Ideal observer analysis of signal quality in retinal circuits

The function of the retina is crucial, for it must encode visual signals so the brain can detect objects in the visual world. However, the biological mechanisms of the retina add noise to the visual signal and therefore reduce its quality and capacity to inform about the world. Because an organism's survival depends on its ability to unambiguously detect visual stimuli in the presence of noise, its retinal circuits must have evolved to maximize signal quality, suggesting that each retinal circuit has a specific functional role. Here we explain how an ideal observer can measure signal quality to determine the functional roles of retinal circuits. In a visual discrimination task the ideal observer can measure from a neural response the increment threshold, the number of distinguishable response levels, and the neural code, which are fundamental measures of signal quality relevant to behavior. It can compare the signal quality in stimulus and response to determine the optimal stimulus, and can measure the specific loss of signal quality by a neuron's receptive field for non-optimal stimuli. Taking into account noise correlations, the ideal observer can track the signal-to-noise ratio available from one stage to the next, allowing one to determine each stage's role in preserving signal quality. A comparison between the ideal performance of the photon flux absorbed from the stimulus and actual performance of a retinal ganglion cell shows that in daylight a ganglion cell and its presynaptic circuit loses a factor of ～10-fold in contrast sensitivity, suggesting specific signal-processing roles for synaptic connections and other neural circuit elements. The ideal observer is a powerful tool for characterizing signal processing in single neurons and arrays along a neural pathway.     

Preliminary investigations into the effects of breathing retraining techniques on end-tidal carbon dioxide measures in patients with asthma and healthy volunteers during a single treatment session

Objectives

Preliminary investigations into the physiological effects of breathing retraining techniques in order to establish the feasibility of the proposed methodology, produce data for power calculations and determine the potential for future research in this area.

Design

Two preliminary, exploratory studies with an experimental design.

Setting

Research laboratories.

Participants

Study 1: 15 patients with mild to moderate asthma and nine healthy volunteers. Study 2: 15 healthy volunteers.

Interventions

Physiological data from asthma patients and healthy volunteers were recorded before, during and after a single session of slow breathing and breath holds. A separate group of healthy participants carried out the slow breathing technique with and without visual biofeedback.

Outcome measures

The primary outcome was end-tidal carbon dioxide (ETCO₂), and the secondary outcomes were respiratory rate, pulse rate, oxygen saturation and lung function.

Results

All groups showed an increase in ETCO₂ from baseline during slow breathing. Study 1 found a mean rise in ETCO₂ of 0.48 kPa [95% confidence interval (CI) 0.28-0.68] for healthy participants and 0.46 kPa (95% CI 0.29-0.63) for asthma patients. In healthy volunteers, ETCO₂ stayed above baseline for 5 minutes after the intervention. ETCO₂ rose minimally (mean 0.06 kPa) in both groups after breath holds. Study 2 found a mean rise in ETCO₂ of 0.35 kPa (95% CI 0.09-0.60) during slow breathing with visual feedback, and 0.36 kPa (95% CI 0.13-0.60) during slow breathing without visual feedback.

Conclusions

The results of these preliminary studies provide data to power larger studies. They suggest that ETCO₂ rises during slow breathing in both asthma patients and healthy volunteers, and that this effect may persist beyond the intervention itself in healthy volunteers. The use of visual biofeedback had no effect on ETCO₂ in healthy volunteers.     

Timing of oral feeding changes in premature infants who underwent osteopathic manipulative treatment

BackgroundThe delayed transition from gavage-to-nipple feeding is one of the most significant factors that may prolong hospital length of stay (LOS). Osteopathic manipulative treatment (OMT) has been demonstrated to be effective regarding LOS reduction, but no investigations have documented its clinical validity for attaining oral feeding.ObjectivesTo assess OMT utility regarding the timing of oral feeding in healthy preterm infants.DesignPreliminary propensity score-matched retrospective cohort study.SettingData were extrapolated from the neonatal intensive care unit (NICU) of Del Ponte Hospital in Varese, Italy, during the period between March 2012 and December 2013.InterventionsTwo propensity score-matched groups of healthy preterm infants aged 28⁺⁰ to 33⁺⁶ were compared, observing those supported with OMT until hospital discharge and control subjects.Main outcome measuresDays from birth to the attainment of oral feeding was the primary endpoint. Body weight, body length, head circumference and LOS were considered as secondary endpoints.ResultsSeventy premature infants were included in the study as the control group (n = 35; body weight (BW) = 1457.9 ± 316.2 g; gestational age (GA) = 31.5 ± 1.73 wk) and the osteopathic group (n = 35; BW = 1509.6 ± 250.8 g; GA = 31.8 ± 1.64 wk). The two groups had analogous characteristics at study entry. In this cohort, we observed a significant reduction in TOF (-5.00 days; p = 0.042) in the osteopathic group with a greater effect in very low birth weight infants.ConclusionsThese data demonstrate the utility and potential efficacy of OMT for the attainment of oral feeding. Further adequately powered clinical trials are recommended.     

Evaluating the use of streaming video to support student learning in a first-year life sciences course for student nurses

Streaming video was used to support the learning of first year student nurses on a Life Sciences module, as one of many innovations designed to increase the range of resources and support available to students. This paper describes the background to this innovation, the procedures adopted and the results of extensive evaluation. The use of streaming video was evaluated in three applications in the module. A total of 656 students used online directed-learning sessions that incorporated streamed video. Just over half of these students actually viewed the video streams. Their feedback showed that 32% found access easy, 59% enjoyed using the resources, and 25% were very confident that they learned from them. Different types of video were used, and embedded in diverse ways, but the results were consistent across the three applications. They suggest that streamed video can contribute to useful resources to support learning by student nurses but, for a variety of reasons, it may not appeal or be adequately accessible to all students at present.     

The development and evaluation of a telepsychiatry service for prisoners

The introduction of increasingly sophisticated telecommunication systems seems to offer opportunities to respond to some of the key problems around structural and spatial inequalities in access to health care. There is evidence which suggests that serious mental health problems are common among prisoners and psychiatric comorbidity is the norm. Many prisoners have complex mental health needs, but more often than not these remain unaddressed. Telepsychiatry is one strategy to improve the accessibility and quality of mental health care in the prison setting. This paper firstly reviews the current prison health care system and then describes a research study which is focused on the development and evaluation of a telepsychiatry service for prisoners. This study has investigated what is lost or gained in a psychiatric assessment when it is conducted via telepsychiatry. The researcher compared the inter-rater reliability between two raters interviewing 80 participants in an observer/interviewer split configuration in telepsychiatry and same room settings. The measure used was the Comprehensive Psychopathology Rating Scale. Prisoners and prison staff also took part in semi-structured interviews which focused on their satisfaction and acceptability of the telepsychiatry service. A cost comparison of the telepsychiatry service with the existing visiting service was conducted. This paper outlines the study design and focuses on the potential impact that telepsychiatry may have upon the practice setting.     

Sickness behaviour is induced by a peripheral CXC-chemokine also expressed in Multiple Sclerosis and EAE

Non-CNS chemokine production may contribute to previously unrecognised components of Multiple Sclerosis (MS) pathology. Here we show that IL-8, a neutrophil chemoattractant, is significantly increased in serum from individuals with MS, and that the rodent homolog of IL-8 (CXCL1) is expressed in the liver in experimental autoimmune encephalomyelitis (EAE), a rodent model of MS. The hepatic expression of CXCL1 in EAE is accompanied by neutrophil recruitment to the liver, and we show that this recruitment is a feature of post mortem liver tissue from MS patients, which is a previously unrecognised phenomenon. We speculated that the presence of peripheral CXC-chemokine expression might contribute to the sickness behaviours associated with MS, which are a significant contributor to morbidity. Peripheral, but not central, administration of CXCL1 to Wistar rats inhibited spontaneous activity in the open field and burrowing behaviour in a dose-dependent manner (5–45 μg). The expression of CXCL1 by the liver and the recruitment of neutrophils can be modelled by the intracerebral injection of IL-1β. Here, we found that interferon-beta (IFN-β) pretreatment significantly inhibited hepatic CXCL1 production and neutrophil recruitment to the liver induced by the microinjection of IL-1β into the brain. Thus while the mechanism by which IFN-β therapy suppresses disease in MS remains unclear, the data presented here suggests that the inhibition of hepatic chemokine synthesis may be a contributing factor.     

Are children with ADHD predominantly inattentive and combined subtypes different in terms of aspects of everyday attention?

The validity of the DSM-IV subtypes is a recurring diagnostic debate in attention deficit/hyperactivity disorder (ADHD). Laboratory measures, such as the test of everyday attention for children (TEA-Ch) can help us address this question. TEA-Ch is a test battery covering different aspects of everyday attention relating to selective and sustained attention and attentional control. The aim of the current study was to investigate whether this instrument can differentiate between combined (ADHD-C) and inattentive subtype (ADHD-I) of ADHD. Subjects were recruited from a multidisciplinary ADHD outpatient unit and tested free of medication. Sixty-four children with a diagnosis of ADHD were included (38 with ADHD-C; 26 with ADHD-I). The control group was 76 children recruited from primary and secondary schools. Children with ADHD performed worse than controls on 6 out of 9 TEA-Ch subtests. However a regression analysis revealed that TEA-Ch subtests made only a marginal contribution to the correct classification of ADHD, once the effects of IQ and age are controlled. Confirmatory factor analysis in our ADHD group demonstrated that the three factor structure achieved a poor fit. More detailed analysis suggested that inferior performance on the tasks designed to test vigilance was not the result of deficient-sustained attention. ADHD-C and ADHD-I showed very few differences across tasks. In conclusion, our results provided not much support for the value of the ADHD-C and ADHD-I distinction in predicting difficulties in everyday attention.     

Multiobjective design optimisation of coronary stents

We present here a multi-objective and multi-disciplinary coronary stent design optimization paradigm. Coronary stents are tubular, often mesh-like, structures which are deployed in diseased (stenosed) artery segments to provide a scaffolding feature that compresses atheromatus plaque, hence restoring luminal area and maintaining vessel patency. A three variable geometry parameterisation of a CYPHER (Cordis Corporation, Johnson & Johnson co.) type stent is proposed to explore the functionality of a sequence of circumferential rings connected by 'n' shaped links. The performance of each design is measured by six figures of merit (objectives/metrics) representing (i) acute recoil, (ii) tissue stresses, (iii) haemodynamic disturbance, (iv) drug delivery, (v) uniformity of drug distribution, and (vi) flexibility. These metrics are obtained from computational simulations of (i) structural deformation through balloon inflated expansion of a stent into contact with a stenosed vessel, (ii) pulsatile flow over the deformed stent embedded in the vessel wall, (iii) steady-state drug distribution into the tissue, and (iv) flexibility of a stent in response to an applied moment. Design improvement is obtained by a multi-objective surrogate modelling approach using a non-dominated sorting genetic algorithm (NSGA-II) to search for an optimal family of designs. A number of trade-offs between the different objectives are identified. In particular a conflict between pairs of the following objectives are shown -- (a) volume average stress vs. recoil, (b) volume average drug vs. volume average stress, (c) flexibility vs. volume average stress, (d) flexibility vs. haemodynamic disturbance, (e) volume average drug vs. haemodynamic disturbance, and (f) uniformity of drug vs. volume average stress. Different paradigms to choose the optimal designs from the obtained Pareto fronts are presented and under each such paradigm, the optimal designs and there relative positions with respect to a representative CYPHER stent are shown. The methodology and the results of this work could potentially be useful in further optimisation studies and development of a family of stents with increased resistance to in-stent restenosis and thrombosis.