After‐effects of near‐threshold stimulation in single human motor axons

Bostock, Hugh; Lin, Cindy S.‐Y.; Howells, James; Trevillion, Louise; Jankelowitz, Stacey; Burke, David

doi:10.1113/jphysiol.2005.083394

Cited by 41 publications

(51 citation statements)

References 22 publications

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“…In addition to the refractory period, axonal ADP and AHP determine super- or sub-excitability of motor axons (Bostock et al, 2005). In the auditory system, the exact timing of spikes is used to encode sound intensity and pitch.…”

Section: Discussionmentioning

confidence: 99%

Dysmyelination of Auditory Afferent Axons Increases the Jitter of Action Potential Timing during High-Frequency Firing

2013

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Auditory neuropathies are linked to loss of temporal acuity of sound-evoked signals, which may be related to myelin loss. However, it is not known how myelin loss affects the waveform and temporal precision of action potentials (APs) in auditory CNS nerve terminals. Here we investigated the excitability of the calyx of Held terminal in dysmyelinated auditory brainstems using the Long-Evans Shaker (LES) rat, a spontaneous mutant where compact myelin wrapping does not occur due to a genetic deletion of myelin basic protein (MBP). We found at relatively mature postnatal ages (15–17 days after birth) LES rat calyces showed prolonged spike latencies, indicative of a 3-fold reduction in the AP propagation velocity. Furthermore, LES rat afferent fiber-evoked APs showed a pronounced loss of temporal precision, even at low stimulation frequencies (10 Hz). While normal calyces were able to fire APs without failures at impressive rates of up to 1 kHz, LES calyces were unable to do so. Direct recordings of the presynaptic calyx terminal AP waveform revealed that myelin loss does not affect the AP spike upstroke and downstroke kinetics, but dysmyelination reduces the after-depolarization and enhances the fast after-hyperpolarization peak following the AP spike in the LES rat. Taken together these findings show that proper myelination is essential not only for fast AP propagation, but also for precise presynaptic AP firing that minimizes both spike jitter and failures, two characteristics critically important for the accurate processing of sound signals in the auditory brainstem.

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Section: Discussionmentioning

confidence: 99%

Dysmyelination of Auditory Afferent Axons Increases the Jitter of Action Potential Timing during High-Frequency Firing

2013

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“…8 Delivering a subthreshold electrical stimulus to enhance the excitability of neural tissue to an added electrical stimulus is not a foreign concept. [8][9][10] The mechanism by which threshold changes occur as a result of a subthreshold stimulus has been explained by a mathematical model of induced ionic currents with enhanced excitability primarily following membrane potential. Persistent and transient Na + currents initiate "superexcitability;" Na + channel inactivation, decay in the leakage current, and activation of outward K + currents ͑pri-marily slow K + channels͒ cause the decline in excitability over time.…”

Section: Resultsmentioning

confidence: 99%

Combined optical and electrical stimulation of neural tissue in vivo

et al. 2009

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Abstract. Low-intensity, pulsed infrared light provides a novel nerve stimulation modality that avoids the limitations of traditional electrical methods such as necessity of contact, presence of a stimulation artifact, and relatively poor spatial precision. Infrared neural stimulation ͑INS͒ is, however, limited by a 2:1 ratio of threshold radiant exposures for damage to that for stimulation. We have shown that this ratio is increased to nearly 6:1 by combining the infrared pulse with a subthreshold electrical stimulus. Our results indicate a nonlinear relationship between the subthreshold depolarizing electrical stimulus and additional optical energy required to reach stimulation threshold. The change in optical threshold decreases linearly as the delay between the electrical and optical pulses is increased. We have shown that the high spatial precision of INS is maintained for this combined stimulation modality. Results of this study will facilitate the development of applications for infrared neural stimulation, as well as target the efforts to uncover the mechanism by which infrared light activates neural tissue. © 2009 Society of Photo-Optical Instrumentation Engineers.

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“…While faster tracking rates were technically possible we wanted to ensure that the interstimulus interval was well above excitability fluctuations induced by single supramaximal (Kiernan et al, 1996b) or submaximal (Bostock et al, 2005) stimuli. In human nerves the Na + /K + pump could be activated by as low as 8 Hz repetitive stimulation .…”

Section: Activity Dependent Threshold Increasementioning

confidence: 99%