Signal propagation along the axon

Rama, Sylvain; Zbili, Mickaël; Debanne, Dominique

doi:10.1016/j.conb.2018.02.017

Cited by 42 publications

(43 citation statements)

References 73 publications

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“…Notably, longer internodes were often accompanied by myelinated branch points in γ2 f/f mice ( Fig. 1c, d, g), a severe defect if we consider that these strategic axonal regions are not usually myelinated, thus ensuring the adequate propagation of action potentials 20 . In addition to internodes and branch points, nodes of Ranvier are important axonal structures whose length contributes to the optimization of action potential propagation and conduction velocity 21 .…”

Section: Resultsmentioning

confidence: 99%

“…While the general maturation of complex and ramified axons did not appear to be affected in FSI of mutants, myelination defects in most if not all FSI caused an abnormal proximal axon morphology, an aberrant myelination of axonal branch points and an increased length of internodes and nodes of Ranvier. Since proximal axon morphology and myelination are critical for the generation and propagation of action potentials 20 , myelination defects of FSI may impact signal propagation and conduction.…”

Section: Resultsmentioning

confidence: 99%

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Myelination of parvalbumin interneurons shapes the function of cortical sensory inhibitory circuits

et al. 2020

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Myelination of projection neurons by oligodendrocytes is key to optimize action potential conduction over long distances. However, a large fraction of myelin enwraps the axons of parvalbumin-positive fast-spiking interneurons (FSI), exclusively involved in local cortical circuits. Whether FSI myelination contributes to the fine‐tuning of intracortical networks is unknown. Here we demonstrate that FSI myelination is required for the establishment and maintenance of the powerful FSI-mediated feedforward inhibition of cortical sensory circuits. The disruption of GABAergic synaptic signaling of oligodendrocyte precursor cells prior to myelination onset resulted in severe FSI myelination defects characterized by longer internodes and nodes, aberrant myelination of branch points and proximal axon malformation. Consequently, high-frequency FSI discharges as well as FSI-dependent postsynaptic latencies and strengths of excitatory neurons were reduced. These dysfunctions generated a strong excitation-inhibition imbalance that correlated with whisker-dependent texture discrimination impairments. FSI myelination is therefore critical for the function of mature cortical inhibitory circuits.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Myelination of parvalbumin interneurons shapes the function of cortical sensory inhibitory circuits

et al. 2020

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“…Variability in diameter together with other parameters will impact on excitability, conduction velocity, and other aspects of signal propagation. Other impacting parameters include width of myelin and intermodal length, and density and distribution of ion channels (reviewed in Debanne et al, 2011 ; Seidl, 2014 ; Bucher, 2016 ; Seidl and Rubel, 2016 ; Rama et al, 2018 ). These would have effects on neural response properties at the microcircuitry level.…”

Section: Functional Significance Of Axon Branchingmentioning

confidence: 99%

Axon Collaterals and Brain States

Rockland

2018

Front. Syst. Neurosci.

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Multiple mechanisms have been identified as relevant to plasticity, functional stability, and reliable processing across brain states. In the context of stability under “ever-changing conditions” (this Topic), the role of axons has been relatively under-investigated. The highly branched topologies of many axons, however, seem well designed to differentially recruit and regulate distributed postsynaptic groups, possibly in a state-dependent fashion. In this Perspective, I briefly discuss several examples of axon collateralization, and then some of the branch-specific features that might subserve differential recruitment and whole brain activation. An emerging principle is that the number of collaterals and number of target structures are not stereotyped. Rather, axons originating from one defined source typically send branches to diversified subsets of target areas. This could achieve heterogeneous inputs, with different degrees of synchronicity. Variability of neuronal responses has been suggested as inversely proportional to the degree of temporally correlated input. Increased input homogeneity, driven by sensory stimulation or behavioral conditions, is reported to reduce neuronal variability, with axon collateralization potentially having an important role.

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“…Questions concerning consequences of changes in the fiber excitability under physiological conditions are also open. They include questions whether changes secondary to electric fields around spinal neurons would modulate conduction velocity of the affected fibers, reduce the branching point failures, affect the release of transmitter from their terminals, and/or contribute to plasticity in the operation of spinal neuronal networks (Debanne 2004;Kaller et al 2017;Rama et al 2018).…”

Section: Discussionmentioning

confidence: 99%

Long-term effects of direct current are reproduced by intermittent depolarization of myelinated nerve fibers

Bączyk

Jankowska

2018

Journal of Neurophysiology

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Direct current (DC) potently increases the excitability of myelinated afferent fibers in the dorsal columns, both during DC polarization of these fibers and during a considerable (>1 h) postpolarization period. The aim of the present study was to investigate whether similarly long-lasting changes in the excitability of myelinated nerve fibers in the dorsal columns may be evoked by field potentials following stimulation of peripheral afferents and by subthreshold epidurally applied current pulses. The experiments were performed in deeply anesthetized rats. The effects were monitored by changes in nerve volleys evoked in epidurally stimulated hindlimb afferents and in the synaptic actions of these afferents. Both were found to be facilitated during as well as following stimulation of a skin nerve and during as well as following epidurally applied current pulses of 5- to 10-ms duration. The facilitation occurring ≤2 min after skin nerve stimulation could be linked to both primary afferent depolarization and large dorsal horn field potentials, whereas the subsequent changes (up to 1 h) were attributable to effects of the field potentials. The findings lead to the conclusion that the modulation of spinal activity evoked by DC does not require long-lasting polarization and that relatively short current pulses and intrinsic field potentials may contribute to plasticity in spinal activity. These results suggest the possibility of enhancing the effects of epidural stimulation in human subjects by combining it with polarizing current pulses and peripheral afferent stimulation and not only with continuous DC. NEW & NOTEWORTHY The aim of this study was to define conditions under which a long-term increase is evoked in the excitability of myelinated nerve fibers. The results demonstrate that a potent and long-lasting increase in the excitability of afferent fibers traversing the dorsal columns may be induced by synaptically evoked intrinsic field as well as by epidurally applied intermittent current pulses. They thus provide a new means for the facilitation of the effects of epidural stimulation.

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Signal propagation along the axon

Cited by 42 publications

References 73 publications

Myelination of parvalbumin interneurons shapes the function of cortical sensory inhibitory circuits

Myelination of parvalbumin interneurons shapes the function of cortical sensory inhibitory circuits

Axon Collaterals and Brain States

Long-term effects of direct current are reproduced by intermittent depolarization of myelinated nerve fibers

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