8 research outputs found
Incremental semi-supervised learning for anomalous trajectory detection
The acquisition of a scene-specific normal behaviour model underlies many existing
approaches to the problem of automated video surveillance. Since it is unrealistic
to acquire a comprehensive set of labelled behaviours for every surveyed scenario,
modelling normal behaviour typically corresponds to modelling the distribution of a
large collection of unlabelled examples. In general, however, it would be desirable to
be able to filter an unlabelled dataset to remove potentially anomalous examples.
This thesis proposes a simple semi-supervised learning framework that could allow
a human operator to efficiently filter the examples used to construct a normal behaviour
model by providing occasional feedback: Specifically, the classification output
of the model under construction is used to filter the incoming sequence of unlabelled
examples so that human approval is requested before incorporating any example classified
as anomalous, while all other examples are automatically used for training.
A key component of the proposed framework is an incremental one-class learning
algorithm which can be trained on a sequence of normal examples while allowing new
examples to be classified at any stage during training. The proposed algorithm represents
an initial set of training examples with a kernel density estimate, before using
merging operations to incrementally construct a Gaussian mixture model while minimising
an information-theoretic cost function. This algorithm is shown to outperform
an existing state-of-the-art approach without requiring off-line model selection.
Throughout this thesis behaviours are considered in terms of whole motion trajectories:
in order to apply the proposed algorithm, trajectories must be encoded
with fixed length vectors. To determine an appropriate encoding strategy, an empirical
comparison is conducted to determine the relative class-separability afforded
by several different trajectory representations for a range of datasets. The results obtained
suggest that the choice of representation makes a small but consistent difference
to class separability, indicating that cubic B-Spline control points (fitted using
least-squares regression) provide a good choice for use in subsequent experiments.
The proposed semi-supervised learning framework is tested on three different real
trajectory datasets. In all cases the rate of human intervention requests drops steadily,
reaching a usefully low level of 1% in one case. A further experiment indicates that
once a sufficient number of interventions has been provided, a high level of classification
performance can be achieved even if subsequent requests are ignored. The automatic
incorporation of unlabelled data is shown to improve classification performance
in all cases, while a high level of classification performance is maintained even when
unlabelled data containing a high proportion of anomalous examples is presented
Temporal dissociation of phencyclidine: Induced locomotor and social alterations in rats using an automated homecage monitoring system – implications for the 3Rs and preclinical drug discovery
Background: Rodent behavioural assays are widely used to delineate the mechanisms of psychiatric disorders and predict the efficacy of drug candidates. Conventional behavioural paradigms are restricted to short time windows and involve transferring animals from the homecage to unfamiliar apparatus which induces stress. Additionally, factors including environmental perturbations, handling and the presence of an experimenter can impact behaviour and confound data interpretation. To improve welfare and reproducibility these issues must be resolved. Automated homecage monitoring offers a more ethologically relevant approach with reduced experimenter bias. Aim: To evaluate the effectiveness of an automated homecage system at detecting locomotor and social alterations induced by phencyclidine (PCP) in group-housed rats. PCP is an NMDA receptor antagonist commonly utilised to model aspects of schizophrenia. Methods: Rats housed in groups of 3 were implanted with radio frequency identification (RFID) tags. Each homecage was placed over a RFID reader baseplate for the automated monitoring of the social and locomotor activity of each individual rat. For all rats, we acquired homecage data for 24 h following administration of both saline and PCP (2.5 mg/kg). Results: PCP resulted in significantly increased distance travelled from 15 to 60 min post injection. Furthermore, PCP significantly enhanced time spent isolated from cage-mates and this asociality lasted from 60 to 105 min post treatment. Conclusions: Unlike conventional assays, in-cage monitoring captures the temporal duration of drug effects on multiple behaviours in the same group of animals. This approach could benefit psychiatric preclinical drug discovery though improved welfare and increased between-laboratory replicability
Assessing mouse behaviour throughout the light/dark cycle using automated in-cage analysis tools
Identification of Altered Evoked and Non-Evoked Responses in a Heterologous Mouse Model of Endometriosis-Associated Pain
The aim of this study was to develop and refine a heterologous mouse model of endometriosis-associated pain in which non-evoked responses, more relevant to the patient experience, were evaluated. Immunodeficient female mice (N = 24) were each implanted with four endometriotic human lesions (N = 12) or control tissue fat (N = 12) on the abdominal wall using tissue glue. Evoked pain responses were measured biweekly using von Frey filaments. Non-evoked responses were recorded weekly for 8 weeks using a home cage analysis (HCA). Endpoints were distance traveled, social proximity, time spent in the center vs. outer areas of the cage, drinking, and climbing. Significant differences between groups for von Frey response, climbing, and drinking were detected on days 14, 21, and 35 post implanting surgery, respectively, and sustained for the duration of the experiment. In conclusion, a heterologous mouse model of endometriosis-associated evoked a non-evoked pain was developed to improve the relevance of preclinical models to patient experience as a platform for drug testing
Automated recording of home cage activity and temperature of individual rats housed in social groups: The Rodent Big Brother project
Measuring the activity and temperature of rats is commonly required in biomedical research. Conventional approaches necessitate single housing, which affects their behavior and wellbeing. We have used a subcutaneous radiofrequency identification (RFID) transponder to measure ambulatory activity and temperature of individual rats when group-housed in conventional, rack-mounted home cages. The transponder location and temperature is detected by a matrix of antennae in a baseplate under the cage. An infrared high-definition camera acquires side-view video of the cage and also enables automated detection of vertical activity. Validation studies showed that baseplate-derived ambulatory activity correlated well with manual tracking and with side-view whole-cage video pixel movement. This technology enables individual behavioral and temperature data to be acquired continuously from group-housed rats in their familiar, home cage environment. We demonstrate its ability to reliably detect naturally occurring behavioral effects, extending beyond the capabilities of routine observational tests and conventional monitoring equipment. It has numerous potential applications including safety pharmacology, toxicology, circadian biology, disease models and drug discovery