Coupling of pupil- and neuronal population dynamics reveals diverse influences of arousal on cortical processing

Fluctuations in arousal, controlled by subcortical neuromodulatory systems, continuously shape cortical state, with profound consequences for information processing. Yet, how arousal signals influence cortical population activity in detail has so far only been characterized for a few selected brain regions. Traditional accounts conceptualize arousal as a homogeneous modulator of neural population activity across the cerebral cortex. Recent insights, however, point to a higher specificity of arousal effects on different components of neural activity and across cortical regions. Here, we provide a comprehensive account of the relationships between fluctuations in arousal and neuronal population activity across the human brain. Exploiting the established link between pupil size and central arousal systems, we performed concurrent magnetoencephalographic (MEG) and pupillographic recordings in a large number of participants, pooled across three laboratories. We found a cascade of effects relative to the peak timing of spontaneous pupil dilations: Decreases in low-frequency (2-8 Hz) activity in temporal and lateral frontal cortex, followed by increased high-frequency (>64 Hz) activity in mid-frontal regions, followed by monotonic and inverted U relationships with intermediate frequency-range activity (8-32 Hz) in occipito-parietal regions. Pupil-linked arousal also coincided with widespread changes in the structure of the aperiodic component of cortical population activity, indicative of changes in the excitation-inhibition balance in underlying microcircuits. Our results provide a novel basis for studying the arousal modulation of cognitive computations in cortical circuits.

Rapid processing of neutral and angry expressions within ongoing facial stimulus streams: Is it all about isolated facial features?

Our visual system extracts the emotional meaning of human facial expressions rapidly and automatically. Novel paradigms using fast periodic stimulations have provided insights into the electrophysiological processes underlying emotional content extraction: the regular occurrence of specific identities and/or emotional expressions alone can drive diagnostic brain responses. Consistent with a processing advantage for social cues of threat, we expected angry facial expressions to drive larger responses than neutral expressions. In a series of four EEG experiments, we studied the potential boundary conditions of such an effect: (i) we piloted emotional cue extraction using 9 facial identities and a fast presentation rate of 15 Hz (N = 16); (ii) we reduced the facial identities from 9 to 2, to assess whether (low or high) variability across emotional expressions would modulate brain responses (N = 16); (iii) we slowed the presentation rate from 15 Hz to 6 Hz (N = 31), the optimal presentation rate for facial feature extraction; (iv) we tested whether passive viewing instead of a concurrent task at fixation would play a role (N = 30). We consistently observed neural responses reflecting the rate of regularly presented emotional expressions (5 Hz and 2 Hz at presentation rates of 15 Hz and 6 Hz, respectively). Intriguingly, neutral expressions consistently produced stronger responses than angry expressions, contrary to the predicted processing advantage for threat-related stimuli. Our findings highlight the influence of physical differences across facial identities and emotional expressions.

Frequency and power of human alpha oscillations drift systematically with time-on-task

Oscillatory neural activity is a fundamental characteristic of the mammalian brain spanning multiple levels of spatial and temporal scale. Current theories of neural oscillations and analysis techniques employed to investigate their functional significance are based on an often implicit assumption: In the absence of experimental manipulation, the spectral content of any given EEG- or MEG-recorded neural oscillator remains approximately stationary over the course of a typical experimental session (∼1 h), spontaneously fluctuating only around its dominant frequency. Here, we examined this assumption for ongoing neural oscillations in the alpha-band (8-13 Hz). We found that alpha peak frequency systematically decreased over time, while alpha-power increased. Intriguingly, these systematic changes showed partial independence of each other: Statistical source separation (independent component analysis) revealed that while some alpha components displayed concomitant power increases and peak frequency decreases, other components showed either unique power increases or frequency decreases. Interestingly, we also found these components to differ in frequency. Components that showed mixed frequency/power changes oscillated primarily in the lower alpha-band (∼8-10 Hz), while components with unique changes oscillated primarily in the higher alpha-band (∼9-13 Hz). Our findings provide novel clues on the time-varying intrinsic properties of large-scale neural networks as measured by M/EEG, with implications for the analysis and interpretation of studies that aim at identifying functionally relevant oscillatory networks or at driving them through external stimulation.

Stimulus-Driven Brain Rhythms within the Alpha Band: The Attentional-Modulation Conundrum

Two largely independent research lines use rhythmic sensory stimulation to study visual processing. Despite the use of strikingly similar experimental paradigms, they differ crucially in their notion of the stimulus-driven periodic brain responses: one regards them mostly as synchronized (entrained) intrinsic brain rhythms; the other assumes they are predominantly evoked responses [classically termed steady-state responses (SSRs)] that add to the ongoing brain activity. This conceptual difference can produce contradictory predictions about, and interpretations of, experimental outcomes. The effect of spatial attention on brain rhythms in the alpha band (8-13 Hz) is one such instance: alpha-range SSRs have typically been found to increase in power when participants focus their spatial attention on laterally presented stimuli, in line with a gain control of the visual evoked response. In nearly identical experiments, retinotopic decreases in entrained alpha-band power have been reported, in line with the inhibitory function of intrinsic alpha. Here we reconcile these contradictory findings by showing that they result from a small but far-reaching difference between two common approaches to EEG spectral decomposition. In a new analysis of previously published human EEG data, recorded during bilateral rhythmic visual stimulation, we find the typical SSR gain effect when emphasizing stimulus-locked neural activity and the typical retinotopic alpha suppression when focusing on ongoing rhythms. These opposite but parallel effects suggest that spatial attention may bias the neural processing of dynamic visual stimulation via two complementary neural mechanisms.SIGNIFICANCE STATEMENT Attending to a visual stimulus strengthens its representation in visual cortex and leads to a retinotopic suppression of spontaneous alpha rhythms. To further investigate this process, researchers often attempt to phase lock, or entrain, alpha through rhythmic visual stimulation under the assumption that this entrained alpha retains the characteristics of spontaneous alpha. Instead, we show that the part of the brain response that is phase locked to the visual stimulation increased with attention (as do steady-state evoked potentials), while the typical suppression was only present in non-stimulus-locked alpha activity. The opposite signs of these effects suggest that attentional modulation of dynamic visual stimulation relies on two parallel cortical mechanisms-retinotopic alpha suppression and increased temporal tracking.

No changes in parieto-occipital alpha during neural phase locking to visual quasi-periodic theta-, alpha-, and beta-band stimulation

Recent studies have probed the role of the parieto-occipital alpha rhythm (8-12 Hz) in human visual perception through attempts to drive its neural generators. To that end, paradigms have used high-intensity strictly-periodic visual stimulation that created strong predictions about future stimulus occurrences and repeatedly demonstrated perceptual consequences in line with an entrainment of parieto-occipital alpha. Our study, in turn, examined the case of alpha entrainment by non-predictive low-intensity quasi-periodic visual stimulation within theta- (4-7 Hz), alpha- (8-13 Hz), and beta (14-20 Hz) frequency bands, i.e., a class of stimuli that resemble the temporal characteristics of naturally occurring visual input more closely. We have previously reported substantial neural phase-locking in EEG recording during all three stimulation conditions. Here, we studied to what extent this phase-locking reflected an entrainment of intrinsic alpha rhythms in the same dataset. Specifically, we tested whether quasi-periodic visual stimulation affected several properties of parieto-occipital alpha generators. Speaking against an entrainment of intrinsic alpha rhythms by non-predictive low-intensity quasi-periodic visual stimulation, we found none of these properties to show differences between stimulation frequency bands. In particular, alpha band generators did not show increased sensitivity to alpha band stimulation and Bayesian inference corroborated evidence against an influence of stimulation frequency. Our results set boundary conditions for when and how to expect effects of entrainment of alpha generators and suggest that the parieto-occipital alpha rhythm may be more inert to external influences than previously thought.

Trial-by-trial co-variation of pre-stimulus EEG alpha power and visuospatial bias reflects a mixture of stochastic and deterministic effects

Human perception of perithreshold stimuli critically depends on oscillatory EEG activity prior to stimulus onset. However, it remains unclear exactly which aspects of perception are shaped by this pre‐stimulus activity and what role stochastic (trial‐by‐trial) variability plays in driving these relationships. We employed a novel jackknife approach to link single‐trial variability in oscillatory activity to psychometric measures from a task that requires judgement of the relative length of two line segments (the landmark task). The results provide evidence that pre‐stimulus alpha fluctuations influence perceptual bias. Importantly, a mediation analysis showed that this relationship is partially driven by long‐term (deterministic) alpha changes over time, highlighting the need to account for sources of trial‐by‐trial variability when interpreting EEG predictors of perception. These results provide fundamental insight into the nature of the effects of ongoing oscillatory activity on perception. The jackknife approach we implemented may serve to identify and investigate neural signatures of perceptual relevance in more detail.

Audio-visual synchrony and spatial attention enhance processing of dynamic visual stimulation independently and in parallel: A frequency-tagging study

The neural processing of a visual stimulus can be facilitated by attending to its position or by a co-occurring auditory tone. Using frequency-tagging, we investigated whether facilitation by spatial attention and audio-visual synchrony rely on similar neural processes. Participants attended to one of two flickering Gabor patches (14.17 and 17 Hz) located in opposite lower visual fields. Gabor patches further "pulsed" (i.e. showed smooth spatial frequency variations) at distinct rates (3.14 and 3.63 Hz). Frequency-modulating an auditory stimulus at the pulse-rate of one of the visual stimuli established audio-visual synchrony. Flicker and pulsed stimulation elicited stimulus-locked rhythmic electrophysiological brain responses that allowed tracking the neural processing of simultaneously presented Gabor patches. These steady-state responses (SSRs) were quantified in the spectral domain to examine visual stimulus processing under conditions of synchronous vs. asynchronous tone presentation and when respective stimulus positions were attended vs. unattended. Strikingly, unique patterns of effects on pulse- and flicker driven SSRs indicated that spatial attention and audiovisual synchrony facilitated early visual processing in parallel and via different cortical processes. We found attention effects to resemble the classical top-down gain effect facilitating both, flicker and pulse-driven SSRs. Audio-visual synchrony, in turn, only amplified synchrony-producing stimulus aspects (i.e. pulse-driven SSRs) possibly highlighting the role of temporally co-occurring sights and sounds in bottom-up multisensory integration.

Flicker-Driven Responses in Visual Cortex Change during Matched-Frequency Transcranial Alternating Current Stimulation

We tested a novel combination of two neuro-stimulation techniques, transcranial alternating current stimulation (tACS) and frequency tagging, that promises powerful paradigms to study the causal role of rhythmic brain activity in perception and cognition. Participants viewed a stimulus flickering at 7 or 11 Hz that elicited periodic brain activity, termed steady-state responses (SSRs), at the same temporal frequency and its higher order harmonics. Further, they received simultaneous tACS at 7 or 11 Hz that either matched or differed from the flicker frequency. Sham tACS served as a control condition. Recent advances in reconstructing cortical sources of oscillatory activity allowed us to measure SSRs during concurrent tACS, which is known to impose strong artifacts in magnetoencephalographic (MEG) recordings. For the first time, we were thus able to demonstrate immediate effects of tACS on SSR-indexed early visual processing. Our data suggest that tACS effects are largely frequency-specific and reveal a characteristic pattern of differential influences on the harmonic constituents of SSRs.

Early Visual Cortex Dynamics during Top–Down Modulated Shifts of Feature-Selective Attention

Shifting attention from one color to another color or from color to another feature dimension such as shape or orientation is imperative when searching for a certain object in a cluttered scene. Most attention models that emphasize feature-based selection implicitly assume that all shifts in feature-selective attention underlie identical temporal dynamics. Here, we recorded time courses of behavioral data and steady-state visual evoked potentials (SSVEPs), an objective electrophysiological measure of neural dynamics in early visual cortex to investigate temporal dynamics when participants shifted attention from color or orientation toward color or orientation, respectively. SSVEPs were elicited by four random dot kinematograms that flickered at different frequencies. Each random dot kinematogram was composed of dashes that uniquely combined two features from the dimensions color (red or blue) and orientation (slash or backslash). Participants were cued to attend to one feature (such as color or orientation) and respond to coherent motion targets of the to-be-attended feature. We found that shifts toward color occurred earlier after the shifting cue compared with shifts toward orientation, regardless of the original feature (i.e., color or orientation). This was paralleled in SSVEP amplitude modulations as well as in the time course of behavioral data. Overall, our results suggest different neural dynamics during shifts of attention from color and orientation and the respective shifting destinations, namely, either toward color or toward orientation.

Sustained Splits of Attention within versus across Visual Hemifields Produce Distinct Spatial Gain Profiles

Visual attention can be focused concurrently on two stimuli at noncontiguous locations while intermediate stimuli remain ignored. Nevertheless, behavioral performance in multifocal attention tasks falters when attended stimuli fall within one visual hemifield as opposed to when they are distributed across left and right hemifields. This "different-hemifield advantage" has been ascribed to largely independent processing capacities of each cerebral hemisphere in early visual cortices. Here, we investigated how this advantage influences the sustained division of spatial attention. We presented six isoeccentric light-emitting diodes (LEDs) in the lower visual field, each flickering at a different frequency. Participants attended to two LEDs that were spatially separated by an intermediate LED and responded to synchronous events at to-be-attended LEDs. Task-relevant pairs of LEDs were either located in the same hemifield ("within-hemifield" conditions) or separated by the vertical meridian ("across-hemifield" conditions). Flicker-driven brain oscillations, steady-state visual evoked potentials (SSVEPs), indexed the allocation of attention to individual LEDs. Both behavioral performance and SSVEPs indicated enhanced processing of attended LED pairs during "across-hemifield" relative to "within-hemifield" conditions. Moreover, SSVEPs demonstrated effective filtering of intermediate stimuli in "across-hemifield" condition only. Thus, despite identical physical distances between LEDs of attended pairs, the spatial profiles of gain effects differed profoundly between "across-hemifield" and "within-hemifield" conditions. These findings corroborate that early cortical visual processing stages rely on hemisphere-specific processing capacities and highlight their limiting role in the concurrent allocation of visual attention to multiple locations.

Audio-visual synchrony and feature-selective attention co-amplify early visual processing

Our brain relies on neural mechanisms of selective attention and converging sensory processing to efficiently cope with rich and unceasing multisensory inputs. One prominent assumption holds that audio-visual synchrony can act as a strong attractor for spatial attention. Here, we tested for a similar effect of audio-visual synchrony on feature-selective attention. We presented two superimposed Gabor patches that differed in colour and orientation. On each trial, participants were cued to selectively attend to one of the two patches. Over time, spatial frequencies of both patches varied sinusoidally at distinct rates (3.14 and 3.63 Hz), giving rise to pulse-like percepts. A simultaneously presented pure tone carried a frequency modulation at the pulse rate of one of the two visual stimuli to introduce audio-visual synchrony. Pulsed stimulation elicited distinct time-locked oscillatory electrophysiological brain responses. These steady-state responses were quantified in the spectral domain to examine individual stimulus processing under conditions of synchronous versus asynchronous tone presentation and when respective stimuli were attended versus unattended. We found that both, attending to the colour of a stimulus and its synchrony with the tone, enhanced its processing. Moreover, both gain effects combined linearly for attended in-sync stimuli. Our results suggest that audio-visual synchrony can attract attention to specific stimulus features when stimuli overlap in space.

Visual, auditory and tactile stimuli compete for early sensory processing capacities within but not between senses

We investigated whether unattended visual, auditory and tactile stimuli compete for capacity-limited early sensory processing across senses. In three experiments, we probed competitive audio-visual, visuo-tactile and audio-tactile stimulus interactions. To this end, continuous visual, auditory and tactile stimulus streams ('reference' stimuli) were frequency-tagged to elicit steady-state responses (SSRs). These electrophysiological oscillatory brain responses indexed ongoing stimulus processing in corresponding senses. To induce competition, we introduced transient frequency-tagged stimuli in same and/or different senses ('competitors') during reference presentation. Participants performed a separate visual discrimination task at central fixation to control for attentional biases of sensory processing. A comparison of reference-driven SSR amplitudes between competitor-present and competitor-absent periods revealed reduced amplitudes when a competitor was presented in the same sensory modality as the reference. Reduced amplitudes indicated the competitor's suppressive influence on reference stimulus processing. Crucially, no such suppression was found when a competitor was presented in a different than the reference modality. These results strongly suggest that early sensory competition is exclusively modality-specific and does not extend across senses. We discuss consequences of these findings for modeling the neural mechanisms underlying intermodal attention.

nestor Guideline for Preservation Planning – a Process Model

The nestor guideline for preservation planning is the latest in a series of nestor publications. nestor is the German competence network for digital preservation and it offers all interested parties from the private and public domains the possibility to participate in working groups. The guideline for preservation planning is the result of such a working group, which discussed the conceptual and practical issues of implementing the OAIS Functional Entity “Preservation Planning”.The guideline describes a process model and offers some guidance on potential implementations. It integrates and builds on recognized community concepts like Significant Properties, the OAIS Designated Community, the National Archives of Australia’s Performance Model, the PREMIS concept of Intellectual Entities and Representations, and the PLANET’s approach to preservation planning. Furthermore, it introduces the concepts “intended use” (Nutzungsziele), “information type” (Informationstyp) and “preservation group” (Erhaltungsgruppe). The purpose of these new categories is that information objects shall be grouped by information type (e.g., audio, video, text…) and intended use (e.g., reading for pleasure, search for specific information…) to preservation groups for automatic processing. Significant properties can then be derived for whole preservation groups. The file format alone is considered as not completely sufficient for such categorisation. Some exemplary implementation solutions of the new concepts are presented in an annex.The guideline takes into account that resources for preservation planning and preservation actions are limited and has therefore adopted 4 premises: adequacy, financial viability, automation, and authenticity of archived objects. Its pragmatic approach becomes apparent in the definition and explanation of these dimensions. The guideline is written from the point of view of representatives of memory institutions, i.e., libraries, archives, museums, and is primarily targeted at this context although it may be useful for other information preserving institutions too.This contribution introduces the nestor guideline for preservation planning (for now only available in German; English translation envisaged for 1st half of 2014) to an international audience for the first time. It also matches the process model and the new concepts intended use, information type and preservation group to the collection and preservation reality of the German National Library.

Concurrent visual and tactile steady-state evoked potentials index allocation of inter-modal attention: a frequency-tagging study

We investigated effects of inter-modal attention on concurrent visual and tactile stimulus processing by means of stimulus-driven oscillatory brain responses, so-called steady-state evoked potentials (SSEPs). To this end, we frequency-tagged a visual (7.5Hz) and a tactile stimulus (20Hz) and participants were cued, on a trial-by-trial basis, to attend to either vision or touch to perform a detection task in the cued modality. SSEPs driven by the stimulation comprised stimulus frequency-following (i.e. fundamental frequency) as well as frequency-doubling (i.e. second harmonic) responses. We observed that inter-modal attention to vision increased amplitude and phase synchrony of the fundamental frequency component of the visual SSEP while the second harmonic component showed an increase in phase synchrony, only. In contrast, inter-modal attention to touch increased SSEP amplitude of the second harmonic but not of the fundamental frequency, while leaving phase synchrony unaffected in both responses. Our results show that inter-modal attention generally influences concurrent stimulus processing in vision and touch, thus, extending earlier audio-visual findings to a visuo-tactile stimulus situation. The pattern of results, however, suggests differences in the neural implementation of inter-modal attentional influences on visual vs. tactile stimulus processing.

Independent effects of attentional gain control and competitive interactions on visual stimulus processing

Attention filters behaviorally relevant stimuli from the constant stream of sensory information comprising our environment. Research into underlying neural mechanisms in humans suggests that visual attention biases mutual suppression between stimuli resulting from competition for limited processing resources. As a consequence, processing of an attended stimulus is facilitated. This account makes 2 assumptions: 1) An attended stimulus is released from mutual suppression with competing stimuli and 2) an attended stimulus experiences greater gain in the presence of competing stimuli than when it is presented alone. Here, we tested these assumptions by recording frequency-tagged potentials elicited in early visual cortex that index stimulus-specific processing. We contrasted the processing of a given stimulus when its location was attended or unattended and in the presence or the absence of a nearby competing stimulus. At variance with previous findings, competition similarly suppressed processing of attended and unattended stimuli. Moreover, the magnitude of attentional gain was comparable in the presence or the absence of competing stimuli. We conclude that visuospatial selective attention does not directly modulate mutual suppression between stimuli but instead acts as a signal gain, which biases processing toward attended stimuli independent of competition.

Electrophysiological evidence for age effects on sensory memory processing of tonal patterns

In older adults, difficulties processing complex auditory scenes, such as speech comprehension in noisy environments, might be due to a specific impairment of temporal processing at early, automatic processing stages involving auditory sensory memory (ASM). Even though age effects on auditory temporal processing have been well-documented, there is a paucity of research on how ASM processing of more complex tone-patterns is altered by age. In the current study, age effects on ASM processing of temporal and frequency aspects of two-tone patterns were investigated using a passive listening protocol. The P1 component, the mismatch negativity (MMN) and the P3a component of event-related brain potentials (ERPs) to tone frequency and temporal pattern deviants were recorded in younger and older adults as a measure of auditory event detection, ASM processing, and attention switching, respectively. MMN was elicited with smaller amplitude to both frequency and temporal deviants in older adults. Furthermore, P3a was elicited only in the younger adults. In conclusion, the smaller MMN amplitude indicates that automatic processing of both frequency and temporal aspects of two-tone patterns is impaired in older adults. The failure to initiate an attention switch, suggested by the absence of P3a, indicates that impaired ASM processing of patterns may lead to less distractibility in older adults. Our results suggest age-related changes in ASM processing of patterns that cannot be explained by an inhibitory deficit.

One for Many: A Metadata Concept for Mixed Digital Content at a State Archive

The Landesarchiv (State Archive) of Baden-Württemberg has designed and implemented a metadata concept for digital content covering a heterogenous range of digital-born and digitised material. Special attention was given to matters of authenticity and to economic ingest and dissemination methods under the requirements of a public archive. This paper describes the outcome of metadata discussions during the implementation period of the DIMAG repository. It treats integration of the repository’s architecture with the archival classification concept, measures for long-term accessibility, the creation of adapted metadata placement, and provisions for exchange with other applications for ingest and use. The deliberately short list of metadata elements is included in this paper. Some existing standards have been evaluated under a real use environment; this paper also introduces modifications applied to them in the project context.

Stable isotope composition of organic compounds transported in the phloem of European beech--evaluation of different methods of phloem sap collection and assessment of gradients in carbon isotope composition during leaf-to-stem transport

The analysis of stable isotope composition (delta13C, delta15N, delta18O) of phloem-transported organic matter is a useful tool for assessing short-term carbon and water balance of trees. A major constraint of the general application of this method to trees at natural field sites is that the collection of phloem sap with the "phloem bleeding" technique is restricted to particular species and plant parts. To overcome this restriction, we compared the contents (amino compounds and sugars) and isotope signatures (delta13C, delta15N, delta18O) of phloem sap directly obtained from incisions in the bark (bleeding technique) with phloem exudates where bark pieces were incubated in aqueous solutions (phloem exudation technique with and without chelating agents [EDTA, polyphosphate] in the initial sampling solution, which prevent blocking of sieve tubes). A comparable spectrum of amino compounds and sugars was detected using the different techniques. O, C, or N compounds in the initial sampling solution originating from the chelating agents always decreased precision of determination of the respective isotopic signatures, as indicated by higher standard deviation, and/or led to a significant difference of mean delta as compared to the phloem bleeding technique. Hence, depending on the element from which the ratio of heavy to light isotope is determined, compounds lacking C, N, and/or O should be used as chelating agents in the exudation solution. In applying the different techniques, delta13C of organic compounds transported in the phloem of the twig (exudation technique with polyphosphate as chelating agent) were compared with those in the phloem of the main stem (phloem bleeding technique) in order to assess possible differences in carbon isotope composition of phloem carbohydrates along the tree axis. In July, organic compounds in the stem phloem were significantly enriched in 13C by > 1.3 per thousand as compared to the twig phloem, whereas this effect was not observed in September. Correlation analysis between delta13C and stomatal conductance (Gs) revealed the gradient from the twigs to the stem observed in July may be attributed to temporal differences rather than to spatial differences in carbon isotope composition of sugars. As various authors have produced conflicting results regarding the enrichment/depletion of 13C in organic compounds in the leaf-to-stem transition, the different techniques presented in this paper can be used to provide further insight into fractionation processes associated with transport of C compounds from leaves to branches and down the main stem.

Water shortage affects the water and nitrogen balance in Central European beech forests

Whilst forest policy promotes cultivation and regeneration of beech dominated forest ecosystems, beech itself is a highly drought sensitive tree species likely to suffer from the climatic conditions prognosticated for the current century. Taking advantage of model ecosystems with cool-moist and warm-dry local climate, the latter assumed to be representative for future climatic conditions, the effects of climate and silvicultural treatment (different thinning regimes) on water status, nitrogen balance and growth parameters of adult beech trees and beech regeneration in the understorey were assessed. In addition, validation experiments with beech seedlings were carried out under controlled conditions, mainly in order to assess the effect of drought on the competitive abilities of beech. As measures of water availability xylem flow, shoot water potential, stomatal conductance as well as delta (13)C and delta (18)O in different tissues (leaves, phloem, wood) were analysed. For the assessment of nitrogen balance we determined the uptake of inorganic nitrogen by the roots as well as total N content and soluble N compounds in different tissues of adult and young trees. Retrospective and current analysis of delta (13)C, growth and meteorological parameters revealed that beech growing under warm-dry climatic conditions were impaired in growth and water balance during periods with low rain-fall. Thinning affected water, N balance and growth mostly of young beech, but in a different way under different local climatic conditions. Under cool, moist conditions, representative for the current climatic and edaphic conditions in beech forests of Central Europe, thinning improves nutrient and water status consistent to published literature and long-term experience of forest practitioners. However, beech regeneration was impaired as a result of thinning at higher temperatures and under reduced water availability, as expected in future climate.

[Outpatient geriatric rehabilitation: an evaluation of two models assessing trends of medical outcomes]

In Germany, complex and intensified outpatient geriatric rehabilitation is currently scarcely practised, mainly in model projects. The evaluation of these projects is exclusively conducted in uncontrolled studies. In our project "AMBRA", two different organisational models of geriatric rehabilitation are compared: a mobile rehabilitation team based at a geriatric hospital department and an outpatient rehabilitation centre run by GPs trained in geriatrics. Outcomes were assessed in terms of capability of self-care (Barthel-Index), mobility (Tinetti-Test, Timed "Up & Go"-Test, TUG), and depression (Geriatric Depression Scale, GDS). They were documented at three points in time (start of rehabilitation, end of rehabilitation, 6 months after end of rehabilitation) and analysed by multivariate analyses of variance (repeated measurements). 162 complete patients histories were taken in the first 18 months of the project. They show significant improvements in capability of self-care and mobility (both Tinetti-Test and TUG) between the beginning and the end of rehabilitation (adjusted for age, sex, cognitive function, diagnosis, rehabilitation model). On a medium-term basis, these results remained stable (TUG declined, however). Average GDS values did not change significantly. There were no significant sex- or age-related effects. The patients' cognitive function influenced changes in the results of the Barthel-Index and the Tinetti-Test. Patients with skeletal diseases showed less favourable trends in the Barthel-Index as did patients with cognitive impairments caused by vascular disease in the TUG, but these patients also benefited in the course of the model rehabilitation procedures. Differences in trends between patient groups of the two models were observed in the Barthel-Index. 96 % of patients previously living at home were still living there at the end of rehabilitation, 91 % were still living there 6 months after the end of rehabilitation. At the end of rehabilitation, 67 % of patients described an improvement of their personal situation associated with the rehabilitation procedure. Six months later, 82 % described an improvement or a stabilisation of their personal situation. Our results show positive medium-term rehabilitation trends concerning medical and subjective outcomes. In order to analyse effectiveness, we will have to wait for the results of a regional control group which is being recruited.

[Outpatient geriatric rehabilitation - the structural and process quality of a geriatric mobile service team and a community-based outpatient center]

The trial "Outpatient Geriatric Rehabilitation (AMBRA)" has been launched to compare two outpatient rehabilitation models close to their place of residence or at home: a mobile rehabilitation team based at a geriatric hospital department and a community-based outpatient rehabilitation center run by GPs. Primary analyses concerning structural and process quality of the models are presented in this paper. They refer to medical features and factors associated with care which were assessed at the beginning of the rehabilitation procedures and during intervention. The models include 60 patients attended by the mobile rehabilitation team and 76 patients attended by the outpatient rehabilitation centre. The patients are suffering from multiple illnesses and are limited in their daily activities. Both teams co-ordinate interdisciplinary rehabilitation programs with an average of 50 therapeutic units per patient under medical supervision. The programs' focus is on physiotherapy and occupational therapy and, if indicated, on logotherapy. Psychosocial and health promotional offers are hardly integrated into the procedures. The mobile rehabilitation team on average cares for patients with better cognitive functions (Mini-Mental State Examination) but worse abilities to cope in daily life (Barthel index) than the outpatient rehabilitation team. These differences between rehabilitation groups remain significant after multivariate consideration of sociodemographic, morbidity and process factors. However, differences in mobility (Tinetti Test) can be explained by these variables. The future comparison of results of the rehabilitation programs must therefore consider the different baseline levels and determinants between both groups.

The response regulator ARR2: a pollen-specific transcription factor involved in the expression of nuclear genes for components of mitochondrial Complex I in Arabidopsis

Two-component signal systems regulate a variety of cellular activities. They involve at least two common signalling molecules: a signal-sensing kinase and a response regulator that mediates the output response. Multistep systems also require proteins containing phosphotransfer domains. Here we report that the response regulator ARR2 from Arabidopsis is predominantly expressed in pollen and is localized in the nuclear compartment of the plant cell. Furthermore, ARR2 is transcriptionally active in yeast and binds to the promoters of nuclear genes for several components of mitochondrial respiratory chain complex I (nCI) from Arabidopsis. The nuclear nCI genes are up-regulated in pollen during spermatogenesis. The transcription factor functions of ARR2 are mediated by its C-terminal output domain. Our data identify ARR2 as the first eukaryotic response regulator which functions as a transcription factor at a known promoter sequence. Yeast two-hybrid analysis and in vitro interaction studies suggest that ARR2 very probably forms part of a multistep two-component signalling mechanism that includes HPt proteins like AHP1 or AHP2. These findings point to an as yet unidentified signal transduction system that may regulate aspects of floral and mitochondrial gene expression.

Childhood immunization: one HMO's experience in benchmarking and improving plan performance

In 1994, Health Net initiated a childhood immunization campaign and research project to improve health plan member immunization rates by motivating and educating parents of children 20-32 months old as to the importance of fully immunizing their child. The findings indicate that 88 percent of those parents with children who were not fully immunized believed their child had been fully immunized by age two. This lack of awareness may explain the unreliability of self-reported immunization status. Future immunization campaigns must include ongoing member reminder systems, educate members as to the immunization schedule, and must take into consideration the barriers, real and perceived, that block full immunization.

Differential expression of the oncoproteins c-myc and c-myb in human lymphoproliferative disorders

Altered regulation of oncogene expression has been described in a variety of hematopoietic malignancies. In this study we analyzed the protein level of c-myc and c-myb in 15 established cell lines derived from lymphopoietic disorders and in 45 samples from patients with acute or chronic lymphatic leukemias. Oncoproteins were assayed by radioimmuno-precipitation with polyclonal rabbit antibodies. In B-cell derived lines, such as Burkitt lymphoma and plasmocytoma lines, we found high amounts of c-myc and no or low amounts of c-myb. In contrast, all T-cell-derived lines revealed high levels of c-myb. In addition, T-lymphoma cell lines of low malignancy also exhibited high levels of c-myc, while T-cell lines of high malignancy (acute T-lymphoblastic leukemias) exhibited moderate levels of c-myc. Of the 45 patient samples analyzed, only three (one B-prolymphocytic and two acute T-lymphoblastic leukemias) contained detectable amounts of myc or myb protein. Corresponding to the results found in established cell lines, the B-cell sample revealed a high level of c-myc but no c-myb, while the T-cell samples revealed high levels of c-myb and no or low levels of c-myc. We therefore conclude that the predominance of c-myc or c-myb expression in malignant lymphoproliferative disorders may be associated to the B-cell or T-cell lineage, respectively. Further, regarding the T-cell lines, there is a possible correlation between cell maturation and the level of c-myc found together with a consistently elevated c-myb.