Familiarity recognition and recollection: A neural network model

The capacities of a specially designed neural network for familiarity recognition and recollection have been compared. Recognition is based on calculating “image familiarity” as a modified Hopfield energy function in which the value of the inner sum is replaced by the sign of this value. This replacement makes the calculation of familiarity compatible with the basic dynamic equations of the Hopfield network and is in fact reduced to calculating the scalar product of the neuronet state vectors at two successive time steps.     

Evolution of life cycle: models based on optimization of energy allocation

A brief history of optimization approach in modern evolutionary ecology is given and author's own results concerning life history evolution are considered in more details. The problem of evolutionary optimization is formulated in terms of mathematical theory of optimal control as a problem of optimal sharing of organism's resources between growth, reproduction, repair, and maintenance. The Malthusian parameter is used as optimality criterion. This approach allows, in particular, to give evolutionary ecological explanations for some well known empirical facts such as attenuation of growth with age (law of Bertalanffi), acceleration of ageing with age (law of Gompertz), human sexual dimorphism in mean lifespan, age and size of maturity.     

Worldwide variation in life-span sexual dimorphism and sex-specific environmental mortality rates

In all human populations mean life span of women generally exceeds that of men, but the extent of this sexual dimorphism varies across different regions of the world. Our purpose here is to study, using global demographic and environmental data, the general tendency of this variation and local deviations from it. We used data on male and female life history traits and environmental conditions for 227 countries and autonomous territories; for each country or territory the life-span dimorphism was defined as the difference between mean life spans of women and men. The general tendency is an increase of life-span dimorphism with increasing average male-female life span; this tendency can be explained using a demographic model based on the Makeham-Gompertz equation. Roughly, the life-span dimorphism increases with the average life span because of an increase in the duration of expressing sex- and age-dependent mortality described by the second (exponential) term of the Makeham-Gompertz equation. Thus we investigated the differences in male and female environmental mortality described by the first term of the Makeham-Gompertz equation fitted to the data. The general pattern that resulted was an increase in male mortality at the highest and lowest latitudes. One plausible explanation is that specific factors tied to extreme latitudes influence males more strongly than females. In particular, alcohol consumption increases with increasing latitude and, on the contrary, infection pressures increase with decreasing latitude. This finding agrees with other observations, such as an increase in male mortality excess in Europe and Christian countries and an increase in female mortality excess in Asia and Muslim countries. An increase in the excess of female mortality may also be due to increased maternal mortality caused by an increase in fertility. However, this relation is not linear: In regions with the highest fertility (e.g., in Africa) the excess of female mortality is smaller than in regions with relatively lower fertility (e.g., in Asia). A possible explanation of this phenomenon is an evolutionary adaptation of women to the pressures of extremely high fertility by means of some reduction of their maternal mortality.     

Memory blocking: Facts,problems, and models

The tip-of-the-tongue state, or memory blocking, is considered with regard to the feasibility of its neural network modeling. The results of psycholinguistic and neurobiological studies on memory blocking are reviewed, and basic problems that need be solved to comprehend this phenomenon are formulated. One such point is the dramatic discrepancy between the subjective assurance that an image is familiar and the inability to recollect it fully. To explain this discrepancy, we propose a biologically plausible neural network model of recognition, demonstrating cardinal superiority in the capacity of image recognition over its recollection.     

Larvae of related Diptera species from thermally contrasting habitats exhibit continuous up-regulation of heat shock proteins and high thermotolerance

A population of Stratiomys japonica, a species belonging to the family Stratiomyidae (Diptera), common name ‘soldier flies’, occurs in a hot volcanic spring, which is apparently among the most inhospitable environments for animals because of chemical and thermal conditions. Larvae of this species, which naturally often experience temperatures more than 40 °C, have constitutively high concentrations of the normally inducible heat-shock protein Hsp70, but very low level of corresponding mRNA. Larvae of three other species of the same family, Stratiomys singularior, Nemotelus bipunctatus and Oxycera pardalina, are confined to different type semi-aquatic habitats with contrasting thermal regime. However, all of them shared the same pattern of Hsp70 expression. Interestingly, heat-shock treatment of S. japonica larvae activates heat-shock factor and significantly induces Hsp70 synthesis, whereas larvae of O. pardalina, a species from constant cold environment, produce significantly less Hsp70 in response to heat shock. Adults of the four species also exhibit lower, but detectable levels of Hsp70 without heat shock. Larvae of all species studied have very high tolerance to temperature stress in comparison with other Diptera species investigated, probably representing an inherent adaptive feature of all Stratiomyidae enabling successful colonization of highly variable and extreme habitats.     

Molecular phylogeny of fungus gnats (Diptera: Mycetophilidae) revisited: position of Manotinae,Metanepsiini, and other enigmatic taxa as inferred from multigene analysis

The phylogeny of selected genera from four subfamilies of fungus gnats (Diptera: Mycetophilidae) – Manotinae, Leiinae, Sciophilinae and Gnoristinae (including Metanepsiini) – is reconstructed based on the combined analysis of five mitochondrial (12S, 16S, COI, COII, cytB) and two nuclear (28S, ITS2) gene markers. Results of the different analyses all support Manotinae as a monophyletic group, with Leiinae as the sister group. Allactoneura DeMeijere is nested in the monophyletic and strongly supported clade of Leiinae. The tribe Metanepsiini is revealed as paraphyletic and the genera Metanepsia Edwards and Chalastonepsia Søli do not appear to be closely related. The genera Docosia Winnertz, Ectrepesthoneura Enderlein, Novakia Strobl and Syntemna Winnertz were placed with a group of genera included traditionally in the Gnoristinae. The monophyly of Dziedzickia Johannsen and Phthinia Winnertz is not supported. The genera of Sciophilinae (excluding Paratinia Mik but including Eudicrana Loew) form a monophyletic group in the Bayesian model.     

A genomic walking method for screening sequence length polymorphism

We adapted a recently developed nonrestrictional, nonligational genome walking method, Universal Fast Walking (UFW), for detection of length polymorphism in the proximal promoter region of genes. We demonstrate its efficacy at discovering naturally occurring transposition into heat‐shock genes of wild Drosophila and show that it surmounts limitations of simple polymerase chain reaction (PCR) approaches. We further present modifications to the standard UFW protocol and provide some guidelines to improve specificity. Although the resultant banding pattern of a standard UFW can be regarded as a DNA fingerprint, many amplicons result from false priming and not real polymorphisms. We describe ways to distinguish between UFW amplicons and false priming products in a high‐throughput assay.