Consolidation of Long-Term Memory: Evidence and Alternatives.

Memory loss in retrograde amnesia has long been held to be larger for recent periods than for remote periods, a pattern usually referred to as the Ribot gradient. One explanation for this gradient is consolidation of long-term memories. Several computational models of such a process have shown how consolidation can explain characteristics of amnesia, but they have not elucidated how consolidation must be envisaged. Here findings are reviewed that shed light on how consolidation may be implemented in the brain. Moreover, consolidation is contrasted with alternative theories of the Ribot gradient. Consolidation theory, multiple trace theory, and semantization can all handle some findings well but not others. Conclusive evidence for or against consolidation thus remains to be found. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

No evidence for a Y chromosomal effect on alternative behavioral strategies in mice

This study takes the first step toward testing a Y chromosomal effect on both aggression and thermoregulatory nest-building behavior in mouse lines either bidirectionally selected for short (SAL) and long (LAL) attack latency or high (HIGH) and low (LOW) nest-building behavior. Using reciprocal crosses between SAL and LAL, and between HIGH and LOW, we found no indications for Y chromosomal effects on thermoregulatory nest-building behavior. As for aggression, we confirmed earlier studies on SAL and LAL, i.e., the origin of the Y chromosome influences attack latency, i.e., aggression. However, we did not find indications for a Y chromosomal effect on aggression in the HIGH and LOW lines. Since aggression and nest-building behavior have been shown to be characteristic parameters of two fundamentally different behavioral strategies, the present data underline the improbability of Y chromosomal genes underlying the genetic architecture of alternative behavioral strategies.     

Influencing factors for railroad-highway grade crossing accidents in Florida

Multiple regression was used to investigate the influence of physical factors on accident rates at 1,140 rail-highway grade crossings in Florida. Selection of the final model involved examination of residuals, transformation of variables. dummy variables and interaction terms. Variables in the final model were functions of average daily traffic, type of crossing protection, maximum train speed, trains per day. crossing speed limit, and number of lanes of traffic. Transformations were made to return estimates to the original scale of the data. Suggestions were made for improving the model and the data.     

Introduction to Numerical Analysis

A development of the mathematical structure of nested designs is presented using, for a general case, a four-stage nested design. For the casea where the variables at each stage are normally distributed, analytical results can be obtained. This is done for the unbalanced “staggered” and “inverted” designns. Empirical estimattas of variance for the non-normal case are obtained. These are compared with the analytical solutions. Also considered is the probability of negative variance estimates. It ia interesting to note that for these alternatives to balanced nested designs, one can decrease the probabilities of negative estimates of some variances at the cost of increasing them for others.     

On Beale's Measures of Non-linearity

Measures of non-linearity that have been developed by Beale (1960a), are designed to indicate when the degree of non-linearity in a non-linear estimation problem is small enough to justify using the usual linear model theory results as approximations. The validity and usefulness of the measures is examined by means of numerical examples. Explanations for the behaviour of the measures is offered and the results are discussed.     

Control of consolidation in neural networks: Avoiding runaway effects

Consolidation has been implemented in two ways: as straight rehearsal of patterns or as pseudorehearsal, in which pseudoitems are created by sampling attractors or input-output combinations from the network. Although both implementations have been investigated by several authors, few have explored how it is decided which pattern or pseudoitem is consolidated. Controlling consolidation is not trivial, as it is susceptible to a corruption. In runaway consolidation, one or two patterns monopolize all consolidation resources and come to dominate the entire network. Runaway consolidation is analysed, and three solutions are explored. Suppressing transmission in the connections in which consolidation takes place is shown to work best. Placing bounds on connections or unlearning attractors also alleviates runaway consolidation, though less effectively so.     

Further studies on the lysozyme-like activity of alpha-lactalbumin: development of alternative methods of assay

Earlier, a sensitive turbidimetric method was reported (H.A. McKenzie and F.H. White, Jr. Biochem. Int. 14, 347-356, 1987), with which evidence was found for weak lysozyme-like activity in alpha-lactalbumin (alpha-LA) against Micrococcus luteus. Alternative methods have been developed for the further study of trace cell-lytic activity, and the results are compared with those of the turbidimetric technique. These methods involve (1) determination of weight loss from a suspension of bacterial cells after exposure to the protein under investigation, and (2) viability studies on the exposed cells. In addition, exposed and control cells were subjected to microscopic examination. Results from all studies were consistent with lysis of cells by alpha-LA as well as by lysozyme. Activities of alpha-LA from the three methods of assay, expressed as ratios to those of lysozyme, were 2.2-5.2 x 10(-5) (mean = 3.6 x 10(-5). The methods were assessed with respect to sources of error characteristic of each and to protein dose requirements for a specified level of cell killing. The turbidimetric approach remains useful for measuring cell-lytic activities as described here. However, caution is urged in its general use.