2,767 research outputs found
Planning with Information-Processing Constraints and Model Uncertainty in Markov Decision Processes
Information-theoretic principles for learning and acting have been proposed
to solve particular classes of Markov Decision Problems. Mathematically, such
approaches are governed by a variational free energy principle and allow
solving MDP planning problems with information-processing constraints expressed
in terms of a Kullback-Leibler divergence with respect to a reference
distribution. Here we consider a generalization of such MDP planners by taking
model uncertainty into account. As model uncertainty can also be formalized as
an information-processing constraint, we can derive a unified solution from a
single generalized variational principle. We provide a generalized value
iteration scheme together with a convergence proof. As limit cases, this
generalized scheme includes standard value iteration with a known model,
Bayesian MDP planning, and robust planning. We demonstrate the benefits of this
approach in a grid world simulation.Comment: 16 pages, 3 figure
A comparison of course-related stressors in undergraduate problem-based learning (PBL) versus non-PBL medical programmes
Background: Medical students report high levels of stress related to their medical training as well as to other personal and financial factors. The aim of this study is to investigate whether there are differences in course-related stressors reported by medical students on undergraduate problem-based learning (PBL) and non-PBL programmes in the UK.
Method: A cross-sectional study of second-year medical students in two UK medical schools (one PBL and one non-PBL programme) was conducted. A 16-question self-report questionnaire, derived from the Perceived Medical Student Stress Scale and the Higher Education Stress Inventory, was used to measure course-related stressors. Following univariate analysis of each stressor between groups, multivariate logistic regression was used to determine which stressors were the best predictors of each course type, while controlling for socio-demographic differences between the groups.
Results: A total of 280 students responded. Compared to the non-PBL students (N = 197), the PBL students (N = 83) were significantly more likely to agree that: they did not know what the faculty expected of them (Odds Ratio (OR) = 0.38, p = 0.03); there were too many small group sessions facilitated only by students resulting in an unclear curriculum (OR = 0.04, p < 0.0001); and that there was a lack of opportunity to explore academic subjects of interest (OR = 0.40, p = 0.02). They were significantly more likely to disagree that: there was a lack of encouragement from teachers (OR = 3.11, p = 0.02); and that the medical course fostered a sense of anonymity and feelings of isolation amongst students (OR = 3.42, p = 0.008).
Conclusion: There are significant differences in the perceived course-related stressors affecting medical students on PBL and non-PBL programmes. Course designers and student support services should therefore tailor their work to minimise, or help students cope with, the specific stressors on each course type to ensure optimum learning and wellbeing among our future doctors
Studying the effects of thalamic interneurons in a thalamocortical neural mass model
Neural mass models of the thalamocortical circuitry are
often used to mimic brain activity during sleep and
wakefulness as observed in scalp electroencephalogram
(EEG) signals [1]. It is understood that alpha rhythms
(8-13 Hz) dominate the EEG power-spectra in the resting-state
[2] as well as the period immediately before
sleep [3]. Literature review shows that the thalamic
interneurons (IN) are often ignored in thalamocortical
population models; the emphasis is on the connections
between the thalamo cortical relay (TCR) and the thalamic
reticular nucleus (TRN). In this work, we look into
the effects of the IN cell population on the behaviour of
an existing thalamocortical model containing the TCR
and TRN cell populations [4]. A schematic of the
extended model used in this work is shown in Fig.1.
The model equations are solved in Matlab using the
Runge-Kutta method of the 4th/5th order. The model
shows high sensitivity to the forward and reverse rates
of reactions during synaptic transmission as well as on
the membrane conductance of the cell populations. The
input to the model is a white noise signal simulating
conditions of resting state with eyes closed, a condition
well known to be associated with dominant alpha band
oscillations in EEG e.g. [5]. Thus, the model parameters
are calibrated to obtain a set of basal parameter values
when the model oscillates with a dominant frequency
within the alpha band. The time series plots and the
power spectra of the model output are compared with
those when the IN cell population is disconnected from
the circuit (by setting the inhibitory connectivity parameter
from the IN to the TCR to zero). We observe
(Fig. 2 inset) a significant difference in time series output
of the TRN cell population with and without the IN
cell population in the model; this in spite of the IN
having no direct connectivity to and from the TRN cell
population (Fig. 1). A comparison of the power spectra
behaviour of the model output within the delta
(1-3.5Hz), theta (3.75-7.5Hz), alpha (7.75-13.5Hz) and
beta (13.75-30.5Hz) bands is shown in Fig. 2. Disconnecting
the IN cell population shows a significant drop in the
alpha band power and the dominant frequency of oscillation
now lies within the theta band. An overall ‘slowing’
(left-side shift) of the power spectra is observed with an
increase within the delta and theta bands and a decrease
in the alpha and beta bands. Such a slowing of EEG is a
signature of slow wave sleep in healthy individuals, and
this suggests that the IN cell population may be centrally
involved in the phase transition to slow wave sleep [6]. It
is also characteristic of the waking EEG in Alzheimer’s
disease, and may help us to understand the role of the IN
cell population in modulating TCR and TRN cell behaviour
in pathological brain conditions
Can Reproductive Health Voucher Programs Improve Quality of Postnatal Care? A Quasi-Experimental Evaluation of Kenya’s Safe Motherhood Voucher Scheme
This study tests the group-level causal relationship between the expansion of Kenya’s Safe Motherhood voucher program and changes in quality of postnatal care (PNC) provided at voucher-contracted facilities. We compare facilities accredited since program inception in 2006 (phase I) and facilities accredited since 2010-2011 (phase II) relative to comparable non-voucher facilities. PNC quality is assessed using observed clinical content processes, as well as client-reported outcome measures. Two-tailed unpaired t-tests are used to identify differences in mean process quality scores and client-reported outcome measures, comparing changes between intervention and comparison groups at the 2010 and 2012 data collection periods. Difference-in-differences analysis is used to estimate the reproductive health (RH) voucher program’s causal effect on quality of care by exploiting group-level differences between voucher-accredited and non-accredited facilities in 2010 and 2012. Participation in the voucher scheme since 2006 significantly improves overall quality of postnatal care by 39% (p=0.02), where quality is defined as the observable processes or components of service provision that occur during a PNC consultation. Program participation since phase I is estimated to improve the quality of observed maternal postnatal care by 86% (p=0.02), with the largest quality improvements in counselling on family planning methods (IRR 5.0; p=0.01) and return to fertility (IRR 2.6; p=0.01). Despite improvements in maternal aspects of PNC, we find a high proportion of mothers who seek PNC are not being checked by any provider after delivery. Additional strategies will be necessary to standardize provision of packaged postnatal interventions to both mother and new-born. This study addresses an important gap in the existing RH literature by using a strong evaluation design to assess RH voucher program effectiveness on quality improvement
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Bereavement, grief and consolation: emotional-affective geographies of loss during COVID-19
COVID-19 has resulted in a new global geographies of death ranging from cellular to global scales. These geographies are uneven, reflecting existing inequalities and failures of governance. In addition to death and bereavement, the pandemic has generated varied forms of loss and consolation, negative and positive affective atmospheres, whereby emotions are mobilised and politicised. Understanding these emotional-affective topographies, including ‘emotional-viral-loads’, is vital to wellbeing, resilience and unfolding policy interventions locally and globally
Clustering in surgical trials : database of intracluster correlations
PMID: 22217216 [PubMed - indexed for MEDLINE] PMCID: PMC3311136 Free PMC ArticlePeer reviewedPublisher PD
Do Interventions Designed to Support Shared Decision-Making Reduce Health Inequalities? : A Systematic Review and Meta-Analysis
Copyright: © 2014 Durand et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Background: Increasing patient engagement in healthcare has become a health policy priority. However, there has been concern that promoting supported shared decision-making could increase health inequalities. Objective: To evaluate the impact of SDM interventions on disadvantaged groups and health inequalities. Design: Systematic review and meta-analysis of randomised controlled trials and observational studies.Peer reviewe
Determinants for receiving acupuncture for LBP and associated treatments: a prospective cohort study
BACKGROUND: Acupuncture is a frequently used but controversial adjunct to the treatment of chronic low back pain (LBP). Acupuncture is now considered to be effective for chronic LBP and health care systems are pressured to make a decision whether or not acupuncture should be covered. It has been suggested that providing such services might reduce the use of other health care services. Therefore, we explored factors associated with acupuncture treatment for LBP and the relation of acupuncture with other health care services. METHODS: This is a post hoc analysis of a longitudinal prospective cohort study. General practitioners (GPs) recruited consecutive adult patients with LBP. Data on physical function, subjective mood and utilization of health care services was collected at the first consultation and at follow-up telephone interviews for a period of twelve months. RESULTS: A total of 179 (13 %) out of 1,345 patients received acupuncture treatment. The majority of those (59 %) had chronic LBP. Women and elderly patients were more likely to be given acupuncture. Additional determinants of acupuncture therapy were low functional capacity and chronicity of pain. Chronic (vs. acute) back pain OR 1.6 (CL 1.4–2.9) was the only significant disease-related factor associated with the treatment. The strongest predictors for receiving acupuncture were consultation with a GP who offers acupuncture OR 3.5 (CL 2.9–4.1) and consultation with a specialist OR 2.1 (CL 1.9–2.3). After adjustment for patient characteristics, acupuncture remained associated with higher consultation rates and an increased use of other health care services like physiotherapy. CONCLUSION: Receiving acupuncture for LBP depends mostly on the availability of the treatment. It is associated with increased use of other health services even after adjustment for patient characteristics. In our study, we found that receiving acupuncture does not offset the use of other health care resources. A significant proportion of patients who received did not meet the so far only known selection criterion (chonicity). Acupuncture therapy might be a reflection of helplessness in both patients and health care providers
Using the MitoB method to assess levels of reactive oxygen species in ecological studies of oxidative stress
In recent years evolutionary ecologists have become increasingly interested in the effects of reactive
oxygen species (ROS) on the life-histories of animals. ROS levels have mostly been inferred indirectly
due to the limitations of estimating ROS from in vitro methods. However, measuring ROS (hydrogen
peroxide, H2O2) content in vivo is now possible using the MitoB probe. Here, we extend and refine
the MitoB method to make it suitable for ecological studies of oxidative stress using the brown trout
Salmo trutta as model. The MitoB method allows an evaluation of H2O2 levels in living organisms over
a timescale from hours to days. The method is flexible with regard to the duration of exposure and
initial concentration of the MitoB probe, and there is no transfer of the MitoB probe between fish. H2O2
levels were consistent across subsamples of the same liver but differed between muscle subsamples
and between tissues of the same animal. The MitoB method provides a convenient method for
measuring ROS levels in living animals over a significant period of time. Given its wide range of possible
applications, it opens the opportunity to study the role of ROS in mediating life history trade-offs in
ecological settings
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