EEG-based functional brain networks: does the network size matter?

Functional connectivity in human brain can be represented as a network using electroencephalography (EEG) signals. These networks--whose nodes can vary from tens to hundreds--are characterized by neurobiologically meaningful graph theory metrics. This study investigates the degree to which various graph metrics depend upon the network size. To this end, EEGs from 32 normal subjects were recorded and functional networks of three different sizes were extracted. A state-space based method was used to calculate cross-correlation matrices between different brain regions. These correlation matrices were used to construct binary adjacency connectomes, which were assessed with regards to a number of graph metrics such as clustering coefficient, modularity, efficiency, economic efficiency, and assortativity. We showed that the estimates of these metrics significantly differ depending on the network size. Larger networks had higher efficiency, higher assortativity and lower modularity compared to those with smaller size and the same density. These findings indicate that the network size should be considered in any comparison of networks across studies.

Repeated Pre-Syncope from Increased Inspired CO2 in a Background of Severe Hypoxia.

We describe a case of experimentally induced pre-syncope in a healthy young man when exposed to increased inspired CO2 in a background of hypoxia. Acute severe hypoxia (FIO2=0.10) was tolerated, but adding CO2 to the inspirate caused pre-syncope symptoms accompanied by hypotension and large reductions in both mean and diastolic middle cerebral artery velocity, while systolic flow velocity was maintained. The mismatch of cerebral perfusion pressure and vascular tone caused unique retrograde cerebral blood flow at the end of systole and a reduction in cerebral tissue oxygenation. We speculate that this occurrence of pre-syncope was due to hypoxia-induced inhibition of brain regions responsible for compensatory sympathetic activity to relative hypercapnia.

Measuring the diffusion of palliative care in long-term care facilities - a death census

ABSTRACT: BACKGROUND: The dissemination of palliative care for patients presenting complex chronic diseases at various stages has become an important matter of public health. A death census in Swiss long-term care facilities (LTC) was set up with the aim of monitoring the frequency of selected indicators of palliative care. METHODS: The survey covered 150 LTC facilities (105 nursing homes and 45 home health services), each of which was asked to complete a questionnaire for every non-accidental death over a period of six months. The frequency of 4 selected indicators of palliative care (resort to a specialized palliative care service, the administration of opiates, use of any pain measurement scale or other symptom measurement scale) was monitored in respect of the stages of care and analysed based on gender, age, medical condition and place of residence. RESULTS: Overall, 1200 deaths were reported, 29.1% of which were related to cancer. The frequencies of each indicator varied according to the type of LTC, mostly regarding the administration of opiate. It appeared that the access to palliative care remained associated with cancer, terminal care and partly with age, whereas gender and the presence of mental disorders had no effect on the indicators. In addition, the use of drugs was much more frequent than the other indicators. CONCLUSION: The profile of patients with access to palliative care must become more diversified. Among other recommendations, equal access to opiates in nursing homes and in home health services, palliative care at an earlier stage and the systematic use of symptom management scales when resorting to opiates have to become of prime concern.

In vivo neuropathology of cortical changes in elderly persons with schizophrenia.

BACKGROUND: Elderly schizophrenia patients frequently develop cognitive impairment of unclear etiology. Magnetic resonance imaging (MRI) studies revealed brain structural abnormalities, but the pattern of cortical gray matter (GM) volume and its relationship with cognitive and behavioral symptoms are unknown. METHODS: Magnetic resonance scans were taken from elderly schizophrenia patients (n = 20, age 67 +/- 6 SD, Mini-Mental State Examination [MMSE] 23 +/- 4), Alzheimer's disease (AD) patients (n = 20, age 73 +/- 9, MMSE 22 +/- 4), and healthy elders (n = 20, age 73 +/- 8, MMSE 29 +/- 1). Patients were assessed with a comprehensive neuropsychological and behavioral battery. Cortical pattern matching and a region-of-interest analysis, based on Brodmann areas (BAs), were used to map three-dimensional (3-D) profiles of differences in patterns of gray matter volume among groups. RESULTS: Schizophrenia patients had 10% and 11% lower total left and right GM volume than healthy elders (p < .001) and 7% and 5% more than AD patients (p = .06 and ns). Regions that had both significantly less gray matter than control subjects and gray matter volume as low as AD mapped to the cingulate gyrus and orbitofrontal cortex (BA 30, 23, 24, 32, 25, 11). The strongest correlate of gray matter volume in elderly schizophrenia patients, although nonsignificant, was the positive symptom subscale of the Positive and Negative Syndrome Scale, mapping to the right anterior cingulate area (r = .42, p = .06). CONCLUSIONS: The orbitofrontal/cingulate region had low gray matter volume in elderly schizophrenia patients. Neither cognitive impairment nor psychiatric symptoms were significantly associated with structural differences, even if positive symptoms tended to be associated with increased gray matter volume in this area.

Second-hand tobacco smoke in prison: tackling a public health matter through research.

OBJECTIVES: This action-research study conducted in a Swiss male post-trial detention centre (120 detainees and 120 staff) explored the attitudes of detainees and staff towards tobacco smoking. Tackling public health matters through research involving stakeholders in prisons implies benefits and risks that need exploration. STUDY DESIGN: The observational study involved multiple strands (quantitative and qualitative components, and air quality measurements). This article presents qualitative data on participants' attitudes and expectations about research in a prison setting. METHODS: Semi-structured interviews were used to explore the attitudes of detainees and staff towards smoking before and after a smoke-free regulation change in the prison in 2009. Specific coding and thematic content analysis for research were performed with the support of ATLAS.ti. RESULTS: In total, 77 interviews were conducted (38 before the regulation change and 39 after the regulation change) with 31 detainees (mean age 35 years, range 22-60 years) and 27 prison staff (mean age 46 years, range 29-65 years). Both detainees and staff expressed satisfaction regarding their involvement in the study, and wished to be informed about the results. They expected concrete changes in smoke-free regulation, and that the research would help to find ways to motivate detainees to quit smoking. CONCLUSION: Active involvement of stakeholders promotes public health. Interviewing detainees and prison staff as part of an action-research study aimed at tackling a public health matter is a way of raising awareness and facilitating change in prisons. Research needs to be conducted independently from the prison administrators in order to increase trust and to avoid misunderstandings.

Quality of care after acute coronary syndromes in a prospective cohort with reasons for non-prescription of recommended medications.

BACKGROUND: Adherence to guidelines is associated with improved outcomes of patients with acute coronary syndrome (ACS). Clinical registries developed to assess quality of care at discharge often do not collect the reasons for non-prescription for proven efficacious preventive medication in Continental Europe. In a prospective cohort of patients hospitalized for an ACS, we aimed at measuring the rate of recommended treatment at discharge, using pre-specified quality indicators recommended in cardiologic guidelines and including systematic collection of reasons for non-prescription for preventive medications. METHODS: In a prospective cohort with 1260 patients hospitalized for ACS, we measured the rate of recommended treatment at discharge in 4 academic centers in Switzerland. Performance measures for medication at discharge were pre-specified according to guidelines, systematically collected for all patients and included in a centralized database. RESULTS: Six hundred and eighty eight patients(54.6%) were discharged with a main diagnosis of STEMI, 491(39%) of NSTEMI and 81(6.4%) of unstable angina. Mean age was 64 years and 21.3% were women. 94.6% were prescribed angiotensin converting enzyme inhibitors/angiotensin II receptor blockers at discharge when only considering raw prescription rates, but increased to 99.5% when including reasons non-prescription. For statins, rates increased from 98% to 98.6% when including reasons for non-prescription and for beta-blockers, from 82% to 93%. For aspirin, rates further increased from 99.4% to 100% and from to 99.8% to 100% for P2Y12 inhibitors. CONCLUSIONS: We found a very high adherence to ACS guidelines for drug prescriptions at discharge when including reasons for non-prescription to drug therapy. For beta-blockers, prescription rates were suboptimal, even after taking into account reason for non-prescription. In an era of improving quality of care to achieve 100% prescription rates at discharge unless contra-indicated, pre-specification of reasons for non-prescription for cardiovascular preventive medication permits to identify remaining gaps in quality of care at discharge. TRIAL REGISTRATION: ClinicalTrials.gov NCT01000701.

White matter maturation reshapes structural connectivity in the late developing human brain.

From toddler to late teenager, the macroscopic pattern of axonal projections in the human brain remains largely unchanged while undergoing dramatic functional modifications that lead to network refinement. These functional modifications are mediated by increasing myelination and changes in axonal diameter and synaptic density, as well as changes in neurochemical mediators. Here we explore the contribution of white matter maturation to the development of connectivity between ages 2 and 18 y using high b-value diffusion MRI tractography and connectivity analysis. We measured changes in connection efficacy as the inverse of the average diffusivity along a fiber tract. We observed significant refinement in specific metrics of network topology, including a significant increase in node strength and efficiency along with a decrease in clustering. Major structural modules and hubs were in place by 2 y of age, and they continued to strengthen their profile during subsequent development. Recording resting-state functional MRI from a subset of subjects, we confirmed a positive correlation between structural and functional connectivity, and in addition observed that this relationship strengthened with age. Continuously increasing integration and decreasing segregation of structural connectivity with age suggests that network refinement mediated by white matter maturation promotes increased global efficiency. In addition, the strengthening of the correlation between structural and functional connectivity with age suggests that white matter connectivity in combination with other factors, such as differential modulation of axonal diameter and myelin thickness, that are partially captured by inverse average diffusivity, play an increasingly important role in creating brain-wide coherence and synchrony.

The correlation between inbreeding and fitness: does allele size matter?

The availability of highly polymorphic genetic markers, in particular microsatellites, has made it possible to test the effect of inbreeding on fitness in the field and in the absence of pedigree information. It has been suggested that the squared difference in allele size at a locus (d(2)) might be a better indicator of the level of inbreeding than is heterozygosity. Using an elegant new analytical model, Tsitrone et al. now put this idea to the test, and to rest.

Magnetic resonance imaging determinants of intraindividual variability in the elderly: combined analysis of grey and white matter.

Elderly individuals display a rapid age-related increase in intraindividual variability (IIV) of their performances. This phenomenon could reflect subtle changes in frontal lobe integrity. However, structural studies in this field are still missing. To address this issue, we computed an IIV index for a simple reaction time (RT) task and performed magnetic resonance imaging (MRI) including voxel based morphometry (VBM) and the tract based spatial statistics (TBSS) analysis of diffusion tensor imaging (DTI) in 61 adults aged from 22 to 88 years. The age-related IIV increase was associated with decreased fractional anisotropy (FA) as well as increased radial (RD) and mean (MD) diffusion in the main white matter (WM) fiber tracts. In contrast, axial diffusion (AD) and grey matter (GM) densities did not show any significant correlation with IIV. In multivariate models, only FA has an age-independent effect on IIV. These results revealed that WM but not GM changes partly mediated the age-related increase of IIV. They also revealed that the association between WM and IIV could not be only attributed to the damage of frontal lobe circuits but concerned the majority of interhemispheric and intrahemispheric corticocortical connections.