35 research outputs found
Generative-Discriminative Low Rank Decomposition for Medical Imaging Applications
In this thesis, we propose a method that can be used to extract biomarkers from medical images toward early diagnosis of abnormalities. Surge of demand for biomarkers and availability of medical images in the recent years call for accurate, repeatable, and interpretable approaches for extracting meaningful imaging features. However, extracting such information from medical images is a challenging task because the number of pixels (voxels) in a typical image is in order of millions while even a large sample-size in medical image dataset does not usually exceed a few hundred. Nevertheless, depending on the nature of an abnormality, only a parsimonious subset of voxels is typically relevant to the disease; therefore various notions of sparsity are exploited in this thesis to improve the generalization performance of the prediction task.
We propose a novel discriminative dimensionality reduction method that yields good classification performance on various datasets without compromising the clinical interpretability of the results. This is achieved by combining the modelling strength of generative learning framework and the classification performance of discriminative learning paradigm. Clinical interpretability can be viewed as an additional measure of evaluation and is also helpful in designing methods that account for the clinical prior such as association of certain areas in a brain to a particular cognitive task or connectivity of some brain regions via neural fibres.
We formulate our method as a large-scale optimization problem to solve a constrained matrix factorization. Finding an optimal solution of the large-scale matrix factorization renders off-the-shelf solver computationally prohibitive; therefore, we designed an efficient algorithm based on the proximal method to address the computational bottle-neck of the optimization problem. Our formulation is readily extended for different scenarios such as cases where a large cohort of subjects has uncertain or no class labels (semi-supervised learning) or a case where each subject has a battery of imaging channels (multi-channel), \etc. We show that by using various notions of sparsity as feasible sets of the optimization problem, we can encode different forms of prior knowledge ranging from brain parcellation to brain connectivity
RFID Technology in Intelligent Tracking Systems in Construction Waste Logistics Using Optimisation Techniques
Construction waste disposal is an urgent issue
for protecting our environment. This paper proposes a
waste management system and illustrates the work
process using plasterboard waste as an example, which
creates a hazardous gas when land filled with household
waste, and for which the recycling rate is less than 10%
in the UK. The proposed system integrates RFID
technology, Rule-Based Reasoning, Ant Colony
optimization and knowledge technology for auditing
and tracking plasterboard waste, guiding the operation
staff, arranging vehicles, schedule planning, and also
provides evidence to verify its disposal. It h relies on
RFID equipment for collecting logistical data and uses
digital imaging equipment to give further evidence; the
reasoning core in the third layer is responsible for
generating schedules and route plans and guidance, and
the last layer delivers the result to inform users. The
paper firstly introduces the current plasterboard
disposal situation and addresses the logistical problem
that is now the main barrier to a higher recycling rate,
followed by discussion of the proposed system in terms
of both system level structure and process structure.
And finally, an example scenario will be given to
illustrate the system’s utilization
Physical and Mental Coordination in the Elderly: A Causal Role for the Cerebellum?
The mechanisms underlying the progressive changes in tissues and organs that characterise normal ageing remain unclear. The cerebellum is known to play a major role in motor function, but recent research suggests it plays an equivalent role in cognition. Working with the hypothesis that cortico-cerebellar loops ensure smooth and coordinated activity in both domains, this thesis investigates the possible role of the cerebellum in normal ageing and in interventions to improve function, seeking to contribute to both theoretical and applied approaches to ageing.
Study one investigated relationships between motor and cognitive function using raw data from a national normative sample of adults aged 16 to 75, employing a test battery assessing motor and cognitive skills. Differences between age groups were demonstrated in some tests of complex processing speed, working memory and executive function, with suggestive evidence that senescence in tests is reflected in tests sensitive to cerebellar function.
Study two refined the battery, while including further measures of motor and memory performance to investigate linkages between cognitive and cerebellar function. Using a sample of 256 older adults, results were variable but provided evidence that pegboard performance could act as a predictor of some cognitive functions.
Study three investigated a proactive intervention for healthy older adults designed to improve cerebellar function, and therefore balance and executive function. This involved an 8-10 week self-administered, internet-based coordinative exercise intervention using a ‘cerebellar challenge’ suite of graded activities. Performance on a basket of tests was assessed before and after, and also compared with performance changes in a no-intervention control group. Significantly greater benefits for the intervention group than the controls were found for balance physical coordination and controlled information processing.
Overall, these studies support current research indicating cerebellar contribution to both cognitive and motor problems arising in old age, and present evidence that non-verbal memory and controlled speeded information problems may be alleviated through targeted activities affecting cerebellar function improving postural stability and physical coordination
The relationship between tinnitus, cognitive performance and demands on the individual
This Thesis attempted to first replicate the work of Andersson et al. (2000) to identify possible cognitive decrements in tinnitus sufferers. In addition, a number of trait variables were measured in comparison to a matched control group. It was discovered that the tinnitus population did not differ in terms of any trait, yet still performed worse on a number of cognitive tasks - performing as accurately, but significantly more slowly. It was thus concluded that the presence of the tinnitus interfered with cognition by consuming valuable and finite attentional resources.A second study attempted to narrow this down further, identifying specific tasks and specific circumstances in which tinnitus sufferers performed less effectively than their non-tinnitus counterparts.From these results, it was postulated that the relationship between tinnitus severity and cognitive performance is moderated by demand and as such, a longitudinal diary study (six weeks) was undertaken to measure (self-rated) effectiveness under a wide range of demands in real life. Moderated hierarchical regression techniques were thus able to identify situations in which mental demand levels drive the relationship between tinnitus and performance, thus supporting the hypothesis
Attention Restraint, Working Memory Capacity, and Mind Wandering: Do Emotional Valence or Intentionality Matter?
Attention restraint appears to mediate the relationship between working memory capacity (WMC) and mind wandering (Kane et al., 2016). Prior work has identifed two dimensions of mind wandering—emotional valence and intentionality. However, less is known about how WMC and attention restraint correlate with these dimensions. Te current study examined the relationship between WMC, attention restraint, and mind wandering by emotional valence and intentionality. A confrmatory factor analysis demonstrated that WMC and attention restraint were strongly correlated, but only attention restraint was related to overall mind wandering, consistent with prior fndings. However, when examining the emotional valence of mind wandering, attention restraint and WMC were related to negatively and positively valenced, but not neutral, mind wandering. Attention restraint was also related to intentional but not unintentional mind wandering. Tese results suggest that WMC and attention restraint predict some, but not all, types of mind wandering
Semantic radical consistency and character transparency effects in Chinese: an ERP study
BACKGROUND: This event-related potential (ERP) study aims to investigate the representation and temporal dynamics of Chinese orthography-to-semantics mappings by simultaneously manipulating character transparency and semantic radical consistency. Character components, referred to as radicals, make up the building blocks used dur...postprin
Investigating which processes influence reading fluency in dyslexic and non-dyslexic groups
This thesis reports an investigation of the component processes underlying reading
fluency.
A current controversy in reading research is whether reading ability and development
is determined solely by linguistic processes such as phonological (sound-based) skill, or
whether it can also be influenced by non-linguistic processes such as visual processing
of print, attention and general timing capacity. One way of addressing this problem is to
investigate naming speed; the speed with which objects, colours, letters or digits can be
named. Letter naming in particular represents a ‘microcosm’ of the processes required
for fluent reading.
The experiments in this thesis systematically manipulate the letter naming process to
investigate a) what determines naming-speed performance and b) which processes, when
aberrant, cause slower naming in dyslexic readers. Results suggest that non-dyslexic
readers are better able to process multiple letter items simultaneously than dyslexic
readers. Further, we find evidence suggesting a strong role for phonological retrieval in
determining naming latencies and contributing to the naming-speed deficit. We also
identify a strong attentional component and a role for visual processing in naming speed
which discriminates dyslexic and non-dyslexic reading groups. The results support
models emphasising the multi-componential nature of reading fluency and suggest that
naming deficits in dyslexia reflect processing difficulties in non-phonological, as well as
phonological domains