A synchronization-desynchronization code for natural communication signals

Synchronous spiking of neural populations is hypothesized to play important computational roles in forming neural assemblies and solving the binding problem. Although the opposite phenomenon of desynchronization is well known from EEG studies, it is largely neglected on the neuronal level. We here provide an example of in vivo recordings from weakly electric fish demonstrating that, depending on the social context, different types of natural communication signals elicit transient desynchronization as well as synchronization of the electroreceptor population without changing the mean firing rate. We conclude that, in general, both positive and negative changes in the degree of synchrony can be the relevant signals for neural information processing.     

A systems approach to animal communication

Why animal communication displays are so complex and how they have evolved are active foci of research with a long and rich history. Progress towards an evolutionary analysis of signal complexity, however, has been constrained by a lack of hypotheses to explain similarities and/or differences in signalling systems across taxa. To address this, we advocate incorporating a systems approach into studies of animal communication—an approach that includes comprehensive experimental designs and data collection in combination with the implementation of systems concepts and tools. A systems approach evaluates overall display architecture, including how components interact to alter function, and how function varies in different states of the system. We provide a brief overview of the current state of the field, including a focus on select studies that highlight the dynamic nature of animal signalling. We then introduce core concepts from systems biology (redundancy, degeneracy, pluripotentiality, and modularity) and discuss their relationships with system properties (e.g. robustness, flexibility, evolvability). We translate systems concepts into an animal communication framework and accentuate their utility through a case study. Finally, we demonstrate how consideration of the system-level organization of animal communication poses new practical research questions that will aid our understanding of how and why animal displays are so complex.     

A collaborative study of a method for enumeration of probiotic enterococci in animal feed

AIMS: Validation of an enumeration method to be used as an official control method in the framework of Council Directive 70/524/EEC for probiotic enterococci used as feed additives. METHODS AND RESULTS: Twenty laboratories in 12 European countries carried out a collaborative study. A plate count method using bile esculin azide (BEA) agar was used. Precision data in terms of repeatability (r) and reproducibility (R) of the method using different feeding stuffs and three inoculation levels were determined. Enterococci were present in the samples as a single component or in mixtures with other probiotic feed additives. The enumeration of enterococci on BEA agar showed a relative standard deviation (RSD)r of 1.5-3.6% and an RSD(R) between 2.9 and 7.4%. BEA agar was selective for enterococci in the presence of other probiotic micro-organisms such as pediococci, lactobacilli and yeast. CONCLUSIONS: For routine analysis of viable enterococci concentrations in feeding stuffs, the use of BEA is recommended. This methodology is not applicable for mineral feeds. SIGNIFICANCE AND IMPACT OF THE STUDY: An official control method for enumeration of authorized probiotic enterococci in feeding stuffs was validated. The results are intended for consideration for adoption as CEN and ISO standards.     

A method for identifying sounds used in the classification of alarm calls

In this study, we present a methodology that identifies acoustic units in Gunnison's prairie dog alarm calls and then uses those units to classify the alarm calls and bouts according to the species of predator that was present when the calls were vocalized. While traditional methods measure specific acoustic parameters in order to describe a vocalization, our method uses the variation in the internal structure of a vocalization to define possible information structures. Using a simple representation similar to that used in human speech to identify vowel sounds, a software system was developed that uses this representation to recognize acoustic units in prairie dog alarm calls. These acoustic units are then used to classify alarm calls and their associated bouts according to the species of predator that was present when the alarm calls were vocalized. Identification of bouts with up to 100% accuracy was obtained. This work represents a first step toward revealing the details of how information is encoded in a complex nonhuman communication system. Furthermore, the techniques discussed in this paper are not restricted to a database of prairie dog alarm calls. They could be applied to any animal whose vocalizations include multiple simultaneous frequencies.     

A generalized linear model for estimating spectrotemporal receptive fields from responses to natural sounds

In the auditory system, the stimulus-response properties of single neurons are often described in terms of the spectrotemporal receptive field (STRF), a linear kernel relating the spectrogram of the sound stimulus to the instantaneous firing rate of the neuron. Several algorithms have been used to estimate STRFs from responses to natural stimuli; these algorithms differ in their functional models, cost functions, and regularization methods. Here, we characterize the stimulus-response function of auditory neurons using a generalized linear model (GLM). In this model, each cell's input is described by: 1) a stimulus filter (STRF); and 2) a post-spike filter, which captures dependencies on the neuron's spiking history. The output of the model is given by a series of spike trains rather than instantaneous firing rate, allowing the prediction of spike train responses to novel stimuli. We fit the model by maximum penalized likelihood to the spiking activity of zebra finch auditory midbrain neurons in response to conspecific vocalizations (songs) and modulation limited (ml) noise. We compare this model to normalized reverse correlation (NRC), the traditional method for STRF estimation, in terms of predictive power and the basic tuning properties of the estimated STRFs. We find that a GLM with a sparse prior predicts novel responses to both stimulus classes significantly better than NRC. Importantly, we find that STRFs from the two models derived from the same responses can differ substantially and that GLM STRFs are more consistent between stimulus classes than NRC STRFs. These results suggest that a GLM with a sparse prior provides a more accurate characterization of spectrotemporal tuning than does the NRC method when responses to complex sounds are studied in these neurons.     

A novel method to derive amniotic fluid stem cells for therapeutic purposes

Background  

Human amniotic fluid stem (hAFS) cells have become an attractive stem cell source for medical therapy due to both their ability to propagate as stem cells and the lack of ethical debate that comes with the use of embryonic stem cells. Although techniques to derive stem cells from amniotic fluid are available, the techniques have limitations for clinical uses, including a requirement of long periods of time for stem cell production, population heterogeneity and xeno-contamination from using animal antibody-coated magnetic beads. Herein we describe a novel isolation method that fits for hAFS derivation for cell-based therapy.     

A more cost-effective method of preoperative computerized imaging

Stimulated by the explosive expansion of the computerized desk top publishing industry during the past few years, microcomputer hardware and software are evolving at a staggering rate. Memory is rapidly increasing, and prices are declining. I have found that with the hardware and software described in this paper, I was able to obtain, in a much more cost-effective manner, as useful preoperative information for my practice as I could obtain with more expensive "turnkey" (only one use) computerized imaging systems. This type of microcomputer, of course, is not limited to just the imaging system, but can be used for a variety of other programs as well, such as word processing, slide labeling and production, spreadsheet functions, billing and filing, and numerous business and other applications. The ease of use with readily available 35-mm slides of my patients has greatly enhanced the appeal of this system. Computerized imaging, when used as an educational tool, can be very helpful in preoperative planning, resident teaching, and for illustration and discussion of a patient's proposed surgery. The electronic imaging disclaimer compiled by the American Society of Plastic and Reconstructive Surgeons has been extremely helpful in clarifying the limits of computerized imaging and reducing any false expectations that my patients might have. All of us are experiencing the dawn of a very exciting evolution.     

Colpohistologic correlations. A computerized study

Data from 300 colposcopic cases were computerized to study the correlations between the colposcopic observations and the histologic and other data. Colposcopy was shown to be most useful in women under 35 years of age. Use of oral contraceptives (the Pill) seemed to relate to a higher level of successful colposcopic visualization and may even prevent the need for conization, based on a higher incidence of negative endocervical curettages. Although 14.5% of the cases were colposcopically undergraded and 17% overgraded when compared to the histopathology, the histologic predictability of the colposcopic observation of white epithelium and vascular changes (punctation and mosaicism) was excellent. Colposcopy remains an essential technique in the appraisal and management of cervical intraepithelial neoplasia.     

A stochastic catch-effort method for estimating animal abundance

A method for estimating the size of a heavily exploited animal population from catch data and relative-harvest-effort data is presented. The method assumes a competing-risk model of adult deaths and captures that is similar to the hazard-regression model of Cox (1972, Journal of the Royal Statistical Society, Series B 34, 187-220). This model avoids making any assumptions about birth rates or juvenile mortality rates, and allows the user to incorporate an arbitrary number of time-dependent covariates into the natural and catch hazard functions. Estimates of the population's size, together with asymptotic error bounds and predictions of subsequent catches, are derived from maximum likelihood estimates of the parameters of the model. A simulation study is presented which indicates that this method is far more accurate than previously available catch-effort techniques. The method is illustrated with some fisheries data. A series of models is fitted to the data with the objective of improving the goodness of fit while maintaining biologic plausibility of the model. In this example a 68% reduction in the mean sum of squares for error is obtained and the accuracy of future catch predictions is greatly improved. This method is particularly appropriate for estimating the sizes of commercially exploited aquatic populations whose sizes are too large to make mark-recapture techniques feasible, and which are not amenable to line-transect techniques.     

A natural communication system on genome evolution

正The central dogma of molecular biology describes the flow of genetic information from DNA via RNA to protein and duplication from ancestral to descendent DNA(Crick,1958).However,the genetic information could not be quantified and mathematically modeled.So it differs from the"information"formulated by Shannon and used in information and coding theories(Shannon,1949).Although physicists have suggested that life absorbs negative entropy(or information)from the environment(Schrodinger et al.,1944),no physical     

Observation of tool use and modification for apparent hygiene purposes in a mandrill

Tool making or modification to produce a tool of apparent improved functionality has rarely been reported in monkeys, especially when tools are used outside the context of food acquisition. We report on an observation of selection, modification and use of splinters for hygiene purposes in a male mandrill. The zoo-housed animal was video-recorded breaking splinters in sequence to use them underneath his toenails. This record brings forward new evidence that the ability to use and modify tools is not limited to apes and some New World monkeys but is also apparent in Old Word monkeys.     

Economic models of animal communication

Many models of animal signal evolution fail to incorporate an explicit strategy for receivers prior to the evolution of signals. When reasonable assumptions are made for such strategies, we have shown that there is a minimal accuracy of signal coding that is required before receivers should attend to signals (Bradbury & Vehrencamp 1998, Principles of Animal Communication). Depending upon the relative payoffs of correct and incorrect decisions by receivers, this minimal accuracy can be quite high. Here we use this result to explain why so many signals appear to be traits that provided useful information to receivers before becoming ritualized into signals. Our model also supports one prediction of sensory drive models: that latent preferences may selectively favour some signal precursors over others. However, it imposes a serious constraint on sensory drive by requiring that there be sufficient benefits to a receiver to compensate for the costs of disrupting the optimal receiver strategy used before exploitation. Finally, we discuss the overlap between signal honesty and accuracy and show how senders that completely disagree with receivers about appropriate receiver decisions may still benefit by providing moderately honest and accurate signals. Copyright 2000 The Association for the Study of Animal Behaviour.     

A new approach to modification of natural adsorbent for heavy metal adsorption

This paper describes modification of a natural adsorbent with Fenton reagent and determines the removal of Cd(II) ions from aqueous solution. Changes of the surface properties of adsorbent materials were determined by the FT-IR analysis after the modification of pine bark. The effect of Fe2+/H2O2 ratio, ORP, pH, and contact time were determined. Different adsorption isotherms were also obtained using concentrations of Cd(II) ions ranging from 0.1 to 100 mg L(-1). The adsorption process follows pseudo-first-order reaction kinetics and follows the Langmuir adsorption isotherm. The paper discusses thermodynamic parameters, including changes in Gibbs free energy, entropy, and enthalpy, for the adsorption of Cd(II) on modified bark, and revealed that the adsorption process was spontaneous and exothermic under natural conditions. The maximum removal efficiency obtained was 97% at pH 7 and with a 90-min contact time (for 35 mg L(-1) initial concentration and a 2.5 g L(-1) solid-to-liquid ratio).