Opioid mechanisms are involved in the disruption of arcaine-induced amnesia by context pre-exposure

Previous exposure to the training context disrupts glutamatergic N-methyl-d-aspartate receptor (NMDAr) antagonist-induced amnesia, indicating that novelty is necessary for such an amnestic effect. While there are reports that novelty-related release of opioids cause amnesia, no study has addressed whether the amnestic effect of NMDAr antagonists involve opioid mechanisms. In this study we investigated whether pharmacological manipulation of the opioid system immediately after context pre-exposure alters the amnestic effect of arcaine, a NMDAr antagonist. Adult male Wistar rats were habituated (pre-exposed) to a fear conditioning training apparatus or to a different context (open field). Immediately after pre-exposure, animals were injected with saline or naloxone (0.5 mg/kg, i.p.) or anti-beta-endorphin antibody (1:500, i.c.v.). Forty eight hours after pre-exposure session, all animals were subjected to fear conditioning acquisition protocol and saline or arcaine (30 mg/kg, i.p.) was administered immediately after training. Testing was carried out 24 h later, and freezing responses due to re-exposure to the training apparatus were recorded. Pre-exposure to the training apparatus prevented the impairment of memory induced by post-training arcaine. Administration of naloxone or anti-beta-endorphin antibody, immediately after pre-exposure to the training apparatus, reinstated the amnesic effect of post-training arcaine. The results suggest that endogenous opioid mechanisms are involved in the pre-exposure-induced loss of the amnestic effect of arcaine.     

Using ambiguous plaid stimuli to investigate the influence of immediate prior experience on perception

In a series of three experiments, we used an ambiguous plaid motion stimulus to explore the behavioral and electrophysiological effects of prior stimulus exposures and perceptual states on current awareness. The results showed that prior exposure to a stimulus biased toward one percept led to subsequent suppression of that percept. In contrast, in the absence of stimulus bias, prior perceptual experience can have a facilitative influence. The suppressive effects caused by the prior stimulus were found to transfer to an ambiguous plaid test stimulus rotated 180º relative to the adaptation stimulus, but were abolished if (1) the ambiguous test stimulus was only rotated 90º relative to the adaptation stimulus or (2) the adaptation stimulus was heavily biased toward the component grating percept. Event-related potential recordings were consistent with the involvement of visual cortical areas and suggested that the influence of recent stimulus exposure may involve recruitment of additional brain processes beyond those responsible for initial stimulus encoding. In contrast, the effects of prior and current perceptual experience appeared to depend on similar brain processes. Although the data presented here focus on vision, the work is discussed within the context of data from a parallel series of experiments in audition.     

You can't get something for nothing: Kierkegaard and Heidegger on how not to overcome Nihilism 1

This paper analyzes Kierkegaard's Religiousness A sphere of existence, presented in his edifying works, and Heidegger's concept of authenticity, proposed in Being and Time, as responses to modern nihilism. While Kierkegaard argues that Religiousness A is an unsuccessful response to modern nihilism, Heidegger claims that authenticity, a secularized version of Religiousness A, is a successful response. We argue that Heidegger's secularization of Religiousness A is incomplete and unsuccessful, that Heidegger's later work offers a reconsideration of the problem of modern nihilism, and that later Heidegger suggests a way out of nihilism which is compatible with Kierkegaard's Religiousness B sphere of existence.     

On measuring fuzziness: a comment on "A fuzzy set approach to modifiers and vagueness in natural language"

Hersh and Caramazza's application of fuzzy set theory to vagueness in natural language is criticized for including in their measures of fuzziness response variability due to experimental and statistical procedures.     

On the Inadmissibility of Some Historical Information

I argue—from a Humean perspective—for the falsity of what I call the “Admissibility of Historical Information Thesis” (AHIT). According to the AHIT, propositions that describe past events are always admissible with respect to propositions that describe future events. I first demonstrate that this thesis has some counter‐intuitive implications and argue that a Humean can explain the intuitive attractiveness of the AHIT by arguing that it results from a wrong understanding of the concept of chance. I then demonstrate how a Humean “best system” analysis of chance predicts the existence of inadmissible historical information and discuss the implications of this conclusion to the debate between Humeans and non‐Humeans.