Perceptual learning in humans

Unsupervised exposure to confusable stimuli facilitates later discrimination between them. It is known that the schedule of exposure is critical to this perceptual learning effect, but several issues remain unresolved: I) it is not known whether a mechanism of mutual inhibition, taken by some to underpin perceptual learning in rats, is also evident in humans. II) Although simultaneous presentation of the to-be- discriminated stimuli has been suggested by some to be the most efficient way to promote perceptual learning, the associative mechanisms proposed by others (e.g., that of mutual inhibition) predict the opposite. Ill) Perceptual learning has been invoked as the process by which a face becomes familiar but surprisingly, this idea has received little empirical evaluation. The experimental work reported in this thesis addresses these three issues. Experiments 1 and 2, using flavours as stimuli, reveal that the inhibitory mechanisms that contribute to perceptual learning in rats also contribute to perceptual learning in humans. Experiments 3 and 4 demonstrate a perceptual learning effect using visual stimuli, pictures of human faces and that these effects too, exhibit parallels with studies of perceptual learning with rats. In particular they demonstrate that intermixed exposure results in greater perceptual learning than does blocked exposure. Experiments 5 to 7 indicate that perceptual learning seen following simultaneous exposure is, in turn, superior to intermixed exposure - implicating a process of stimulus comparison. Experiment 8 confirms that this novel effect is also observed with other visual stimuli, chequerboards, while those of Experiments 9 and 10 indicate that the face stimuli used exhibit some of the hallmarks of face processing. These findings establish, along with Experiments 3 to 6, that perceptual learning contributes to the process by which a face becomes familiar

Novel opsin gene variation in large-bodied, diurnal lemurs

Some primate populations include both trichromatic and dichromatic (red-green colour blind) individuals due to allelic variation at the X-linked opsin locus. This polymorphic trichromacy is well described in day-active New World monkeys. Less is known about colour vision in Malagasy lemurs, but, unlike New World monkeys, only some day-active lemurs are polymorphic, while others are dichromatic. The evolutionary pressures underlying these differences in lemurs are unknown, but aspects of species ecology, including variation in activity pattern, are hypothesized to play a role. Limited data on X-linked opsin variation in lemurs make such hypotheses difficult to evaluate. We provide the first detailed examination of X-linked opsin variation across a lemur clade (Indriidae). We sequenced the X-linked opsin in the most strictly diurnal and largest extant lemur, Indri indri, and nine species of smaller, generally diurnal indriids (Propithecus). Although nocturnal Avahi (sister taxon to Propithecus) lacks a polymorphism, at least eight species of diurnal indriids have two or more X-linked opsin alleles. Four rainforest-living taxa-I. indri and the three largest Propithecus species-have alleles not previously documented in lemurs. Moreover, we identified at least three opsin alleles in Indri with peak spectral sensitivities similar to some New World monkeys

The CORE Service Improvement Programme for mental health Crisis Resolution Teams: results from a cluster-randomised trial

Background: Crisis Resolution Teams (CRTs) offer brief, intensive home treatment for people experiencing mental health crisis. CRT implementation is highly variable; positive trial outcomes have not been reproduced in scaled up CRT care. Aims: To evaluate a one-year programme to improve CRTs’ model fidelity in a non-blind, cluster randomised trial. Methods: Fifteen CRTs in England received an intervention, informed by the US Implementing Evidence Based Practice project, involving support from a CRT Facilitator, online implementation resources and regular team fidelity reviews. Ten control CRTs received no additional support. The primary outcome was service user satisfaction, measured by the Client Satisfaction Questionnaire (CSQ-8), completed by fifteen service users per team at CRT discharge (N=375). Secondary outcomes: CRT model fidelity, continuity of care, staff wellbeing, inpatient admissions and bed use and CRT readmissions were also evaluated. Results: All CRTs were retained in the trial. Median follow-up CSQ-8 score was 28 in each group: the adjusted average in the intervention group was higher than in the control group by 0.97 (CI -1.02, 2.97) but this was not significant (p=0.34). There were fewer inpatient admissions, lower inpatient bed use and better staff psychological health in intervention teams. Model fidelity rose in most intervention teams and was significantly higher than in control teams at follow up. There were no significant effects for other outcomes. Conclusions: The CRT Service Improvement Programme did not achieve its primary aim of improving service user satisfaction. It showed some promise in improving CRT model fidelity and reducing acute inpatient admissions

Insights into hominid evolution from the gorilla genome sequence.

Gorillas are humans' closest living relatives after chimpanzees, and are of comparable importance for the study of human origins and evolution. Here we present the assembly and analysis of a genome sequence for the western lowland gorilla, and compare the whole genomes of all extant great ape genera. We propose a synthesis of genetic and fossil evidence consistent with placing the human-chimpanzee and human-chimpanzee-gorilla speciation events at approximately 6 and 10 million years ago. In 30% of the genome, gorilla is closer to human or chimpanzee than the latter are to each other; this is rarer around coding genes, indicating pervasive selection throughout great ape evolution, and has functional consequences in gene expression. A comparison of protein coding genes reveals approximately 500 genes showing accelerated evolution on each of the gorilla, human and chimpanzee lineages, and evidence for parallel acceleration, particularly of genes involved in hearing. We also compare the western and eastern gorilla species, estimating an average sequence divergence time 1.75 million years ago, but with evidence for more recent genetic exchange and a population bottleneck in the eastern species. The use of the genome sequence in these and future analyses will promote a deeper understanding of great ape biology and evolution

Inhibitory associations contribute to perceptual learning in humans

Perceptual learning in humans was examined in 2 experiments. In Experiment 1, participants received intermixed exposure to 2 similar compounds (AX, BX, AX, BX, . . .) and blocked exposure to a 2nd pair of similar compounds (CY, CY, . . . , DY, DY, . . .). Aversions established to AX and CY generalized less to BX than to DY. In Experiment 2, 1 pair of compounds was presented in a forward order (i.e., AX3BX), whereas the 2nd pair of compounds was presented in a backward order (i.e., DY→CY). Aversions established to AX and CY generalized less to BX than to DY. These results indicate that inhibitory associations contribute to perceptual learning in humans and thereby establish a fundamental similarity between the mechanisms that underlie perceptual learning in humans and rats

Realising context-oriented information filtering

The notion of information overload is an increasing factor in modern information service environments where information is ‘pushed’ to the user. As increasing volumes of information are presented to computing users in the form of email, web sites, instant messaging and news feeds, there is a growing need to filter and prioritise the importance of this information. ‘Information management’ needs to be undertaken in a manner that not only prioritises what information we do need, but to also dispose of information that is sent, which is of no (or little) use to us.The development of a model to aid information filtering in a context-aware way is developed as an objective for this thesis. A key concern in the conceptualisation of a single concept is understanding the context under which that concept exists (or can exist). An example of a concept is a concrete object, for instance a book. This contextual understanding should provide us with clear conceptual identification of a concept including implicit situational information and detail of surrounding concepts.Existing solutions to filtering information suffer from their own unique flaws: textbased filtering suffers from problems of inaccuracy; ontology-based solutions suffer from scalability challenges; taxonomies suffer from problems with collaboration. A major objective of this thesis is to explore the use of an evolving community maintained knowledge-base (that of Wikipedia) in order to populate the context model from prioritise concepts that are semantically relevant to the user’s interest space. Wikipedia can be classified as a weak knowledge-base due to its simple TBox schema and implicit predicates, therefore, part of this objective is to validate the claim that a weak knowledge-base is fit for this purpose. The proposed and developed solution, therefore, provides the benefits of high recall filtering with low fallout and a dependancy on a scalable and collaborative knowledge-base.A simple web feed aggregator has been built using the Java programming language that we call DAVe’s Rss Organisation System (DAVROS-2) as a testbed environment to demonstrate specific tests used within this investigation. The motivation behind the experiments is to demonstrate that the combination of the concept framework instantiated through Wikipedia can provide a framework to aid in concept comparison, and therefore be used in news filtering scenario as an example of information overload. In order to evaluate the effectiveness of the method well understood measures of information retrieval are used. This thesis demonstrates that the utilisation of the developed contextual concept expansion framework (instantiated using Wikipedia) improved the quality of concept filtering over a baseline based on string matching. This has been demonstrated through the analysis of recall and fallout measures.EThOS - Electronic Theses Online ServiceGBUnited Kingdo