Simulation of mechanisms responsible for initiation and modulation of bursting activity in RPa1 neuron of theHelix snail

A mathematical model of bursting activity in the RPa1 neuron of theHelix snail has been developed. The model allowed us to describe the processes of initiation and augmentation of the bursting activity related to transient secretion of a modulatory factor. Based on the analysis of computer simulations of various mechanisms underlying the effect of a modulating factor on the ionic membrane conductances in the bursting neuron, we suggested that modulating factor evokes a transition of non-voltage-dependent sodium channels and hyperpolarization-activated outward current channels to an active state and influences the gating of voltage-dependent sodium channels.Neirofiziologiya/Neurophysiology, Vol. 27, No. 1, pp. 11–17, January–February, 1995.     

Multiple modes of a conditional neural oscillator

We present a model for a conditional bursting neuron consisting of five conductances: Hodgkin-Huxley type time- and voltage-dependent Na⁺ and K⁺ conductances, a calcium activated voltage-dependent K⁺ conductance, a calcium-inhibited time- and voltage-dependent Ca⁺⁺ conductance, and a leakage Cl(_– conductance. With an initial set of parameters (versionS), the model shows a hyperpolarized steady-state membrane potential at which the neuron is silent. Increasingg _Na and decreasingg _Cl, whereg _i , is the maximal conductance for speciesi, produces bursts of action potentials (BursterN). Alternatively, an increase ing _Ca produces a different bursting state (BursterC). The two bursting states differ in the periods and amplitudes of their bursting pacemaker potentials. They show different steady-stateI–V curves under simulated voltage-clamp conditions; in simulations that mimic a steady-stateI–V curve taken under experimental conditions only BursterN shows a negative slope resistance region. ModelC continues to burst in the presence of TTX, while bursting in ModelN is suppressed in TTX. Hybrid models show a smooth transition between the two states.     

Modulation of endogenous bursting pacemaker activity in a Helix pomatia neuron

Considerable membrane depolarization was shown to arise periodically, at intervals of up to a few minutes, in the PPa1 bursting neuron ofHelix pomatia. Pulses of slow depolarizing current were found by the voltage clamping method. The frequency of the pulses was independent of the holding potential. The equilibrium potential for the slow depolarizing current was about 45 mV. During development of the depolarizing current a region of negative conductivity was observed on the steady-state voltage-current characteristic curve of the membrane. It is suggested that the pulses of slow depolarizing current are associated with the presence of secretory connections between the molluscan neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 6, pp. 606–612, November–December, 1977.     

Postsynaptic mechanisms initiating bursting activity in theHelix pomatia RPal neuron under the influence of an interneuron

Postsynaptic mechanisms of the connection between the interneuron in the visceral ganglion initiating bursting activity in RPal and B7 neurons and these neurons themselves were investigated in the snail (Helix pomatia). Using voltage clamping at the membrane of these cells, stimulation of the interneuron gave rise to a slow inward current with a 2 sec latency; it rose in amplitude as stimulation increased in duration. Reducing the temperature from 25 to 5°C diminished the rise and decay rate of this current with a temperature coefficient of about 10. The current-voltage relationship of the slow inward current was nonlinear, with a maximum of –65 mV. Reducing the concentration of sodium ions in the extracellular fluid increased the amplitude of the current. While hyperpolarization of the burster neuron membrane produced a burst of inward current prior to stimulation, this same hyperpolarization induced a pulse of outward current at the peak of the slow inward current. Stimulating the interneuron is thus thought to activate at least two types of ionic channel in the cell body of the burster neurons: a steady sodium and a voltage- and time-dependent channel for outward current. This process could well be mediated by a biochemical cytoplasmic chain reaction.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 28–36, January–February, 1987.     

Travelling wave patterns in a model of the spinal pattern generator using spiking neurons

The aim of this study is to produce travelling waves in a planar net of artificial spiking neurons. Provided that the parameters of the waves – frequency, wavelength and orientation – can be sufficiently controlled, such a network can serve as a model of the spinal pattern generator for swimming and terrestrial quadruped locomotion. A previous implementation using non-spiking, sigmoid neurons lacked the physiological plausibility that can only be attained using more realistic spiking neurons. Simulations were conducted using three types of spiking neuronal models. First, leaky integrate-and-fire neurons were used. Second, we introduced a phenomenological bursting neuron. And third, a canonical model neuron was implemented which could reproduce the full dynamics of the Hodgkin–Huxley neuron. The conditions necessary to produce appropriate travelling waves corresponded largely to the known anatomy and physiology of the spinal cord. Especially important features for the generation of travelling waves were the topology of the local connections – so-called off-centre connectivity – the availability of dynamic synapses and, to some extent, the availability of bursting cell types. The latter were necessary to produce stable waves at the low frequencies observed in quadruped locomotion. In general, the phenomenon of travelling waves was very robust and largely independent of the network parameters and emulated cell types.     

Cooperation of intrinsic bursting and calcium oscillations underlying activity patterns of model pre-Bötzinger complex neurons

Activity of neurons in the pre-Bötzinger complex (pre-BötC) within the mammalian brainstem drives the inspiratory phase of the respiratory rhythm. Experimental results have suggested that multiple bursting mechanisms based on a calcium-activated nonspecific cationic (CAN) current, a persistent sodium (NaP) current, and calcium dynamics may be incorporated within the pre-BötC. Previous modeling works have incorporated representations of some or all of these mechanisms. In this study, we consider a single-compartment model of a pre-BötC inspiratory neuron that encompasses particular aspects of all of these features. We present a novel mathematical analysis of the interaction of the corresponding rhythmic mechanisms arising in the model, including square-wave bursting and autonomous calcium oscillations, which requires treatment of a system of differential equations incorporating three slow variables.     

Investigations of the ionic mechanisms of bursting activity in Helix pomatia neurons

Steady-state current-voltage characteristics of the membrane and ionic currents arising during changes in membrane potential in bursting neurons ofHelix pomatia were studied by the voltage clamp method. The steady-state current-voltage characteristics of the membrane were shown to have a nonlinear region. Replacement of sodium ions by Tris-HC1 ions in the external solution completely abolishes this nonlinearity. Hyperpolarization of the membrane under voltage clamp conditions leads to the development of an outward current which reaches a maximum and then is inactivated. This current has a reversal potential in the region of the potassium equilibrium potential. Depolarization of the membrane to the threshold value for excitation of uncontrollable regions of the axon hillock causes the appearance of a slow inward current. After reaching a maximum, the inward current falls to zero. A model of generation of waves in a bursting neuron is suggested.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 2, pp. 193–202, March–April, 1978.     

Monosynaptic pathway responsible for generation of bursting activity in theHelix pomatia RPal neuron

The connection between a visceral ganglia interneuron initiating bursting pacemaker activity in the RPal neuron and the RPal neuron itself was investigated inHelix pomatia. Stimulating the interneuron either initiated or intensified bursting activity in the RPal neuron, depending on initial electrical activity in this cell. Replacing calcium with magnesium ions in the extracellular fluid and adding CdCl₂ to this fluid reversibly inhibited the effect of interneuronal stimulation on the RPal neuron. The latter effect was unaffected by increasing the concentration of extracellular Ca²⁺ 10 to 70 mM. Intracellular injection of both Cs⁺ and TEA into the interneuron produced an increase in the duration of its action potentials and rendered the link connecting the neurons more effective. It is deduced that a monosynaptic chemical connection exists between the interneuron and the RPal neuron for which a peptide compound serves as transmitter.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 20–28, January–February, 1987.     

Helix neurons invovled in control of rhythmic movement in the pneumostome

Three neurons capable of generating coordinated bursting activity or synchronized slow-wave fluctuations in membrane potential (MP) were identified in the left parietal ganglion ofHelix pomatia. The function of these units contributes to regulating rhythmic opening and closing movements in the pneumostome. Both bursting activity and slow-wave neuronal MP synchronize with rhythmic movements of the pneumostome. Onset of bursting activity and fluctuations in MP on the one hand or suppression of these effects due to different influences on the cells on the other leads to initiation or extinction of pneumostome movements respectively. These neurons do not exhibit endogenous bursting activity but do produce a fairly high rate of firing activity without bursting pattern and without slow-waves in MP in isolation. Bursting activity occurs in these neurons in the intact central nervous system (CNS) as a result of gigantic synchronized IPSP in some cases and due to the aforementioned slow waves in MP and in others. No direct chemically- or electrically-operated synaptic connections exist between the three cells. Serotonin triggers both waves in MP and bursting activity in all three neurons in the intact CNS and exerts a pronounced hyperpolarizing action on each of these factors in isolation.N. K. Kol'tsov Institute of Developmental Biology, Academy of Sciences of the USSR. Moscow. Balaton Limnological Research Institute of the Hungarian Academy of Sciences, Tihany. Translated from Neirofiziologiya, Vol. 20, No. 4, pp. 509–517, July–August, 1988.     

Ionic requirements for bursting activity in lobster stomatogastric neurons

Summary The ionic requirements for bursting activity have been investigated in the electrically coupled PD-AB cells group of the Stomatogastric ganglion in the lobster.The passive electrical properties and coupling parameters have been determined in either current or voltage clamp conditions. In voltage clamped cells, the current displayed slow inward transients with superimposed fast transients corresponding respectively to the slow waves and spikes of the coupled undamped cells. The amplitude and frequency of the slow transients were reduced upon hyperpolarization.Cyclic conductance changes were observed with short current pulses, the coupling ratio also changes cyclically being lower during the bursts and slowly increasing during the interburst interval.The slow wave amplitude increased in low K-saline. The post-burst hyperpolarization but not the top level of the wave behaved like a potassium electrode for [K]_o higher than 10 mM/l.TEA at low concentration (1 to 5 mM/l) increased the slow wave amplitude by lifting its top level by 10 to 20 mV. The post-burst hyperpolarization remained almost unchanged and its K-dependence was not altered by TEA.Low Na-saline reduced the slow wave amplitude (6 to 11 mV per decade). The Na-dependence increased in the presence of TEA. Slow waves devoid of spikes persisted in 10% Na saline containing TEA. 10^–9 M/1 TTX blocked the spikes. 10^–7 M/1 TTX blocked the slow waves.Mg-free saline had no effect on the slow wave. In Ca-free saline the cells depolarized and the bursting activity tended to vanish. Repolarization with current led to long lasting slow waves deprived of post-burst hyperpolarization. The bursting ceased when EDTA was added to the Ca-free saline.Cobalt (up to 10 mM/l) was similar to Ca-free saline in its effects; lengthening of the wave and blockage of the repolarization. Replacing Ba for Ca produced large (up to 70 mV) slow waves which were reduced by Co and Ca.Bistable states were observed in various experimental conditions. It is concluded that the slow waves are produced by activation of sodium and calcium currents. The amplitude of the slow wave is modulated by the simultaneous activation of a TEA-sensitive K current. The repolarization is caused by increased K current activated by the inward calcium current. The slow pacemaker potential in the interburst interval corresponds to the slow disappearance of the K current.This work was supported by N.I.H. grant no. 09322, NSF grant no. 00250, and a Guggenheim Foundation Fellowship to A.D.S. and by the CNRS and a DGRST grant no. 16501891 to M. Gola. We are grateful to Stuart Thompson and Felix Strumwasser for helpful comments and to Barbara McLean for technical assistance.     

Structure Dependence of the Calcium Dynamics in Purkinje Neuron Dendrites during Generation of Bursting Discharges: a Simulation Study

In the model of a cerebellar Purkinje neuron with reconstructed active dendrites, we investigated the impact of the ratio between volumes of the endoplasmic reticulum (organellar calcium store) and cytosol on the Ca²⁺ dynamics in asymmetrical parts of the dendritic arborization during generation of different structure-dependent patterns of bursting activity. Tonic synaptic excitation homogeneously distributed over the dendrites (a spatially homogeneous stationary input signal) caused spatially heterogeneous variations of the dendritic membrane potential (MP) accompanied by periodical or nonperiodical bursts of action potentials at the cell output. The MP waveforms recorded from the segments of asymmetrical dendrites were then applied to the membrane of selected dendrite segments as command voltages in a dynamic clamp mode. In these segments, the relative size of the stores was varied. This provided equal to each other local calcium currents and influxes into the cytosol of the segment differently filled with the organellar store. Regardless of the impulse pattern, microgeometry of the segment and the store modulated calcium transients exactly in the same way as in previous studies of electrical and concentration responses to local phasic synaptic excitation of the modeled neuron. Peak values of depolarization-induced elevations of the cytosolic Ca²⁺ concentration increased with the portion of the intracellular volume occupied by the store. The most important factor defining this dependence was the ratio of the membrane area vs the organelle-free cytosol volume of the dendritic segment. Concentrations of Са²⁺ deposited in equal-sized segments of asymmetrical parts of the dendritic arborization where asynchronous unequal variations of the MP were observed during generation of nonperiodical bursting at the output demonstrated considerable specificity. A greater amount of calcium was deposited in the segments staying, on average, in a high-depolarization state for a longer time (this intensified activation of calcium channels and amplified the corresponding Ca²⁺ influx into the cytosol). Hence, local dynamics of the Ca²⁺ concentration depend directly on local microgeometry and indirectly on global macrogeometry of the dendrite arborization, as the latter determines spatial asymmetry-related unequal transients in different parts of the dendritic arborization having active membrane properties.     

Effect of high intracellular calcium ion concentration on the transmembrane current induced by iontophoretic injection of cAMP inHelix pomatia neurons

The effect of increasing the intracellular calcium ion concentration by various methods (iontophoretic injection into the cytoplasm, generation of a burst of action potentials, addition of uncouplers of oxidative phosphorylation to the external solution, causing release of calcium from mitochondria) on the inward current induced by injection of cAMP into the neuron (the cAMP current) was investigated on the neuron membrane ofHelix pomatia under voltage clamp conditions. In all cases an increase in the intracellular calcium ion concentration was found to lead to an increase in amplitude, and in many cases duration, of the cAMP current. It is suggested that membrane structures responsible for appearance of the cAMP current have two phosphorylation centers: cAMP-dependent and calcium-calmodulin-dependent. The possible role of this process in signal integration at the intraneuronal level is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 1, pp. 78–84, January–February, 1985.     

A model of a thalamic neuron

We modify our recent three equilibrium-point model of neuronal bursting by a means of a small deformation of the nullclines in the x-y phase plane to give a model that can have as many as five equilibrium points. In this model the middle stable equilibrium point (e.p.) is separated from the outer stable and unstable e.ps by two saddle points. If the system is started at rest at the middle stable e.p. it has the following complex properties: A short suprathreshold current pulse switches the model from a silent state to a bursting state, or to give a single burst, depending on the choice of parameters. A subthreshold depolarizing current step gives a passive response at rest, but if the model is either constantly hyperpolarized or constantly depolarized, then the same current step gives different active responses. At a hyperpolarized level this consists of a burst response that shows refractoriness. At a depolarized level it consists of tonic firing with a linear frequency--current relationship. Hyperpolarization from rest is followed by post-inhibitory rebound. The model responds in a unique and characteristic way to an applied current ramp. These properties are very similar to those that have been recently recorded intracellularly from neurons in the mammalian thalamus. In the x-y phase plane our models of the repetitively firing neuron, the bursting neuron and the thalamic neuron form a progression of models in which the y nullcline in the subthreshold region is deformed once to give the burst neuron model, and a second time to give the thalamic neuron model. Each deformation can be interpreted as corresponding to the inclusion of a slow inward current in the model. As these currents are included so the associated firing properties increase in complexity.     

Mechanisms of membrane potential oscillation in bursting neurons on the snail,Helix pomatia

• 1.1. The mechanism of generation of membrane potential (MP) oscillations was studied in identified bursting neurons from the snail Helix pomatia.
• 2.2. Long-lasting stimulation of an identified peptidergic interneuron produced a persistent bursting activity in a non-active burster.
• 3.3. External application of calcium channel blockers (1 mM Cd²⁺ or 5 mM La²⁺) resulted in a transient increase in the slow-wave amplitude and subsequent prevention of pacemaker activity generation in bursting neurons. Application of these blockers together with endogenous neuropeptide initiating bursting activity generation, increased MP wave amplitude without prevention of bursting activity generation.
• 4.4. Replacement of all NaCl in normal Ringer's solution with isoosmotic CaCl₂, glucose or Tris-HCl produced a reversible block of bursting activity generation. Stationary current-voltage relation (CVR) of bursting neuron membrane has a region of negative resistance (NRR) and does not intersect the potential axis in threshold region for action potential (AP) generation in normal Ringer's solution. In Na-free solution stationary CVR is linear and intersects the potential axis near — 52 mV.
• 5.5. Novel potential- and time-dependent outward (E_rev = − 58 mV) current, I_B, activated by hyperpolarization was found in the bursting neuron membrane. Having achieved a maximal value, this current decayed with a time constant of about 1 sec. Hyperpolarization inactivated maximal conductance, g_B, responsible for I_B, and depolarization abolished inactivation of g_B.
• 6.6. Short-lasting (0.01 sec) hyperpolarization of the bursting neuron membrane by inward current pulse induced the development of prolonged hyperpolarization wave lasting up to 10 sec.
• 7.7. These results suggest that: (a) persistent bursting activity of RPal neuron in the snail Helix pomatia is not endogenous but is due to a constant activation of peptidergic synaptic inputs of these neurons; (b) Ca²⁺ ions do not play a pivotal role in the ionic mechanism of MP oscillations but play a determining role in the process of secretion of a peptide initiating bursting activity by the interneuron presynaptic terminal; (c) depolarizing phase of the MP wave is due to specific properties of stationary CVR and hyperpolarization phase is due to regenerative properties of hyperpolarization-activated outward current I_B. The minimal mathematical version of MP oscillations based on the experimental data is presented.

     

Reliability of spike and burst firing in thalamocortical relay cells

The reliability and precision of the timing of spikes in a spike train is an important aspect of neuronal coding. We investigated reliability in thalamocortical relay (TCR) cells in the acute slice and also in a Morris-Lecar model with several extensions. A frozen Gaussian noise current, superimposed on a DC current, was injected into the TCR cell soma. The neuron responded with spike trains that showed trial-to-trial variability, due to amongst others slow changes in its internal state and the experimental setup. The DC current allowed to bring the neuron in different states, characterized by a well defined membrane voltage (between ?80 and ?50 mV) and by a specific firing regime that on depolarization gradually shifted from a predominantly bursting regime to a tonic spiking regime. The filtered frozen white noise generated a spike pattern output with a broad spike interval distribution. The coincidence factor and the Hunter and Milton measure were used as reliability measures of the output spike train. In the experimental TCR cell as well as the Morris-Lecar model cell the reliability depends on the shape (steepness) of the current input versus spike frequency output curve. The model also allowed to study the contribution of three relevant ionic membrane currents to reliability: a T-type calcium current, a cation selective h-current and a calcium dependent potassium current in order to allow bursting, investigate the consequences of a more complex current-frequency relation and produce realistic firing rates. The reliability of the output of the TCR cell increases with depolarization. In hyperpolarized states bursts are more reliable than single spikes. The analytically derived relations were capable to predict several of the experimentally recorded spike features.     

Inhibition of slow TTX-insensitive inward current by the anticonvulsant carbamazepine in an identified neuron of Lymnaea stagnalis

1. Pentylenetetrazol (PTZ), induces tonic depolarization and bursting activity in an identified neuron, B1, of Lymnaea stagnalis. This is due in part to activation of a slow, tetrodotoxin-insensitive inward sodium current.2. Carbamazepine (CBZ) reversed the effect of PTZ on both membrane potential and inward current, after a delay of up to 5 min. CBZ alone had no effect on voltage or current responses.3. These results suggest that CBZ blocks the slow sodium current, possibly via a decrease in intracellularly stored calcium ions.     

A comparative analysis of multi-conductance neuronal models <Emphasis Type="Italic">in silico</Emphasis>

We demonstrate that a previously presented flexible silicon–neuron architecture can implement three disparate conductance-based neuron models with both fast and slow dynamics. By exploiting the real-time nature of this physical implementation, we mapped the model dynamics across a large region of parameter space. We also found that two of these dynamically different models represent points in a contiguous bursting space that spans between the two models. By systematically varying the model parameters, we also found that multiple, diverse trajectories in parameter space connected the two canonical bursting points. In addition, we found that the combination of parameter values keeps the neuron in the bursting region. These findings demonstrate the usefulness of the silicon–neuron architecture as a neural-modeling tool and illustrate its versatility as a platform for a multi-behavioral neuron that resembles its living analog.     

A unified model for two modes of bursting in GnRH neurons

Gonadotropin-releasing hormone (GnRH) neurons exhibit at least two intrinsic modes of action potential burst firing, referred to as parabolic and irregular bursting. Parabolic bursting is characterized by a slow wave in membrane potential that can underlie periodic clusters of action potentials with increased interspike interval at the beginning and at the end of each cluster. Irregular bursting is characterized by clusters of action potentials that are separated by varying durations of interburst intervals and a relatively stable baseline potential. Based on recent studies of isolated ionic currents, a stochastic Hodgkin-Huxley (HH)-like model for the GnRH neuron is developed to reproduce each mode of burst firing with an appropriate set of conductances. Model outcomes for bursting are in agreement with the experimental recordings in terms of interburst interval, interspike interval, active phase duration, and other quantitative properties specific to each mode of bursting. The model also shows similar outcomes in membrane potential to those seen experimentally when tetrodotoxin (TTX) is used to block action potentials during bursting, and when estradiol transitions cells exhibiting slow oscillations to irregular bursting mode in vitro. Based on the parameter values used to reproduce each mode of bursting, the model suggests that GnRH neurons can switch between the two through changes in the maximum conductance of certain ionic currents, notably the slow inward Ca²⁺ current I _s, and the Ca²⁺ -activated K⁺ current I _KCa. Bifurcation analysis of the model shows that both modes of bursting are similar from a dynamical systems perspective despite differences in burst characteristics.     

Effect of cadmium ions on bursting electrical activity of an identified snail neuron

The effect of cadmium ions, a specific blocker of the inward calcium current in molluscan neurons, on electrical activity of identified neuron RPal ofHelix pomatia was studied. Cadmium ions in a concentration of 1 mM were shown to block bursting activity of the neuron completely. The membrane potential increased under these circumstances to about ?65 mV. After rinsing out the cadmium ions electrical activity in the neuron was fully restored. If a modulating factor (a peptide fraction obtained from the water-soluble part of snail brain homogenate) was added to the solution containing cadmium ions, however, not only was bursting activity not blocked, but it was actually intensified. Addition of modulating factor to the solution after blocking induced by cadmium ions led to the reappearance of bursting activity if not more than a few tens of seconds had elapsed after blocking developed. As the time after the beginning of blocking increased, addition of the modulating factor became less effective and caused only rhythmic activity to develop. It was concluded from the results of these experiments that bursting activity of neuron RPal is not endogenous but is induced in it by a modulating factor secreted by an unidentified peptidergic interneuron. Calcium ions do not play an essential role in the generation of slow depolarization waves in the neuron under these circumstances but they are essential for secretion of the modulating factor.     

Modulation of electrical activity of neuron RPa2 ofHelix pomatia

Neuron RPa2 ofHelix pomatia can generate rhythmic (beating) or periodic (bursting) activity. A spontaneous switch from beating to bursting activity takes place in the course of tens of minutes. Similar changes in electrical activity can be induced by the addition of the water-soluble fraction obtained from a homogenate of snail ganglia to the experimental chamber. Artificial polarization of the membrane of neuron RPa2 by asteady inward current leads to an increase in the duration of intervals between bursts and to a decrease in the number of action potentials in the burst. With an increase in amplitude of the polarizing current, action potential generation ceases completely, but generation of waves of membrane potential persists. If the voltage on the neuron membrane is clamped, periodic fluctuations of membrane current disappear. It is suggested that action potential generation by neurons RPa2 is determined by the properties of the potential-dependent conductance of its membrane, i.e., that it is endogenous in origin and can be regulated by compounds acting on the membrane. These compounds, secreted by other neurons, resemble neurotransmitters or neurohormones.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 4, pp. 406–412, July–August, 1981.