Hippocampal train stimulation modulates recall of fear extinction independently of prefrontal cortex synaptic plasticity and lesions

It has been shown that long-term potentiation (LTP) develops in the connection between the mediodorsal thalamus (MD) and the medial prefrontal cortex (mPFC) and between the hippocampus (HPC) and the mPFC following fear extinction, and correlates with extinction retention. However, recent lesion studies have shown that combined lesions of the MD and mPFC do not interfere with extinction learning and retention, while inactivation of the dorsal HPC disrupts fear extinction memory. Here we found in rats that immediate post-training HPC low-frequency stimulation (LFS) suppressed extinction-related LTP in the HPC-mPFC pathway and induced difficulties in extinction recall. HPC tetanus, applied several hours later, failed to re-establish mPFC LTP but facilitated recall of extinction. Delayed post-training HPC LFS also provoked mPFC depotentiation and difficulties with extinction recall. HPC tetanus abolished these two effects. We also found that damage to the mPFC induced fear return only in rats that received HPC LFS following extinction training. HPC tetanus also reversed this behavioral effect of HPC LFS in lesioned rats. These data suggest that the HPC interacts with the mPFC during fear extinction, but can modulate fear extinction independently of this interaction.     

Responsible conduct in research

Science is not taken for granted any longer. Society, politics and the media pose critical questions tending to censorship or at least control of science. How does science respond? It cannot exist and develop without freedom, but this does not mean freedom to amass knowledge and apply technological applications at any price and without restrictions. Science should be autonomous, but is not value-free. A distintion is made between external and internal social/ethical problems. The former refer to questions of the social/ethical context and consequences of scientific research, and the latter to the rules of ‘good practice’ and scientific integrity. The role of academies of science, and of associations of such academies (e.g. All European Academies (ALLEA)) in developing codes of good scientific practice and fostering a proper sense of scientific values and standards is further discussed.     

Follow-up of a cross-national comparison on flashbulb and event memory for the September 11th attacks

Flashbulb memories are defined as vivid and long-lasting memories for the reception context of an important public event (Brown & Kulik, 1977). They are supposed to be triggered by both emotional reactions to the original event and rehearsal processes (Brown & Kulik, 1977; Finkenauer, Luminet, Gisle, El-Ahmadi, van der Linden, & Philippot, 1998; Neisser & Harsch, 1992). A test-retest design (21 vs 524 days after the event on average) was employed to assess flashbulb memory and event memory for the September 11th attacks and the impact of their emotional and rehearsal predictors in a sample of 985 respondents coming from six countries (i.e., Belgium, Italy, the Netherlands, Romania, Japan, and the USA). Results showed that national membership had a significant impact on event memory, and the emotional and rehearsal variables, but flashbulb memories for the September 11th attacks were found to be high and consistent across different countries. The implications of these findings for the debate about the nature and maintenance of flashbulb memories are discussed.     

Evaluative conditioning of high-novelty stimuli does not seem to be based on an automatic form of associative learning

Evaluative conditioning (EC) refers to the change in valence of initially neutral stimuli (conditioned stimuli, or CSs) as a result of their pairing with positive or negative stimuli (unconditioned stimuli, or USs). EC is critical to dual-attitudes models as it is often presented as an evaluative effect that results from a purely automatic form of associative learning. Although evidence suggests that EC does not occur without contingency awareness, Ruys, and Stapel (2009) recently argued that contingency awareness is unnecessary for high-novelty stimuli. Researchers may thus be tempted to conclude that EC rests on an automatic form of associative learning, at least for CSs associated with little prior evaluative knowledge. Taking issue with this claim, the present study reveals that EC of high-novelty stimuli is dependent on attentional resources. The role of contingency awareness in EC of high-novelty stimuli is also discussed.     

The long‐term effect of social comparison on academic performance

The present study was part of a large‐scale cohort study among several thousand students in the Netherlands. The purpose of the study was to investigate the long‐term effects of comparison choice, i.e., comparison with a target performing better or worse than oneself, and academic comparative evaluation, i.e., the extent to which one thinks one's performance is better or worse than that of others, on scores on standardized tests for reading comprehension and mathematics. While controlling for earlier performance, the results showed that both comparison choice and academic comparative evaluation positively predicted test scores over a period of 2 years. Moreover, it was found that the positive effect of comparison choice only applied to students with a favorable comparative evaluation. Copyright © 2009 John Wiley & Sons, Ltd.     

Direct Comparison of Episodic Encoding and Retrieval of Words: An Event-related fMRI Study

Functional magnetic resonance imaging (fMRI) was used to compare directly episodic encoding and retrieval. During encoding, subjects studied visually presented words and reported via keypress whether each word represented a pleasant or unpleasant concept (intentional, deep encoding). During the retrieval phase, subjects indicated (via keypress) whether visually presented words had previously been studied. No reliable differences were found during the recognition phase for words that had been previously studied and those that had not been studied. Areas preferentially active during encoding (relative to retrieval) included left superior frontal cortex, medial frontal cortex, left superior temporal cortex, posterior cingulate, left parahippocampal gyrus, and left inferior frontal gyrus. Regions more active in retrieval than encoding included bilateral inferior parietal cortex, bilateral precuneus, right frontal polar cortex, right dorsolateral prefrontal cortex, and right inferior frontal/insular cortex.