A Markovian event-based framework for stochastic spiking neural networks

In spiking neural networks, the information is conveyed by the spike times, that depend on the intrinsic dynamics of each neuron, the input they receive and on the connections between neurons. In this article we study the Markovian nature of the sequence of spike times in stochastic neural networks, and in particular the ability to deduce from a spike train the next spike time, and therefore produce a description of the network activity only based on the spike times regardless of the membrane potential process. To study this question in a rigorous manner, we introduce and study an event-based description of networks of noisy integrate-and-fire neurons, i.e. that is based on the computation of the spike times. We show that the firing times of the neurons in the networks constitute a Markov chain, whose transition probability is related to the probability distribution of the interspike interval of the neurons in the network. In the cases where the Markovian model can be developed, the transition probability is explicitly derived in such classical cases of neural networks as the linear integrate-and-fire neuron models with excitatory and inhibitory interactions, for different types of synapses, possibly featuring noisy synaptic integration, transmission delays and absolute and relative refractory period. This covers most of the cases that have been investigated in the event-based description of spiking deterministic neural networks

Authenticity and the interview : a positive response to a radical critique

We respond to recent discussions of the interview, and the ‘radical critique’ of interviewing, as reiterated in publications by Silverman and Hammersley. Reviewing and extending the critical commentary on the social life of the interview and its implications for qualitative research, we endorse criticism of the Romantic view of the informant as a speaking subject, arguing that the interview does not give access to the interiority or private emotions of social actors. We focus especially on the search for the ‘authentic’ voice of experience and feeling, arguing that the expression of authenticity is performative, and that such interviews need to be analysed for their performative features. The biographical work of the interview demands close, formal analysis, and not mere celebration. The argument is illustrated with a single case-study, derived from an ethnographic study of a social-work service in the UK. We suggest that it is possible to derive constructive responses to the radical critique, by adopting an analytic stance towards respondents’ biographical work, as expressed through extended, qualitative interviewing. The speaker’s use of positioning rhetoric is discussed

Electrolytic ablation of the rat pancreas: a feasibility trial

BACKGROUND: Pancreatic cancer is a biologically aggressive disease with less than 20% of patients suitable for a "curative" surgical resection. This, combined with the poor 5-year survival indicates that effective palliative methods for symptom relief are required. Currently there are no ablative techniques to treat pancreatic cancer in clinical use. Tissue electrolysis is the delivery of a direct current between an anode and cathode to induce localised necrosis. Electrolysis has been shown to be safe and reliable in producing hepatic tissue and tumour ablation in animal models and in a limited number of patients. This study investigates the feasibility of using electrolysis to produce localised pancreatic necrosis in a healthy rat model. METHOD: Ten rats were studied in total. Eight rats were treated with variable "doses" of coulombs, and the systemic and local effects were assessed; 2 rats were used as controls. RESULTS: Seven rats tolerated the procedure well without morbidity or mortality, and one died immediately post procedure. One control rat died on induction of anaesthesia. Serum amylase and glucose were not significantly affected. CONCLUSION: Electrolysis in the rat pancreas produced localised necrosis and appears both safe, and reproducible. This novel technique could offer significant advantages for patients with unresectable pancreatic tumours. The next stage of the study is to assess pancreatic electrolysis in a pig model, prior to human pilot studies

Photo-antagonism of the GABAA receptor

Neurotransmitter receptor trafficking is fundamentally important for synaptic transmission and neural network activity. GABAA receptors and inhibitory synapses are vital components of brain function, yet much of our knowledge regarding receptor mobility and function at inhibitory synapses is derived indirectly from using recombinant receptors, antibody-tagged native receptors and pharmacological treatments. Here we describe the use of a set of research tools that can irreversibly bind to and affect the function of recombinant and neuronal GABAA receptors following ultraviolet photoactivation. These compounds are based on the competitive antagonist gabazine and incorporate a variety of photoactive groups. By using site-directed mutagenesis and ligand-docking studies, they reveal new areas of the GABA binding site at the interface between receptor β and α subunits. These compounds enable the selected inactivation of native GABAA receptor populations providing new insight into the function of inhibitory synapses and extrasynaptic receptors in controlling neuronal excitation

Quantitative analysis of single bacterial chemotaxis using a linear concentration gradient microchannel

A microfluidic device to quantify bacterial chemotaxis has been proposed, which generates a linear concentration gradient of chemoattractant in the main channel only by convective and molecular diffusion, and which enables the bacteria to enter the main channel in a single file by hydrodynamic focusing technique. The trajectory of each bacterium in response to the concentration gradient of chemoattractant is photographed by a CCD camera and its velocity is acquired by a simple PTV (Particle Tracking Velocimetry) algorithm. An advantage of this assay is to measure the velocity of a single bacterium and to quantify the degree of chemotaxis by analyzing the frequency of velocities concurrently. Thus, the parameter characterizing the motility of wild-type Escherichia coli strain RP437 in response to various concentration gradients of L-aspartate is obtained in such a manner that the degree of bacterial chemotaxis is quantified on the basis of a newly proposed Migration Index

Cost-utility analysis of interventions to improve effectiveness of exercise therapy for adults with knee osteoarthritis: The BEEP trial

© The Author(s) 2018. Objectives. Evidence regarding the cost-effectiveness of enhancing physical therapy exercise programmes in order to improve outcomes for patients with knee OA remains unclear. This study investigates the cost-effectiveness of two enhanced physical therapy interventions compared with usual physical therapy care (UC) for adults with knee OA. Methods. A trial-based cost-utility analysis of individually tailored exercise (ITE) or targeted exercise adherence (TEA) compared with UC was undertaken over a period of 18 months. Patient-level costs were obtained, and effectiveness was measured in terms of quality-adjusted life years (QALYs), allowing the calculation of cost per QALY gained from a base-case UK health-care perspective. Results. The UC group was associated with lower National Health Service (NHS) costs [ITE-UC: £273.30, 95% CI: £-62.10 to £562.60; TEA-UC: £141.80, 95% CI: £-135.60 to £408.10)] and slightly higher QALY gains (ITE-UC: -0.015, 95% CI: -0.057 to 0.026; TEA-UC: -0.003, 95% CI: -0.045 to 0.038). In the base case, UC was the most likely cost-effective option (probability < 40% of ITE or TEA cost-effective at £20 000/QALY). Differences in total costs were attributable to intervention costs, number of visits to NHS consultants and knee surgery, which were higher in both ITE and TEA groups. Conclusion. This is the first economic evaluation comparing usual physical therapy care vs enhanced exercise interventions for knee OA that involves greater exercise individualization, supervision and progression or that focuses on exercise and physical activity adherence over the longer term. Our findings show that UC is likely to be the most cost-effective option.This paper presents independent research funded by the National Institute for Health Research (NIHR) under its Programme Grants for Applied Research (grant number: RP-PG-0407-10386) and the Arthritis Research UK Centre in Primary Care grant (grant number: 18139). Time from E.L.H. was supported, in part, by the NIHR Collaborations for Leadership in Applied Health Research and Care West Midlands and time from M.A.H. was supported, in part, by the NIHR School for Primary Care Research. N.E.F. was supported through an NIHR Research Professorship (NIHR-RP-011-015). N.E.F. and E.M.H. are NIHR Senior Investigators. The NIHR Clinical Research Network West Midlands (previously PCRN West Midlands North) and North Staffordshire Primary Care Research Consortium provided additional funding for GP and physical therapy Research Facilitators to support engagement of NHS providers in the BEEP trial; NIHR PCRN West Midlands North funded NHS service support costs for the delivery of the trial