Functional coupling of sensorimotor and associative areas during a catching ball task: a qEEG coherence study

Abstract Background Catching an object is a complex movement that involves not only programming but also effective motor coordination. Such behavior is related to the activation and recruitment of cortical regions that participates in the sensorimotor integration process. This study aimed to elucidate the cortical mechanisms involved in anticipatory actions when performing a task of catching an object in free fall. Methods Quantitative electroencephalography (qEEG) was recorded using a 20-channel EEG system in 20 healthy right-handed participants performed the catching ball task. We used the EEG coherence analysis to investigate subdivisions of alpha (8-12 Hz) and beta (12-30 Hz) bands, which are related to cognitive processing and sensory-motor integration. Results Notwithstanding, we found the main effects for the factor block; for alpha-1, coherence decreased from the first to sixth block, and the opposite effect occurred for alpha-2 and beta-2, with coherence increasing along the blocks. Conclusion It was concluded that to perform successfully our task, which involved anticipatory processes (i.e. feedback mechanisms), subjects exhibited a great involvement of sensory-motor and associative areas, possibly due to organization of information to process visuospatial parameters and further catch the falling object.

Increased coherence among striatal regions in the theta range during attentive wakefulness

The striatum, the largest component of the basal ganglia, is usually subdivided into associative, motor and limbic components. However, the electrophysiological interactions between these three subsystems during behavior remain largely unknown. We hypothesized that the striatum might be particularly active during exploratory behavior, which is presumably associated with increased attention. We investigated the modulation of local field potentials (LFPs) in the striatum during attentive wakefulness in freely moving rats. To this end, we implanted microelectrodes into different parts of the striatum of Wistar rats, as well as into the motor, associative and limbic cortices. We then used electromyograms to identify motor activity and analyzed the instantaneous frequency, power spectra and partial directed coherence during exploratory behavior. We observed fine modulation in the theta frequency range of striatal LFPs in 92.5 ± 2.5% of all epochs of exploratory behavior. Concomitantly, the theta power spectrum increased in all striatal channels (P < 0.001), and coherence analysis revealed strong connectivity (coefficients >0.7) between the primary motor cortex and the rostral part of the caudatoputamen nucleus, as well as among all striatal channels (P < 0.001). Conclusively, we observed a pattern of strong theta band activation in the entire striatum during attentive wakefulness, as well as a strong coherence between the motor cortex and the entire striatum. We suggest that this activation reflects the integration of motor, cognitive and limbic systems during attentive wakefulness.

Time lags of the kilohertz quasi-periodic oscillations in the low-mass X-ray binaries 4U 1608−52 and 4U 1636−53

We studied the energy and frequency dependence of the Fourier time lags and intrinsic coherence of the kilohertz quasi-periodic oscillations (kHz QPOs) in the neutron-star lowmass X-ray binaries 4U 1608−52 and 4U 1636−53, using a large data set obtained with the Rossi X-ray Timing Explorer. We confirmed that, in both sources, the time lags of the lower kHz QPO are soft and their magnitude increases with energy. We also found that: (i) In 4U 1636−53, the soft lags of the lower kHz QPO remain constant at∼30 μs in the QPO frequency range 500–850 Hz, and decrease to ∼10 μs when the QPO frequency increases further. In 4U 1608−52, the soft lags of the lower kHz QPO remain constant at 40 μs up to 800 Hz, the highest frequency reached by this QPO in our data. (ii) In both sources, the time lags of the upper kHz QPO are hard, independent of energy or frequency and inconsistent with the soft lags of the lower kHz QPO. (iii) In both sources the intrinsic coherence of the lower kHz QPO remains constant at ∼0.6 between 5 and 12 keV, and drops to zero above that energy. The intrinsic coherence of the upper kHz QPO is consistent with being zero across the full energy range. (iv) In 4U 1636−53, the intrinsic coherence of the lower kHz QPO increases from ∼0 at ∼600 Hz to ∼1, and it decreases to ∼0.5 at 920 Hz; in 4U 1608−52, the intrinsic coherence is consistent with the same trend. (v) In both sources the intrinsic coherence of the upper kHz QPO is consistent with zero over the full frequency range of the QPO, except in 4U 1636−53 between 700 and 900 Hz where the intrinsic coherence marginally increases. We discuss our results in the context of scenarios in which the soft lags are either due to reflection off the accretion disc or up-/down-scattering in a hot medium close to the neutron star. We finally explore the connection between, on one hand the time lags and the intrinsic coherence of the kHz QPOs, and on the other the QPOs’ amplitude and quality factor in these two sources.

Magnitude and controls of N2 fixation in the subtropical Northeast Atlantic

Programa de doctorado en Oceanografía

Optical flow estimation with consistent spatio-temporal coherence models

[EN] In this work we propose a new variational model for the consistent estimation of motion fields. The aim of this work is to develop appropriate spatio-temporal coherence models. In this sense, we propose two main contributions: a nonlinear flow constancy assumption, similar in spirit to the nonlinear brightness constancy assumption, which conveniently relates flow fields at different time instants; and a nonlinear temporal regularization scheme, which complements the spatial regularization and can cope with piecewise continuous motion fields. These contributions pose a congruent variational model since all the energy terms, except the spatial regularization, are based on nonlinear warpings of the flow field. This model is more general than its spatial counterpart, provides more accurate solutions and preserves the continuity of optical flows in time. In the experimental results, we show that the method attains better results and, in particular, it considerably improves the accuracy in the presence of large displacements.

Fault delineation and stress orientations from the analysis of background, low magnitude seismicity in Southern Apennines (Italy)

The aim of this work was to show that refined analyses of background, low magnitude seismicity allow to delineate the main active faults and to accurately estimate the directions of the regional tectonic stress that characterize the Southern Apennines (Italy), a structurally complex area with high seismic potential. Thanks the presence in the area of an integrated dense and wide dynamic network, was possible to analyzed an high quality microearthquake data-set consisting of 1312 events that occurred from August 2005 to April 2011 by integrating the data recorded at 42 seismic stations of various networks. The refined seismicity location and focal mechanisms well delineate a system of NW-SE striking normal faults along the Apenninic chain and an approximately E-W oriented, strike-slip fault, transversely cutting the belt. The seismicity along the chain does not occur on a single fault but in a volume, delimited by the faults activated during the 1980 Irpinia M 6.9 earthquake, on sub-parallel predominant normal faults. Results show that the recent low magnitude earthquakes belongs to the background seismicity and they are likely generated along the major fault segments activated during the most recent earthquakes, suggesting that they are still active today thirty years after the mainshock occurrences. In this sense, this study gives a new perspective to the application of the high quality records of low magnitude background seismicity for the identification and characterization of active fault systems. The analysis of the stress tensor inversion provides two equivalent models to explain the microearthquake generation along both the NW-SE striking normal faults and the E- W oriented fault with a dominant dextral strike-slip motion, but having different geological interpretations. We suggest that the NW-SE-striking Africa-Eurasia convergence acts in the background of all these structures, playing a primary and unifying role in the seismotectonics of the whole region.

Toward a Magnitude Scale for Low Frequency Seismicity The LP energy for Campi Flegrei caldera

The energy released during a seismic crisis in volcanic areas is strictly related to the physical processes in the volcanic structure. In particular Long Period seismicity, that seems to be related to the oscillation of a fluid-filled crack (Chouet , 1996, Chouet, 2003, McNutt, 2005), can precedes or accompanies an eruption. The present doctoral thesis is focused on the study of the LP seismicity recorded in the Campi Flegrei volcano (Campania, Italy) during the October 2006 crisis. Campi Flegrei Caldera is an active caldera; the combination of an active magmatic system and a dense populated area make the Campi Flegrei a critical volcano. The source dynamic of LP seismicity is thought to be very different from the other kind of seismicity ( Tectonic or Volcano Tectonic): it’s characterized by a time sustained source and a low content in frequency. This features implies that the duration–magnitude, that is commonly used for VT events and sometimes for LPs as well, is unadapted for LP magnitude evaluation. The main goal of this doctoral work was to develop a method for the determination of the magnitude for the LP seismicity; it’s based on the comparison of the energy of VT event and LP event, linking the energy to the VT moment magnitude. So the magnitude of the LP event would be the moment magnitude of a VT event with the same energy of the LP. We applied this method to the LP data-set recorded at Campi Flegrei caldera in 2006, to an LP data-set of Colima volcano recorded in 2005 – 2006 and for an event recorded at Etna volcano. Experimenting this method to lots of waveforms recorded at different volcanoes we tested its easy applicability and consequently its usefulness in the routinely and in the quasi-real time work of a volcanological observatory.

Entwicklung kohärenter Lichtquellen im XUV-Regime

Plasmabasierte Röntgenlaser sind aufgrund ihrer kurzen Wellenlänge und schma-rnlen spektralen Bandbreite attraktive Diagnose-Instrumente in einer Vielzahl potentieller Anwendungen, beispielsweise in den Bereichen Spektroskopie, Mikroskopie und EUV-Lithografie. Dennoch sind Röntgenlaser zum heutigen Stand noch nicht sehr weit verbreitet, was vorwiegend auf eine zu geringe Pulsenergie und für manche Anwendungen nicht hinreichende Strahlqualität zurückzuführen ist. In diesem Zusammenhang wurden in den letzten Jahren bedeutende Fortschritte erzielt. Die gleichzeitige Weiterentwicklung von Pumplasersystemen und Pumpmechanismen ermöglichte es, kompakte Röntgenlaserquellen mit bis zu 100 Hz zu betreiben. Um gleichzeitig höhere Pulsenergien, höhere Strahlqualität und volle räumliche Kohärenz zu erhalten, wurden intensive Studien theoretischer und experimenteller Natur durchgeführt. In diesem Kontext wurde in der vorliegenden Arbeit ein experimenteller Aufbau zur Kombination von zwei Röntgenlaser-Targets entwickelt, die sogenannte Butterfly-Konfiguration. Der erste Röntgenlaser wird dabei als sogenannter Seed für das zweite, als Verstärker dienende Röntgenlasermedium verwendet (injection-seeding). Aufrndiese Weise werden störende Effekte vermieden, welche beim Entstehungsprozessrndes Röntgenlasers durch die Verstärkung von spontaner Emission zustande kom-rnmen. Unter Verwendung des ebenfalls an der GSI entwickelten Double-Pulse Gra-rnzing Incidence Pumpschemas ermöglicht das hier vorgestellte Konzept, erstmaligrnbeide Röntgenlasertargets effizient und inklusive Wanderwellenanregung zu pum-rnpen.rnBei einer ersten experimentellen Umsetzung gelang die Erzeugung verstärkter Silber-Röntgenlaserpulse von 1 µJ bei 13.9 nm Wellenlänge. Anhand der gewonnenen Daten erfolgte neben dem Nachweis der Verstärkung die Bestimmung der Lebensdauer der Besetzungsinversion zu 3 ps. In einem Nachfolgeexperiment wurden die Eigenschaften eines Molybdän-Röntgenlaserplasmas näher untersucht. Neben dem bisher an der GSI angewandten Pumpschema kam in dieser Strahlzeit noch eine weitere Technik zum Einsatz, welche auf einem zusätzlichen Pumppuls basierte. In beiden Schemata gelang neben dem Nachweis der Verstärkung die zeitliche und räumliche Charakterisierung des Verstärkermediums. Röntgenlaserpulse mit bis zu 240 nJ bei einer Wellenlänge von 18.9 nm wurden nachgewiesen. Die erreichte Brillanz der verstärkten Pulse lag ca. zwei Größenordnungen über der des ursprünglichen Seeds und mehr als eine Größenordnung über der Brillanz eines Röntgenlasers, dessen Erzeugung auf der Verwendung eines einzelnen Targets basierte. Das in dieser Arbeitrnentwickelte und experimentell verifizierte Konzept birgt somit das Potential, extrem brillante plasmabasierte Röntgenlaser mit vollständiger räumlicher und zeitlicher Kohärenz zu erzeugen.rnDie in dieser Arbeit diskutierten Ergebnisse sind ein wesentlicher Beitrag zu der Entwicklung eines Röntgenlasers, der bei spektroskopischen Untersuchungen von hochgeladenen Schwerionen eingesetzt werden soll. Diese Experimente sind amrnExperimentierspeicherring der GSI und zukünftig auch am High-Energy StoragernRing der FAIR-Anlage vorgesehen.rn

Search for a spin-dependent short-range force between nucleons with a 3 He, 129 Xe clock-comparison experiment

Light pseudoscalar bosons, such as the axion that was originally proposed as a solution of the strong CP problem, would cause a new spin-dependent short-range interaction. In this thesis, an experiment is presented to search for axion mediated short-range interaction between a nucleon and the spin of a polarized bound neutron. This interaction cause a shift in the precession frequency of nuclear spin-polarized gases in the presence of an unpolarized mass. To get rid of magnetic field drifts co-located, nuclear spin polarized 3He and 129Xe atoms were used. The free nuclear spin precession frequencies were measured in a homogeneous magnetic guiding field of about 350nT using LTc SQUID detectors. The whole setup was housed in a magnetically shielded room at the Physikalisch Technische Bundesanstalt (PTB) in Berlin. With this setup long nuclear spin-coherence times, respectively, transverse relaxation times of 5h for 129Xe and 53h for 3He could be achieved. The results of the last run in September 2010 are presented which give new upper limits on the scalar-pseudoscalar coupling of axion-like particles in the axion-mass window from 10^(-2) eV to 10^(-6) eV. The laboratory upper bounds were improved by up to 4 orders of magnitude.

An optical coherence tomography study of a biodegradable vs. durable polymer-coated limus-eluting stent: a LEADERS trial sub-study

Incomplete endothelialization has been found to be associated with late stent thrombosis, a rare but devastating phenomenon, more frequent after drug-eluting stent implantation. Optical coherence tomography (OCT) has 10 times greater resolution than intravascular ultrasound and thus appears to be a valuable modality for the assessment of stent strut coverage. The LEADERS trial was a multi-centre, randomized comparison of a biolimus-eluting stent (BES) with biodegradable polymer with a sirolimus-eluting stent (SES) using a durable polymer. This study sought to evaluate tissue coverage and apposition of stents using OCT in a group of patients from the randomized LEADERS trial.

Reproducibility of retinal thickness measurements in patients with age-related macular degeneration using 3D Fourier-domain optical coherence tomography (OCT) (Topcon 3D-OCT 1000)

Conventional time-domain optical coherence tomography (OCT) has become an important tool for following dry or exudative age-related macular degeneration (AMD). Fourier-domain three-dimensional (3D) OCT was recently introduced. This study tested the reproducibility of 3D-OCT retinal thickness measurements in patients with dry and exudative AMD.

Small dense particles in the retina observable by spectral-domain optical coherence tomography in age-related macular degeneration

To observe detailed changes in neurosensory retinal structure after anti-VEGF upload in age-related macular degeneration (AMD), by using spectral domain optical coherence tomography (SD-OCT).

Spectral-domain optical coherence tomography use in macular diseases: a review

The introduction of spectral-domain optical coherence tomography (SD-OCT) has improved the clinical value for assessment of the eyes with macular disease. This article reviews the advances of SD-OCT for the diagnostic of various macular diseases. These include vitreomacular traction syndrome, cystoid macular edema/diabetic macular edema, epiretinal membranes, full-thickness macular holes, lamellar holes, pseudoholes, microholes, and schisis from myopia. Besides offering new insights into the pathogenesis of macular abnormalities, SD-OCT is a valuable tool for monitoring macular disease.