[Neurotheology: neurobiological models of religious experience]. / Neurotheologie : Neurobiologische Modelle religiöser Erfahrungen.

Religions are evolutionary selected social and cultural phenomena. They represent today belief and normative systems on which the main parts of our culture are based. For a long time religions have been seen as mainly originating from a spectrum of religious experiences. These include a broad spectrum of experiences and are astonishingly widespread in the population. The most consistent and transculturally uniform religious experiences are the mystical experiences. Only these (and the prayer experience) have factually been researched in detail neurobiologically. This article presents a review of empirical results and hypothetical approaches to explain mystical religious experiences neurobiologically. Some of the explanatory hypotheses possess logical evidence, some are even supported by neurobiological studies, but all of them have their pitfalls and are at best partially consistent. One important insight from the evidence reviewed here is that there may be a whole array of different neurophysiological conditions which may result in the same core religious mystical experiences.

2 kW incoherent beam combining of four narrow-linewidth photonic crystal fiber amplifiers.

We report on beam combining of four narrow-linewidth fiber amplifier chains, running at different wavelengths and each delivering 500 W optical output power. The main amplifier stage consists of a large mode area photonic crystal fiber. The four output beams of the amplifier chains are spectrally (incoherent) combined using a polarization-independent dielectric reflective diffraction grating to form an output beam of 2 kW continuous-wave optical power with good beam quality (M(2)x = 2.0, M(2)y = 1.8).

Spectral beam combination of fiber amplified ns-pulses by means of interference filters.

In this paper we introduce a simple scheme to spectrally combine four single beams using three low-cost dielectric interference filters as combining elements. 25 ns pulses from four independent and actively Q-switched fiber seed-sources are amplified in a single stage fiber-amplifier. Temporally and spatially combined 208 W of average power and 6.3 mJ of pulse energy are obtained at two different repetition frequencies. A detailed analysis of beam quality as well as the thermal behavior of the combining elements is carried out and reveals mutual dependency.

Changes in processing of proprioceptive information in Parkinson's disease and multiple system atrophy.

OBJECTIVE: Changes in processing of proprioceptive information are known in idiopathic Parkinson's disease (IPD) and may contribute to motor deficits. This study used transcranial magnetic stimulation (TMS) to investigate the processing of proprioceptive information induced by muscle vibration (MV) in 10 patients with IPD and 10 patients with multiple system atrophy of the parkinsonian type (MSA-P) in comparison to 10 controls. METHODS: Single and paired-pulses were used, and motor evoked potentials (MEPs) were recorded in the extensor and flexor carpi radialis muscles (ECR and FCR) without and with MV (80Hz) to the ECR. Cortical silent periods (SP) were also studied. RESULTS: Controls showed the known MV-induced focal MEP augmentation which was lacking in IPD and intermediate and less focal in MSA-P. Intracortical inhibition and facilitation were not influenced by MV. SP was not changed by MV in controls and IPD while it was significantly prolonged in MSA-P. CONCLUSIONS: Processing of proprioceptive information is differently changed in IPD and MSA-P. Cortical facilitation by MV is more impaired in IPD than MSA-P, and these changes are less focal in MSA-P than in controls. SIGNIFICANCE: Our results support the view that changes in processing of proprioceptive information may contribute to motor deficits in patients with IPD and MSA-P.

[Presbyopia treatment using a femtosecond laser]. / Presbyopietherapie mit Femtosekundenlaser.

Presbyopia is by far the most common refractive error worldwide, with no permanent therapeutic option available. All efforts to restore accommodation by the use of surgery have not led to a generally accepted therapy. However, there is evidence from an animal model that the use of a femtosecond (fs) laser might influence the modulus of elasticity in the lens. Fs-laser impulses can create intralenticular disruption in animal eyes as well as human cadaver lenses and improve elasticity. The concept of treating presbyopia with fs-laser requires a new, complex theory combining the optical and the mechanical aspects of accommodation in the eye. Diagnostic tools for measuring optical change in power and geometrical modification as the eye views from far to near are needed to obtain objective clinical data. A non-invasive treatment of presbyopia to restore accommodation might be possible in the future.

Increased pre-SMA activation in early PD patients during simple self-initiated hand movements.

The slowness of movement, termed bradykinesia, is one of the main symptoms of Parkinson's disease (PD). This symptom may be due to the inability of PD patients to maximise the speed of internally driven movements. The mesial premotor areas and in particular the pre-supplementary motor area (pre-SMA) seem to play a crucial role in the temporal initiation of movements in humans and animals. However, this activation seems to be debatable in imaging studies of PD patients. We performed a motor paradigm with temporally self-initiated movements in nine de novo PD patients before and after initiation of dopaminergic medication. The main finding was an increased activation of the pre-SMA in de novo PD patients compared with healthy age-matched control subjects. This result indicates the contribution of the pre-SMA in the temporal initiation of self-generated movements and in the disease pathology of PD. Increased bilateral activation of the superior cerebellum, mainly on the ipsilateral side, and a decreased activation of the ipsilateral inferior cerebellum in PD patients were also present. These findings provide new insights into the activation pattern of the cerebellum in PD patients.

Thermo-optical behavior of rare-earth-doped low-NA fibers in high power operation.

The influence of the internal temperature gradient in rare-earth-doped low-numerical-aperture fibers on modal properties is analyzed for step-index and photonic crystal fibers. We provide guidelines when a single-mode fiber turns into a multimode fiber and how the mode-field-diameter is affected.

Thermo-optical properties of air-clad photonic crystal fiber lasers in high power operation.

We report on the investigation of the thermo-optical behavior of air-clad ytterbium-doped large-mode-area photonic crystal fiber lasers. Analytical and numerical models are applied to calculate the heat distribution and induced stresses in a microstructured fiber. The results are compared to conventional double-clad fiber lasers and design guidelines are provided to ensure maximum heat dissipation and scalability to power levels of several kWs.

Effects of subthalamic nucleus (STN) stimulation on motor cortex excitability.

BACKGROUND: Deep brain stimulation of the internal global pallidus (GPi) and the subthalamic nucleus (STN) has become a treatment alternative in advanced PD. Although the effects of GPi stimulation have been examined recently, little is known about STN stimulation effects on motor cortex excitability. METHODS: The effects of STN stimulation were studied in eight patients with advanced PD using paired-pulse transcranial magnetic stimulation (TMS) in comparison with healthy control subjects. Motor evoked potentials following paired-pulse TMS (interstimulus interval 3 ms to test for corticocortical inhibition vs 13 ms for facilitation) have been recorded from the extensor carpi radialis and its functional antagonist, the flexor carpi radialis muscle. Silent period (SP) was also determined. Patients were examined under four conditions: medication "off"/stimulator "off" vs medication "on"/stimulator "off" vs medication "off"/stimulator "on" vs medication "on"/stimulator "on." RESULTS: Although the mean values for intracortical inhibition (ICI) were not significantly different, data variation was smaller and levels of significance higher with the STN stimulator switched "on," suggesting that ICI was more consistent. SP during stimulator "on"/medication "on" was longer than during stimulator "off"/medication "off." Motor performance as indicated by a finger-tapping test and Unified PD Rating Scale III was significantly better with dopaminergic medication and further improved with stimulator "on." CONCLUSIONS: Results suggest an effect of subthalamic nucleus stimulation on intracortical inhibitory mechanisms. This hypothesis could at least partially explain a more consistent depression of motor evoked potentials following inhibiting paired-pulse transcranial magnetic stimulation, a longer silent period (under stimulator "on"/medication "on"), and a reduction of akinesia and rigidity leading to a better motor performance in subthalamic nucleus-stimulated patients.

Resting regional cerebral glucose metabolism in advanced Parkinson's disease studied in the off and on conditions with [(18)F]FDG-PET.

Studies of resting regional cerebral glucose consumption (rCMRGlc) in nondemented patients with Parkinson's disease (PD) have produced conflicting results, reporting both reduced and normal metabolism in advanced disease and reduced or normal metabolism after dopaminergic therapy. To investigate these issues, [(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET) was performed in 11 nondemented PD patients with advanced disease and 10 age-matched controls. PD patients were studied after withdrawal of all dopaminergic medication to produce a practically defined off condition, and a second time 1 hour after levodopa, resulting in a clinical on state. Dynamic PET scans and simultaneous arterialised venous blood samples of [(18)F] activity were obtained. A graphical approach was used to generate parametric images of rCMRGlc and statistical parametric mapping to localise significant metabolic changes in PD. Compared with controls, global rCMRGlc was reduced in the on but not in the off condition in PD. In both states, significant regional reductions of glucose uptake were found in the parietal, frontal, temporal cortex, and caudate nucleus. Reductions correlated with the severity of disability in frontal and temporal cortex. Direct comparison between on and off conditions revealed relatively greater reductions of uptake in the ventral/orbital frontal cortex and the thalamus during on. Results suggest that cortical and caudate hypometabolism are common in advanced PD and that caution is mandatory if [(18)F]FDG PET is being used to differentiate advanced PD from dementia and progressive supranuclear palsy where similar reductions are seen. Furthermore, in PD, administration of levodopa is associated with further hypometabolism in orbitofrontal cortex; an area known to be relevant for reversal learning where performance is typically impaired after dopaminergic treatment.

Assessment of chemoreflex sensitivity in free breathing young subjects by correction for respiratory influence.

BACKGROUND: The assessment of autonomic function is an important tool for risk stratification in critically ill patients. Peripheral cardiac chemoreflex sensitivity has been considered a marker for increased risk of sudden cardiac death. In normals, the evaluation of peripheral cardiac chemoreflex sensitivity is performed under controlled breathing conditions during inhalation of hypoxic gas. Since this is poorly tolerated by patients, they are commonly studied under hyperoxic conditions, which are not physiological. METHODS: We studied 20 healthy volunteers who underwent free and controlled breathing of a hypoxic gas mixture (10% O2 in N2) over 5 min. Values of peripheral cardiac chemoreflex sensitivity, corrected for respiratory influence, were compared with the results obtained experimentally under controlled breathing conditions in the same subjects. RESULTS: We found a substantial difference between values obtained during free and controlled breathing (3.64 +/- 0.81 vs. 1.53 +/- 0.32 ms/mmHg, respectively; P < 0.05). After application of a respiratory correction, described and validated in this article, no significant difference was seen for these values (0.89 +/-0.91 vs. 1.53 +/- 0.32 ms/mmHg, P = 0.46). CONCLUSIONS: This approach allows the evaluation of peripheral cardiac chemoreflex sensitivity in free breathing subjects. This correction could improve the assessment of cardiac chemoreflex sensitivity in patients with cardiorespiratory disorders, who find it difficult to control their breathing according to an experimental protocol.

Assessment of dynamic finger forces in pianists: effects of training and expertise.

Playing a musical instrument requires complex sensorimotor programming of hand and finger movements. During musical training motor programs are optimized to achieve highest accuracy with a minimum of effort. In the lack of handy measurement tools these rational assumptions of piano theorists did not undergo an experimental evaluation up to now. In the present pilot study we used a dynamic pressure measurement system with the pianoforte. Three finger exercises with increasing degrees of difficulty had to be performed by a group of musical amateurs and a group of expert players. From the dynamic force measurements we calculated (a) the mean pulse per touch and (b) the mean touch-duration for each exercise and each subject. To achieve the same tempo and the same loudness, amateurs applied significantly more and longer force to the keys, leading to higher mean pulses per touch. Pulse and duration values increased with higher demands on finger coordination in both, expert pianists and amateurs. The results show that dynamic force measurement systems can support music learners and teachers in training a relaxed piano technique and preventing musicians from overuse injuries.

Bright solitary pulses in AlGaAs waveguides at half the band gap.

We show that bright temporal solitonlike pulses can propagate in AlGaAs waveguides excited in the half-bandgap spectral regime. The use of an antiresonant reflecting optical waveguide permits the dispersion of the waveguide to be controlled so that a mode with anomalous dispersion can propagate.

Nonlinear guided waves in saturable nonlinear media.

The behavior of nonlinear waves guided by a film configuration with a nonlinear cladding is investigated. The intensity-dependent dielectric function of the cladding is characterized by saturation effects. The field patterns that arise are discussed, and the dispersion relations are derived. Several dispersion curves are plotted. The results are compared with those familiar from nonlinear guided-wave propagation along configurations with Kerr-like cladding dielectric functions.