Computer simulation of rhythmic oscillations in neuron pools

This paper describes computer simulation of 100 artificial neurons interconnected in mutually exciting random pools. The individual neuromimes include accommodation according to an extended version of Hill's model and adaptation according to an extended version of Kernell's model. The main finding is that the constituent cells of the pools tend to fire in coordinated bursts and that these bursts recur rhythmically. The rate of burst recurrence depends primarily on the time constant of recovery of the after-hyperpolarization conductance change although it may be slightly altered by the average level of random background activity. It does not seem possible to attribute the salient slow rhythm observed in the rat mesencephalic reticular formation to this mechanism, as matching the data requires absurdly large values of the conductance change recovery time constant.     

2 pools of mitochondria in a single mechanoreceptor neuron]

The microspectrofluorimetric technique was applied to measure the intracellular ratio of oxidized flavoproteins and NADH in isolated neuron preparation from the stretch receptor organ of the crayfish Astacus leptodactilus. Two pools of mitochondria were detected differing from each other in their functional activity in the single cell at the same time. The mitochondria of the pool are localized near the nucleus, those of the other one being placed along the cell membrane. Physiological treatments (stretch, calcium deficient media) produce different changes in the activity of mitochondria belonging to the different pools. It is suggested that these pools of mitochondria furnish with energy different functional mechanisms within the same cell.     

Firing statistics of inhibitory neuron with delayed feedback. II: Non-Markovian behavior

The instantaneous state of a neural network consists of both the degree of excitation of each neuron the network is composed of and positions of impulses in communication lines between the neurons. In neurophysiological experiments, the neuronal firing moments are registered, but not the state of communication lines. But future spiking moments depend essentially on the past positions of impulses in the lines. This suggests, that the sequence of intervals between firing moments (inter-spike intervals, ISIs) in the network could be non-Markovian.     

Some considerations on relational equilibria

A previous study (Bull. Math. Biophysics,31, 417–427, 1969) on the definitions of stability of equilibria in organismic sets determined byQ relations is continued. An attempt is made to bring this definition into a form as similar as possible to that used in physical systems determined byF-relations. With examples taken from physics, biology and sociology, it is shown that a definition of equilibria forQ-relational systems similar to the definitions used in physics can be obtained, provided the concept of stable or unstable structures of a system determined byQ-relations is considered in a probabilistic manner. This offers an illustration of “fuzzy categories,” a notion introduced by I. Bąianu and M. Marinescu (Bull. Math. Biophysics,30, 625–635, 1968), in their paper on organismic supercategories, which is designed to provide a mathematical formalism for Rashevsky's theory of Organismic Sets (Bull. Math. Biophysics,29, 389–393, 1967;30, 163–174, 1968;31, 159–198, 1969). A suggestion is made for a method of mapping the abstract discrete space ofQ-relations on a continuum of variables ofF-relations. Problems of polymorphism and metamorphosis, both in biological and social organisms, are discussed in the light of the theory.     

Some elementary considerations of neural models

The outputs of nervous systems (as expressed in motor activity) are viewed as mathematical transformations on the inputs which enter via the sensory nerves. Simple nerve-ganglion models are exhibited which theoretically account for the arithmetic computations necessary to expedite such transformations.     

Firing statistics of inhibitory neuron with delayed feedback. I. Output ISI probability density

Activity of inhibitory neuron with delayed feedback is considered in the framework of point stochastic processes. The neuron receives excitatory input impulses from a Poisson stream, and inhibitory impulses from the feedback line with a delay. We investigate here, how does the presence of inhibitory feedback affect the output firing statistics. Using binding neuron (BN) as a model, we derive analytically the exact expressions for the output interspike intervals (ISI) probability density, mean output ISI and coefficient of variation as functions of model's parameters for the case of threshold 2. Using the leaky integrate-and-fire (LIF) model, as well as the BN model with higher thresholds, these statistical quantities are found numerically. In contrast to the previously studied situation of no feedback, the ISI probability densities found here both for BN and LIF neuron become bimodal and have discontinuity of jump type. Nevertheless, the presence of inhibitory delayed feedback was not found to affect substantially the output ISI coefficient of variation. The ISI coefficient of variation found ranges between 0.5 and 1. It is concluded that introduction of delayed inhibitory feedback can radically change neuronal output firing statistics. This statistics is as well distinct from what was found previously (Vidybida and Kravchuk, 2009) by a similar method for excitatory neuron with delayed feedback.     

Some observations on the simple neuron circuit

A new point of view in the theory of neuron networks is here adumbrated in its relation to the simple circuit: it is shown how these methods enable us to extend considerably and unify previous results for this case in a much simpler way.     

Some considerations when comparing SABAP 1 with SABAP 2 data

Jouanin's Petrel Bulweria fallax mainly occurs in the western Indian Ocean. Prior to our study there were only two records from east of 82° E. We show that small numbers of Jouanin's Petrels are regular visitors to the eastern Indian Ocean, occurring to 15° N 90° E in the Bay of Bengal and 15° S 123° E off northern Australia. Although seasonal coverage is limited, they have been recorded east of 80° E from April–July and October–December, but not in February–March. Most sightings are from oceanic waters at least 20 km offshore where depths exceed 500 m.     

Some considerations on mathematical molecular biophysics

The possibility of a single molecule or of a few molecules controlling the basic metabolic reactions in a cell is discussed from the molecular-kinetic point of view. For such a control by a single molecule to be possible, it is necessary to assume a chain reaction, consisting of at least two steps.     

Taxonomy and phylogenetics: Some considerations

The relationships between taxonomy and phylogenetics are discussed. It is suggested that they are distinct biological subdisciplines and some consequences of this position are set out.     

Some order-disorder considerations in living systems

Order and disorder in biological systems are considered quantitatively in terms of information and entropy. After discussing the factors contributing to the information content of a living cell, a calculation is made of this parameter. The value for a typical bacterial cell is 4.6×10¹⁰ bits. This value is compared with an experimental value of the heat of growth and entropy production ofE. Coli. A discussion of methods of improving the calculation is also presented.     

Some considerations for optimization of desorption chromatography

The effect of isotherm parameters of a displacer on the efficiency of desorption Chromatography has been investigated numerically. A general nonlinear multicomponent rate equation model with Langmuir isotherm was used in this study. It was found that the best displacer in this kind of operation is usually not the one that is more strongly adsorbed than the adsorbates when the operation is to displace and concentrate the adsorbates from a saturated or partially saturated column and to minimize the amount of displacer used. The desorption Chromatography is different from the classical displacement development in both operational purpose and the requirement for the displacer. The desorption Chromatography in industrial practice was also analyzed and discussed for the case in which the displacer is introduced in either the same or the reverse flow direction after an incomplete frontal adsorption operation.     

Characteristic structures of serotonin neuron system

Summary Since 1982, the authors have carried out intensive immunohistochemical studies on the distribution of serotonin neurons in the central nervous system and have reported the distinctive structures of these nerve cells. In the present study, two characteristic findings are described with special regard to the histophysiological significance: (1) direct innervation of the cerebral arteries by central serotonin neurons and (2) the perineuronal ivylike serotonin plexus.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthdaySupported by grants from the Ministry of Education, Science and Culture of Japan (nos. 60440024, 61218015 and 61231026)