Complexity measures from interaction structures.

We evaluate information-theoretic quantities that quantify complexity in terms of kth-order statistical dependences that cannot be reduced to interactions among k-1 random variables. Using symbolic dynamics of coupled maps and cellular automata as model systems, we demonstrate that these measures are able to identify complex dynamical regimes.

Analysis of oscillatory patterns in the human sleep EEG using a novel detection algorithm.

The different brain states during sleep are characterized by the occurrence of distinct oscillatory patterns such as spindles or delta waves. Using a new algorithm to detect oscillatory events in the electroencephalogram (EEG), we studied their properties and changes throughout the night. The present approach was based on the idea that the EEG may be described as a superposition of stochastically driven harmonic oscillators with damping and frequency varying in time. This idea was implemented by fitting autoregressive models to the EEG data. Oscillatory events were detected, whenever the damping of one or more frequencies was below a predefined threshold. Sleep EEG data of eight healthy young males were analyzed (four nights per subject). Oscillatory events occurred mainly in three frequency ranges, which correspond roughly to the classically defined delta (0-4.5 Hz), alpha (8-11.5 Hz) and sigma (11.5-16 Hz) bands. Their incidence showed small intra- but large inter-individual differences, in particular with respect to alpha events. The incidence and frequency of the events was characteristic for sleep stages and non-rapid eye movement (REM)-REM sleep cycles. The mean event frequency of delta and sigma (spindle) events decreased with the deepening of sleep. It was higher in the second half of the night compared with the first one for delta, alpha and sigma oscillations. The algorithm provides a general framework to detect and characterize oscillatory patterns in the EEG and similar signals.

[Effects of distress and coping on quality of life in HIV-positive patients: results of a longitudinal study]. / Wirkung von Belastung und Krankheitsbewältigung auf die Lebensqualität bei HIV-Positiven. Ergebnisse einer Längsschnittuntersuchung.

Preserving health-related quality of life (QOL) is an important approach with HIV-positive patients. In a longitudinal study over 3 years, with three measurements each 18 months, we examined 56 of these patients for the influence of distress and coping (assessed by interviews) on physical, cognitive-emotional, and social QOL (using the SEL questionnaire). The patients were 32.9 years old on average, with 28.3 months since diagnosis. Seventy percent were male, 82% asymptomatic, 14% with ARC, and 4% with AIDS. Forty-five percent had been infected by homosexual intercourse, 14% by heterosexual intercourse, and 41% by iv drug abuse. The patients reported significantly worse physical and cognitive-emotional QOL than healthy subjects. Those HIV-positive persons with great distress showed significantly lower QOL scores. Multiple analyses of regression showed evasive-regressive coping at the T1, T2, and T3 levels as negative predictors, vs active, problem-focused coping as a positive predictor for nearly all QOL parameters at T3. HIV-positive patients with ARC or AIDS reported more physical complaints and lower physical QOL than asymptomatic persons. Physicians should suggest psychosocial support to patients with poor QOL scores.

Dimensional complexity and spectral properties of the human sleep EEG. Electroencephalograms.

OBJECTIVE: The relevance of the dimensional complexity (DC) for the analysis of sleep EEG data is investigated and compared to linear measures. METHODS: We calculated DC of artifact-free 1 min segments of all-night sleep EEG recordings of 4 healthy young subjects. Non-linearity was tested by comparing with DC values of surrogate data. Linear properties of the segments were characterized by estimating the self-similarity exponent alpha based on the detrended fluctuation analysis which quantifies the persistence of the signal and by calculating spectral power in the delta, theta, alpha and sigma bands, respectively. RESULTS: We found weak nonlinear signatures in all sleep stages, but most pronounced in sleep stage 2. Strong correlations between DC and linear measures were established for the self-similarity exponent alpha and delta power, respectively. CONCLUSIONS: The dimensional complexity of the sleep EEG is influenced by both linear and nonlinear features. It cannot be directly interpreted as a nonlinear synchronization measure of brain activity, but yields valuable information when combined with the analysis of linear measures.

Reconstruction of the parameter spaces of dynamical systems.

Parameter variations in the equations of motion of dynamical systems are identified by time series analysis. The information contained in time series data is transformed and compressed to feature vectors. The space of feature vectors is an embedding for the unobserved parameters of the system. We show that the smooth variation of d system parameters can lead to paths of feature vectors on smooth d-dimensional manifolds in feature space, provided the latter is high-dimensional enough. The number of varying parameters and the nature of their variation can thus be identified. The method is illustrated using numerically generated data and experimental data from electromotors. Complications arising from bifurcations in deterministic dynamical systems are shown to disappear for slightly noisy systems.

Chaos or noise: difficulties of a distinction

In experiments, the dynamical behavior of systems is reflected in time series. Due to the finiteness of the observational data set, it is not possible to reconstruct the invariant measure up to an arbitrarily fine resolution and an arbitrarily high embedding dimension. These restrictions limit our ability to distinguish between signals generated by different systems, such as regular, chaotic, or stochastic ones, when analyzed from a time series point of view. We propose to classify the signal behavior, without referring to any specific model, as stochastic or deterministic on a certain scale of the resolution epsilon, according to the dependence of the (epsilon,tau) entropy, h(epsilon, tau), and the finite size Lyapunov exponent lambda(epsilon) on epsilon.

Local estimates for entropy densities in coupled map lattices

We present a method to derive an upper bound for the entropy density of coupled map lattices with local interactions from local observations. To do this, we use an embedding technique that is a combination of time delay and spatial embedding. This embedding allows us to identify the local character of the equations of motion. Based on this method we present an approximate estimate of the entropy density by the correlation integral.

Longitudinal development of distress, coping and quality of life in HIV-positive persons.

BACKGROUND: Longitudinal study on burdens, quality of life and coping strategies of HIV-positive persons to identify patterns of successful adaptation to the demands of the infection. METHODS: In a semiprospective multimodal approach, 61 HIV-positive persons in all stages of the infection attending an HIV ambulatorium were assessed by inventories (3 times) and by a half-standardized interview (baseline T1 focussing on first reactions after diagnosis, follow-up T3 1.5 years later). Subjects had a mean age of 35.3 years and 69% were male. Forty-four percent were infected via homosexual intercourse, 46% via intravenous needle sharing and 10% via heterosexual intercourse or an unknown source. RESULTS: Global, psychic and familial distress decreased significantly from the first period after the diagnosis of HIV to the third time of measurement, while somatic complaints increased. Most test persons were able to deal effectively with the demands of the infection and showed a great degree of flexibility in their use of cognitive-actional and emotional-palliative strategies; they achieved a high quality of life. In contrast, highly distressed individuals, mainly drug users, tended to cope in an evasive-regressive way and reported a low quality of life. Correlations between ineffective coping strategies and low quality of life were found to be significant. CONCLUSIONS: After an initial phase of sorrow and lack of orientation regarding their future life, most HIV-positive persons deal effectively with the demands of the HIV infection and report a good quality of life. In contrast, HIV-positive persons with a high degree of distress and an evasive-regressive coping pattern need professional support, such as psychotherapy.

[Human-accessible environment design. Crossroads between persons and environment]. / Menschengerechte Umweltgestaltung. Schnittstelle zwischen Person und Umgebung.

The competence model of aging emphasizes transactions between the person and his/her environment. Adaptation of the environment to the person's resources gets equal status to the adaptation of the person to environmental demands. This becomes relevant for persons in need of help and care. Adapting their environment leads to a reduction of their environmental docility. It also becomes relevant for persons with higher potentials: Optimizing their environment contributes to environmental proactivity. For all groups, an increase of quality of life is correlated to optimized environments. While human factors design has created favorable conditions in the work place for many persons, it has not been applied often to the construction of home environments and to the production of equipment for everyday use. Results from a study on "Chances for and limitations of independent life in old age" are presented. They prove that elderly people in the new states of the Federal Republic of Germany not only differ from those in the old states with regard to the help and care they need. In the new states, environmental factors contribute considerably to limitations of independent life. Potentials of an optimally designed environment for the reduction of help and care are utilized even less in the eastern states of Germany than in the west. Arguments for the design of the furniture, equipment for communication and transportation, etc. are presented which emphasize ergonomic principles. They require that products should be adapted to the sensory potentials of their users, that they should allow an understanding or an easy cognitive processing of their functions, and that they should match the motor potentials of persons handling them. In short, products should be designed for a use that matches the "human model" as closely as possible. Thus, they will contribute to enhance the environmental proactivity of elderly people.

[Social support by professional personnel during inpatient treatment of cancer patients. "Chronic disease and coping with illness" research project]. / Soziale Unterstützung durch professionelle Helfer bei stationär behandelten Krebspatienten. Forschungsprojekt "chronische Krankheit und Krankheitsbewältigung".

We examined 63 in-patients in a medical hospital with a semi-structured and video-taped interview about the professional social support they had received. Patients were quite satisfied with physicians' and nurses' support, still more than one third of them had missed appraisal support from physicians. We found evidence that older, more ill and female patients perceived more professional social support was given. With the help of a hierarchical cluster analysis it was shown that the importance of professional social support depended remarkably on individual factors as identity or partner relation.

[Forms of independence and the residential environment--an empirical contribution from the study "Possibilities and limits of independent living for elderly patients"]. / Formen der Selbständigkeit und Wohnumwelt--ein empirischer Beitrag aus der Studie "Möglichkeiten und Grenzen der selbständigen Lebensführung im Alter".

In a study on the chances and limits of independent living in old age, we collected data about difficulties in 23 activities of daily living in two sub-samples: participants from the western part of Germany (n = 745), and from the eastern part of Germany (n = 347). Participants were grouped into three patterns of competence by means of cluster analysis. Cluster analyses were calculated separately for participants in the western and eastern parts of Germany. In both sub-samples, we found three patterns of competence: "High competence in most activities of daily living", "reduced competence in some activities of daily living" and "reduced competence in most activities of daily living". Patterns of competence were similar in the sub-samples, but important differences were found in some activities of daily living between participants from the eastern and western parts of Germany (e.g., in "heating home," "washing clothes," "banking"). These differences were due to unfavorable conditions in physical environment. Analysis of the relationship between objective housing conditions (assessed by our research team) and patterns of competence strongly supported this interpretation. Participants in the two sub-samples were more satisfied with their housing conditions as could be expected from our assessment of housing conditions. Successful adaptation to environmental conditions and changes in the aspiration-level can explain these differences. The degree of satisfaction with housing conditions is only a poor predictor for possibilities in increasing competence by intervention and rehabilitation. Most participants wished to keep their household independently as long as possible. Acceptance for homes for the elderly was low.

[Constancy or change in personality in the elderly? Findings and discussion of a controversy]. / Konstanz oder Veränderung der Persönlichkeit im Alter? Befunde und Diskussion einer Kontroverse.

Research on personality development in the second half of life is reviewed, making a distinction between studies following a trait-oriented and studies using a process-oriented approach. A methodological and theoretical discussion of results not only explains differences in results, it also allows to conclude that the two approaches describe and explain complementary facets of the field. A synthesis between approaches is proposed in order to understand part of the controversy on constancy and change of personality development.

[The quality of life of tumor patients as a multidimensional concept]. / Lebensqualität von Tumorkranken als multidimensionales Konzept.

An important aim of supportive care for cancer patients (pts) is the maintenance or improvement of their life quality. Therefore it is interesting to measure pts' LQ while testing new cytotoxic drugs or palliative therapy like artificial nutrition. A short questionnaire also is helpful in order to inform physicians and psychooncologists about pts' needs for psychosocial intervention. Based on coping-research, gerontology and well-being-psychology we have developed a 69-item-questionnaire "Scales for Measuring LQ" with good test-statistics. This instrument emphasizes pts' life experiences and subjective appraisal of objective life conditions. Basic state, internalized life experiences and life orientations in a sample of 179 pts with chemo- or radiotherapy are more important for LQ than objective symptoms, subjectively perceived physical condition and mood. The surprisingly high LQ scores in cancer pts can best be explained by their reduced aspiration levels. Correlations with emotional and belonging support obtained from the partner or confidant are significant. Social support is before all related to our pts' positive life experiences (.68; .59) and to their life satisfaction (.58; .47).

[Potentials in old age: personal and social processes of their development]. / Potentiale des Alters: Persönliche und soziale Prozesse ihrer Entwicklung.

In developed societies, antecedents of and conditions for the development of older people's potentials are favorable. Longevity and wellbeing have increased through progress in hygiene, medicines economy, and ecology. Nevertheless, potentials of the elderly are a neglected theme in the media, in social policy, and in scientific discourse. Along with Riley and Riley's statement that individual potential is outrunning the social potential, it is argued that aging persons have indeed developed potentials, while institutions and society have contributed little. Institutionalization rather seems to veil the potentials of the elderly and to disregard their manifestations. Potentials of the elderly are described as abilities to realistically perceive chances and limitations of life in old age, reappraise life after experiencing loss, and accept expressed in sympathy for children and grandchildren, in sharing their concerns, and taking responsibility for human and social issues in life. Older people can develop potentials, which allow them to focus less on many of their own needs and to invest energies and commitment in persons, ideas, values, or activities that can continue beyond their own lifetime.

[Competence in the aged]. / Kompetenz im Alter.

Cohort-sequential analyses of intelligence, personality variables, health and social data show that prerequisites for aging in competence today are better met in industrialized societies than a few decades ago. It is argued that a competence model of aging should complement the traditional defect and disuse models. Competence is defined by situational demands as well as by a person's resources to meet these. Emphasis on competence allows for specific (not general), variable (not constant), and relatively individual (not universal) descriptions and explanations of development. Chances for intervention with the aged are illustrated.

[Gerontologic and geriatric education in the USA]. / Gerontologisch-geriatrische Ausbildung in den USA.

Training in gerontology in American institutes of higher education is conceptualized and realized in response to present societal demands. Although plurality of approaches prevails, gerontology has become an institutionalized discipline which in its research, training and application is formally sponsored by the national government. Programs are offered in many colleges and universities and assessed in terms of scientific excellence, of efficiency in teaching knowledge from multiple disciplines, and in terms of practicality. But still, problems of poor research and "quasi-professional" teaching, as well as of insufficiently founded practical work concern gerontologists. In a time of expansion, "instant gerontologists" have become a threat to the field. A brief "instant gerontologists" have become a threat to the field. A brief overview on questions presently discussed among teachers in gerontology is given, and a model-institution for gerontological training is briefly described, the Andrus Gerontology Center at the University of Southern California.