A core task in the analysis of functional magnetic resonance imaging (fMRI) data is to detect groups of voxels that exhibit synchronous activity while the subject is performing a certain task. Synchronous activity is typically interpreted as functional connectivity between brain regions. We compare classical approaches like statistical parametric mapping (SPM) and some new approaches that are loosely based on frequent pattern mining principles, but restricted to the local neighborhood of a voxel. In particular, we examine how a soft notion of activity (rather than a binary one) can be modeled and exploited in the analysis process. In addition, we explore a fault-tolerant notion of synchronous activity of groups of voxels in both the binary and the soft/fuzzy activity setting. We apply the methods to fMRI data from a visual stimulus experiment to demonstrate their usefulness.
Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation tool suited to alter cortical excitability and activity via application of direct currents. The long-lasting synaptic modifications induced by this stimulation technique have been shown to result in behavioral functional improvements. This might be related to tDCS-induced modulations of associations among populations of neurons which improve the functional connectivity between local and segregated cortical areas involved in the respective functional networks. In this chapter, we describe the effects of tDCS-induced neuroplasticity on human brain functional networks at the large-scale level, and how different functional connectivity techniques might be used to track for such induced alterations.
OBJECTIVE: We sought to elucidate the influence of centrally active drugs on interhemispheric inhibition (IHI) between primary motor cortices in healthy humans.
METHODS: We therefore studied IHI before and 2h after intake of a single oral dose of carbamazepine, dextrometorphane, lorazepam, or placebo and compared it with the well known results for short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). Drugs were tested in separate sessions and in random order.
RESULTS: While SICI and ICF were not altered by carbamazepine, IHI was reduced at the interstimulus interval of 8 ms. Dextrometorphane tended to enhance SICI and to reduce ICF and had no effect on IHI. Lorazepam reduced ICF as expected and enhanced IHI at the long intervals of 50 and 80ms. A moderate trend for interhemispheric facilitation was inconsistently observed at the interval 2 ms and blocked by carbamazepine. In addition, carbamazepine increased the motor threshold.
CONCLUSIONS: We conclude that circuits mediating short interstimulus intervals of IHI are susceptible to sodium channel blockade.
SIGNIFICANCE: The results increase our knowledge of interhemispheric transmission.
Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that has been shown to alter cortical excitability and activity via application of weak direct currents. Beyond intracortical effects, functional imaging as well as behavioral studies are suggesting additional tDCS-driven alterations of subcortical areas, however, direct evidence for such effects is scarce. We aimed to investigate the impact of tDCS on cortico-subcortical functional networks by seed functional connectivity analysis of different striatal and thalamic regions to prove tDCS-induced alterations of the cortico-striato-thalamic circuit. fMRI resting state data sets were acquired immediately before and after 10 min of bipolar tDCS during rest, with the anode/cathode placed over the left primary motor cortex (M1) and the cathode/anode over the contralateral frontopolar cortex. To control for possible placebo effects, an additional sham stimulation session was carried out. Functional coupling between the left thalamus and the ipsilateral primary motor cortex (M1) significantly increased following anodal stimulation over M1. Additionally, functional connectivity between the left caudate nucleus and parietal association cortices was significantly strengthened. In contrast, cathodal tDCS over M1 decreased functional coupling between left M1 and contralateral putamen. In summary, in this study, we show for the first time that tDCS modulates functional connectivity of cortico-striatal and thalamo-cortical circuits. Here we highlight that anodal tDCS over M1 is capable of modulating elements of the cortico-striato-thalamo-cortical functional motor circuit.
Functional cortical circuits for central executive functions have been shown to emerge by theta (~6 Hz) phase-coupling of distant cortical areas. It has been repeatedly shown that frontoparietal theta coupling at ~0° relative phase is associated with recognition, encoding, short-term retention, and planning; however, a causal link has not been demonstrated so far. Here we used transcranial alternating current stimulation simultaneously applied at 6 Hz over left prefrontal and parietal cortices with a relative 0° ("synchronized" condition) or 180° ("desynchronized" condition) phase difference or a placebo stimulation condition, whereas healthy subjects performed a delayed letter discrimination task. We show that exogenously induced frontoparietal theta synchronization significantly improves visual memory-matching reaction times as compared to placebo stimulation. In contrast, exogenously induced frontoparietal theta desynchronization deteriorates performance. The present findings provide for the first time evidence of causality of theta phase-coupling of distant cortical areas for cognitive performance in healthy humans. Moreover, the results demonstrate the suitability of transcranial alternating current stimulation to artificially induce coupling or decoupling of behaviorally relevant brain rhythms between segregated cortical regions.
We analyze the emergence of the first socioeconomic institution in history limiting fertility: west of a line from St. Petersburg to Trieste, the European Marriage Pattern (EMP) reduced childbirths by approximately one-third between the fourteenth and eighteenth century. To explain the rise of EMP we build a two-sector model of agricultural production—grain and livestock. Women have a comparative advantage in animal husbandry. After the Black Death in 1348–1350, land abundance triggered a shift toward the pastoral sector. This improved female employment prospects, leading to later marriages. Using detailed data from England, we provide strong evidence for our mechanism.
In den letzten zwanzig Jahren hat der Bund zahlreiche Anstrengungen unternommen, um die Innovationsleistungen
von Unternehmen und Hochschulen zu fördern. Die Massnahmen der Kommission für Technologie und Innovation (KTI) wurden im Kontext der «evidenzbasierten Politik» durch eine Vielzahl von Evaluationen untersucht. Eine Auswertung der
vorliegenden Studien aus dem Zeitraum von 1997 bis 2011 zeigt, dass die Massnahmen positive Effekte zu erzielen vermochten, wenn auch in unterschiedlichem Ausmass.
The paper offers an empirical taxonomy of the factors driving China's current account. A simple present-value model with non-tradeable goods explains more than 70 percent of current account variability over the period 1982–2007, including the persistent surpluses since 2001. It also correctly predicts the decline of China's current account since 2008. Expected increases in the prices of non-tradeables (e.g. housing and medical care) and expected declines in net output (GDP less investment and government spending) are the main channels of external adjustment. Much of China's current account surplus seems driven by shocks that have global effects by persistently depressing the world real interest rate. This is consistent with recent theoretical models that suggest that factors related to China's domestic financial development are key in understanding global imbalances.
Der biologische Lebensstandard bezeichnet die Erfassung des Wohlstandes von Bevölkerungsgruppen anhand von Körpergrössen. Insbesondere werden in der historischen Anthropometrie sozioökonomische Erklärungen für die Entwicklung der Körpergrössen gesucht. Die durchschnittliche Körperhöhe ist hierbei ein geeignetes Mass für das langfristige Wohlbefinden. Vor allem die Lebensumstände in den ersten drei Lebensjahren sind wichtig. Das mittlere Körpergewicht und der Body-Mass-Index (BMI) sind Indikatoren für die gegenwärtigen Lebensumstände. Der vorliegende Beitrag analysiert den biologischen Lebensstandard im Kanton Zürich zwischen 1919 und 1951. Die ausgewerteten Daten stammen aus den sanitarischen Rekrutenkontrollen der Schweizer Armee zwischen 1938 und 1951. Bis heute gilt in der Schweiz die allgemeine Wehrpflicht, sodass die militärische Tauglichkeit aller Schweizer Männer überprüft wird. Der vorliegende Datensatz ist somit nicht systematisch verzerrt. Drei Fragestellungen wurden bearbeitet: Wie entwickelte sich die durchschnittliche Körperhöhe der Jahrgänge 1919 bis 1932? Wie entwickelten sich das mittlere Körpergewicht und der BMI im Zweiten Weltkrieg? Treten saisonale Schwankungen in den Körpergrössen auf? Die durchschnittliche Körperhöhe der Jahrgänge 1919 bis 1932 nimmt zu. Die Entwicklung der Körperhöhe deckt sich aber nicht mit der wirtschaftlichen Entwicklung in den 1920er Jahren. Die städtischen Stellungspflichtigen sind grösser als die ländlichen. Es sind Körperhöhenunterschiede nach Schichten und Berufen zu finden. Die Entwicklung des mittleren Körpergewichtes und BMI im Zweiten Weltkrieg kann mit den behördlichen Kriegsmassnahmen erklärt werden (Rationierung, agrarischer Mehranbau). Der Geburtsmonat hat einen signifikanten Einfluss auf die Körpergrössen.
