was well fitted by a power function, similar to those reported for intact cats and adult humans. The change in step cycle duration resulted almost entirely from a change in the extensor burst duration, whereas the flexor burst duration remained constant. Airstepping could be elicited in some infants. The cycle durations for airstepping were close to the shortest cycles recorded on the treadmill. In conclusion, the system for generating rhythmic, alternating activity of the lower limbs for stepping is clearly developed by birth. The stepping is sustained and regular, particularly if stepping practice is incorporated briefly each day. The infant population provides a good subject pool for studying the afferent control of walking in the human, before cerebral influences are fully developed. The characteristics and maturity of the system remain to be determined.

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Section: Discussionmentioning

confidence: 99%

Infant stepping: a method to study the sensory control of human walking

Yang

Stephens

Vishram

1998

The Journal of Physiology

129

116

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“…These inputs allow for rapid quantitative and qualitative changes in locomotor function in order to respond promptly to new environmental requirements. Because these neuromodulatory systems are in place during embryonic life they are in position to also be involved in neural circuitry maturation (Sillar, 1994). In fact, serotonergic inputs during embryonic life can influence the ontogeny of spinal pattern generators, although the precise mechanism by which this occurs has not been fully delineated (Sillar et al ., 1995).…”

Section: Introductionmentioning

confidence: 99%

Embryonic motor neuron dendrite growth is stunted by inhibition of nitric oxide‐dependent activation of soluble guanylyl cyclase and protein kinase G

Xiong

Mojsilovic-Petrovic

Pérez

et al. 2007

Eur J of Neuroscience

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We have examined the participation of a neuronal nitric oxide synthase (nNOS) signaling pathway in the elaboration of motor neuron dendrites during embryonic life. During chick embryogenesis, nNOS is expressed by interneurons that surround the motor neuron pools in the ventral horn. Pseudorabies virus tracing suggests that these cells, while juxtaposed to motor neurons are not synaptically connected to them. The downstream effectors, soluble guanylyl cyclase (sGC) and protein kinase G (PKG), are found in motor neurons as well as several other populations of spinal cord cells. To determine the functional significance of the nNOS/sGC/PKG signaling pathway, pharmacological inhibitors were applied to chick embryos and the effects on motor neuron dendrites monitored. Inhibition of nNOS activity led to a lasting reduction in the overall size and degree of branching of the dendritic tree. These alterations in dendritic architecture were also seen when the activity of sGC or PKG was blocked. Our results suggest that normal motor neuron dendrite elaboration depends, in part, on the activity-dependent generation of NO by ventral horn interneurons, which then activates sGC and PKG in motor neurons.

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“…Casasnovas and Meyrand (1995) showed that the STG is present and active by midembryonic development, before the stomach is functional and connected to the hindgut. Early spontaneous and irregular neural activity without obvious functional or behavioral relevance has been seen in many systems and may be important for tuning developing networks (Bradley and Bekoff 1992;O'Donovan 1999;Sillar 1994;Wong 1999). Understanding the role of embryonic and larval rhythms in the maturation of adult circuits requires their quantitative characterization.…”

Section: Introductionmentioning

confidence: 99%

Maturation of Lobster Stomatogastric Ganglion Rhythmic Activity

Richards

Miller

Marder

1999

Journal of Neurophysiology

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The stomatogastric ganglion of the adult lobster, Homarus americanus generates extremely regular pyloric rhythms with a characteristic period of 0.5-1.5 Hz. To study the changes in the pyloric rhythm during embryonic and larval development, we recorded excitatory junctional potentials evoked by lateral pyloric (LP) neuron activity. Early in development the motor discharge of the LP neuron was often irregular, preventing use of conventional analysis methods that rely on extracting burst times to calculate cycle frequency and its variability. Instead, cycle frequency was determined for the LP neuron from the peak of the power spectrum obtained from the occurrence times of excitatory junctional potentials in the p1 muscle. The ratio of the power in the peak to the power from 0 to 3 Hz was used as a relative measure of the regularity of the rhythm. Throughout embryonic and the first larval stage, LP neuron activity is slow, irregular, and only weakly periodic. The regularity of the rhythm increased during midlarval stages, and both the frequency and regularity increased considerably by the postlarval stage LIV.

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Synaptic specificity: development of locomotor rhythmicity

Cited by 26 publications

References 34 publications

Infant stepping: a method to study the sensory control of human walking

Infant stepping: a method to study the sensory control of human walking

Embryonic motor neuron dendrite growth is stunted by inhibition of nitric oxide‐dependent activation of soluble guanylyl cyclase and protein kinase G

Maturation of Lobster Stomatogastric Ganglion Rhythmic Activity

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