A Plausibility Semantics for Abstract Argumentation Frameworks

We propose and investigate a simple ranking-measure-based extension semantics for abstract argumentation frameworks based on their generic instantiation by default knowledge bases and the ranking construction semantics for default reasoning. In this context, we consider the path from structured to logical to shallow semantic instantiations. The resulting well-justified JZ-extension semantics diverges from more traditional approaches.Comment: Proceedings of the 15th International Workshop on Non-Monotonic Reasoning (NMR 2014). This is an improved and extended version of the author's ECSQARU 2013 pape

The Use of Physical Context Information in Psychological Processing: An Investigation Into the Environmental Context Reinstatement Effect

A great deal of anecdotal evidence indicates that people employ context as an aid to memory. Psychological accounts of memory also have made much use of context as a theoretical construct. An examination of the psychological literature revealed that the term "context" has been used to refer to four classes of information; process, semantic, physiological and environmental. Studies investigating the use of process, semantic and physiological information in psychological processing were reviewed generally, while a much more detailed review was carried out with respect to studies investigating the use of environmental context information. The review of environmental context studies reported numerous investigations obtaining such effects and identified several factors that may have been responsible for the reputed unreliability of such phenomena. Consideration of the reviews of the four types of context also indicated that there was greater similarity than difference in their effects suggesting a possible equivalence of psychological function

Post-Transcriptional Regulation of Addiction-Related Behaviors: Opposing Roles of Nucleus Accumbens miR-495 and HuD

Substance use Disorders (SUDs) are characterized by chronic relapse after periods without symptoms. This has been hypothesized to stem from persistent alterations in corticolimbic circuit function and structure caused by drug-induced alterations in addiction-related gene (ARG) expression. Transcriptional and epigenetic regulation of ARGs and addiction-like behaviors have been well characterized but the role of post-transcriptional regulation is an understudied, yet promising field. RNA binding proteins (RBPs) are one post-transcriptional regulator of mRNA stability. HuD is a neuronal specific RBP that stabilizes mRNAs and is regulated by neuronal activity and cocaine. Another type of post-transcriptional regulator, microRNAs (miRNAs), are non-coding RNAs that target specific mRNAs for degradation or translational repression. Since both RBPs and miRNAs target the 3’UTR, this opens the possibility that these two classes of molecules could compete for access to a specific recognition site. We have found that miR-495 and HuD target a set of shared mRNAs via binding to the same GUUUGUUUG sequence. Many of these shared targets, including Bdnf and Camk2a mRNAs have been implicated in addiction and are considered ARGs. This led to my hypothesis that cocaine CPP differentially regulates HuD and miR-495 leading to a synergistic increase in ARG expression and addiction-like behaviors. We found that miR-495 was significantly decreased within the NAc while HuD protein and mRNA was significantly increased. CaMKIIα and BDNF mRNA and protein levels were increased in a similar fashion. Overexpression of HuD or miR-495 caused opposite effects on ARG expression and CPP behavior. Finally, to determine the in vivo capability of these two regulators to compete for behavior, we infused LV-miR-495 in HuDOE mice and trained them in CPP. We found that HuDOE + LV-miR-495 completely blocked the development of CPP compared to LV-GFP controls as well as diminishing expression of shared target mRNA and protein. This suggests that miR-495 and HuD have bidirectional roles in the regulation of CPP behavior. Further research on the role of post-transcriptional competition of shared targets on cellular dynamics and behavior may inform new pharmacological treatments that tip the balance of this post-transcriptional competition mechanism in the favor of remission.Substance use Disorders (SUDs) are characterized by chronic relapse after periods without symptoms. This has been hypothesized to stem from persistent alterations in corticolimbic circuit function and structure caused by drug-induced alterations in addiction-related gene (ARG) expression. Transcriptional and epigenetic regulation of ARGs and addiction-like behaviors have been well characterized but the role of post-transcriptional regulation is an understudied, yet promising field. RNA binding proteins (RBPs) are one post-transcriptional regulator of mRNA stability. HuD is a neuronal specific RBP that stabilizes mRNAs and is regulated by neuronal activity and cocaine. Another type of post-transcriptional regulator, microRNAs (miRNAs), are non-coding RNAs that target specific mRNAs for degradation or translational repression. Since both RBPs and miRNAs target the 3’UTR, this opens the possibility that these two classes of molecules could compete for access to a specific recognition site. We have found that miR-495 and HuD target a set of shared mRNAs via binding to the same GUUUGUUUG sequence. Many of these shared targets, including Bdnf and Camk2a mRNAs have been implicated in addiction and are considered ARGs. This led to my hypothesis that cocaine CPP differentially regulates HuD and miR-495 leading to a synergistic increase in ARG expression and addiction-like behaviors. We found that miR-495 was significantly decreased within the NAc while HuD protein and mRNA was significantly increased. CaMKIIα and BDNF mRNA and protein levels were increased in a similar fashion. Overexpression of HuD or miR-495 caused opposite effects on ARG expression and CPP behavior. Finally, to determine the in vivo capability of these two regulators to compete for behavior, we infused LV-miR-495 in HuDOE mice and trained them in CPP. We found that HuDOE + LV-miR-495 completely blocked the development of CPP compared to LV-GFP controls as well as diminishing expression of shared target mRNA and protein. This suggests that miR-495 and HuD have bidirectional roles in the regulation of CPP behavior. Further research on the role of post-transcriptional competition of shared targets on cellular dynamics and behavior may inform new pharmacological treatments that tip the balance of this post-transcriptional competition mechanism in the favor of remission

The retrieval-related anterior shift is moderated by age and correlates with memory performance

Recent research suggests that episodic memory is associated with systematic differences in the localization of neural activity observed during memory encoding and retrieval. The retrieval-related anterior shift is a phenomenon whereby the retrieval of a stimulus event (e.g., a scene image) is associated with a peak neural response which is localized more anteriorly than the response elicited when the stimulus is experienced directly. Here, we examine whether the magnitude of the anterior shift (i.e., the distance between encoding- and retrieval-related response peaks) is moderated by age, and also whether the shift is associated with memory performance. Younger and older human subjects of both sexes underwent fMRI as they completed encoding and retrieval tasks on word-face and word-scene pairs. We localized peak scene and face selectivity for each individual participant within the face-selective precuneus and in three scene-selective (parahippocampal place area [PPA], medial place area, occipital place area) ROIs. In line with recent findings, we identified an anterior shift in the PPA and occipital place area in both age groups and, in older adults only, in the medial place area and precuneus also. Of importance, the magnitude of the anterior shift was larger in older than in younger adults. The shift within the PPA exhibited an age-invariant across-participant negative correlation with source memory performance, such that a smaller displacement between encoding- and retrieval-related neural activity was associated with better performance. These findings provide novel insights into the functional significance of the anterior shift, especially in relation to memory decline in older age

A psychological analysis of the effects of memory retrieval prior to extinction on the reacquisition of a conditioned fear association

The successful reduction of fear is the aim of clinicians treating people with anxiety disorders such as post-traumatic stress disorder or phobias. Existing treatments for these conditions, however, require many treatment sessions and are prone to relapse. A new technique, first demonstrated in rats by Monfils, Cowansage, Klann, & LeDoux (2009) and later shown to be effective in humans (Schiller et al., 2010), provides a method of efficiently reducing fear in a manner which is resistant to various known triggers of relapse. This procedure involves a single presentation of the fear-inducing stimulus one hour prior to extinction training. This procedure produces extinction learning that is resistant to the return of fear resulting from a change of context, the passage of time, exposure to the unconditioned stimulus, and even further conditioning of the stimulus with an aversive stimulus. This dissertation focuses on one particular property of this procedure: that a stimulus extinguished using this procedure is resistant to subsequent retraining of the fear association. The first four experiments presented here are aimed at replicating this phenomenon and determining whether prediction error at retrieval is necessary for the effect to occur. Following on from these studies, the next chapter presents three experiments which investigate whether trial spacing effects could explain the enhanced extinction and highlights conditions under which the effect is weakened, or possibly reversed. The next three experiments compare the properties of a stimulus extinguished under these conditions with a stimulus extinguished under normal conditions. These studies focus on explanations involving inhibition, inattention and the disruption of stimulus representations. In the final three experiments, the possibility of reversing the effect is investigated. These studies look at the effect of memory retrieval prior to retraining of the stimulus to determine the conditions under which the stimulus can again come to elicit a fear response.Medical Research Council Programme Grant; Overseas Research Studentship; Poynton Cambridge Commonwealth Trust; Oon Khye Beng Ch‟hia Tsio Bursar

Functional Brain Oscillations: How Oscillations Facilitate Information Representation and Code Memories

The overall aim of the modelling works within this thesis is to lend theoretical evidence to empirical findings from the brain oscillations literature. We therefore hope to solidify and expand the notion that precise spike timing through oscillatory mechanisms facilitates communication, learning, information processing and information representation within the brain. The primary hypothesis of this thesis is that it can be shown computationally that neural de-synchronisations can allow information content to emerge. We do this using two neural network models, the first of which shows how differential rates of neuronal firing can indicate when a single item is being actively represented. The second model expands this notion by creating a complimentary timing mechanism, thus enabling the emergence of qualitive temporal information when a pattern of items is being actively represented. The secondary hypothesis of this thesis is that it can be also be shown computationally that oscillations might play a functional role in learning. Both of the models presented within this thesis propose a sparsely coded and fast learning hippocampal region that engages in the binding of novel episodic information. The first model demonstrates how active cortical representations enable learning to occur in their hippocampal counterparts via a phase-dependent learning rule. The second model expands this notion, creating hierarchical temporal sequences to encode the relative temporal position of cortical representations. We demonstrate in both of these models, how cortical brain oscillations might provide a gating function to the representation of information, whilst complimentary hippocampal oscillations might provide distinct phasic reference points for learning

Derrota y defensa en argumentación rebatible

Argumentative systems formalized common sense reasoning through construction, comparison and evaluation of arguments for or against certain conclusions. In such systems, there are two central notions: Defeat and Defense. In this paper we characterize both notions and we show and comment some challenges for proposals characterizations of defeat and defense.Los sistemas argumentativos formalizan razonamiento de sentido común mediante la construcción, comparación y evaluación de argumentos a favor o en contra de ciertas afirmaciones. En tales sistemas existen dos nociones centrales: derrota y defensa. En el presente trabajo caracterizan ambas nociones y se discuten algunos desafíos para las caracterizaciones propuestas. Además, se realizan algunos comentarios al respecto