Influence of chronic corticosterone and glucocorticoid receptor antagonism in the amygdala on fear conditioning

Glucocorticoid receptor activation within the basolateral amygdala (BLA) during fear conditioning may mediate enhancement in rats chronically exposed to stress levels of corticosterone. Male Sprague-Dawley rats received corticosterone (400 microg/ml) in their drinking water (days 1-21), a manipulation that was previously shown to cause hippocampal CA3 dendritic retraction. Subsequently, rats were adapted to the fear conditioning chamber (day 22), then trained (day 23), and tested for conditioned fear to context and tone (day 25). Training consisted of two tone (20s) and footshock (500 ms, 0.25 mA) pairings. In Experiment 1, muscimol (4.4 nmol/0.5 microl/side), a GABAergic agonist, was microinfused to temporarily inactivate the BLA during training. Rats given chronic corticosterone showed enhanced freezing to context, but not tone, compared to vehicle-supplemented rats. Moreover, BLA inactivation impaired contextual and tone conditioning, regardless of corticosterone treatment. In Experiment 2, RU486 (0, 0.3, and 3.0 ng/0.2 microl/side) was infused on training day to antagonize glucocorticoid receptors in the BLA. Corticosterone treatment enhanced fear conditioning to context and tone when analyzed together, but not separately. Moreover, RU486 (3.0 ng/side) selectively exacerbated freezing to context in chronic corticosterone-exposed rats only, but failed to alter tone conditioning. Serum corticosterone levels were negatively correlated with contextual, not tone, conditioning. Altogether, these suggest that chronic corticosterone influences fear conditioning differently than chronic stress as shown previously. Moreover, chronic exposure to corticosteroids alters BLA functioning in a non-linear fashion and that contextual conditioning is influenced more than tone conditioning by chronic corticosterone and BLA glucocorticoid receptor stimulation.     

Interpretation of pronouns in VP-ellipsis constructions in Dutch Broca's and Wernicke's aphasia

In this paper, we investigate the ability of Dutch agrammatic Broca's and Wernicke's aphasics to assign reference to possessive pronouns in elided VP constructions. The assumption is that the comprehension problems in these two populations have different sources that are revealed in distinct patterns of responses. The focus is primarily on the performance of the agrammatic group whose errors in comprehension are not viewed as a consequence of a breakdown of grammatical knowledge but as a result of limited processing resources (for an overview see Grodzinsky, 2000). The results of the present study provide evidence for the psycholinguistic reality of the economy hierarchy as proposed in the Primitives of Binding (Reuland, 2001). According to the economy hierarchy proposed for the non-brain-damaged, the more economical semantic dependencies are preferred over the costlier discourse dependencies. This hierarchy is reflected in agrammatic aphasia where the semantic dependencies are available on time and preferred over the discourse dependences that are not available on time as a result of the lack of processing resources with consequences for comprehension.     

Reference assignment: using language breakdown to choose between theoretical approaches

We report results of an experimental study with Dutch agrammatic aphasics that investigated their ability to interpret pronominal elements in transitive clauses and Exceptional Case Marking constructions (ECM). Using the obtained experimental results as a tool, we distinguish between three competing linguistic theories that aim at determining principles responsible for pronoun distribution: Government and Binding (Chomsky, 1981), Reflexivity (Reinhart & Reuland, 1993), and Primitives of Binding (Reuland, 2001). The obtained results are inconsistent with Government and Binding, but consistent with the latter two theories. We further show that the Primitives of Binding framework most naturally explains our results. Our proposal is based on the different performance demonstrated by patients in transitive clauses and ECM constructions, in combination with the often-made claim in the literature regarding the limitation of processing resources in this population (e.g., Haarmann and Kolk, 1991, Haarmann and Kolk, 1994 and Zurif et al., 1993, among others).     

Heidegger and Derrida on the Nature of Questioning: Towards the Rehabilitation of Questioning in Contemporary Philosophy

In this article, the Heidegger and Derrida controversy about the nature of questioning is revisited in order to rehabilitate questioning as an essential characteristic of contemporary philosophy. After exploring Heidegger's characterization of philosophy as questioning and Derrida's criticism of the primacy of questioning, we will evaluate Derrida's criticism and articulate three characteristics of Heidegger's concept of questioning. After our exploration of Heidegger's concept of questioning, we critically evaluate Heidegger's later rejection of questioning. With this, we not only contribute to the discussion about why Heidegger rejected questioning in his later thought and whether this rejection is legitimized, but also to the rehabilitation of questioning in contemporary philosophy.