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Learner corpus research : new perspectives and applications
This volume showcases original, agenda-setting studies in the field of learner corpus research of both spoken and written production. The studies have important applications for classroom pedagogy. The volume brings readers up-to-date with new written and spoken learner corpora, often looking at previously under-examined variables in learner corpus investigations. It also demonstrates innovative applications of learner corpus findings, addressing issues such as the effect of task, the effect of learner variables and the nature of learner language. The volume is of significant interest to researchers working in corpus linguistics, learner corpus research, second language acquisition and English for Academic and Specific Purposes, as well to practitioners interested in the application of the findings in language teaching and assessment.
Book
Striatal dopamine D2/D3 receptor regulation of human reward processing and behaviour
Signalling at dopamine D2/D3 receptors is thought to underlie motivated behaviour, pleasure experiences and emotional expression based on animal studies, but it is unclear if this is the case in humans or how this relates to neural processing of reward stimuli. Using a randomised, double-blind, placebo-controlled, crossover neuroimaging study, we show in healthy humans that sustained dopamine D2/D3 receptor antagonism for 7 days results in negative symptoms (impairments in motivated behaviour, hedonic experience, verbal and emotional expression) and that this is related to blunted striatal response to reward stimuli. In contrast, 7 days of partial D2/D3 agonism does not disrupt reward signalling, motivated behaviour or hedonic experience. Both D2/D3 antagonism and partial agonism induce motor impairments, which are not related to striatal reward response. These findings identify a central role for D2/D3 signalling and reward processing in the mechanism underlying motivated behaviour and emotional responses in humans, with implications for understanding neuropsychiatric disorders such as schizophrenia and Parkinson’s disease.
Osugo et al show in healthy humans that sustained dopamine D2/D3 receptor antagonism impairs motivated behaviour, hedonic experience, and emotional expression, and that this is related to blunted striatal reward response following D2/D3 antagonism.
Journal Article
High-frequency neuromodulation improves obsessive–compulsive behavior
Nearly one billion people worldwide suffer from obsessive–compulsive behaviors
1
,
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, yet our mechanistic understanding of these behaviors is incomplete, and effective therapeutics are unavailable. An emerging perspective characterizes obsessive–compulsive behaviors as maladaptive habit learning
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,
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, which may be associated with abnormal beta–gamma neurophysiology of the orbitofrontal–striatal circuitry during reward processing
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,
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. We target the orbitofrontal cortex with alternating current, personalized to the intrinsic beta–gamma frequency of the reward network, and show rapid, reversible, frequency-specific modulation of reward- but not punishment-guided choice behavior and learning, driven by increased exploration in the setting of an actor-critic architecture. Next, we demonstrate that chronic application of the procedure over 5 days robustly attenuates obsessive–compulsive behavior in a non-clinical population for 3 months, with the largest benefits for individuals with more severe symptoms. Finally, we show that convergent mechanisms underlie modulation of reward learning and reduction of obsessive–compulsive symptoms. The results contribute to neurophysiological theories of reward, learning and obsessive–compulsive behavior, suggest a unifying functional role of rhythms in the beta–gamma range, and set the groundwork for the development of personalized circuit-based therapeutics for related disorders.
Selective and personalized neuromodulation of orbitofrontal beta–gamma rhythms in humans, achieved with an alternating current, robustly attenuates obsessive–compulsive behavior for 3 months.
Journal Article
Striatal dopamine can enhance both fast working memory, and slow reinforcement learning, while reducing implicit effort cost sensitivity
Associations can be learned incrementally, via reinforcement learning (RL), or stored instantly in working memory (WM). While WM is fast, it is also capacity-limited and effortful. Striatal dopamine may promote WM, by facilitating WM updating and effort exertion and also RL, by boosting plasticity. Yet, prior studies have failed to distinguish between the effects of dopamine manipulations on RL versus WM. N = 100 participants completed a paradigm isolating these systems in a double-blind study measuring dopamine synthesis with [
18
F]-FDOPA PET imaging and manipulating dopamine with methylphenidate and sulpiride. We find that learning is enhanced among high synthesis capacity individuals and by methylphenidate, but impaired by sulpiride. Methylphenidate also blunts implicit effort cost learning. Computational modeling reveals that individuals with higher dopamine synthesis capacity rely more on WM, while methylphenidate boosts their RL rates. The D2 receptor antagonist sulpiride reduces accuracy due to diminished WM involvement and faster WM decay. We conclude that dopamine enhances both slow RL, and fast WM, by promoting plasticity and reducing implicit effort sensitivity. This work was completed as part of a registered trial with the Overview of Medical Research in the Netherlands (NL-OMON43196).
Striatal dopamine signaling accelerates reinforcement learning while also boosting reliance on working memory and making working memory less effortful as revealed in this pharmaco-PET study of healthy young adults.
Journal Article
Effect of Exercise Training on Striatal Dopamine D2/D3 Receptors in Methamphetamine Users during Behavioral Treatment
Methamphetamine use disorder is associated with striatal dopaminergic deficits that have been linked to poor treatment outcomes, identifying these deficits as an important therapeutic target. Exercise attenuates methamphetamine-induced neurochemical damage in the rat brain, and a preliminary observation suggests that exercise increases striatal D2/D3 receptor availability (measured as nondisplaceable binding potential (BPND)) in patients with Parkinson's disease. The goal of this study was to evaluate whether adding an exercise training program to an inpatient behavioral intervention for methamphetamine use disorder reverses deficits in striatal D2/D3 receptors. Participants were adult men and women who met DSM-IV criteria for methamphetamine dependence and were enrolled in a residential facility, where they maintained abstinence from illicit drugs of abuse and received behavioral therapy for their addiction. They were randomized to a group that received 1 h supervised exercise training (n=10) or one that received equal-time health education training (n=9), 3 days/week for 8 weeks. They came to an academic research center for positron emission tomography (PET) using [(18)F]fallypride to determine the effects of the 8-week interventions on striatal D2/D3 receptor BPND. At baseline, striatal D2/D3 BPND did not differ between groups. However, after 8 weeks, participants in the exercise group displayed a significant increase in striatal D2/D3 BPND, whereas those in the education group did not. There were no changes in D2/D3 BPND in extrastriatal regions in either group. These findings suggest that structured exercise training can ameliorate striatal D2/D3 receptor deficits in methamphetamine users, and warrants further evaluation as an adjunctive treatment for stimulant dependence.
Journal Article
The undergraduate learner translator corpus: a new resource for translation studies and computational linguistics
Around the world, a growing interest has been seen in learner translator corpora, which are invaluable resources for teaching and research. This paper introduces a new resource to support researchers from different interdisciplinary areas such as computational linguistics, descriptive translation studies, computer-aided translation technology, Arabic machine translation applications, cognitive science, and translation pedagogy. Motivated by the lack of learner translator resources that provide data about learners of translation from and into Arabic, the undergraduate learner translator corpus (ULTC) is an ongoing, error-tagged sentence-aligned parallel corpus of English, Arabic, and French, with Arabic as its main language. The present corpus, consisting of parallel texts of female learners of translation from English or French into Arabic, is the first of its kind in terms of the languages represented, tasks covered, and number of students involved. It is also unique in terms of combining many complementary corpora of cross-lingual data, each of which has its own web-based query interface and corpus analysis tools. This paper describes the ULTC compilation process, preliminary findings, and planned future expansion and research.
Journal Article