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Biomedical subjects

Michael Denham

Publications and source records attributed to Michael Denham.

6 recordsLinked to original sources
PubMed2005

A population-based model of the nonlinear dynamics of the thalamocortical feedback network displays intrinsic oscillations in the spindling (7-14 Hz) range.

The thalamocortical network is modelled using the Wilson-Cowan equations for neuronal population activity. We show that this population model with biologically derived parameters possesses intrinsic nonlinear oscillatory dynamics, and that the frequency of oscillation lies within the spindle range. Spindle oscillations are an early sleep oscillation characterized by high-frequency bursts of action potentials followed by a period of quiescence, at a frequency of 7-14 Hz. Spindles are generally regarded as being generated by intrathalamic circuitry, as decorticated thalamic slices and the isolated thalamic reticular nucleus exhibit spindles. However, the role of cortical feedback has been shown to regulate and synchronize the oscillation. Previous modelling studies have mainly used conductance-based models and hence the mechanism relied upon the inclusion of ionic currents, particularly the T-type calcium current. Here we demonstrate that spindle-frequency oscillatory activity can also arise from the nonlinear dynamics of the thalamocortical circuit, and we use bifurcation analysis to examine the robustness of this oscillation in terms of the functional range of the parameters used in the model. The results suggest that the thalamocortical circuit has intrinsic nonlinear population dynamics which are capable of providing robust support for oscillatory activity within the frequency range of spindle oscillations.

Animals↗
PubMed2005

Fast access to concepts in concept lattices via bidirectional associative memories.

Bidirectional associative memories (BAMs) are shown to be capable of precisely learning concept lattice structures by Radim Belohlávek. The focus of this letter is to show that the BAM, when set up with a concept lattice by setting up connection weights according to the rule proposed by Belohlávek, always returns the most specific or most generic concept containing the given set of objects or attributes when a set of objects or attributes is presented as input to the object or attribute layer. A proof of this property is given here, together with an example, and a brief application of the property is provided.

Association Learning↗
PubMed2005

Switching of prescription drugs to over-the-counter status: is it a good thing for the elderly?

Prescription medicines are increasingly being switched to over-the-counter (OTC, nonprescription) status in the developed world, with the support of government policy. These changes may provide greater choice for individuals and offer potential savings in government spending on health while expanding the market for pharmaceutical companies. However, there is concern regarding the safety of these reclassifications. Elderly people are the largest consumers of prescription and OTC medicines and are more vulnerable to drug adverse effects and the risks of multiple or inappropriate medications. Commonly purchased agents such as NSAIDs have recognised adverse effects which have been shown to be more common in the elderly. Furthermore, all sedatives, including antihistamines, have a propensity to cause falls in older people. As many doctors do not ask patients about OTC medicine use, problems related to use of these drugs may go undetected. Furthermore, the increased availability of OTCs may result in a delay in patients consulting medical practitioners for potentially serious conditions, although this has not so far been investigated. In the UK, the recent switch of a low-dose HMG-CoA reductase inhibitor (statin) to OTC status has caused concern. Although there might theoretically be some benefits from improved access to medications used in primary and secondary prevention of heart disease, the actual outcomes of use of this reduced dose of the statin will be difficult or impossible for patients or practitioners to monitor. OTC drug use implies a mutual responsibility for communication between patients and health professionals that in practice is not always achieved. Epidemiological research is needed to investigate patterns of OTC use and evaluate the potential risks of OTC medicines in elderly people. Governments, regulatory bodies, professionals and the drug industry have a responsibility to ensure that robust systems are in place if the increased use of OTC medicines by elderly people is to be safe and effective.

Aged↗
PubMed2003

A multi-centre survey among informal carers who manage medication for older care recipients: problems experienced and development of services.

The UK Government has highlighted the need to develop appropriate information and support services for informal carers. Previous research that has investigated informal caring has found that managing medication is one aspect of the caring role that presents its own problems; however, these have not been subject to detailed examination. The objective of the present paper was to report the number and type of problems experienced by informal carers when managing medication for older care recipients, and to relate these to measures of coping and health. This was a cross-sectional survey undertaken in one district in each of four randomly selected health authority areas in England. Structured interviews, comprising closed and open questions, with 184 informal carers and 93 associated older care recipients were conducted in participants' own homes. Data were gathered on the number and type of medication-related problems experienced in relation to the informal caring role, and the impact of these from carers' perspectives in terms of coping and health. Sixty-seven per cent of carers reported problems with at least one medication-related activity. Problems were associated with all types of medication-related activities, and experienced by carers providing different levels of care for older people. Four themes were identified from carers' accounts which illustrated a diversity of practical problems and anxieties: maintaining continuous supplies of medication in the home; assisting with administration; making clinical judgements; and communicating with care recipients and health professionals. Carers reporting greater numbers of medication-related problems were more likely to experience higher levels of carer strain (P < 0.001) and poorer mental health status (P < 0.001). The findings of the present study provide insights to inform the development of primary care services to support informal carers in the management of medication for older people.

Adaptation, Psychological↗
PubMed2002

Long-term care. The best of both worlds.

An NHS/housing association venture has produced good accommodation for 30 elderly people in need of long-term care. The housing organisation takes responsibility for support services such as laundry, cleaning, security and catering. The unit remains part of the NHS. Patients appreciate the environment and staff turnover is low.

Aged↗