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Using the in vitro Hippocampal Slice as a Model to Teach Methods in Neurophysiology
Published in Avital Schurr, Benjamin M. Rigor, BRAIN SLICES in BASIC and CLINICAL RESEARCH, 2020
Strength-Duration Curve — Generate a strength-duration curve. To prevent damage to the tissue from excessive stimulation, start with a stimulus intensity of 100 μA and a stimulus duration of 50 μsec. Measure the peak-to-peak amplitude of your field potential response with these stimulus parameters. Increase the stimulus intensity to 200 μA and decrease the duration until the response is the same amplitude as the initial response. Make a note of the stimulus duration and repeat this procedure at intensities of 300 μA and 400 μA. Next, decrease the current intensity to 50 μA and increase the stimulus duration until the response once again reaches the amplitude of the initial response. Repeat this procedure at decrementing current intensities. Do not exceed a stimulus duration of 1 msec. Plot your data. How does your curve differ from the theoretical curve? What is your estimate of rheobase and chronaxie? What factors in the procedure above will prevent you from getting exact measurements of rheobase and chronaxie? What would be a better parameter to measure to determine rheobase and chronaxie for the Schaffer collaterals? How would you produce a strength-duration curve for the axons of the CA1 pyramidal cells? Describe the interplay between the strength-duration relationship and the membrane time constant. If you have time, use your electronics kit to simulate the neuronal membrane. Set an arbitrary voltage as threshold and then try to reproduce the strength-duration relationship in your stimulated membrane.
Role of the Nucleus of the Solitary Tract (NTS) in Pain Control
Published in I. Robin A. Barraco, Nucleus of the Solitary Tract, 2019
Alan Randich, Stephen T. Meller
A strength-duration analysis was also performed on sites of electrical stimulation in the lateral NTS that produced inhibition of the TF reflex. The upper panel of Figure 4 shows the mean current intensities for nine pulse durations required to inhibit the TF reflex to the cutoff latency of 10 s, and the bottom panel shows these values expressed as a proportion of the rheobase current. The rheobase current is defined as the intensity of electrical stimulation in the NTS necessary to produce inhibition of the TF reflex to the cut-off latency of 10 s at a long pulse duration. This intensity plateaus at pulse durations of approximately 600 to 800 βs. Since a mean intensity of 30 μA of stimulation was required to inhibit the TF reflex at the 800-βs pulse duration, it was designated as the rheobase current or 1.0 r. The chronaxie is then defined as the pulse duration required to produce a given effect at twice the rheobase current, and was approximately 170 βs. This chronaxie indicates that inhibition of the TF reflex produced by electrical stimulation in the NTS was not exclusively due to the stimulation of fiber passage in the region, but probably represented activation of both cells and fibers of passage.
C
Published in Anton Sebastian, A Dictionary of the History of Medicine, 2018
Chronaxia The period of excitation of animal tissue. Defined by Louis Lapicque (1866–1952) of France in 1909. It denotes the shortest time that a current twice the strength of the rheobase must be applied to stimulate a response.
Neuromuscular disorders in women and men with spinal cord injury are associated with changes in muscle and tendon architecture
Published in The Journal of Spinal Cord Medicine, 2023
Larissa Santana, Emerson Fachin-Martins, David Lobato Borges, Jonathan Galvão Tenório Cavalcante, Nicolas Babault, Frederico Ribeiro Neto, João Luiz Quagliotti Durigan, Rita de Cássia Marqueti
A universal pulse generator (Dualpex 071, Quark Medical LTDA) was used to assess the five target muscles through a reference electrode (anode) with an area of 100 cm2 placed on the ankle. An active pen electrode (cathode) with an area of 1 cm2 was used to find the motor-points.38 The rheobase was defined as the minimal current intensity necessary to reach the neuromuscular excitability threshold, applied with a rectangular pulse with an infinite duration, varying from 0 up to 69 mA, with increments of 1 mA until the point at which a slight but visible muscle contraction appeared. During the assessments, the stimulation protocol consisted of a rectangular pulse width of 1s and a rest interval of 2s.21 The chronaxie was represented by the shortest pulse duration required to reach the neuromuscular excitability threshold by a current with twice the intensity of the rheobase; values higher than 1000 µs indicated NED.21,24 The pulse width increased from 20 µs to 1s, using 100 µs increments until 1000 µs, followed by 1000 µs increments from this point.21 An exponential pulse monopolar current with a pulse width of 1000 µs was applied to define the accommodation values, increasing the electrical current from 0 to 69 mA with increments of one mA until the visible muscle contraction. The accommodation index (AI) was calculated as the ratio between the accommodation and rheobase (AI = accommodation/rheobase).21,25
Differences in nerve excitability properties between isolated bulbar palsy and bulbar-dominant amyotrophic lateral sclerosis
Published in Neurological Research, 2020
So Young Pyun, Yerim Kim, Seong-Il Oh, Jong Seok Bae
We compared the cALS group with normal controls (Table 2). Our analysis also revealed a pattern of excitability changes reflecting LMN axonal dysfunction in ALS that was similar to previous reports [3,14]in that compared with normal controls, the cALS group showed a greater change in the depolarizing phase of TE (TEd) after 90–100 msof depolarizing current[TEd(90–100)] (53.3 ± 1.3 for the ALS group and 49.0 ± 0.7 for the control group, P < 0.01) and lower S2 accommodation (19.6 ± 0.8 and 22.6 ± 0.7, respectively;P = 0.01) (Table 2). Our analysis also showed that the SDTC was higher in cALS, but this difference was not statistically significant (0.50 ± 0.02 for the ALS group and 0.48 ± 0.03 for the control group, P = 0.5). Instead, the rheobase was significantly lower in the cALS group than for normal controls (1.38 ± 1.05 and 1.71 ± 1.07, respectively;P = 0.03). There were no significant intergroup differences in the RC or CTR (Table 2).
Intra and inter-raters reliability and agreement of stimulus electrodiagnostic tests with two different electrodes in sedated critically-ill patients
Published in Physiotherapy Theory and Practice, 2020
Amaro Eduardo Tavares de Araujo, Paulo Eugênio Silva, Karina Livinode de Carvalho, Emerson Fachin-Martins, Nicolas Babault, João Luiz Quagliotti Durigan
The SET is a validated, low cost, and non-invasive exam for diagnosing NEDs. Its sensitivity ranged from 88% to 100% when compared to needle electromyography (Paternostro-Sluga et al., 2002). During the SET, rheobase and chronaxie are obtained. Rheobase is the minimum current in milliamperes (mA) necessary to produce a slight muscle contraction, with a square pulse of 1000 ms and interval between pulses equal to 2000 ms. Chronaxie is the minimal pulse duration necessary to produce a visible muscle contraction with a square pulse. To calculate chronaxie, double the intensity of rheobase is used with intervals between pulses equal to 2000 ms. Chronaxie values higher than 1000 μs characterize the presence of a NED (Paternostro-Sluga et al., 2002).