Environmental enrichment modifies the PKA-dependence of hippocampal LTP and improves hippocampus-dependent memory

cAMP-dependent protein kinase (PKA) is critical for the expression of some forms of long-term potentiation (LTP) in area CA1 of the mouse hippocampus and for hippocampus-dependent memory. Exposure to spatially enriched environments can modify LTP and improve behavioral memory in rodents, but the molecular bases for the enhanced memory performance seen in enriched animals are undefined. We tested the hypothesis that exposure to a spatially enriched environment may alter the PKA dependence of hippocampal LTP. Hippocampal slices from enriched mice showed enhanced LTP following a single burst of 100-Hz stimulation in the Schaffer collateral pathway of area CA1. In slices from nonenriched mice, this single-burst form of LTP was less robust and was unaffected by Rp-cAMPS, an inhibitor of PKA. In contrast, the enhanced LTP in enriched mice was attenuated by Rp-cAMPS. Enriched slices expressed greater forskolin-induced, cAMP-dependent synaptic facilitation than did slices from nonenriched mice. Enriched mice showed improved memory for contextual fear conditioning, whereas memory for cued fear conditioning was unaffected following enrichment. Our data indicate that exposure of mice to spatial enrichment alters the PKA dependence of LTP and enhances one type of hippocampus-dependent memory. Environmental enrichment can transform the pharmacological profile of hippocampal LTP, possibly by altering the threshold for activity-dependent recruitment of the cAMP-PKA signaling pathway following electrical and chemical stimulation. We suggest that experience-dependent plasticity of the PKA dependence of hippocampal LTP may be important for regulating the efficacy of hippocampus-based memory.     

Global Zimbabweans: Diaspora Engagement and Disengagement

Since 2000, migration from crisis-ridden Zimbabwe has led to almost one million people leaving the country. The majority migrate to neighbouring South Africa and Botswana, and most of the research on the Zimbabwean diaspora to date has focused on South Africa and the UK. However, the Zimbabwean diaspora is now truly global in its distribution. This paper argues that more attention should therefore be paid to Zimbabweans in other jurisdictions in the Global South and North. Zimbabweans began migrating to Canada in increasing numbers after 2000, most as refugees but also as immigrants and students. Based on a survey of the Zimbabwean diaspora in Canada, this paper focuses on their migration history, demographic characteristics and backward linkages with Zimbabwe. Given the interest in diaspora engagement in the global migration and development literature, it is important to understand the nature of these linkages in order to assess the potential for diaspora involvement in Zimbabwean development. The paper argues that under current economic and political conditions in Zimbabwe, this potential remains weak.     

Rorschach Comprehensive System data for a sample of 309 adult nonpatients from Portugal

Three hundred and nine nonpatient adults, evenly distributed according to sex, age, educational level, and residence, took part in the Rorschach test study carried out in Portugal. The sample was drawn from selected regions of the country and was balanced for population density in urban and rural areas. Test administration was controlled through the services of psychologists familiar with the Rorschach Comprehensive System (CS; Exner, 1993). Results indicate that, in Portugal (Pires, 2000), level of education is the variable that seems to have the largest effect on Rorschach responding.     

Lefties are still a little shorter

Heights and weights of right- and left-handed major league baseball pitchers (N=5780) were analyzed, adjusted for birth year. Right-handed pitchers were about 1.6 cm taller and 1.9 kg heavier than left-handed pitchers. The results corroborated other studies and suggest body size is related to handedness, although the average difference in height between right- and left-handed pitchers was very small.     

Descartes’ Dog: a Clock with Passions?

Although much has been written on Descartes’ thought on animals, not so much has originated in, or has taken full account of, Descartes’ views on (human) emotions. I explore here the extent to which the latter can contribute to the debate on whether he embraced, and to which extent, the doctrine of the bête machine. I first try to show that Descartes’ views on emotions can help offer new support to the skeptical position without necessarily creating new tensions with other central aspects of his philosophy. And second, I sketch the type of theory of animal passions which Descartes could have accepted. The general conclusion I draw is not that Descartes did not hold the view of the bête machine but rather that we can find within his thought a solid stream of ideas, which became stronger towards the end of his life, that points in the opposite direction.     

An efficient coding approach to the debate on grounded cognition

The debate between the amodal and the grounded views of cognition seems to be stuck. Their only substantial disagreement is about the vehicle or format of concepts. Amodal theorists reject the grounded claim that concepts are couched in the same modality-specific format as representations in sensory systems. The problem is that there is no clear characterization of (modal or amodal) format or its neural correlate. In order to make the disagreement empirically meaningful and move forward in the discussion we need a neurocognitive criterion for representational format. I argue that efficient coding models in computational neuroscience can be used to characterize modal codes: These are codes which satisfy special informational demands imposed by sensory tasks. Additionally, I examine recent studies on neural coding and argue that although they do not provide conclusive evidence for either the grounded or the amodal views, they can be used to determine what predictions these approaches can make and what experimental and theoretical developments would be required to settle the debate.     

An immediate-shock freezing deficit with discrete cues: a possible role for unconditioned stimulus processing mechanisms.

Five experiments with C57BL/6 mice (Mus musculus) investigated whether failures in shock processing might contribute to deficits in freezing that occur after an animal receives a shock immediately on exposure to a conditioning context. Experiment 1 found that more contextual freezing resulted from delayed shocks than from immediate shocks across 4 shock intensities. Experiment 2 extended the immediate-shock freezing deficit to discrete stimuli. Experiment 3 found that preexposure to the to-be-conditioned cue did not facilitate immediate cued conditioning. Experiment 4 found that context preexposure enhanced context-evoked fear after an immediate shock. Experiment 5 found that context preexposure also enhanced immediate cued conditioning. These findings are problematic for current theories of the immediate-shock freezing deficit that focus exclusively on processing of the conditioned stimulus, and they suggest that failures in shock processing may contribute to the deficit.