Temporal generalization accounts for response resurgence in the peak procedure

The peak interval (PI) procedure is commonly used to evaluate animals' ability to produce timed intervals. It consists of presenting fixed interval (FI) schedules in which some of the trials are replaced by extended non-reinforced trials. Responding will often resume (resurge) at the end of the non-reinforced trials unless precautions are taken to prevent it. Response resurgence was replicated in rats and pigeons. Variation of the durations of the FI and the non-reinforced probe trials showed it to be dependent on the time when reinforcement is expected. Timing of both the normal time to reinforcement, and the subsequent time to reinforcement during the probe trials followed Weber's law. A quantitative model of resurgence is described, suggesting how animals respond to the signaling properties of reinforcement omission. Model results were simulated using a stochastic binary counter.     

On a generalization of a result of W. G. Cochran

A relationship due to W.G. Cochran showing the effect on leastsquares regression coefficients of marginalizing over or conditioningon an explanatory variable is generalized to quantile regressioncoefficients. The condition under which conditioning does notinduce interaction or effect reversal is shown. Examples aregiven. The discussion is simplest when all variables are continuous;the extension to discrete variables is outlined.     

Hallucinogens as a discriminative stimuli: generalization of DOM to a 5-methoxy-N, N-dimethyltryptamine stimulus.

Hallucinogens (psychotomimetic agents) are capable of producing various discriminative stimuli for animals. Serotonergic involvement has been implicated as playing a role in the behavioral effects elicited by, for example, mescaline and DOM. Because certain tryptamine analogs possess high serotonin (5-HT) receptor binding affinities, it was of interest to examine one of the more potent agents. Employing a standard operant test chamber, six rats were trained to respond under a variable-interval 15-second schedule of sweetened-milk reinforcement. 5-Methoxy-N, N-dimethyltryptamine (5-OMe DMT), which possesses a 5-HT receptor affinity much higher than that of mescaline, but nearly equivalent to that of DOM, was found to serve as a discriminative stimulus. Furthermore, the 5-OMe DMT stimulus could be attenuated by the 5-HT antagonist BC-105. The 5-OMe DMT stimulus generalized with DOM suggesting that these two hallucinogens produce qualitatively similar interoceptive cues in rats.     

The principle of interval constraints: a generalization of the symmetric Dirichlet distribution.

A structure for representing problems in decision analysis and in expert systems, which reason under uncertainty, is the influence diagram or causal network. A causal network consists of an underlying joint probability distribution and a directed acyclic graph in which a propositional variable that represents a marginal distribution is stored at each vertex in the graph. This paper is concerned with two of the problems in applications that use causal networks. The first problem is the determination of the conditional probabilities of the values of remaining propositional variables in the network given that certain variables are instantiated for particular values. This is called probability propagation. The second problem is the determination of the most probable, second most probable, third most probable, and so on sets of values of a particular set of variables (called the explanation set) given that certain variables are instantiated for particular values. This problem is called abductive inference. There exists a class of causal networks in which each variable has only two parents, for which the time is required, by any known method, for probability propagation is exponential relative to the number of vertices in the network. The determination of a new method that would be efficient for all causal networks appears unlikely, because probability propagation has been shown to be #P-complete. In many medical applications, networks are often large and not sparsely connected. Therefore a method for the exact determination of probability values appears unlikely for such applications, and the development of approximation methods seems to be the best solution. The current approximation methods obtain interval bounds for the probability values. When such intervals are obtained, it is not possible in general to rank the alternatives. In this paper, a method is developed for obtaining expected values for the point probabilities from interval constraints on the probabilities. The method is based on an application of the principle of indifference to the probability values themselves. The distributions obtained with the principle of indifference are a generalization of the symmetric Dirichlet distribution in which prior ignorance is assumed.     

Neural-space generalization of a topological transformation

An investigation is performed to assess the generalization capability found in neural network paradigms to approximate a 2-dimensional coordinate (topological) transformation. A developed strategy uses the example to give a physical meaning to what is meant by generalization. The example shows how to use a neural network paradigm to generalize a two-degree of freedom topological transformation from cartesian end-point coordinates to corresponding joint angle coordinates based only on examples of the mapping. The importance of this example is that it provides a clear understanding of how and what a neural network is actually communications and brings a theoretical idea to a useful understanding. When examples characterize the topology, a collective generalization property begins to emerge and the network learns the topology. If the network is presented with additional examples of the transformation, the network can generate the corresponding joint angles to any unseen position, that is, by generalization. It is also significant that the network's generalization property emerges from the network based on very few training examples! Further, the networks power exists with very few neurons. Results suggest the use of the paradigm's generalization capability to provide solutions to unknown or intractable algorithms for applications.     

A generalization of Pielou's index of non-randomness.

Pielou's index of non-randomness a measuring the distribution of point spatial patterns on a plane generalizes to an index in n-dimensional Euclidean space Eⁿ. This defines an index of non-randomness measuring the extent of regularity, randomness, or aggregation in distributions of point spatial patterns in Eⁿ.     

Frontal electromyographic feedback. Stress attenuation and generalization.

This study evaluated the effects of one session of frontal electromyographic (EMG) feedback on (1) frontal EMG, (2) frontal EMG response to stress, (3) cardiovascular variables, and (4) cardiovascular responses to stress. Eighteen male and female undergraduate volunteers received either frontal EMG feedback or a relaxation instructions control procedure and were then exposed to a fear stimulus (visualization of a feared situation) and a post-stress adaptation period while several cardiovascular measures were monitored. In comparison to the control group, frontal EMG feedback significantly reduced resting levels of frontal EMG and frontal EMG response to stress but had no significant effect on cardiovascular measures. The results of this study suggest that one session of frontal EMG feedback may attenuate response to stress but, within the paradigm utilized, may be confined to the specific muscle groups monitored. Additional areas of needed research were noted including individual differences in generalization, the effects of EMG feedback from multiple sites sequentially and concomitantly, and the generalized effects from symptom-specific sites.     

Clinical assay of the human erythrocyte lactate transporter. I. Principles, procedure, and validation

A clinically applicable method for the assay of lactate efflux from human red cells has been developed and described in detail. It requires only small volumes of blood and routine chemicals, and evaluates the process under physiological conditions and direction of lactate loading and transport. The decline of red cell lactate level fit a first order decay curve reasonably well, and better than the fit to zero order or second order plots. Bias is controlled by the use of least-squares curve fitting for all assays, and constraints on the elimination of outlier points. The assay shows a variety of inhibitor effects that may be considered typical for this transporter: potent inhibition by p-hydroxymercuribenzoate, but not by other types of sulfhydryl reagents; marked inhibition by phloretin, quercitin, and 1-fluoro-2,4-dinitrobenzene; lack of inhibition by the amine-reactive agents that block the chloride/carbonate exchanger, DIDS and SITS; and reversible competitive inhibition by alpha-cyano-4-OH-cinnamic acid. Harmaline and N-I-succinimide also produced effective inhibition. The assay also demonstrated transacceleration of L-lactate efflux in the presence of external additions of D-lactate, glycollate, iodoacetate, fluoropyruvate, and bromopyruvate, which are substituted monocarboxylates like lactate, but not by iodoacetamide or L-alanine. Such activation is a manifestation of a macromolecular carrier in operation, and cannot be explained by a pore or channel. These findings satisfy all reasonable criteria for a satisfactory and sensitive lactate transporter assay, which should be adequate to evaluate volunteers and patients for the normal range of this carrier, and to seek possible deficient states.     

Direct determination of the properties of peptide transport systems in Escherichia coli, using a fluorescent-labeling procedure.

A direct study of peptide uptake by Escherichia coli was made using a fluorescent procedure. After incubation with the bacteria, peptides remaining in the medium were dansylated, separated chromatographically, and quantitated from their fluorescent intensities and/or from their incorporated radioactivity when tritiated dansyl derivatives were prepared. Peptide uptake was apparently not regulated and proceeded continuously until complete, with the absorbed peptides undergoing rapid intracellular hydrolysis and the excess amino acid residues leaving the cell. Thus, peptide uptake and amino acid exodus occur concurrently. However, peptidase-resistant substrates, e.g. triornithine and glycylsarcosine, which can be similarly estimated in cell extracts, were accumulated about 1,000-fold. The influence of amino acid composition and chain length on rates of transport was assessed. Different strains of E. coli showed variability in their rates of di- and oligopeptide transport. With respect to energy coupling, both the di- and oligopeptide permeases behaved like shock-sensitive transport systems.     

Optimizing the northern blot procedure.

We describe methods for preparing formaldehyde-agarose gels for use in Northern blotting which yield consistent high quality results. Using these methods, we tested seven different commercially available membranes in Northern blots. Each membrane was handled as specified by the manufacturer in a course of hybridization, stripping and rehybridization. Filter background was low in all cases, but the intensity of the signal generated by specific hybridization varied markedly between filters after both the first and second hybridization.     

Toward a generalization of the Clough-Lutz-Jirgensons effect: Chiral organic acids with alkyl, hydroxyl, and halogen substituents

The optical rotation of natural amino acids becomes more positive when the medium is changed from approximately neutral to strongly acidic (Clough-Lutz-Jirgensons (CLJ) effect). In this work, it is shown by time-dependent density functional computations that the effect can be generalized to other α-substituted chiral carboxylic acids. The physical origin of the generalized CLJ effect is similar to that in amino acids, linking the absolute configuration directly to the sign of CLJ. For conformationally flexible molecules with small magnitudes of the optical rotation, the presence of a CLJ effect might aid the assignment of absolute configurations based on comparing experimental data with computed chiroptical responses.     

Automated weighing procedure for toxicological studies on small animals, using a minicomputer.

A compact system was designed for weighing procedures in toxicological studies on small animals that integrated 4 basic functions: data acquistion, record keeping, statistical analysis, and report preparation. An electric balance, a minicomputer, and a typewriter were incorporated into the system. Elimination of clerical work and accelerated flow of information between planning, operation, and evaluation of experiments were found to be the main advantages.