A Symbiotic Brain-Machine Interface through Value-Based Decision Making

BACKGROUND: In the development of Brain Machine Interfaces (BMIs), there is a great need to enable users to interact with changing environments during the activities of daily life. It is expected that the number and scope of the learning tasks encountered during interaction with the environment as well as the pattern of brain activity will vary over time. These conditions, in addition to neural reorganization, pose a challenge to decoding neural commands for BMIs. We have developed a new BMI framework in which a computational agent symbiotically decoded users' intended actions by utilizing both motor commands and goal information directly from the brain through a continuous Perception-Action-Reward Cycle (PARC). METHODOLOGY: The control architecture designed was based on Actor-Critic learning, which is a PARC-based reinforcement learning method. Our neurophysiology studies in rat models suggested that Nucleus Accumbens (NAcc) contained a rich representation of goal information in terms of predicting the probability of earning reward and it could be translated into an evaluative feedback for adaptation of the decoder with high precision. Simulated neural control experiments showed that the system was able to maintain high performance in decoding neural motor commands during novel tasks or in the presence of reorganization in the neural input. We then implanted a dual micro-wire array in the primary motor cortex (M1) and the NAcc of rat brain and implemented a full closed-loop system in which robot actions were decoded from the single unit activity in M1 based on an evaluative feedback that was estimated from NAcc. CONCLUSIONS: Our results suggest that adapting the BMI decoder with an evaluative feedback that is directly extracted from the brain is a possible solution to the problem of operating BMIs in changing environments with dynamic neural signals. During closed-loop control, the agent was able to solve a reaching task by capturing the action and reward interdependency in the brain

Organ-specific inhibition of metastatic colon carcinoma by CXCR3 antagonism

Liver and lung metastases are the predominant cause of colorectal cancer (CRC)-related mortality. Recent research has indicated that CXCR3/chemokines interactions that orchestrate haematopoetic cell movement are implicated in the metastatic process of malignant tumours, including that of CRC cells to lymph nodes. To date, however, the contribution of CXCR3 to liver and lung metastasis in CRC has not been addressed. To determine whether CXCR3 receptors regulate malignancy-related properties of CRC cells, we have used CXCR3-expressing CRC cell lines of human (HT29 cells) and murine (C26 cells) origins that enable the development of liver and lung metastases when injected into immunodeficient and immunocompetent mice, respectively, and assessed the effect of CXCR3 blockade using AMG487, a small molecular weight antagonist. In vitro, activation of CXCR3 on human and mouse CRC cells by its cognate ligands induced migratory and growth responses, both activities being abrogated by AMG487. In vivo, systemic CXCR3 antagonism by preventive or curative treatments with AMG487 markedly inhibited the implantation and the growth of human and mouse CRC cells within lung without affecting that in the liver. In addition, we measured increased levels of CXCR3 and ligands expression within lung nodules compared with liver tumours. Altogether, our findings indicate that activation of CXCR3 receptors by its cognate ligands facilitates the implantation and the progression of CRC cells within lung tissues and that inhibition of this axis decreases pulmonary metastasis of CRC in two murine tumour models

[Introduction] Toward an anthropology of the just price: history, ethnography, critique

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Temporal-Difference Reinforcement Learning with Distributed Representations

Temporal-difference (TD) algorithms have been proposed as models of reinforcement learning (RL). We examine two issues of distributed representation in these TD algorithms: distributed representations of belief and distributed discounting factors. Distributed representation of belief allows the believed state of the world to distribute across sets of equivalent states. Distributed exponential discounting factors produce hyperbolic discounting in the behavior of the agent itself. We examine these issues in the context of a TD RL model in which state-belief is distributed over a set of exponentially-discounting “micro-Agents”, each of which has a separate discounting factor (γ). Each µAgent maintains an independent hypothesis about the state of the world, and a separate value-estimate of taking actions within that hypothesized state. The overall agent thus instantiates a flexible representation of an evolving world-state. As with other TD models, the value-error (δ) signal within the model matches dopamine signals recorded from animals in standard conditioning reward-paradigms. The distributed representation of belief provides an explanation for the decrease in dopamine at the conditioned stimulus seen in overtrained animals, for the differences between trace and delay conditioning, and for transient bursts of dopamine seen at movement initiation. Because each µAgent also includes its own exponential discounting factor, the overall agent shows hyperbolic discounting, consistent with behavioral experiments

Introduction

Drawing on new research material from ten European countries, Asylum Determination in Europe: Ethnographic Perspectives brings together a range of detailed accounts of the legal and bureaucratic processes by which asylum claims are decided.The book includes a legal overview of European asylum determination procedures, followed by sections on the diverse actors involved, the means by which they communicate, and the ways in which they make life and death decisions on a daily basis. It offers a contextually rich account that moves beyond doctrinal law to uncover the gaps and variances between formal policy and legislation, and law as actually practiced. The contributors employ a variety of disciplinary perspectives – sociological, anthropological, geographical and linguistic – but are united in their use of an ethnographic methodological approach. Through this lens, the book captures the confusion, improvisation, inconsistency, complexity and emotional turmoil inherent to the process of claiming asylum in Europe

Improvising border security: 'a situation of security pluralism' along South Sudan’s borders with the Democratic Republic of Congo

This article compares two cases of securitization along South Sudan’s border with the Democratic Republic of the Congo. By comparing how a security concern – the presence of the Lord’s Resistance Army – was interpreted and responded to, the article shows that border security practices in two borderscapes are improvised, contradictory and contested, and serve to establish authority rather than actually securing the border. This is apparent on three levels: (a) through the multiplicity of security actors vying for authority; (b) in how they interpret security concerns; and (c) in terms of what practice follows. The article argues that by allowing authority at the border to be taken by actors that are not under direct control of the central government, the South Sudanese state is developing as one that controls parts of the country in absentia, either by granting discretionary powers to low-level government authorities at the border or through tactical neglect. Processes of securitization by both state and non-state actors in the borderland are largely disconnected from the South Sudanese central government, which does not claim authority over this border and thus seemingly does not consider the lack of security for its citizens, and the parallel authorities, as a threat to central stability