Alexander's Law in Patients with Acute Vestibular Tone Asymmetry—Evidence for Multiple Horizontal Neural Integrators

Alexander's law (AL) states that the slow-phase velocity of spontaneous nystagmus of peripheral vestibular origin is dependent on horizontal gaze position, with greater velocity when gaze is directed in the fast-phase direction. AL is thought to be a compensatory reaction resulting from adaptive changes in the horizontal ocular motor neural integrator. Until now, only horizontal eye movements have been investigated with respect to AL. Because spontaneous nystagmus usually includes vertical and torsional components, we asked whether horizontal gaze changes would have an effect on the 3D drift of spontaneous nystagmus and, thus, on the vertical/torsional neural integrator. We hypothesized that AL reduces all nystagmus components proportionally. Moreover, we questioned the classical theory of a single bilaterally organized horizontal integrator and searched for nonlinearities of AL implying a network of multiple integrators. Using dual scleral search coils, we measured AL in 17 patients with spontaneous nystagmus. Patients followed a pulsed laser dot at eye level jumping in 5° steps along the horizontal meridian between 25° right and left in otherwise complete darkness. AL was observed in 15 of 17 patients. Whereas individual patients typically showed a change of 3D-drift direction at different horizontal eye positions, the average change in direction was not different from zero. The strength of AL (= rate of change of total velocity with gaze position) correlated with nystagmus slow-phase velocity (Spearman's rho = 0.5; p < 0.05) and, on average, did not change the 3D nystagmus drift direction. In general, eye velocity did not vary linearly with eye position. Rather, there was a stronger dependence of velocity on horizontal position when subjects looked in the slow-phase direction compared to the fast-phase direction. We conclude that the theory of a simple leak of a single horizontal neural integrator is not sufficient to explain all aspects of A

Error Resilient Quantum Amplitude Estimation from Parallel Quantum Phase Estimation

We show how phase and amplitude estimation algorithms can be parallelized. This can reduce the gate depth of the quantum circuits to that of a single Grover operator with a small overhead. Further, we show that for quantum amplitude estimation, the parallelization can lead to vast improvements in resilience against quantum errors. The resilience is not caused by the lower gate depth, but by the structure of the algorithm. Even in cases with errors that make it impossible to read out the exact or approximate solutions from conventional amplitude estimation, our parallel approach provided the correct solution with high probability. The results on error resilience hold for the standard version and for low depth versions of quantum amplitude estimation. Methods presented are subject of a patent application [Quantum computing device: Patent application EP 21207022.1]

Quantum amplitude estimation with error mitigation for time-evolving probabilistic networks

We present a method to model a discretized time evolution of probabilistic networks on gate-based quantum computers. We consider networks of nodes, where each node can be in one of two states: good or failed. In each time step, probabilities are assigned for each node to fail (switch from good to failed) or to recover (switch from failed to good). Furthermore, probabilities are assigned for failing nodes to trigger the failure of other, good nodes. Our method can evaluate arbitrary network topologies for any number of time steps. We can therefore model events such as cascaded failure and avalanche effects which are inherent to financial networks, payment and supply chain networks, power grids, telecommunication networks and others. Using quantum amplitude estimation techniques, we are able to estimate the probability of any configuration for any set of nodes over time. This allows us, for example, to determine the probability of the first node to be in the good state after the last time step, without the necessity to track intermediate states. We present the results of a low-depth quantum amplitude estimation on a simulator with a realistic noise model. We also present the results for running this example on the AQT quantum computer system PINE. Finally, we introduce an error model that allows us to improve the results from the simulator and from the experiments on the PINE system

The effect of alcohol on cervical and ocular vestibular evoked myogenic potentials in healthy volunteers

OBJECTIVE: We investigated the effect of alcohol on the cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs). As alcohol produces gaze-evoked nystagmus (GEN), we also tested the effect of nystagmus independent of alcohol by recording oVEMPs during optokinetic stimulation (OKS). METHODS: The effect of alcohol was tested in 14 subjects over multiple rounds of alcohol consumption up to a maximum breath alcohol concentration (BrAC) of 1.5‰ (mean 0.97‰). The effect of OKS was tested in 11 subjects at 5, 10 and 15deg/sec. RESULTS: oVEMP amplitude decreased from baseline to the highest BrAC level by 27% (range 5-50%, P<0.001), but there was no significant effect on oVEMP latency or cVEMP amplitude or latency. There was a significant negative effect of OKS on oVEMP amplitude (16%, P=0.006). CONCLUSIONS: We found a selective effect of alcohol on oVEMP amplitude, but no effect on the cVEMP. Vertical nystagmus elicited by OKS reduced oVEMP amplitude. SIGNIFICANCE: Alcohol selectively affects oVEMP amplitude. Despite the effects of alcohol and nystagmus, both reflexes were reliably recorded in all subjects and conditions. An absent response in a patient affected by alcohol or nystagmus indicates a vestibular deficit

Rotational vertebral artery syndrome: 3D kinematics of nystagmus suggest bilateral labyrinthine dysfunction

Whether the rotational vertebral artery syndrome (RVAS), consisting of attacks of vertigo, nystagmus and tinnitus elicited by head-rotation induced compression of the dominant vertebral artery (VA), reflects ischemic dysfunction of uni- or bilateral peripheral or central vestibular structures, is still debated. We report on a patient with bilateral high-grade carotid stenoses, in whom rightward headrotation led to RVAS symptoms including a prominent nystagmus. Three-dimensional kinematic analysis of the nystagmus pattern, recorded with search coils, revealed major downbeat nystagmus with minor horizontal and torsional components. Magnetic resonance angiography demonstrated a hypoplastic right VA terminating in the posterior inferior cerebellar artery, a dominant left VA, and a hypoplastic P1-segment of the left posterior cerebral artery (PCA) that was supplied by the left posterior communicating artery (PCoA). The right PCA and both anterior inferior cerebellar arteries were supplied by the basilar artery. The right PCoA originated from the right internal carotid artery. Color duplex sonography showed severe reduction of diastolic blood flow velocities in the left VA during RVAS attacks. The nystagmus pattern can be best explained by vectorial addition of 3D sensitivity vectors of stimulated right and left anterior and horizontal semicircular canals with slightly stronger stimulation on the left side. We hypothesize that in RVAS, compression of dominant VA leads to acute vertebrobasilar insufficiency with bilateral, but asymmetric ischemia of the superior labyrinth. With regard to RVAS etiology, our case illustrates a type of pure vascular RVAS. Severity of attacks markedly decreased after successful bilateral carotid endarterectom

Acute onset of tinnitus in patients with sudden deafness

Objective: We made hypotheses that tinnitus will appear more likely in patients with sudden deafness with superior hearing in unaffected ear or with more severe acute hearing loss. Methods: A retrospective cohort study was performed. Five hundred forty-one patients were identified with idiopathic sudden sensorineural hearing loss (ISSHL) from January 1995 to August 2006. The exclusion criteria for this study were as follows: bilateral sudden hearing loss and Meniere disease, previous tinnitus or bilateral tinnitus at initial evaluation, and onset of hearing loss less than 7 days. The cohort enrolled 454 patients. The enrolled patients were classified into two groups: patient with acute onset tinnitus in the affected ear and patients without tinnitus at initial visit. Main outcome measures were patient age, the presence or absence of vertigo and tinnitus, audiometric patterns, the severity of hearing loss, and hearing in the unaffected ear. Results: Better contralateral hearing (n = 220 versus n = 72, P < 0.001) and younger age (48 versus 55 years, P < 0.001) were independently associated with the acute onset of tinnitus in patients with ISSHL. The degree of asymmetry between the ears did not differ significantly between patients with and without tinnitus. The sex, presence of vertigo, shape of audiogram, and severity of hearing loss were not correlated with tinnitus occurrence. Conclusions: Tinnitus triggered by ISSHL was more frequent in patients with better contralateral hearing and of a younger age, irrespective of the severity of hearing loss on the affected side or the asymmetry between the ears

Visual contribution to postural stability: Interaction between target fixation or tracking and static or dynamic large-field stimulus

Stationary visual information has a stabilizing effect on posture, whereas moving visual information is destabilizing. We compared the influence of a stationary or moving fixation point to the influence of stationary or moving large-field stimulation, as well as the interaction between a fixation point and a large-field stimulus. We recorded body sway in 20 healthy subjects who were fixating a stationary or oscillating dot (vertical or horizontal motion, 1/3Hz, +/-12 degrees amplitude, distance 96cm). In addition, a large-field random dot pattern (extension: approximately 80x70 degrees ) was stationary, moving or absent. Visual fixation of a stationary dot in darkness did not reduce antero-posterior (AP) sway compared to the situation in total darkness, but slightly reduced lateral sway at frequencies below 0.5Hz. In contrast, fixating a stationary dot on a stationary large-field pattern reduced both AP and lateral body sway at all frequencies (0.1-2Hz). Ocular tracking of the oscillating dot caused a peak in body sway at 1/3Hz, i.e. the stimulus frequency, but there was no influence of large-field stimulus at this frequency. A stationary large-field pattern, however, reduced AP and lateral sway at frequencies between 0.1 and 2Hz when subjects tracked a moving dot, compared to tracking in darkness. Our results demonstrate that a stationary large-field pattern has a stabilizing effect in all conditions, independent of whether the eyes are fixing on a stationary target or tracking a moving target

Microcapsule Buckling Triggered by Compression-Induced Interfacial Phase Change

There is an emerging trend towards the fabrication of microcapsules at liquid interfaces. In order to control the parameters of such capsules, the interfacial processes governing their formation must be understood. Here, poly(vinyl alcohol) films are assembled at the interface of water-in-oil microfluidic droplets. The polymer is cross-linked using cucurbit[8]uril ternary supramolecular complexes. It is shown that compression-induced phase change causes the onset of buckling in the interfacial film. On evaporative compression, the interfacial film both increases in density and thickens, until it reaches a critical density and a phase change occurs. We show that this increase in density can be simply related to the film Poisson ratio and area compression.This description captures fundamentals of many compressive interfacial phase changes and can also explain the observation of a fixed thickness-to-radius ratio at buckling, $\left(\frac TR\right)$$_{buck}$

'Brain Circulation' – Diaspora als treibende Kraft bei der Entwicklung der Herkunftsländer:Seminar "Brain Drain und Brain Gain. Migration und Entwicklung"

Seit Beginn des 21. Jahrhunderts hat die Diskussion über den Zusammenhang von Migration und Entwicklung eine neue Richtung bekommen. Wurde die Emigration von Hochqualifizierten aus Entwicklungsländern bislang zumeist als ein abgeschlossener Prozess gesehen, der für die Abgabeländer in einem Humankapitalverlust (brain drain) und für die Aufnahmeländer (meistenteils Industrieländer) in einem Humankapitalgewinn (brain gain) resultiert, so wird Elitenmigration heute mehr und mehr als ein zirkulärer Prozess der Hin- und Her- bzw. Weiterwanderung angesehen (brain circulation), von dem nicht nur Industrieländer, sondern potentiell auch Entwicklungsländer profitieren können. Alle hier veröffentlichten Arbeiten des Politikwissenschaftsseminars "Brain Drain und Brain Gain. Migration und Entwicklung" unter Leitung von Prof. Thränhardt und Dr. Uwe Hunger aus dem Sommersemester 2005 stellen originäre und eigenständige Forschungsarbeiten dar und tragen durch ihre sorgfältige Recherche dazu bei, weitere neue, wichtige Erkenntnisse für diese immer noch junge Forschungsrichtung zusammenzutragen. Die eigenständigen Arbeiten der Studierenden behandeln ein Thema, das sich in der Forschung gerade durchzusetzen beginnt und Lösungsansätze für die Probleme einer globalisierten und zusammenwachsenden Welt öffnet

No downregulation of immune function during breeding in two year-round breeding bird species in an equatorial East African environment

Some equatorial environments exhibit substantial within-location variation in environmental conditions throughout the year and yet have year-round breeding birds. This implies that breeding in such systems are potentially unrelated to the variable environmental conditions. By breeding not being influenced by environmental conditions, we become sure that any differences in immune function between breeding and non-breeding birds do not result from environmental variation, therefore allowing for exclusion of the confounding effect of variation in environmental conditions. This create a unique opportunity to test if immune function is down-regulated during reproduction compared to non-breeding periods. We compared the immune function of sympatric male and female chick-feeding and non-breeding red-capped Calandrella cinerea and rufous-naped larks Mirafra africana in equatorial East Africa. These closely-related species occupy different niches and have different breeding strategies in the same grassland habitat. Red-capped larks prefer areas with short grass or almost bare ground, and breed during low rainfall periods. Rufous-naped larks prefer areas of tall grass and scattered shrubs and breed during high rainfall. We measured the following immune indices: nitric oxide, haptoglobin, agglutination and lysis, and measured total monthly rain, monthly average minimum (T-min) and maximum (T-max) temperatures. Contrary to our predictions, we found no down-regulation of immune function during breeding; breeding birds had higher nitric oxide than non-breeding ones in both species, while the other three immune indices did not differ between breeding phases. Red-capped larks had higher nitric oxide concentrations than Rufous-naped larks, which in turn had higher haptoglobin levels than red-capped larks. T-max was higher during breeding than during non-breeding for red-capped larks only, suggesting potential confounding effect of T-max on the comparison of immune function between breeding and non-breeding birds for this species. Overall, we conclude that in the two year-round breeding equatorial larks, immune function is not down-regulated during breeding