When behavior suggests that the value of a reinforcer depends inversely on the value of the events that precede or follow it, the behavior has been described as a "contrast" effect. Three major forms of contrast have been studied: "incentive contrast," in which a downward (or upward) shift in the magnitude of reinforcement produces a relatively…

Mice from replicate lines, selectively bred based on high daily wheel-running rates, run more total revolutions and at higher average speeds than do mice from nonselected control lines. Based on this difference it was assumed that selected mice would find the opportunity to run in a wheel a more efficacious consequence. To assess this assumption…

Exposure to an enriched environment (EE) has been shown to induce cortical plasticity. Considerable amount of research is focused on the effects of EE in the hippocampus; however, effects of EE on other brain regions and the mechanisms involved are not well known. To investigate this, we induced cortical plasticity by placing mice in an EE for one…

Relating storage of specific information to a particular neuromorphological change is difficult because behavioral performance factors are not readily disambiguated from underlying cognitive processes. This issue is addressed here by demonstrating robust reorganization of the hippocampal mossy fiber terminal field (MFTF) when adult rats learn the…

Previous reports have shown that overexpression of the growth- and plasticity-associated protein GAP-43 improves memory. However, the relation between the levels of this protein to memory enhancement remains unknown. Here, we studied this issue in transgenic mice (G-Phos) overexpressing native, chick GAP-43. These G-Phos mice could be divided at…

Stimulation paradigms that induce perforant path long-term potentiation (LTP) initiate phosphorylation of ERK1/2 and induce expression of a variety of immediate early genes (IEGs). These events are thought to be critical components of the mechanism for establishing the changes in synaptic efficacy that endure for hours or longer. Here we show that…

This document describes a game that provides students with practice in learning vocabulary and concepts associated with wolves. Directions for play and play cards (four to a page) are included. (ASK)

The present article discusses the possibility that behavioral recovery following brain damage is not dependent on the functional reorganization of neural tissue but is rather the result of the continued normal operation of spared neural mechanisms. (Editor)

Rat received conditioning based upon a food unconditioned stimulus and then received manipulations designed to reduce the value of that food. The effects of these manipulations were assessed during extinction tests of the conditioned stimuli. (Editor/RK)

Three experiments are reported in which rats first received 50 escapable or inescapable signaled-shock trials. The results of the experiments are discussed in terms of a learned active-inactive predisposition to respond. (Editor/RK)

This article demonstrated that equations derived from Herrnstein's matching law can make quantitative predictions for many of the effects David Premack has studied on the relative nature of reinforcement. (Author/RK)

Progress is now being made toward ascertaining the specific effects of rearing conditions on brain and behavior, the properties of the environment that contribute to these effects, and the developmental periods in which brain tissue is most sensitive to environmental modification. (Author/RH)

A Klamath Indian story about why the rabbit is timid. (AH)