The activity‐dependent plasticity of segmental and intersegmental synaptic connections in the lamprey spinal cord

Parker, Dianne; Grillner, Sten

doi:10.1046/j.1460-9568.2000.00095.x

Cited by 46 publications

(44 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This work on development points to common features shared by different classes of vertebrate and supports the view that the study of simpler groups can give us insights into the organization of more complex ones. Currently, the best understood spinal interneurons are probably those that coordinate locomotor movements in the adult lamprey and frog tadpole (Parker and Grillner, 2000;Roberts, 2000;Buchanan, 2001;Parker, 2003). Detailed information on spinal neuron classes is also becoming available for the developing zebrafish (Bernhardt et al, 1990;Hale et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Primitive Roles for Inhibitory Interneurons in Developing Frog Spinal Cord

Higashijima²,

Parry³

et al. 2004

J. Neurosci.

105

135

View full text Add to dashboard Cite

Understanding the neuronal networks in the mammal spinal cord is hampered by the diversity of neurons and their connections. The simpler networks in developing lower vertebrates may offer insights into basic organization. To investigate the function of spinal inhibitory interneurons in Xenopus tadpoles, paired whole-cell recordings were used. We show directly that one class of interneuron, with distinctive anatomy, produces glycinergic, negative feedback inhibition that can limit firing in motoneurons and interneurons of the central pattern generator during swimming. These same neurons also produce inhibitory gating of sensory pathways during swimming. This discovery raises the possibility that some classes of interneuron, with distinct functions later in development, may differentiate from an earlier class in which these functions are shared. Preliminary evidence suggests that these inhibitory interneurons express the transcription factor engrailed, supporting a probable homology with interneurons in developing zebrafish that also express engrailed and have very similar anatomy and functions.

show abstract

Section: Introductionmentioning

confidence: 99%

Primitive Roles for Inhibitory Interneurons in Developing Frog Spinal Cord

Higashijima²,

Parry³

et al. 2004

J. Neurosci.

105

135

View full text Add to dashboard Cite

show abstract

“…For example, excitatory synapses between excitatory interneurons and motoneurons or crossed-caudal (CC) interneurons can be either facilitating or depressing (Parker 2000(Parker , 2003, whereas inhibitory synapses from small inhibitory interneurons are depressing in motoneurons and facilitating in CC interneurons (Parker 2000). Different cell types can be differently modulated by neuromodulators; for example, substance P has opposite effects on the postinhibitory rebound in inhibitory interneurons and motoneurons (Svensson 2003).…”

Section: Discussionmentioning

confidence: 99%

Roles of Ionic Currents in Lamprey CPG Neurons: A Modeling Study

Huss

Lansner²,

Wallén³

et al. 2007

Journal of Neurophysiology

Self Cite

View full text Add to dashboard Cite

Huss M, Lansner A, Wallén P, El Manira A, Grillner S, Kotaleski JH. Roles of ionic currents in lamprey CPG neurons: a modeling study. J Neurophysiol 97: 2696 -2711. First published February 7, 2007 doi:10.1152/jn.00528.2006. The spinal network underlying locomotion in the lamprey consists of a core network of glutamatergic and glycinergic interneurons, previously studied experimentally and through mathematical modeling. We present a new and more detailed computational model of lamprey locomotor network neurons, based primarily on detailed electrophysiological measurements and incorporating new experimental findings. The model uses a HodgkinHuxley-like formalism and consists of 86 membrane compartments containing 12 types of ion currents. One of the goals was to introduce a fast, transient potassium current (K t ) and two sodium-dependent potassium currents, one faster (K NaF ) and one slower (K NaS ), in the model. Not only has the model lent support to the interpretation of experimental results but it has also provided predictions for further experimental analysis of single-network neurons. For example, K t was shown to be one critical factor for controlling action potential duration. In addition, the model has proved helpful in investigating the possible influence of the slow afterhyperpolarization on repetitive firing during ongoing activation. In particular, the balance between the simulated slow sodium-dependent and calcium-dependent potassium currents has been explored, as well as the possible involvement of dendritic conductances. I N T R O D U C T I O NThe lamprey CNS has widely served as a model system of the neural basis of vertebrate locomotion. There are fewer neurons in the lamprey than in higher vertebrates and the motor activity underlying locomotion can be maintained in the isolated spinal cord for days . The core of the lamprey spinal central pattern generator (CPG) consists of ipsilaterally projecting glutamatergic neurons and contralaterally projecting glycinergic neurons (Buchanan et al. 1982(Buchanan et al. , 1987Grillner 2003). One tool for investigating the lamprey CPG, in addition to the experimental approach, has been extensive modeling at different levels of abstraction ). Both biophysical single-cell and network models of the lamprey spinal CPG were previously described (see, e.g., Ekeberg et al. 1991;Grillner et al. 1988;Hellgren et al. 1992; for more abstract types of models also see Buchanan 1992;McClellan and Hagevik 1997;Williams 1992). Different aspects of the local spinal network were previously simulated using Hodgkin-Huxley types of models, including its modulation by sensory feedback, activation by supraspinal structures, and coordination along the spinal cord Ekeberg et al. 1991; Hellgren et al. 1999a,b;Kozlov et al. 2001;Tegnér et al. 1998Tegnér et al. , 1999Tråvén et al. 1993;Ullström et al. 1998;Wadden et al. 1997;Wallén et al. 1992). Understanding such systems at the neuronal network level is very demanding because of the complexity of the dynamic interactions within an...

show abstract

“…In these reduced lamprey preparations, the bursting is thought to be sustained by positive feedback among the excitatory interneurons (EIN; [65]). EINs are shown to excite other EINs, and in one case a mutually excitatory pair was observed [62]. Although it is unclear what role these processes observed in the hemicord play in the intact swim system, it is intriguing that such similar results were observed in the two species.…”

Section: Comparison To the Lamprey Hemicordmentioning

confidence: 91%

“…The view that mutually excitatory circuits sustain locomotory behavior is gaining traction. They are thought to contribute to swimming in the Xenopus tadpole [27,61] and are viewed as one source of excitation for burst generation in lamprey swimming [62][63][64]. We posit that there is at least one additional mutually excitatory interneuron in many, perhaps all, segmental ganglia that excite the swim-gating cells, and this is perhaps cell 208.…”

Section: Swim Maintenance Via Positive Feedbackmentioning

confidence: 95%

Positive feedback loops sustain repeating bursts in neuronal circuits

et al. 2010

View full text Add to dashboard Cite

Voluntary movements in animals are often episodic, with abrupt onset and termination. Elevated neuronal excitation is required to drive the neuronal circuits underlying such movements; however, the mechanisms that sustain this increased excitation are largely unknown. In the medicinal leech, an identified cascade of excitation has been traced from mechanosensory neurons to the swim oscillator circuit. Although this cascade explains the initiation of excitatory drive (and hence swim initiation), it cannot account for the prolonged excitation (10-100 s) that underlies swim episodes. We present results of physiological and theoretical investigations into the mechanisms that maintain swimming activity in the leech. Although intrasegmental mechanisms can prolong stimulus-evoked excitation for more than one second, maintained excitation and sustained swimming activity requires chains of several ganglia. Experimental and modeling studies suggest that mutually excitatory intersegmental interactions can drive bouts of swimming activity in leeches. Our model neuronal circuits, which incorporated mutually excitatory neurons whose activity was limited by impulse adaptation, also replicated the following major experimental findings: (1) swimming can be initiated and terminated by a single neuron, (2) swim duration decreases with experimental reduction in nerve cord length, and (3) swim duration decreases as the interval between swim episodes is reduced.

show abstract

The activity‐dependent plasticity of segmental and intersegmental synaptic connections in the lamprey spinal cord

Cited by 46 publications

References 50 publications

Primitive Roles for Inhibitory Interneurons in Developing Frog Spinal Cord

Primitive Roles for Inhibitory Interneurons in Developing Frog Spinal Cord

Roles of Ionic Currents in Lamprey CPG Neurons: A Modeling Study

Positive feedback loops sustain repeating bursts in neuronal circuits

Contact Info

Product

Resources

About