Induction of Rhythmic Activity by Harmaline

1974 ◽  
Vol 52 (4) ◽  
pp. 905-908 ◽  
Author(s):  
Y. Lamarre ◽  
E. Puil
Keyword(s):  
High Frequency ◽  
Inferior Olive ◽  
Rhythmic Activity ◽  
Multiunit Activity ◽  
Strong Excitation ◽  
Decerebrate Cats

Microiontophoretic application of harmaline evoked rhythmic multiunit activity in the inferior olive of decerebrate cats. Harmaline caused strong excitation of individual olivary neurones but did not seem to cause them to discharge in high frequency bursts. These effects suggest that the tremorgenic action of harmaline may be due to an exaggeration of the normal tendency of olivary neurones to fire rhythmically in multiunit bursts.

Effects Produced by Local Applications of Harmaline in the Inferior Olive

1975 ◽  
Vol 53 (5) ◽  
pp. 845-849 ◽  
Author(s):  
C. De Montigny ◽  
Y. Lamarre
Keyword(s):  
Inferior Olive ◽  
Rhythmic Activity ◽  
Coupling Mechanism ◽  
Electrotonic Coupling ◽  
Accessory Nuclei ◽  
Inferior Olivary ◽  
Decerebrate Cats ◽  
Inferior Olivary Complex

Local microinjections of harmaline evoked sustained rhythmic activity in the inferior olive of decerebrate cats. Harmaline appears to exert its action within restricted areas of the inferior olivary complex: the caudal halves of the dorsal and medial accessory nuclei. Since the highly synchronized activity generated by harmaline can be attributed to extensive electrotonic coupling between olivary neurones, it is postulated that such a coupling mechanism is weaker if not absent in the principal olive and in the rostral parts of the accessory nuclei.

IID Sensitivity Differs Between Two Principal Centers in the Interaural Intensity Difference Pathway: the LSO and the IC

1998 ◽  
Vol 79 (5) ◽  
pp. 2416-2431 ◽  
Author(s):  
Thomas J. Park
Keyword(s):  
High Frequency ◽  
Direct Evidence ◽  
Extracellular Recording ◽  
Intensity Difference ◽  
Interaural Intensity Difference ◽  
Pharmacological Studies ◽  
Strong Excitation ◽  
The Difference ◽  
Intense Signal ◽  
Response Feature

Park, Thomas J. IID sensitivity differs between two principal centers in the interaural intensity difference pathway: the LOS and the IC. J. Neurophysiol. 79: 2416–2431, 1998. Interaural intensity differences (IIDs) are the chief cues that animals use to localize high-frequency sounds. Neurons that are sensitive to IIDs are excited by sound at one ear and inhibited by sound at the other. Thus a given IID generates a combination of excitation and inhibition that is reflected in a cell's spike count. In mammals, the so-called “IID pathway” begins in the lateral superior olive (LSO), which is dominated by the type of IID-sensitive neurons just described. The LSO then sends a prominent projection to the inferior colliculus (IC), which also contains a substantial population of IID-sensitive cells. Recent pharmacological studies have suggested that the response properties of IID-sensitive neurons in the IC undergo considerable processing and thus should not simply reflect the output of the LSO. However, we have no direct evidence as to whether IID sensitivity, the defining response feature of these cells, differs at these two levels. The present study makes this direct comparison in the Mexican free-tailed bat, a species that relies greatly on high-frequency hearing and thus on IIDs for localizing sounds in space. Extracellular recording techniques were used to obtain IID functions from 50 IC neurons. Comparable data from 50 LSO cells were available from a previous study. The main result was that IID sensitivity significantly differed between cells in the LSO and the IC. Among LSO cells, sensitivity was centered ∼0 dB (no intensity difference between the ears) whereas, in the IC, sensitivity was biased toward the inhibitory ear: on average, IC cells required a more intense signal at the inhibitory ear to reach the same degree of suppression as observed in LSO cells. Further analysis showed that the vast majority of IC cells (88%) exhibited a mismatch in the latencies of their inputs: inhibition arrived later when an equally strong excitation and inhibition were elicited; this reduced the effectiveness of the inhibition. Because latency shortens with increasing stimulus intensity, an IID with a more intense signal at the inhibitory ear could equate the latencies of excitation and inhibition, increasing the effectiveness of the inhibition. This result suggests that latency mismatches account, to a great extent, for the difference in sensitivity between the LSO and the IC; and when mismatches were negated by electronically time shifting the signals to the ears, sensitivity was no longer significantly different between the two nuclei.

Deletions of Rhythmic Motoneuron Activity During Fictive Locomotion and Scratch Provide Clues to the Organization of the Mammalian Central Pattern Generator

2005 ◽  
Vol 94 (2) ◽  
pp. 1120-1132 ◽  
Author(s):  
Myriam Lafreniere-Roula ◽  
David A. McCrea
Keyword(s):  
Central Pattern Generator ◽  
Rhythmic Activity ◽  
Pattern Generator ◽  
Cycle Period ◽  
Fictive Locomotion ◽  
Integer Multiple ◽  
Extensor Motoneuron ◽  
Complete Failure ◽  
Motoneuron Activity ◽  
Decerebrate Cats

We examined the features of spontaneous deletions of bursts of motoneuron activity that can occur within otherwise rhythmic alternating flexor and extensor activity during fictive locomotion and scratch in adult decerebrate cats. Deletions of activity were observed both in hindlimb flexor and extensor motoneuron pools during brain stem–stimulation-evoked fictive locomotion but only in extensors during fictive scratch. Paired intracellular motoneuron recordings showed that deletions reduced the depolarization of homonymous motoneurons in qualitatively similar ways. Differences occurred in the extent to which activity in synergist motoneuron pools operating at other joints within the limb was reduced during deletions. The timing of the rhythmic activity that followed a deletion was often at an integer multiple of the preexisting locomotor or scratch cycle period. This maintenance of cycle period was also seen during deletions in which there was a complete failure of motoneuron depolarization. The activity of antagonist motoneurons was usually sustained during deletions with some rhythmic modulation at intervals of the preexisting cycle period. We discuss an organization of the central pattern generator for locomotion and scratch that functions as a single rhythm generator with separate and multiple pattern formation modules for controlling the hyper- and depolarization of subsets of motoneurons within the limb.

scholarly journals Quasiperiodic Rhythms of the Inferior Olive

2018 ◽  
Author(s):  
Mario Negrello ◽  
Pascal Warnaar ◽  
Vincenzo Romano ◽  
Cullen B Owens ◽  
Sander Lindeman ◽  
...  
Keyword(s):  
Inferior Olive ◽  
Rhythmic Activity ◽  
Sensory Stimulation ◽  
Short Term ◽  
Subthreshold Oscillations ◽  
Electrophysiological Recordings ◽  
Long Term Changes ◽  
Inferior Olivary ◽  
Spiking Activity

Inferior olivary activity causes both short-term and long-term changes in cerebellar output underlying motor performance and motor learning. Many of its neurons engage in coherent subthreshold oscillations and are extensively coupled via gap junctions. Studies in reduced preparations suggest that these properties promote rhythmic, synchronized output. However, how these properties interact with synaptic inputs controlling inferior olivary output in intact, awake behaving animals is poorly understood. Here we combine electrophysiological recordings in awake mice with a novel and realistic tissue-scale computational model of the inferior olive to study the relative impact of intrinsic and extrinsic mechanisms governing its activity. Our data and model suggest that if subthreshold oscillations are present in the awake state, the period of these oscillations will be transient and variable. Accordingly, by using different temporal patterns of sensory stimulation, we found that complex spike rhythmicity was readily evoked but limited to short intervals of no more than a few hundred milliseconds and that the periodicity of this rhythmic activity was not fixed but dynamically related to the synaptic input to the inferior olive as well as to motor output. In contrast, in the long-term the average olivary spiking activity was not affected by the strength and duration of the sensory stimulation, while the level of gap junctional coupling determined the stiffness of the rhythmic activity in the olivary network during its dynamic response to sensory modulation. Thus, interactions between intrinsic properties and extrinsic inputs can explain the variations of spiking activity of olivary neurons, providing a conceptual framework for the creation of both the short-term and long-term changes in cerebellar output.

Neuromuscular blockade enhances phrenic nerve activity during high-frequency ventilation

1984 ◽  
Vol 56 (1) ◽  
pp. 31-34 ◽  
Author(s):  
S. J. England ◽  
A. Onayemi ◽  
A. C. Bryan
Keyword(s):  
Neuromuscular Blockade ◽  
Phrenic Nerve ◽  
High Frequency ◽  
Intact Animal ◽  
Rhythmic Activity ◽  
High Frequency Ventilation ◽  
Nerve Activity ◽  
Arterial Pco2 ◽  
Phrenic Nerve Activity ◽  
Frequency Ventilation

Phrenic nerve activity was monitored in anesthetized cats during high-frequency ventilation (HFV). Rhythmic phrenic discharge disappeared during HFV in all animals at normal arterial PCO2 levels. Rhythmic activity returned after neuromuscular blockade in the vagally intact animal. Although vagotomy alone also restored phrenic discharge, this activity was further enhanced by subsequent neuromuscular blockade. Therefore we suggest that apnea during HFV results from inspiratory inhibition mediated by both chest wall and vagal afferent mechanisms.

Computer modeling of chaoticity degree of ventricular fibrillations in humans and dogs

2018 ◽  
pp. 69-73
Author(s):  
Л.В. Мезенцева
Keyword(s):  
Ventricular Fibrillation ◽  
Computer Modeling ◽  
High Frequency ◽  
Computer Experiments ◽  
Rhythmic Activity ◽  
Electric Activity ◽  
Phase Portraits ◽  
Method Of Least Squares ◽  
Study Results ◽  
Clinical Records

Для анализа фибрилляторного хаоса в настоящее время используются методы математического моделирования и теории детерминированного хаоса. Ранее нами была разработана математическая модель, позволяющая выполнять компьютерное моделирование фибрилляции желудочков в условиях различного числа источников ритмической активности (эктопических фокусов). Модель позволяет выполнять оценку количества фокусов по экспериментальным записям электрической активности сердца у животных и человека. Целью настоящего исследования является использование этой модели для изучения взаимосвязи между степенью хаотичности процесса фибрилляции желудочков и количеством эктопических фокусов, функционирующих в миокарде желудочков у человека и собак. Методом компьютерного моделирования рассчитывали теоретические зависимости степени хаотичности фибриллярных осцилляций от количества импульсных потоков. Результаты вычислительных экспериментов сравнивали с результатами экспериментов, выполненных на собаках, и клиническими записями фрагментов ЭКГ у больных с эпизодами фибрилляции желудочков. Степень хаотичности электрической активности сердца оценивали с помощью энтропии, корреляционной размерности хаоса и фазовых портретов амплитуд фибриллярных осцилляций. Далее методом наименьших квадратов решали задачу поиска вариантов моделей, наилучшим образом аппроксимирующих экспериментальные записи фибриллярных осцилляций. Это позволяло рассчитать количество эктопических фокусов и их амплитудно-частотные характеристики. Результаты исследований показали, что степень хаотичности фибриллярных осцилляций зависит от числа эктопических фокусов, функционирующих в миокарде желудочков. Расчетные значения числа эктопических фокусов у собак превышали аналогичные значения для человека. Если для собак были характерны многоочаговые типы моделей фибрилляции желудочков (4-5 фокусов), то для человека были характерны 2-3-фокусные модели. Показатели степени хаотичности фибриллярных осцилляций у собак также были выше, чем у человека. Заключение. Результаты, исследований свидетельствуют о наличии взаимосвязи между количеством независимых источников высокочастотной ритмической активности, функционирующих в миокарде желудочков, и показателями степени хаотичности фибрилляторого хаоса. For analysis of fibrillation chaos, methods of mathematical modeling and the theory of determined chaos are currently used. Earlier we have proposed a mathematical model, which allows computer modeling of ventricular fibrillation in the conditions of different number of pacemakers (ectopic foci). The model estimates the number of ectopic foci on experimental records of heart electric activity in animals and humans. The aim of this work was to use this model for studying the interrelation between degrees of ventricular fibrillation chaoticity and quantity of ectopic foci in the myocardium of humans and dogs. Methods. Theoretical dependences of fibrillation oscillation chaoticity degree on pacemaker numbers were constructed using computer modeling. Results of computer experiments were compared with those of physiological experiments on dogs and clinical records of ECG fragments from patients with episodes of ventricular fibrillation. The degree of chaoticity of heart electric activity was estimated by entropy, correlation dimension of chaos and phase portraits of fibrillary oscillation amplitudes. Further, the method of least squares was used to solve the task of finding the best model characteristics for achieving optimum correspondence between results of computed and real physiological experiments. This allowed us to calculate the number of ectopic foci and their amplitude-frequency characteristics. The results showed that the degree of chaoticity of fibrillation oscillations depended on the number of active ectopic foci in the myocardium. Calculated values for the number of ectopic foci for dogs exceeded similar values for humans. While multifocal types of models of ventricular fibrillation (4-5 foci) were characteristic of dogs, bi- and three-focal models were characteristic of humans. Characteristics of the chaoticity degree of fibrillation oscillations for dogs were also higher than similar values for humans. Conclusion. The study results showed an interrelation between the number of independent myocardial sources of high-frequency rhythmic activity and the degree of chaoticity of fibrillation chaos.

Respiratory changes induced by kainic acid lesions in rostral ventral respiratory group of rabbits

2002 ◽  
Vol 283 (1) ◽  
pp. R227-R242 ◽  
Author(s):  
Donatella Mutolo ◽  
Fulvia Bongianni ◽  
Marco Carfì ◽  
Tito Pantaleo
Keyword(s):  
Kainic Acid ◽  
High Frequency ◽  
Rhythmic Activity ◽  
Respiratory Frequency ◽  
Ventral Respiratory Group ◽  
High Frequency Oscillations ◽  
Bötzinger Complex ◽  
Inspiratory Activity ◽  
Low Amplitude

The role played by the Bötzinger complex (BötC), the pre-Bötzinger complex (pre-BötC), and the more rostral extent of the inspiratory portion of the ventral respiratory group (iVRG) in the genesis of the eupneic pattern of breathing was investigated in anesthetized, vagotomized, paralyzed, and artificially ventilated rabbits by means of kainic acid (KA, 4.7 mM) microinjections (20–30 nl). Unilateral KA microinjections into all of the investigated VRG subregions caused increases in respiratory frequency associated with moderate decreases in peak phrenic amplitude in the BötC and pre-BötC regions. Bilateral KA microinjections into either the BötC or pre-BötC transiently eliminated respiratory rhythmicity and caused the appearance of tonic phrenic activity (“tonic apnea”), whereas injections into the rostral iVRG completely suppressed inspiratory activity. Rhythmic activity resumed as low-amplitude, high-frequency oscillations and displayed a progressive, although incomplete, recovery. Combined bilateral KA microinjections (BötC and pre-BötC) caused persistent (>3 h) tonic apnea. Results show that all of the investigated VRG subregions exert a potent control on both the intensity and frequency of inspiratory activity, thus suggesting that these areas play a major role in the genesis of the eupneic pattern of breathing.

Acoustic reflex frequency selectivity in single stapedius motoneurons of the cat

1992 ◽  
Vol 68 (3) ◽  
pp. 807-817 ◽  
Author(s):  
J. B. Kobler ◽  
J. J. Guinan ◽  
S. R. Vacher ◽  
B. E. Norris
Keyword(s):  
Auditory Nerve ◽  
High Frequency ◽  
Low Frequency ◽  
Nerve Fibers ◽  
Main Function ◽  
Acoustic Reflex ◽  
Tuning Curves ◽  
Acoustic Reflexes ◽  
Auditory Nerve Fibers ◽  
Decerebrate Cats

1. The sound frequency selectivities of single stapedius motoneurons were investigated in ketamine anesthetized and in decerebrate cats by recording from axons in the small nerve fascicles entering the stapedius muscle. 2. Stapedius motoneuron tuning curves (TCs) were very broad, similar to the tuning of the overall acoustic reflexes as determined by electromyographic recordings. The lowest thresholds were usually for sound frequencies between 1 and 2 kHz, although many TCs also had a second sensitive region in the 6- to 12-kHz range. The broad tuning of stapedius motoneurons implies that inputs derived from different cochlear frequency regions (which are narrowly tuned) must converge at a point central to the stapedius motoneuron outputs, possibly at the motoneuron somata. 3. There were only small differences in tuning among the four previously described groups of stapedius motoneurons categorized by sensitivity to ipsilateral and contralateral sound. The gradation in high-frequency versus low-frequency sensitivity across motoneurons suggests there are not distinct subgroups of stapedius motoneurons, based on their TCs. 4. The thresholds and shapes of stapedius motoneuron TCs support the hypothesis that the stapedius acoustic reflex is triggered by summed activity of low-spontaneous-rate auditory nerve fibers with both low and high characteristic frequencies (CFs). Excitation of high-CF auditory nerve fibers by sound in their TC “tails” is probably an important factor in eliciting the reflex. 5. In general, the most sensitive frequency for stapedius motoneurons is higher than the frequency at which stapedius contractions produce the greatest attenuation of middle ear transmission. We argue that this is true because the main function of the stapedius acoustic reflex is to reduce the masking of responses to high-frequency sounds produced by low-frequency sounds.

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