Identification of criticality in neuronal avalanches: II. A theoretical and empirical investigation of the Driven case

The observation of apparent power laws in neuronal systems has led to the suggestion that the brain is at, or close to, a critical state and may be a self-organised critical system. Within the framework of self-organised criticality a separation of timescales is thought to be crucial for the observation of power-law dynamics and computational models are often constructed with this property. However, this is not necessarily a characteristic of physiological neural networks—external input does not only occur when the network is at rest/a steady state. In this paper we study a simple neuronal network model driven by a continuous external input (i.e. the model does not have an explicit separation of timescales from seeding the system only when in the quiescent state) and analytically tuned to operate in the region of a critical state (it reaches the critical regime exactly in the absence of input—the case studied in the companion paper to this article). The system displays avalanche dynamics in the form of cascades of neuronal firing separated by periods of silence. We observe partial scale-free behaviour in the distribution of avalanche size for low levels of external input. We analytically derive the distributions of waiting times and investigate their temporal behaviour in relation to different levels of external input, showing that the system’s dynamics can exhibit partial long-range temporal correlations. We further show that as the system approaches the critical state by two alternative ‘routes’, different markers of criticality (partial scale-free behaviour and long-range temporal correlations) are displayed. This suggests that signatures of criticality exhibited by a particular system in close proximity to a critical state are dependent on the region in parameter space at which the system (currently) resides

Identification of criticality in neuronal avalanches: I. A theoretical investigation of the non-driven case

In this paper, we study a simple model of a purely excitatory neural network that, by construction, operates at a critical point. This model allows us to consider various markers of criticality and illustrate how they should perform in a finite-size system. By calculating the exact distribution of avalanche sizes, we are able to show that, over a limited range of avalanche sizes which we precisely identify, the distribution has scale free properties but is not a power law. This suggests that it would be inappropriate to dismiss a system as not being critical purely based on an inability to rigorously fit a power law distribution as has been recently advocated. In assessing whether a system, especially a finite-size one, is critical it is thus important to consider other possible markers. We illustrate one of these by showing the divergence of susceptibility as the critical point of the system is approached. Finally, we provide evidence that power laws may underlie other observables of the system that may be more amenable to robust experimental assessment

Mercury and Prenatal Growth: A Systematic Review

The intrauterine environment is critical for healthy prenatal growth and affects neonatal survival and later health. Mercury is a toxic metal which can freely cross the placenta and disrupt a wide range of cellular processes. Many observational studies have investigated mercury exposure and prenatal growth, but no prior review has synthesised this evidence. Four relevant publication databases (Embase, MEDLINE/PubMed, PsycINFO, and Scopus) were systematically searched to identify studies of prenatal mercury exposure and birth weight, birth length, or head circumference. Study quality was assessed using the NIH Quality Assessment Tool, and results synthesised in a narrative review. Twenty-seven studies met the review criteria, these were in 17 countries and used 8 types of mercury biomarker. Studies of birth weight (total = 27) involving populations with high levels of mercury exposure, non-linear methods, or identified as high quality were more likely to report an association with mercury, but overall results were inconsistent. Most studies reported no strong evidence of association between mercury and birth length (n = 14) or head circumference (n = 14). Overall, our review did not identify strong evidence that mercury exposure leads to impaired prenatal growth, although there was some evidence of a negative association of mercury with birth weight

Informational interviews help undergraduate students at the mid-point of non-vocational STEM degrees confirm their career aspirations

Higher education institutions are expected to produce career-ready graduates who are equipped for the challenges of the 21st century. Employability experts argue that this can be achieved by integrating career development learning (CDL) into the curriculum. The informational interview helps students learn more about a career by interviewing a professional working in a field of interest, and helps students to make decisions regarding their career plans. The aims of the study were to determine students’: 1) preferred career paths and career identity at the midpoint of their non-vocational degree; 2) experiences and perceptions of an informational interview module. An informational interview module was embedded into a second-year human biosciences subject taken by students in undergraduate non-specialist health-related STEM degrees. Students indicated their preferred career, learned about informational interviews, and conducted an interview with a professional working in the field they wished to enter. After the interview, students completed reflection activities, responding to open-ended and Likert-scale questions. 91 student reflections were analysed to determine students’ career identity, and their experiences and perceptions of the module. Descriptive statistical analysis was conducted on Likert-scale answers and inductive thematic analysis was conducted on open-ended answers. Students’ career preferences were wide-ranging, with allied health the most popular. Career identity was reasonably well established in this cohort. The student experience was overall positive, and students’ thought the module was useful in supporting their career planning and career development. In conclusion, an informational interview assignment is an effective career development tool for human biosciences students

Prenatal Mercury Exposure and Neurodevelopment up to the Age of 5 Years:A Systematic Review

Neurodevelopmental delays can interfere with children’s engagement with the world and further development, and may have negative consequences into adulthood. Mercury is highly toxic and may negatively influence neurodevelopment because it can freely cross the placenta and accumulate in the fetal brain. We searched four publication databases (Embase, PsycINFO, PubMed/MEDLINE, Scopus) for studies examining the relationship between early life mercury exposure and scores on neurodevelopmental performance measures in children aged 0 to 5 years old. Study quality was assessed using the National Institutes of Health (NIH) Quality Assessment Tool. Thirty-two prospective studies were included in the review. Neurodevelopmental performance was measured using 23 different scales, most commonly the Bayley Scales of Infant and Toddler Development (BSID). In most cases, the evidence for an association between mercury and neurodevelopment was weak. There did not appear to be exceptions for particular childhood ages, outcome scales, or mercury levels. The small number of results to the contrary were more likely to be studies which did not meet our high-quality criteria, and could be a consequence of multiple testing, selection bias, or incomplete confounder adjustment. Based on current evidence, dietary mercury exposure during pregnancy is unlikely to be a risk factor for low neurodevelopmental functioning in early childhood

What do we want to get out of this?:a critical interpretive synthesis of the value of process evaluations, with a practical planning framework

BACKGROUND: Process evaluations aim to understand how complex interventions bring about outcomes by examining intervention mechanisms, implementation, and context. While much attention has been paid to the methodology of process evaluations in health research, the value of process evaluations has received less critical attention. We aimed to unpack how value is conceptualised in process evaluations by identifying and critically analysing 1) how process evaluations may create value and 2) what kind of value they may create. METHODS: We systematically searched for and identified published literature on process evaluation, including guidance, opinion pieces, primary research, reviews, and discussion of methodological and practical issues. We conducted a critical interpretive synthesis and developed a practical planning framework. RESULTS: We identified and included 147 literature items. From these we determined three ways in which process evaluations may create value or negative consequences: 1) through the socio-technical processes of ‘doing’ the process evaluation, 2) through the features/qualities of process evaluation knowledge, and 3) through using process evaluation knowledge. We identified 15 value themes. We also found that value varies according to the characteristics of individual process evaluations, and is subjective and context dependent. CONCLUSION: The concept of value in process evaluations is complex and multi-faceted. Stakeholders in different contexts may have very different expectations of process evaluations and the value that can and should be obtained from them. We propose a planning framework to support an open and transparent process to plan and create value from process evaluations and negotiate trade-offs. This will support the development of joint solutions and, ultimately, generate more value from process evaluations to all. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12874-022-01767-7

Oxidation of tertiary amine-derivatized surfaces to control protein adhesion

Selective oxidation of omega-tertiary amine self-assembled thiol monolayers to tertiary amine N-oxides is shown to transform the adhesion of model proteins lysozyme and fibrinogen upon them. Efficient preparation of both secondary and tertiary linker amides as judged by X-ray photoelectron spectroscopy (XPS) and water droplet contact angle was achieved with an improved amide bond formation on gold quartz crystal microbalance (QCM) sensors using 2-(1H-7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyl hexafluorophosphate methanaminium uronium (HATU). Oxidation with hydrogen peroxide was similarly assessed, and adhesion of lysozyme and fibrinogen from phosphate buffered saline was then assayed by QCM and imaged by AFM. Tertiary amine-functionalized sensors adsorbed multilayers of aggregated lysozyme, whereas tertiary amine N-oxides and triethylene glycol-terminated monolayers are consistent with small protein aggregates. The surface containing a dimethylamine N-oxide headgroup and ethyl secondary amide linker showed the largest difference in adsorption of both proteins. Oxidation of tertiary amine decorated surfaces therefore holds the potential for selective deposition of proteins and cells through masking and other patterning techniques

Pericardial Fat and Echocardiographic Measures of Cardiac Abnormalities

Objective: Pericardial adipose tissue (PAT), a regional fat depot adjacent to the myocardium, may mediate the complex relation between obesity and cardiac left ventricular (LV) abnormalities. We sought to evaluate the association of PAT with echocardiographic measures of LV abnormalities in the Jackson Heart Study (JHS). Research Design and Methods: A total of 1,414 African Americans (35% men; mean age 58 years) from the JHS underwent computed tomographic assessment of PAT and abdominal visceral adipose tissue (VAT) from 2007 to 2009 and echocardiography examination between 2000 and 2004. Echocardiographic measures of left atrial (LA) internal diameter, LV mass, LV ejection fraction (LVEF), and E-wave velocity-to-A-wave velocity ratio (E/A ratio) were examined in relation to PAT, VAT, BMI, and waist circumference (WC). Results: All adiposity measures were positively correlated with LA diameter and LV mass and negatively correlated with E/A ratio (P = 0.02 to 0.0001) and were not with LVEF (P = 0.36–0.61). In women, per 1-SD increment of PAT, we observed association with higher LV mass (9.0 $\pm$ 1.7 gm, P = 0.0001) and LA diameter (1.0 $\pm$ 0.1 mm, P = 0.0001). However, the magnitude of the association between PAT and cardiac measures was similar compared with VAT (P = 0.65 [LV mass]; P = 0.26 [LA diameter]) and was smallercompared with BMI (P = 0.002 [LV mass]; P = 0.01 [LA diameter]) and WC (P = 0.009 [LA diameter]). Conclusions: PAT is correlated with echocardiographic measures of cardiac LV abnormalities, but the association is not stronger than other adiposity measures

Effects of Non-Pharmacological Interventions as Vaccine Adjuvants in Humans:a systematic review and network meta-analysis

Declaration of interest: We have read and understood the policy on declaration of interests and declare that CMT has received funding from Nestle Nutrition for projects unconnected with this study. All other authors do not have any conflicting interests