Implications of single-neuron gain scaling for information transmission in networks

Summary: 

Many neural systems are equipped with mechanisms to efficiently encode sensory information. To represent natural stimuli with time-varying statistical properties, neural systems should adjust their gain to the inputs' statistical distribution. Such matching of dynamic range to input statistics has been shown to maximize the information transmitted by the output spike trains (Brenner et al., 2000, Fairhall et al., 2001). Gain scaling has not only been observed as a system response property, but also in single neurons in developing somatosensory cortex stimulated with currents of different amplitude (Mease et al., 2010). While gain scaling holds for cortical neurons at the end of the first post-natal week, at birth these neurons lack this property. The observed improvement in gain scaling coincides with the disappearance of spontaneous waves of activity in cortex (Conheim et al., 2010).

We studied how single-neuron gain scaling affects the dynamics of signal transmission in networks, using the developing cortex as a model. In a one-layer feedforward network, we showed that the absence of gain control made the network relatively insensitive to uncorrelated local input fluctuations. As a result, these neurons selectively and synchronously responded to large slowly-varying correlated input--the slow build up of synaptic noise generated in pacemaker circuits which most likely triggers waves. Neurons in gain scaling networks were more sensitive to the small-scale input fluctuations, and responded asynchronously to the slow envelope. Thus, gain scaling both increases information in individual neurons about private inputs and allows the population average to encode the slow fluctuations in the input. Paradoxically, the synchronous firing that corresponds to wave propagation is associated with low information transfer. We therefore suggest that the emergence of gain scaling may help the system to increase information transmission on multiple timescales as sensory stimuli become important later in development. 

Methods:

Networks with one and two layers consisting of hundreds of model neurons were constructed. The ability of single neurons to gain scale was controlled by changing the ratio of sodium to potassium conductances in Hodgkin-Huxley neurons (Mainen et al., 1995). The response of single layer networks was studied with ramp-like stimuli with slopes that varied over several hundreds of milliseconds. Fast fluctuations were superimposed on this slowly-varying mean. Then the response to these networks was tested with continuous stimuli. Gain scaling networks captured the slow fluctuations in the inputs, while non-scaling networks simply thresholded the input. Quantifying information transmission confirmed that gain scaling neurons transmit more information about the stimulus. With the two-layer networks we simulated a cortical network where waves could spontaneously emerge, propagate and degrade, based on the gain scaling properties of the neurons in the network

Accountability and the Framing Power of Visual Technologies: How Do Visualized Reconstructions of Incidents Influence Public and Political Accountability Discussions?

__Abstract__ In this article visual technologies and their use in three reconstructions after an incident are linked with accountability issues. Conclusions are drawn on the relation between administration, the choice of technology to create and distribute visual occurrences, and society and how visualizations are used to frame accountability issues

Lipase catalysed kinetic resolutions of 3-aryl alkanoic acids

Hydrolase catalysed kinetic resolutions leading to a series of 3-aryl alkanoic acids (≥94% ee) is described. Hydrolysis of the ethyl esters with a series of hydrolases was undertaken to identify biocatalysts that yield the corresponding acids with excellent enantiopurity in each case. Steric and electronic effects on the efficiency and enantioselectivity of the biocatalytic transformation was also explored

Establishing the international prevalence of self-reported child maltreatment: a systematic review by maltreatment type and gender

Background Estimating the prevalence of child maltreatment is challenging due to the absence of a clear ‘gold standard’ as to what constitutes maltreatment. This systematic review aims to review studies using self-report maltreatment to capture prevalence rates worldwide. Methods PubMed, Ovid SP and grey literature from the NSPCC, UNICEF, The UK Government, and WHO from 2000 to 2017 were searched. The literature review focused on the variation found in self-reported lifetime prevalence for each type of maltreatment between studies by continent and gender, and how methodological differences may explain differences found. Results Sexual abuse is the most commonly studied form of maltreatment across the world with median (25th to 75th centile) prevalence of 20.4% (13.2% to 33.6%) and 28.8% (17.0% to 40.2%) in North American and Australian girls respectively, with lower rates generally for boys. Rates of physical abuse were more similar across genders apart from in Europe, which were 12.0% (6.9% to 23.0%) and 27.0% (7.0% to 43.0%) for girls and boys respectively, and often very high in some continents, for example, 50.8% (36.0% to 73.8%) and 60.2% (43.0% to 84.9%) for girls and boys respectively in Africa. Median rates of emotional abuse were nearly double for girls than boys in North America (28.4% vs 13.8% respectively) and Europe (12.9% vs 6.2% respectively) but more similar across genders groups elsewhere. Median rates of neglect were highest in Africa (girls: 41.8%, boys: 39.1%) and South America (girls: 54.8%, boys: 56.7%) but were based on few studies in total, whereas in the two continents with the highest number of studies, median rates differed between girls (40.5%) and boys (16.6%) in North America but were similar in Asia (girls: 26.3%, boys: 23.8%). Conclusions Median prevalence rates differ substantially by maltreatment category, gender and by continent. The number of studies and available data also varies and relatively little is known about prevalence for some forms of maltreatment, particularly outside of the North American context. Prevalence rates require caution in interpretation as some variation will reflect methodological differences, including the data collection methods, and how the maltreatment is defined

Intrinsic Neuronal Properties Switch the Mode of Information Transmission in Networks

Diverse ion channels and their dynamics endow single neurons with complex biophysical properties. These properties determine the heterogeneity of cell types that make up the brain, as constituents of neural circuits tuned to perform highly specific computations. How do biophysical properties of single neurons impact network function? We study a set of biophysical properties that emerge in cortical neurons during the first week of development, eventually allowing these neurons to adaptively scale the gain of their response to the amplitude of the fluctuations they encounter. During the same time period, these same neurons participate in large-scale waves of spontaneously generated electrical activity. We investigate the potential role of experimentally observed changes in intrinsic neuronal properties in determining the ability of cortical networks to propagate waves of activity. We show that such changes can strongly affect the ability of multi-layered feedforward networks to represent and transmit information on multiple timescales. With properties modeled on those observed at early stages of development, neurons are relatively insensitive to rapid fluctuations and tend to fire synchronously in response to wave-like events of large amplitude. Following developmental changes in voltage-dependent conductances, these same neurons become efficient encoders of fast input fluctuations over few layers, but lose the ability to transmit slower, population-wide input variations across many layers. Depending on the neurons' intrinsic properties, noise plays different roles in modulating neuronal input-output curves, which can dramatically impact network transmission. The developmental change in intrinsic properties supports a transformation of a networks function from the propagation of network-wide information to one in which computations are scaled to local activity. This work underscores the significance of simple changes in conductance parameters in governing how neurons represent and propagate information, and suggests a role for background synaptic noise in switching the mode of information transmission

Assessing the impact of specialist home visiting upon maltreatment in England: a feasibility study of data linkage from a public health trial to routine health and social care data

Background Follow-up for public health trials may benefit from greater use of routine data. Our trial of a home-visiting intervention for first-time teenage mothers assessed outcomes to the child’s second birthday. To examine its medium-term impact, particularly upon maltreatment outcomes, we designed a study using routine records. Methods We aimed to establish the feasibility of our study design, which combines trial data with routine health, social care and education data using a dissent-based linkage model. Trial participant identifiers were linked to routine health, social care and education data if women did not dissent. Data were forwarded to a safe haven and further linked to de-identified trial outcome data. The feasibility study aimed first to establish the acceptability of data linkage through a discussion group of young mothers and by levels of dissent received by the research team. Second, we assessed levels of accurate linkage to both health (via NHS Digital) and education and social care (both via National Pupil Database, NPD). Third, we assessed the availability of data and levels of missingness for key outcomes received for a sample of target study years. Results Of 1545 mother-child dyads contacted, eight women opted out. The engagement exercise with stakeholders found support for the principle of data linkage, including in the context of maltreatment. Some contributors preferred opt-in consent. Most (99.9%) health records were matched on either three or all four identifiers. Fifty participants were not matched to any health data. Primary outcome data from NPD are derived from any one of three fields, all of which were satisfactorily returned and provided an indication of cases for analysis. Missing data for secondary outcomes varied from 0% (Child looked after status) to 70% (Anatomical Area A&E diagnosis) however when combined with other variables the levels of missingness for outcome decrease. Conclusions Through study set-up and in this pilot, we provide evidence that the main study is feasible, satisfies governance requirements and is likely to generate data of sufficient quality to address our main research questions. Observed levels of missingness or low event rates are likely to affect some secondary analysis (e.g. state transition modelling) although overall were satisfactory

Evaluating the long-term impact of the Fostering Changes training programme for foster carers in Wales, the Confidence in Care trial: study protocol for a randomized controlled trial

Background The Fostering Changes programme was developed by the Adoption and Fostering National Team at the Maudsley Hospital, South London, in conjunction with King’s College London. It is a 12-week group-based training programme for foster and kin carers, which aims to build positive relationships between carers and children, encourage positive child behaviour and set appropriate limits, through a practical skills-based approach. The programme also aims to improve foster carers’ understanding of the causes of children’s social and emotional difficulties and their confidence in applying this knowledge in various situations. Methods This is a pragmatic open-label individually randomised controlled trial, with embedded process evaluation. A total of 237 participants will be recruited from Welsh Local Authorities and Independent Fostering Providers; those allocated to the intervention group will be offered enrolment in the next Fostering Changes programme group at their site. Participants in the control group will be offered the Fostering Changes programme at the end of the follow-up period. Data will be collected at baseline, immediately following the 12 week Fostering Changes intervention, and 12 months from the start of the Fostering Changes programme. The primary outcome measure assesses the extent to which carers feel able to cope with and make positive changes to the lives of their foster children and is measured by the Carer Efficacy Questionnaire at 12 months. Discussion The trial will determine whether the Fostering Changes programme, in the long term, can deliver important, significant differences to the way foster carers build positive relationships with their foster children, encourage positive child behaviour and set appropriate limits, compared with usual care

Adoção de redes sociais por cidadãos no Paraguai

This article aims to identify factors associated with the use of social media by Paraguayan citizens in their relationship with the government. We gathered data using a vignette survey, which recorded the responses to four public service problems and collected scores on perceived effectiveness, capability, social influence, trust in government, trust in social media infrastructure, and social media anxiety. Multivariate analysis was used to test the hypotheses. Perceived effectiveness, social influence, and trust in social media infrastructures were found to be significantly correlated with citizens’ use of such media to report public service issues. On the other hand, capability, trust in government, and social media anxiety were not found to be associated with citizens’ social media use. The results urge further theorization to disentangle how perceived effectiveness, social influence, and trust in social media infrastructures affect digital citizen engagement and participation and under what conditions proprietary social media platforms such as Facebook and Twitter contribute to a vibrant democracy.Este artículo tiene como objetivo identificar qué factores están asociados con el uso de las redes sociales por parte de los ciudadanos paraguayos en las relaciones ciudadano-gobierno. Recopilamos datos mediante una encuesta basada en técnica de viñeta en la que se registraron las respuestas a cuatro problemas de servicio público, además de puntuaciones sobre la eficacia percibida, la capacidad, la influencia social, la confianza en el Gobierno, la confianza en la infraestructura de las redes sociales y la ansiedad con relación a las redes sociales. Se utilizó un análisis multivariado para probar las hipótesis. Se encontró que hay una correlación entre la efectividad percibida, la influencia social y la confianza en las infraestructuras de las redes sociales con el uso de las redes sociales por parte de los ciudadanos para informar sobre problemas de servicio público. Por otro lado, no se encontró que la capacidad, la confianza en el Gobierno y la ansiedad con relación a las redes sociales estuvieran asociadas con el uso de las redes sociales por parte de los ciudadanos. Los resultados nos instan a teorizar y desentrañar aún más cómo la efectividad percibida, la influencia social y la confianza en las infraestructuras propietarias de las redes sociales afectan el compromiso y la participación digital de los ciudadanos, y bajo qué condiciones las plataformas propietarias de las redes sociales propietarias ‒como Facebook y Twitter‒ contribuyen a una democracia vibrante.Este artigo tem como objetivo identificar os fatores associados ao uso das redes sociais pelos cidadãos paraguaios nas relações cidadão-governo. A coleta dos dados foi feita usando uma pesquisa com vinhetas na qual as respostas a quatro problemas com serviços públicos foram registrados. Também foram coletadas pontuações sobre a percepção de eficácia, capacidade, influência social, confiança no governo, confiança na infraestrutura das redes sociais e ansiedade em relação às redes sociais. Uma análise multivariada foi usada para testar as hipóteses. A percepção de eficácia, a influência social e a confiança nas infraestruturas das redes sociais estão significativamente correlacionadas com o uso que os cidadãos fazem das redes sociais para relatar problemas nos serviços públicos. Por outro lado, a capacidade, a confiança no governo e a ansiedade em relação às redes sociais não foram associadas ao uso das redes sociais pelos cidadãos. Os resultados nos incentivam a formular mais teorias e desvendar como a percepção de eficácia, a influência social e a confiança nas infraestruturas das redes sociais afetam o envolvimento e a participação digital do cidadão, e em que condições as plataformas proprietárias de redes sociais, como o Facebook e o Twitter, contribuem para uma democracia vibrante

Is stroke early supported discharge still effective in practice? A prospective comparative study

Objective: Randomised controlled trials have shown the benefits of Early Supported Discharge (ESD) of stroke survivors. Our aim was to evaluate whether ESD is still beneficial when operating in the complex context of frontline healthcare provision. Design: We conducted a cohort study with quasi experimental design. A total of 293 stroke survivors (transfer independently or with assistance of one, identified rehabilitation goals) within two naturally formed groups were recruited from two acute stroke units: ‘ESD’ n=135 and ‘Non ESD’ n=158 and 84 caregivers. The ‘ESD’ group accessed either of two ESD services operating in Nottinghamshire, UK. The ‘Non ESD’ group experienced standard practices for discharge and onward referral. Outcome measures (primary: Barthel Index) were administered at baseline, 6 weeks, 6 months and 12 months. Results: The ESD group had a significantly shorter length of hospital stay (P=0.029) and reported significantly higher levels of satisfaction with services received (P<0.001). Following adjustment for age differences at baseline, participants in the ESD group (n=71) had significantly higher odds (compared to the Non ESD group, n=85) of being in the ⩾90 Barthel Index category at 6 weeks (OR = 1.557, 95% CI 2.579 to 8.733), 6 months (OR = 1.541, 95% CI 2.617 to 8.340) and 12 months (OR 0.837, 95% CI 1.306 to 4.087) respectively in relation to baseline. Carers of patients accessing ESD services showed significant improvement in mental health scores (P<0.01). Conclusion: The health benefits of ESD are still evident when evidence based models of these services are implemented in practice

“@Government There’s a pothole in my street!”: Canadian citizens’ adoption choices of social media use in citizen-government relations

Social media platforms such as Twitter and Facebook offer new opportunities for co-production and interaction between citizens and government agencies. Until now, explanations of why citizens use social media to interact with government have been lacking in the literature. This article concludes on the basis of survey data gathered among Canadian citizens that social media use in citizen-government relations is explained by citizens’ perceived effectiveness and trust in social media organizational infrastructure, with trust in government, social media anxiety and ease of use not having an impact. Implications for research and practice are discussed