The use of the asymptotic expansion to speed up the computation of a series of spherical harmonics

When a function is expressed as an infinite series of spherical harmonics the convergence can be accelerated by subtracting its asymptotic expansion and adding it in analytically closed form. In the present article this technique is applied to two biophysical cases: to the potential distribution in a spherically symmetric volume conductor and to the covariance matrix of biomagnetic measurements

The use of the asymptotic expansion to speed up the computation of a series of spherical harmonics

When a function is expressed as an infinite series of spherical harmonics the convergence can be accelerated by subtracting its asymptotic expansion and adding it in analytically closed form. In the present article this technique is applied to two biophysical cases: to the potential distribution in a spherically symmetric volume conductor and to the covariance matrix of biomagnetic measurements

Neural activity underlying the detection of an object movement by an observer during forward self-motion: Dynamic decoding and temporal evolution of directional cortical connectivity.

Relatively little is known about how the human brain identifies movement of objects while the observer is also moving in the environment. This is, ecologically, one of the most fundamental motion processing problems, critical for survival. To study this problem, we used a task which involved nine textured spheres moving in depth, eight simulating the observer's forward motion while the ninth, the target, moved independently with a different speed towards or away from the observer. Capitalizing on the high temporal resolution of magnetoencephalography (MEG) we trained a Support Vector Classifier (SVC) using the sensor-level data to identify correct and incorrect responses. Using the same MEG data, we addressed the dynamics of cortical processes involved in the detection of the independently moving object and investigated whether we could obtain confirmatory evidence for the brain activity patterns used by the classifier. Our findings indicate that response correctness could be reliably predicted by the SVC, with the highest accuracy during the blank period after motion and preceding the response. The spatial distribution of the areas critical for the correct prediction was similar but not exclusive to areas underlying the evoked activity. Importantly, SVC identified frontal areas otherwise not detected with evoked activity that seem to be important for the successful performance in the task. Dynamic connectivity further supported the involvement of frontal and occipital-temporal areas during the task periods. This is the first study to dynamically map cortical areas using a fully data-driven approach in order to investigate the neural mechanisms involved in the detection of moving objects during observer's self-motion.R01 NS104585 - NINDS NIH HHS; U01 EB023820 - NIBIB NIH HHSPublished versio

Integrated analysis of environmental and genetic influences on cord blood DNA methylation in new-borns

Epigenetic processes, including DNA methylation (DNAm), are among the mechanisms allowing integration of genetic and environmental factors to shape cellular function. While many studies have investigated either environmental or genetic contributions to DNAm, few have assessed their integrated effects. Here we examine the relative contributions of prenatal environmental factors and genotype on DNA methylation in neonatal blood at variably methylated regions (VMRs) in 4 independent cohorts (overall n = 2365). We use Akaike’s information criterion to test which factors best explain variability of methylation in the cohort-specific VMRs: several prenatal environmental factors (E), genotypes in cis (G), or their additive (G + E) or interaction (GxE) effects. Genetic and environmental factors in combination best explain DNAm at the majority of VMRs. The CpGs best explained by either G, G + E or GxE are functionally distinct. The enrichment of genetic variants from GxE models in GWAS for complex disorders supports their importance for disease risk

Toward noninvasive monitoring of ongoing electrical activity of human uterus and fetal heart and brain

Objective: To evaluate whether a full-coverage fetal-maternal scanner can noninvasively monitor ongoing electrophysiological activity of maternal and fetal organs. Methods: A simulation study was carried out for a scanner with an array of magnetic field sensors placed all around the torso from the chest to the hip within a horizontal magnetic shielding enclosure. The magnetic fields from internal organs and an external noise source were computed for a pregnant woman with a 35-week old fetus. Signal processing methods were used to reject the external and internal interferences, to visualize uterine activity, and to detect activity of fetal heart and brain. Results: External interference was reduced by a factor of 1000, sufficient for detecting signals from internal organs when combined with passive and active shielding. The scanner rejects internal interferences better than partial-coverage arrays. It can be used to estimate currents around the uterus. It clearly detects spontaneous activity from the fetal heart and brain without averaging and weaker evoked brain activity at all fetal head positions after averaging. Conclusion: The simulated device will be able to monitor the ongoing activity of the fetal and maternal organs. Significance This type of scanner may become a novel tool in fetal medicine

Learning from each other’s struggles

Sociology has always been in dialogue with social movements, from Tocqueville, Marx and Durkheim to Angela Davis, Herbert Marcuse, Frances Piven and Toni Negri. As a young activist, wanting to understand the movements I was involved in and see how we could take them further, sociology was the obvious starting-point. I had grown up around human rights and anti-apartheid, the peace and ecology movements. Travel and study around Europe showed me whole movement scenes and subcultures – feminist, libertarian, socialist – with roots in the 1960s and 1970s and still generating new movements in the 1980s and 1990s. I started to research where these shared histories and cultures had come from, and how we could draw on them to build new alliances. My PhD, on the potential for radical alliances developing the everyday popular rationalities expressed by these cultures, was written against the background of the Zapatistas and submitted just in time to see the Seattle protests against the WTO validate its conclusions and change the movement landscape across the industrialised North. Writing the thesis went hand-in-hand with editing an activist magazine which tried to make those links in practical ways, and with small gatherings of activists from different movements – around the possibility of a new left, networking independent media, reviving the older alternative movements and trying to create cross-movement dialogues