Torsional control of eye-head saccades

Under natural conditions the head and the eye are both free to rotate about three mutuall orthogonal axes each (horizontal, vertical and torsional). Theoretically, these six degrees of freedom would allow any two-dimensional direction of the line of sight to be obtained by infinitely many torsional head and eye orientations. Yet, for any one gaze direction our brain chooses specific angles of torsion for the head and the eye. For steady fixation of distant targets with the head fixed and upright this observation is known as Donders' law (1847). It has been shown to hold independently of the direction of the rapid gaze shift (saccade) preceding a fixation. Surprisingly, despite considerable research on head and eye coordination the full implications of Donders' law still have not been analyzed for head-unrestrained gaze shifts. It has merely been studied whether torsional constraints hold, when gaze is returned repeatedly to the targets from single initial positions. The aim of this study was to see whether Donders' law holds after head-unrestrained saccades, independently of the saccade direction. Secondary objectives were to analyze whether the neural controls of the eye and the head are dependent or independent during this task and to collect and present control data for comparison with patient recordings in clinical context. Therefore, seven healthy human subjects made large head-unrestrained gaze shifts to a single set of visual targets during two separate conditions: 1) Repeated saccades to individual target positions from the same direction respectively (Star paradigm). 2) Repeated saccades to every target position from several different directions (Diamond paradigm). Three-dimensional orientations of head and eye were measured simultaneously with the magnetic search coil technique and consecutively plotted in three-dimensional space so that those orientations obeying Donders' law formed a surface. For each of the three body units the static orientations formed subspaces that resembled surfaces in the shape of twisted double saddles. Surfaces of head orientations had the most pronounced twist, eye in head surfaces were the most planar and surfaces of gaze orientations showed intermediate twist. The standard deviation of torsional residuals of the approximated surfaces (torsional thickness) was bigger for gaze than for the eye and smallest for the head. Head and eye torsion, as averaged over individual fixations, were correlated differently within every subject, but between subjects there was no correlation. In summary, neither surface shapes nor torsional thickness of gaze, head or eye differed between the two conditions (Star/Diamond). With this it is shown for the first time that Donders' law of torsional control holds true for gaze, head and eye orientations independently of the direction of the preceding saccade. The absence of correlation between head and eye torsion can be explained by independent controllers of head and eye movements. This yields a new, further argument supporting recent models of neuronal gaze control that are based on the assumption of independent head and eye controllers. Studies with patients carrying lesions in possible target structures of such neuronal controllers are needed to further investigate these models. Finally, clinically-diagnostic relevance of this study arises from the comparison to results of studies on gaze coordination after midbrain lesions where patients exhibit an altered form of Donders' law.Unter natürlichen Bedingungen sind Rotationen von Kopf und Auge um jeweils drei voneinander unabhängige Raumachsen (Quer-, Hoch- und Längsachse) möglich. Diese sechs Freiheitsgrade würden beim Blick in jede zweidimensionale Richtung beliebige Drehungen um die Längsachse (Torsion) sowohl des Kopfes als auch des Auges erlauben. Unser Gehirn wählt jedoch in jeder Blickrichtung je einen spezifischen Torsionswinkel für Kopf und Auge. Für die Fixation entfernter Blickziele bei aufrechtem, unbewegtem Kopf wurde diese Tatsache als Donders' Law (1847) bekannt. Das Gesetz gilt unabhängig von der Richtung der der Fixation vorhergehenden raschen Blickbewegung (Sakkade). Überraschenderweise wurde trotz zahlreicher Untersuchungen zur Kopf- und Augenkoordination die vollständige Gültigkeit von Donders' Law bei Blickbewegungen mit bewegtem Kopf noch nicht gezeigt. Es wurde lediglich untersucht, ob die resultierenden Torsionsbeschränkungen weiter gelten, wenn der Blick wiederholt von denselben Ausgangspositionen auf verschiedene Punkte gerichtet wird. Hauptziel dieser Arbeit war zu prüfen, ob Donders' Law nach Sakkaden mit bewegtem Kopf unabhängig von der Sakkadenrichtung gilt. Zudem wurde analysiert, ob Kopf und Auge dabei einer gemeinsamen oder separaten neuronalen Kontrolle unterliegen, und es wurden Kontrolldaten zum Vergleich mit Patientenmessungen im klinischen Kontext gesammelt. Dazu führten sieben gesunde menschliche Probanden Sakkaden mit bewegtem Kopf zwischen einer Anordnung visueller Blickziele unter zwei Versuchsbedingungen durch: 1) Wiederholte Sakkaden auf jedes Ziel aus der jeweils gleichen Richtung (Star Paradigma). 2) Wiederholte Sakkaden auf jedes Ziel aus mehreren verschiedenen Richtungen (Diamond Paradigma). Die dreidimensionalen Kopf- und Augenbewegungen wurden simultan mit der magnetischen Search-Coil-Technik gemessen und zur Analyse räumlich dargestellt, so dass Positionen, die Donders' Law entsprechen, eine Fläche bilden. Für jede der drei Körpereinheiten lagen die statischen Positionen in Unterräumen, die Flächen in Form verdrehter (getwisteter) Doppelsättel ähnelten. Die Flächen der Kopfpositionen wiesen den deutlichsten Twist auf, die der Auge-im-Kopf Positionen waren nahezu eben und die Flächen der Blickpositionen zeigten einen mittleren Twist. Die Standardabweichung der Torsionsresiduen der genäherten Flächen (Torsionsdicke) war größer für den Blick als für das Auge und am kleinsten für den Kopf. Kopf- und Augentorsion, gemittelt über die Einzelfixationen, waren für jeden einzelnen Probanden unterschiedlich korreliert; über alle Probanden ergab sich jedoch keine signifikante Korrelation. Zusammenfassend unterschieden sich weder Flächenform noch Torsionsdicke von Blick, Kopf oder Auge zwischen den beiden Bedingungen (Star/ Diamond). Damit ist zum ersten Mal gezeigt, dass Donders' Law für Blick-, Kopf- und Augenpositionen unabhängig von der Richtung der vorangegangenen Sakkade gilt. Die fehlende Korrelation der Kopf- und Augentorsion ist auf eine unabhängige Kontrolle von Kopf- und Augenbewegungen zurückzuführen. Dies ist ein neues, weiteres Argument zur Bestätigung aktueller Modelle der neuronalen Kontrolle von Blickbewegungen, die von der Annahme unabhängiger Kopf- und Augencontroller ausgehen. Studien mit Patienten, die Läsionen in möglichen Zielstrukturen für solche neuronalen Controller tragen, sind zur weiteren Untersuchung dieser Modelle nötig. Abschließend ergibt sich klinisch-diagnostische Relevanz der Arbeit aus dem Vergleich mit Studiendaten zur Blickkoordination nach Mittelhirnläsionen, bei denen Patienten eine veränderte Form von Donders' Law aufweisen

Heterophoria: Vergence stability and visual acuity after asymmetric saccades

Many patients with heterophoria report on symptoms related to impaired vision. To investigate whether these symptoms are provoked by saccades this study examines whether in heterophoria effects on intrasaccadic and postsaccadic vergence movements are linked to effects on visual performance. Visual acuity was measured in 35 healthy subjects during fixation and immediately after asymmetric diverging saccades. Binocular position traces were recorded by video-oculography. Subjects with exophoria showed larger intrasaccadic divergence amplitudes, which in turn led to smaller postsaccadic divergence amplitudes. Visual acuity did not depend on heterophoria or vergence amplitudes. The results suggest that compensating for exophoria requires increased convergence activity as compared to orthophoria or compensated esophoria. Visual acuity seemed relatively robust with respect to postsaccadic vergence movements

Resonant Raman scattering by collective modes of the one-dimensional electron gas

We show that the low-energy peak in the polarized resonant Raman spectra of quantum wires, which is commonly associated with ``single particle excitations'', can be interpreted as signature of intra-band collective spin excitations. A broad maximum in the resonant depolarized spectra is predicted to exist above the frequency of the spin density excitation, due to simultaneous but independent propagation of spin- and charge-density modes.Comment: 4 pages, accepted for publication in Phys. Rev. Let

Effects of dignity therapy on psychological distress and wellbeing of palliative care patients and family caregivers – a randomized controlled study

Background This study extended the original Dignity Therapy (DT) intervention by including partners and family caregivers (FCs) of terminally-ill cancer patients with the overall aim of evaluating whether DT can mitigate distress in both patients nearing the end of life and their FCs. Methods In this multicenter, randomized controlled trial (RCT), a total of 68 patients with life expectancy < 6 months and clinically-relevant stress levels (Hospital Anxiety Depression total score; HADS$_{tot}$ ≥ 8) including their FCs were randomly assigned to DT, DT + (including their FCs), or standard palliative care (SPC) in a 1:1:1 ratio. Study participants were asked to complete a set of questionnaires pre- and post-intervention. Results The coalesced group (DT and DT +) revealed a significant increase in patients’ perceived quality of life (FACIT-Pal-14) following the intervention (mean difference 6.15, SD = 1.86, p < 0.01). We found a statistically significant group-by-time interaction effect: while the HADS$_{tot}$ of patients in the intervention group remained stable over the pre-post period, the control group’s HADS$_{tot}$ increased (F = 4.33, df = 1, 82.9; p < 0.05), indicating a protective effect of DT. Most patients and their FCs found DT useful and would recommend it to other individuals in their situation. Conclusions The DT intervention has been well-received and shows the potential to increase HRQoL and prevent further mental health deterioration, illness burden and suffering in terminally-ill patients. The DT intervention holds the potential to serve as a valuable tool for facilitating end-of-life conversations among terminally-ill patients and their FCs. However, the implementation of DT within the framework of a RCT in a palliative care setting poses significant challenges. We suggest a slightly modified and less resource-intensive version of DT that is to provide the DT inventory to FCs of terminally-ill patients, empowering them to ask the questions that matter most to them over their loved one’s final days. Trial registration This study was registered with Clinical Trial Registry (ClinicalTrials.gov -Protocol Record NCT02646527; date of registration: 04/01/2016). The CONSORT 2010 guidelines were used for properly reporting how the randomized trial was conducted

Vertigo and dizziness in adolescents: Risk factors and their population attributable risk

Objectives: To assess potential risk factors for vertigo and dizziness in adolescents and to evaluate their variability by different vertigo types. The role of possible risk factors for vertigo and dizziness in adolescents and their population relevance needs to be addressed in order to design preventive strategies. Study design: The study population consisted of 1482 school-children between the age of 12 and 19 years, who were instructed to fill out a questionnaire on different vertigo types and related potential risk factors. The questionnaire specifically asked for any vertigo, spinning vertigo, swaying vertigo, orthostatic dizziness, and unspecified dizziness. Further a wide range of potential risk factors were addressed including gender, stress, muscular pain in the neck and shoulder region, sleep duration, migraine, coffee and alcohol consumption, physical activity and smoking. Results: Gender, stress, muscular pain in the neck and shoulder region, sleep duration and migraine were identified as independent risk factors following mutual adjustment: The relative risk was 1.17 [1.10 - 1.25] for female sex, 1.07 [1.02 - 1.13] for stress, 1.24 [1.17 - 1.32] for muscular pain, and 1.09 [1.03 - 1.14] for migraine. The population attributable risk explained by these risk factors was 26%, with muscular pain, stress, and migraine accounting for 11%, 4%, and 3% respectively. Conclusion: Several established risk factors in adults were also identified in adolescents. Risk factors amenable to prevention accounted for 17% of the total population risk. Therefore, interventions targeting these risk factors may be warranted

Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal

Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC

Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H →γ γ, H → Z Z∗ →4l and H →W W∗ →lνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV, corresponding to an integrated luminosity of about 25 fb−1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson

Standalone vertex finding in the ATLAS muon spectrometer

A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at √s = 7 TeV collected with the ATLAS detector at the LHC during 2011

Measurement of the top quark-pair production cross section with ATLAS in pp collisions at \sqrt{s}=7\TeV

A measurement of the production cross-section for top quark pairs(\ttbar) in $pp$ collisions at \sqrt{s}=7 \TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different topologies: single lepton (electron $e$ or muon $\mu$) with large missing transverse energy and at least four jets, and dilepton ($ee$, $\mu\mu$ or $e\mu$) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb-1, 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-\ttbar Standard Model processes are estimated using data-driven methods and determined to be $12.2 \pm 3.9$ events and $2.5 \pm 0.6$ events, respectively. The kinematic properties of the selected events are consistent with SM \ttbar production. The inclusive top quark pair production cross-section is measured to be \sigmattbar=145 \pm 31 ^{+42}_{-27} pb where the first uncertainty is statistical and the second systematic. The measurement agrees with perturbative QCD calculations.Comment: 30 pages plus author list (50 pages total), 9 figures, 11 tables, CERN-PH number and final journal adde