The Chronaxie Time and Its Practical Importance

Irnich, Werner

doi:10.1111/j.1540-8159.1980.tb05236.x

Cited by 109 publications

(64 citation statements)

References 5 publications

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“…Similarly complicated is the relation between the initiation site, the threshold, and the pulse duration. With idealised axon, the initiation site is stationary and the strength-duration curve is smooth (Pashut et al 2011;McNeal 1976), similar to the chronaxy-rheobase curve intrinsic to current injection (Irnich 1980). But with realistic morphology, sometimes more than one aligned segments are presented for a specific direction.…”

Section: Competition Between Activation-capable Componentsmentioning

confidence: 98%

Cortical neuron activation induced by electromagnetic stimulation: a quantitative analysis via modelling and simulation

Fan

Lee

et al. 2015

J Comput Neurosci

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Previous simulation works concerned with the mechanism of non-invasive neuromodulation has isolated many of the factors that can influence stimulation potency, but an inclusive account of the interplay between these factors on realistic neurons is still lacking. To give a comprehensive investigation on the stimulation-evoked neuronal activation, we developed a simulation scheme which incorporates highly detailed physiological and morphological properties of pyramidal cells. The model was implemented on a multitude of neurons; their thresholds and corresponding activation points with respect to various field directions and pulse waveforms were recorded. The results showed that the simulated thresholds had a minor anisotropy and reached minimum when the field direction was parallel to the dendritic-somatic axis; the layer 5 pyramidal cells always had lower thresholds but substantial variances were also observed within layers; reducing pulse length could magnify the threshold values as well as the variance; tortuosity and arborization of axonal segments could obstruct action potential initiation. The dependence of the initiation sites on both the orientation and the duration of the stimulus implies that the cellular excitability might represent the result of the competition between various firing-capable axonal components, each with a unique susceptibility determined by the local geometry. Moreover, the measurements obtained in simulation intimately resemble recordings in physiological and clinical studies, which seems to suggest that, with minimum simplification of the neuron model, the cable theory-based simulation approach can have sufficient verisimilitude to give quantitatively accurate evaluation of cell activities in response to the externally applied field.

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Section: Competition Between Activation-capable Componentsmentioning

confidence: 98%

Cortical neuron activation induced by electromagnetic stimulation: a quantitative analysis via modelling and simulation

Fan

Lee

et al. 2015

J Comput Neurosci

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“…Der Batteriestrom (I Bat ) (µA) wurde für jede Sicherheitsmarge als Mittelwert aus 5 Messungen im D00-Modus mit 70 bpm telemetriert. I Bat aller Patienten lag mit 2× Q RS signifikant niedriger als mit 2× U RS (13,43 ± 1,0 vs. 14,20 ± 1,2 µA, p < 0,01) und als mit 3× t RS (13, Veränderungen der Stimulationsamplitude und der Impulsdauer sind in ihren Auswirkungen auf den Stromverbrauch eines Schrittmachersystems gut untersucht (5,10,13,20,24). Wie sich unterschiedliche Sicherheitsmargen auf den Stromverbrauch eines modernen Zweikammer-Schrittmachers auswirken, ist jedoch bisher nicht bekannt.…”

Section: Abstract Safety Margin -Battery Current -Longevity -Ddd Pacunclassified

Einfluß der programmierten Sicherheitsmarge auf die Funktionszeit moderner Zweikammer-Schrittmacher

Schwaab¹,

Schwerdt²,

Fröhlig³

et al. 1998

Z Kardiol

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In 55 consecutive patients with the same dual chamber pacemaker (Relay, Intermedics) and different pacing leads, the influence of different safety margins for pacing on battery current was investigated. 2.8 +/- 0.9 years after implantation, atrial and ventricular pulse-width thresholds (tRS) (ms) were determined at 0.5, 1.0, and 2.0 V, and the charge delivered at threshold was telemetered. If tRS was < 1.50 ms at 0.5 V, an amplitude of 1.0 V was programmed in the atrium and the ventricule; if tRS was < 1.50 ms at 1.0 V, then an amplitude of 2.0 V was chosen. Two times the charge threshold (2 x QRS), two times the voltage threshold (2 x URS), and three times the pulse-width threshold (3 x tRS) were programmed as the safety margins for pacing. With every safety margin, battery current (IBat) (microA) was averaged from 5 telemetric readings in D00 mode with 70 bpm. IBat was significantly lower with 2 x QRS as compared with 2 x URS (13.43 +/- 1.0 vs. 14.20 +/- 1.2 microA, p < 0.01) and as compared with 3 x tRS (13.99 +/- 1.2 microA, p < 0.05). Pacemaker longevity derived from these current data was significantly longer with 2 x QRS (112 +/- 8 months) as compared with 2 x URS (106 +/- 9, p < 0.01) and as compared with 3 x tRS (108 +/- 8, p < 0.05). If current consumption is compared intraindividually in dependance on the programmed amplitude, battery current is significantly lower at 1.0 V as compared with 2.0 V resulting in a mean reduction of 0.63 microA (-4.9%, p < 0.05) and an average gain in longevity of 5 months. This applies to every safety margin tested. Differences in battery current caused by the safety margins will translate into a greater gain in longevity in future pacemaker models with reduced internal current consumption.

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“…In curve d, the subcutaneous stimuli bypass the high-resistance layer of skin: these discharges have extremely short time constants, less than 1 JJsec for all of the data plotted. It is a safe assumption that neural membrane time constants, T m , are at least an order of magnitude greater (cf, Aidley, 1971;Irnich, 1980;Ranck, 1975). Consequently, the entire subcutaneous curve lies in the constant charge region of the theoretical strength/ duration relationship (Figure 6), and the data have the linear profile and slope required by this relationship.…”

Section: Methodsmentioning

confidence: 99%

Strength/duration relationships for electrocutaneous sensitivity: Stimulation by capacitive discharges

Larkin

Reilly

1984

Perception & Psychophysics

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Methods of stimulating the skin by capacitive electrical discharges are described and properties of the stimulus waveforms are discussed. A neural excitation model is invoked to account for electrocutaneous sensitivity. The model gives a good account of threshold data from several experiments in which the methods of stimulation are compared. Sensitivity is shown to be chargedependent for stimuli that are brief relative to the exponential time constant of the neural membrane model. Systematic departures from charge-dependence occur when the stimulus discharge time constant is made to exceed a depolarization time constant: these departures follow a strength/duration relationship predicted by the model.When the skin contacts an electrically charged object, and so provides a ground path for a capacitive discharge, a variety of cutaneous sensations are possible. Near threshold, the sensations commonly resemble touch or mild pinprick. Above threshold, the pinprick may be followed by a burning sensation akin to the delayed pain related to C-fiber activity. Bishop (1943) reported other sense qualities as well, and suggested that a punctate "spark" from a capacitor could be used selectively on the skin to excite discrete neural channels. If the difference of potential is great enough, a spark discharge may be seen and heard as well as felt.To investigate the neural basis for transcutaneous electrical stimulation, it is useful to explore the sensory effects of variations in stimulus parameters. Much has been learned from such work (see, e.g

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The Chronaxie Time and Its Practical Importance

Cited by 109 publications

References 5 publications

Cortical neuron activation induced by electromagnetic stimulation: a quantitative analysis via modelling and simulation

Cortical neuron activation induced by electromagnetic stimulation: a quantitative analysis via modelling and simulation

Einfluß der programmierten Sicherheitsmarge auf die Funktionszeit moderner Zweikammer-Schrittmacher

Strength/duration relationships for electrocutaneous sensitivity: Stimulation by capacitive discharges

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