296 research outputs found

    Holistic processing of hierarchical structures in connectionist networks

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    Despite the success of connectionist systems to model some aspects of cognition, critics argue that the lack of symbol processing makes them inadequate for modelling high-level cognitive tasks which require the representation and processing of hierarchical structures. In this thesis we investigate four mechanisms for encoding hierarchical structures in distributed representations that are suitable for processing in connectionist systems: Tensor Product Representation, Recursive Auto-Associative Memory (RAAM), Holographic Reduced Representation (HRR), and Binary Spatter Code (BSC). In these four schemes representations of hierarchical structures are either learned in a connectionist network or constructed by means of various mathematical operations from binary or real-value vectors.It is argued that the resulting representations carry structural information without being themselves syntactically structured. The structural information about a represented object is encoded in the position of its representation in a high-dimensional representational space. We use Principal Component Analysis and constructivist networks to show that well-separated clusters consisting of representations for structurally similar hierarchical objects are formed in the representational spaces of RAAMs and HRRs. The spatial structure of HRRs and RAAM representations supports the holistic yet structure-sensitive processing of them. Holistic operations on RAAM representations can be learned by backpropagation networks. However, holistic operators over HRRs, Tensor Products, and BSCs have to be constructed by hand, which is not a desirable situation. We propose two new algorithms for learning holistic transformations of HRRs from examples. These algorithms are able to generalise the acquired knowledge to hierarchical objects of higher complexity than the training examples. Such generalisations exhibit systematicity of a degree which, to our best knowledge, has not yet been achieved by any other comparable learning method.Finally, we outline how a number of holistic transformations can be learned in parallel and applied to representations of structurally different objects. The ability to distinguish and perform a number of different structure-sensitive operations is one step towards a connectionist architecture that is capable of modelling complex high-level cognitive tasks such as natural language processing and logical inference

    Combined Imaging Markers Dissociate Alzheimer's Disease and Frontotemporal Lobar Degeneration ‚Äď An ALE Meta-Analysis

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    To compare and dissociate the neural correlates of Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD), we combine and synthesize here recent comprehensive meta-analyses. Systematic and quantitative meta-analyses were conducted according to the QUOROM statement by calculating anatomical likelihood estimates (ALE). AD (n‚ÄČ=‚ÄČ578) and the three subtypes of FTLD, frontotemporal dementia, semantic dementia (SD), and progressive non-fluent aphasia (n‚ÄČ=‚ÄČ229), were compared in conjunction analyses, separately for atrophy and reductions in glucose metabolism. Atrophy coincided in the amygdala and hippocampal head in AD and the FTLD subtype SD. The other brain regions did not show any overlap between AD and FTLD subtypes for both atrophy and changes in glucose metabolism. For AD alone (n‚ÄČ=‚ÄČ826), another conjunction analysis revealed a regional dissociation between atrophy and hypoperfusion/hypometabolism, whereby hypoperfusion and hypometabolism coincided in the angular/supramarginal gyrus and inferior precuneus/posterior cingulate gyrus. Our data together with other imaging studies suggest a specific dissociation of AD and FTLD if, beside atrophy, additional imaging markers in AD such as abnormally low parietal glucose utilization and perfusion are taken into account. Results support the incorporation of standardized imaging inclusion criteria into future diagnostic systems, which is crucial for early individual diagnosis and treatment in the future

    Year 7 and 8 Teachers' Understandings, Beliefs and Practices around the Teaching of Grammar in Relation to the Teaching of Writing

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    In recent times, and in fact over the past five decades, the importance of teachers’ knowledge of grammar and the teaching of grammar has encountered a resurgence of interest on the world stage as it has done within the research and educational communities of New Zealand (Hudson, 2004; Andrews, Torgerson, Beverton, Locke, Low, Robinson & Zhu 2004; Gordon, 2005; Locke, 2010; Myhill, Jones, Lines & Watson, 2012). Various contemporary studies into teachers’ understandings of grammar and the ways it is taught have utilised the knowledge and experiences of ESL (English as a Second Language) and pre-service teachers (Borg, 1999, 2001; Farrell, 1999; Burgess, Turvey & Quarshie, 2000; Nicholson, 2007; Harper & Rennie, 2008; Basturkmen, 2010). Some studies have emphasised linguistic elements related to the teaching of reading and spelling (Nicholson, 2007; Stainthorp, 2010; Cheesman, McGuire, Shankweiler & Coyne, 2009). However, there appears to be little research involving practising teacher participants, with a specific focus on grammar and its relationship to the teaching of writing. This study explores the broad grammatical knowledge and teaching practices within writing of in-service, generalist teachers of intermediate-aged (year 7 and 8) children. It addresses issues of importance regarding the grammatical understandings, beliefs and teaching practices of teachers within a specific New Zealand educational context. A mixed methods approach to gathering data was utilised in this study. A survey involving 26 year 7 and 8 intermediate school teachers was implemented, followed by a series of semi-structured interviews with a sub-group of six of these participants. The findings of this case study strongly suggest that, although many of the participants were uncertain of how to define grammar and lacked confidence in teaching grammar, their understandings and teaching pedagogies were stronger than they had perceived them to be. A clear majority of participants considered grammatical instruction to be important in improving student writing outcomes, and most revealed that this was an element included within their teaching practices. Findings also indicate that teachers experience distinct limitations in developing their understandings around grammar and grammatical instruction and that their perception of these limitations affects their confidence in teaching grammar. This study also points to a lack of conformity or standard of learning around teacher professional development in grammar. Moving forward, it would be interesting to determine whether there is, in fact, any form of standardised training around the teaching of grammar within and/or across other New Zealand schools, and what this might look like. Evidence from this study suggests that we need to understand more about what New Zealand teachers know about grammar and the teaching of grammar, specifically within school and classroom writing programmes. Future studies in this vein would benefit from including an element of observation as a methodological tool to help validate reported findings, particularly when investigating teachers’ approaches to teaching grammar.

    Dopamine release, diffusion and uptake : A computational model for synaptic and volume transmission

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    Computational modeling of dopamine transmission is challenged by complex underlying mechanisms. Here we present a new computational model that (I) simultaneously regards release, diffusion and uptake of dopamine, (II) considers multiple terminal release events and (III) comprises both synaptic and volume transmission by incorporating the geometry of the synaptic cleft. We were able to validate our model in that it simulates concentration values comparable to physiological values observed in empirical studies. Further, although synaptic dopamine diffuses into extra-synaptic space, our model reflects a very localized signal occurring on the synaptic level, i.e. synaptic dopamine release is negligibly recognized by neighboring synapses. Moreover, increasing evidence suggests that cognitive performance can be predicted by signal variability of neuroimaging data (e.g. BOLD). Signal variability in target areas of dopaminergic neurons (striatum, cortex) may arise from dopamine concentration variability. On that account we compared spatio-temporal variability in a simulation mimicking normal dopamine transmission in striatum to scenarios of enhanced dopamine release and dopamine uptake inhibition. We found different variability characteristics between the three settings, which may in part account for differences in empirical observations. From a clinical perspective, differences in striatal dopaminergic signaling contribute to differential learning and reward processing, with relevant implications for addictive- and compulsive-like behavior. Specifically, dopaminergic tone is assumed to impact on phasic dopamine and hence on the integration of reward-related signals. However, in humans DA tone is classically assessed using PET, which is an indirect measure of endogenous DA availability and suffers from temporal and spatial resolution issues. We discuss how this can lead to discrepancies with observations from other methods such as microdialysis and show how computational modeling can help to refine our understanding of DA transmission. Author summary The dopaminergic system of the brain is very complex and affects various cognitive domains like memory, learning and motor control. Alterations have been observed e.g. in Parkinson's or Huntington's Disease, ADHD, addiction and compulsive disorders, such as pathological gambling and also in obesity. We present a new computational model that allows to simulate the process of dopamine transmission from dopaminergic neurons originated in source brain regions like the VTA to target areas such as the striatum on a synaptic and on a larger, volume-spanning level. The model can further be used for simulations of dopamine related diseases or pharmacological interventions. In general, computational modeling helps to extend our understanding, gained from empirical research, to situations were in vivo measurements are not feasible.Peer reviewe

    Enhanced Go and NoGo Learning in Individuals With Obesity

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    Overeating in individuals with obesity is hypothesized to be partly caused by automatic action tendencies to food cues that have the potential to override goal-directed dietary restriction. Individuals with obesity are often characterized by alterations in the processing of such rewarding food, but also of non-food stimuli, and previous research has suggested a stronger impact on the execution of goal-directed actions in obesity. Here, we investigated whether Pavlovian cues can also corrupt the learning of new approach or withdrawal behavior in individuals with obesity. We employed a probabilistic Pavlovian-instrumental learning paradigm in which participants (29 normal-weight and 29 obese) learned to actively respond (Go learning) or withhold a response (NoGo learning) in order to gain monetary rewards or avoid losses. Participants were better at learning active approach responses (Go) in the light of anticipated rewards and at learning to withhold a response (NoGo) in the light of imminent punishments. Importantly, there was no evidence for a stronger corruption of instrumental learning in individuals with obesity. Instead, they showed better learning across conditions than normal-weight participants. Using a computational reinforcement learning model, we additionally found an increased learning rate in individuals with obesity. Previous studies have mostly reported a lower reinforcement learning performance in individuals with obesity. Our results contradict this and suggest that their performance is not universally impaired: Instead, while previous studies found reduced stimulus-value learning, individuals with obesity may show better action-value learning. Our findings highlight the need for a broader investigation of behavioral adaptation in obesity across different task designs and types of reinforcement learning.Peer Reviewe

    The significance of work allocation in the professional apprenticeship of solicitors

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    It is a peculiarity of the solicitors‚Äô profession that it has historically relied on methods of pre-qualification ‚Äėtraining‚Äô by way of apprenticeship and that an entirely respectable non-graduate route into the profession remains. In a political context, however, where the profession is called upon positively to demonstrate its standards of performance, the professional regulator seeks to attach a competence framework to the existing model; shifting the focus from how the trainee learns to what the trainee learns. This paper will explore the period of traineeship from the perspective of the trainees themselves, drawing on two small qualitative studies, focussing on the fundamental context factor of the allocation and structuring of their work. In the first study the context for this evaluation is the set of outcomes being tested by the professional regulator and in the second, the perceptions of qualified individuals looking back at their apprenticeship, The paper concludes that there remains work for the profession to do not only in fostering supportive and expansive apprenticeships, but in attending, however, supportive the surrounding environment, to the work being carried out by trainees and its relationship with the work carried out by newly qualified solicitors

    The efficacy of self-management strategies for females with endometriosis : a systematic review

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    Self-management is critical for the care of endometriosis. Females with endometriosis frequently use self-management strategies to manage associated symptoms; however, the efficacy of such strategies is unknown. The aim of this review was to systematically appraise the evidence concerning efficacy of self-management strategies for endometriosis symptoms. Electronic databases, including Medline, Embase, Emcare, Web of Science Core Collection, Scopus, and the Cochrane Central Register of Controlled Trials, were searched from inception to March 2021. We included peer-reviewed experimental studies published in English evaluating the efficacy of self-management strategies in human females laparoscopically diagnosed with endometriosis. Studies underwent screening, data extraction, and risk of bias appraisal (randomised studies: Risk of Bias 2 tool; non-randomised studies: Risk Of Bias In Non-randomized Studies ‚Äď of Interventions tool). Of the fifteen studies included, 10 evaluated dietary supplements, three evaluated dietary modifications, one evaluated over-the-counter medication, and one evaluated exercise. Most studies had a high-critical risk of bias. Many self-management strategies were not more effective at reducing endometriosis symptoms compared to placebo or hormonal therapies. Where studies suggest efficacy for self-management strategies, no recommendations can be made due to the poor quality and heterogeneity of evidence. High-quality empirical evidence is required to investigate the efficacy of self-management strategies for females with endometriosis

    Slave to habit?: obesity is associated with decreased behavioural sensitivity to reward devaluation.

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    The motivational value of food is lower during satiety compared to fasting. Dynamic changes in motivational value promote food seeking or meal cessation. In obesity this mechanism might be compromised since obese subjects ingest energy beyond homeostatic needs. Thus, lower adaptation of eating behaviour with respect to changes in motivational value might cause food overconsumption in obesity. To test this hypothesis, we implemented a selective satiation procedure to investigate the relationship between obesity and the size of the behavioural devaluation effect in humans. Lean to obese men (mean age 25.9, range 19‚Äď30 years; mean BMI 29.1, range 19.2‚Äď45.1 kg/m2) were trained on a free operant paradigm and learned to associate cues with the possibility to win different food rewards by pressing a button. After the initial training phase, one of the rewards was devalued by consumption. Response rates for and wanting of the different rewards were measured pre and post devaluation. Behavioural sensitivity to reward devaluation, measured as the magnitude of difference between pre and post responses, was regressed against BMI. Results indicate that (1) higher BMI compared to lower BMI in men led to an attenuated behavioural adjustment to reward devaluation, and (2) the decrease in motivational value was associated with the decrease in response rate between pre and post. Change in explicitly reported motivational value, however, was not affected by BMI. Thus, we conclude that high BMI in men is associated with lower behavioural adaptation with respect to changes in motivational value of food, possibly resulting in automatic overeating patterns that are hard to control in daily life

    Social capital factors affecting uptake of sustainable soil management practices: a literature review

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    Soil quality is in decline in many parts of the world, in part due to the intensification of agricultural practices. Whilst economic instruments and regulations can help incentivise uptake of more sustainable soil management practices, they rarely motivate long-term behavior change when used alone. There has been increasing attention towards the complex social factors that affect uptake of sustainable soil management practices. To understand why some communities try these practices whilst others do not, we undertook a narrative review to understand how social capital influences adoption in developed nations. We found that the four components of social capital ‚Äď trust, norms, connectedness and power ‚Äď can all influence the decision of farmers to change their soil management. Specifically, information flows more effectively across trusted, diverse networks where social norms exist to encourage innovation. Uptake is more limited in homogenous, close-knit farming communities that do not have many links with non-farmers and where there is a strong social norm to adhere to the status quo. Power can enhance or inhibit uptake depending on its characteristics. Future research, policy and practice should consider whether a lack of social capital could hinder uptake of new practices and, if so, which aspects of social capital could be developed to increase adoption of sustainable soil management practices. Enabling diverse, collaborative groups (including farmers, advisers and government officials) to work constructively together could help build social capital, where they can co-define, -develop and -enact measures to sustainably manage soils

    Glycocalyx dynamics and the inflammatory response of genetically modified porcine endothelial cells.

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    Xenotransplantation is a promising approach to reduce organ shortage, while genetic modification of donor pigs has significantly decreased the immunogenic burden of xenotransplants, organ rejection is still a hurdle. Genetically modified pig organs are used in xenotransplantation research, and the first clinical pig-to-human heart transplantation was performed in 2022. However, the impact of genetic modification has not been investigated on a cellular level yet. Endothelial cells (EC) and their sugar-rich surface known as the glycocalyx are the first barrier encountering the recipient's immune system, making them a target for rejection. We have previously shown that wild type venous but not arterial EC were protected against heparan sulfate (HS) shedding after activation with human serum or human tumor necrosis factor alpha (TN
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