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PubMed2001

Predictability, complexity, and learning.

We define predictive information I(pred)(T) as the mutual information between the past and the future of a time series. Three qualitatively different behaviors are found in the limit of large observation times T:I(pred)(T) can remain finite, grow logarithmically, or grow as a fractional power law. If the time series allows us to learn a model with a finite number of parameters, then I(pred)(T) grows logarithmically with a coefficient that counts the dimensionality of the model space. In contrast, power-law growth is associated, for example, with the learning of infinite parameter (or nonparametric) models such as continuous functions with smoothness constraints. There are connections between the predictive information and measures of complexity that have been defined both in learning theory and the analysis of physical systems through statistical mechanics and dynamical systems theory. Furthermore, in the same way that entropy provides the unique measure of available information consistent with some simple and plausible conditions, we argue that the divergent part of I(pred)(T) provides the unique measure for the complexity of dynamics underlying a time series. Finally, we discuss how these ideas may be useful in problems in physics, statistics, and biology.

Forecasting↗
PubMed2007

Analysis and design of echo state networks.

The design of echo state network (ESN) parameters relies on the selection of the maximum eigenvalue of the linearized system around zero (spectral radius). However, this procedure does not quantify in a systematic manner the performance of the ESN in terms of approximation error. This article presents a functional space approximation framework to better understand the operation of ESNs and proposes an information-theoretic metric, the average entropy of echo states, to assess the richness of the ESN dynamics. Furthermore, it provides an interpretation of the ESN dynamics rooted in system theory as families of coupled linearized systems whose poles move according to the input signal dynamics. With this interpretation, a design methodology for functional approximation is put forward where ESNs are designed with uniform pole distributions covering the frequency spectrum to abide by the richness metric, irrespective of the spectral radius. A single bias parameter at the ESN input, adapted with the modeling error, configures the ESN spectral radius to the input-output joint space. Function approximation examples compare the proposed design methodology versus the conventional design.

Entropy↗
PubMed1994

Farming systems and sanitary problems in mountain cattle farms.

On the basis of concepts established by ecopathology and the systems theory, certain aspects of the 'Ecosanitary System', which forms part of the 'Farming System', were studied. Multivariant statistical methods were used to analyze and classify 69 mountain cattle farms into different types and to establish relationships between variables relating to pathological problems and others relating to aspects of production and farm structure. Stable mastitis characterized farms with a higher milk production, more intensive farming and greater hygiene measures. The pattern of diarrhoea in the calves was similar. Problems relating to reproduction and calving were more characteristic of traditional, small farms.

Abortion, Veterinary↗
PubMed2004

[The search for theory-practice interaction in the nursing information system -- approach from grounded theory].

This qualitative study aimed to understand, through nursing discourse, the relation between theory and practice in nursing and its implications for the development of information systems. Grounded theory was used as a methodological reference framework. The study population consisted of nurses who work at the clinic of a school hospital. Data analysis resulted in the main category: The search for theory-practice interaction in the nursing information system. This process was formed by the integration among categories, based on Strauss and Corbin's paradigm as a model with two phenomena: the attempt to apply the formal models in nursing practice and the perspective of the theory-practice gap in the nursing information system.

Information Systems↗
PubMed2001

Adolescent addiction and delinquency in the family system.

Drug abuse and delinquent behavior in adolescents have been closely linked in the literature. It is possible that these links are not causal, but rather covariates of the common factor of family. This paper seeks to examine the behaviors of addiction and delinquency within the framework of family systems theory.

Adolescent↗
PubMedDate not supplied

[Dynamic paradigm in psychopathology: "chaos theory", from physics to psychiatry].

For the last thirty years, progress in the field of physics, known as "Chaos theory"--or more precisely: non-linear dynamical systems theory--has increased our understanding of complex systems dynamics. This framework's formalism is general enough to be applied in other domains, such as biology or psychology, where complex systems are the rule rather than the exception. Our goal is to show here that this framework can become a valuable tool in scientific fields such as neuroscience and psychiatry where objects possess natural time dependency (i.e. dynamical properties) and non-linear characteristics. The application of non-linear dynamics concepts on these topics is more precise than a loose metaphor and can throw a new light on mental functioning and dysfunctioning. A class of neural networks (recurrent neural networks) constitutes an example of the implementation of the dynamical system concept and provides models of cognitive processes (15). The state of activity of the network is represented in its state space and the time evolution of this state is a trajectory in this space. After a period of time those networks settle on an equilibrium (a kind of attractor). The strength of connections between neurons define the number and relations between those attractors. The attractors of the network are usually interpreted as "mental representations". When an initial condition is imposed to the network, the evolution towards an attractor is considered as a model of information processing (27). This information processing is not defined in a symbolic manner but is a result of the interaction between distributed elements. Several properties of dynamical models can be used to define a way where the symbolic properties emerge from physical and dynamical properties (28) and thus they can be candidates for the definition of the emergence of mental properties on the basis of neuronal dynamics (42). Nevertheless, mental properties can also be considered as the result of an underlying dynamics without explicit mention of the neuronal one (47). In that case, dynamical tools can be used to elucidate the Freudian psychodynamics (34, 35). Recurrent neuronal networks have been used to propose interpretation of several mental dysfunctions (12). For example in the case of schizophrenia, it has been proposed that troubles in the cortical pruning during development (13) may cause a decrease in neural network storage ability and lead to the creation of spurious attractors. Those attractors do not correspond to stored memories and attract a large amount of initial conditions: they were thus associated to reality distorsion observed in schizophrenia (14). Nevertheless, the behavior of these models are too simple to be directly compared with real physiological data. In fact, equilibrium attractors are hardly met in biological dynamics. More complex behaviors (such as oscillations or chaos) should thus to be taken into account. The study of chaotic behavior have lead to the development of numerical methods devoted to the analysis of complex time series (17). These methods may be used to characterise the dynamical processes at the time-scales of both the cerebral dynamics and the clinical symptoms variations. The application of these methods to physiological signals have shown that complex behaviors are related to healthy states whereas simple dynamics are related to pathology (8). These studies have thus confirmed the notion of "dynamical disease" (20, 21) which denotes pathological conditions characterised by changes in physiological rhythms. Depression has been studied within this framework (25, 32) in order to define possible changes in brain electrical rhythms related to this trouble and its evolution. It has been shown that controls' brain dynamics is more complex than depressive one and that the recovery of a complex brain activity depends on the number of previous episodes. In the case of the symptoms time evolution, several studies have demonstrated that non-linear dynamical process may be involved in the recurrence of symptoms in troubles such as manic-depressive illness (9) or schizophrenia (51). These observations can contribute to more parcimonious interpretation of the time course of these illnesses than usual theories. In the search of a relationship between brain dynamics and mental troubles, it has been shown in three depressed patients an important correlation between the characteristics of brain dynamics and the intensity of depressive mood (49). This preliminary observation is in accordance with the emergence hypothesis according which changes in neuronal dynamics should be related to changes in mental processes. We reviewed here some theoretical and experimental results related to the use of "physical" dynamical theory in the field of psychopathology. It has been argued that these applications go beyond metaphor and that they are empirically founded. Nevertheless, these studies only constitute first steps on the way of a cautious development and definition of a "dynamical paradigm" in psychopathology. The introduction of concepts from dynamics such as complexity and dynamical changes (i.e. bifurcations) permits a new perspective on function and dysfunction of the mind/brain and the time evolution of symptoms. Moreover, it offers a ground for the hypothesis of the emergence of mental properties on the basis of neuronal dynamics (42). Since this theory can help to throw light on classical problems in psychopathology, we consider that a precise examination of both its theoretical and empirical consequences is requested to define its validity on this topic.

Brain↗
PubMed2005

Approximation of delays in biochemical systems.

In the past metabolic pathway analyses have mostly ignored the effects of time delays that may be due to processes that are slower than biochemical reactions, such as transcription, translation, translocation, and transport. We show within the framework of biochemical systems theory (BST) that delay processes can be approximated accurately by augmenting the original variables and non-linear differential equations with auxiliary variables that are defined through a system of linear ordinary differential equations. These equations are naturally embedded in the structure of S-systems and generalized mass action systems within BST and can be interpreted as linear signaling pathways or cascades. We demonstrate the approximation method with the simplest generic modules, namely single delayed steps with and without feedback inhibition. These steps are representative though, because they are easily incorporated into larger systems. We show that the dynamics of the approximated systems reflects that of the original delay systems well, as long as the systems do not operate in very close vicinity of threshold values where the systems lose stability. The accuracy of approximation furthermore depends on the selected number of auxiliary variables. In the most relevant situations where the systems operate at states away from their critical thresholds, even a few auxiliary variables lead to satisfactory approximations.

Biochemistry↗
PubMed1990

Fractal dynamics of polarized bioelectrodes.

This study is concerned with mathematical modelling of the fundamental relationship which exists between the current density and the overpotential across the metal-solution interface in the linear range using methods of system theory enhanced by 'fractal' concepts. A primer for both 1/f-type scaling and 'anomalous' relaxation/dispersion concepts is provided followed by a brief review of the research history pertinent to the metal electrode polarization dynamics. Next, the 'fractal relaxation systems' approach is introduced to characterize systems which attenuate with a fractional power-low dependence on frequency through a 'scaling exponent'. The 'singularity structure' which is a scaling rational system function is proposed to expand fractal systems in terms of basic subsystems individually representing elementary exponential relaxations and collectively exhibiting scaling properties. We stres that the 'singularity structure' carries scaling information identical to the conventional 'distribution of relaxation times' function. 'Structure scale' and 'view scale' concepts are presented in the due course to streamline the analysis of scaling phenomena in general and the polarization impedance in particular. System theory-wise, the notable result is that the fractional power function attenuation, or equivalently, the logarithmic nature of the distribution function translates into the 'self-similar' pattern replication of the system singularities in the s-plane. The singularity arrangement is governed by a recursive rule solely based on the knowledge of the fractional power factor or the scaling exponent.

Biomedical Engineering↗
PubMed1998

Cultural intersections and systems levels in counseling.

A clinical case is presented in which a systemic approach to psychotherapy was used. This approach to clinical work is crucial in that the interactive pattern of social and institutional relationships is seen as the context for treatment. Systems theory allows the clinician to move away from a cultural way of thinking about clinical work focused on the individual, and instead views the individual in interaction with multiple systems as the focus for clinical intervention. This case study illustrates the nature of systemic work by demonstrating four levels of systems that have an impact on work with the patient: the individual level, the family systems level, the clinic system level, and the agency level. The case highlights how therapists in training might consider the context of larger systems that influence the environmental and psychological factors in their patients' lives.

Adult↗
PubMedDate not supplied

A systems process of reinforcement.

Functional systems theory was used to consider the process of reinforcement of the actions on the body of reinforcing factors, i.e., the results of behavior satisfying the body's original needs. The systems process of reinforcement includes reverse afferentation entering the CNS from receptors acted upon by various parameters of the desired results, and mechanisms for comparing reverse afferentation with the apparatus which accepts the results of the action and the corresponding emotional component. A tight interaction between reinforcement and the dominant motivation is generated on the basis of the hologram principle. Reinforcement forms an apparatus for predicting a desired result, i.e. a result-of-action acceptor. Reinforcement procedures significant changes in the activities of individual neurons in the various brain structures involved in dominant motivation, transforming their spike activity for a burst pattern to regular discharges; there are also molecular changes in neuron properties. After preliminary reinforcement, the corresponding motivation induces the ribosomal system of neurons to start synthesizing special effector molecules, which organize molecular engrams of the acceptor of the action's result. Sensory mechanisms of reinforcement are considered, with particular reference to the information role of emotions.

Animals↗
PubMed2001

Group therapy and complexity theory.

Complexity theory, also called dynamical self-organizing systems theory, is a new scientific way of viewing the natural world. It is being applied to a vast range of multiply determined systems, as well as to created systems including psychoanalysis, and in this article to analytically informed group therapy. Examples of prominent features of group therapy lend themselves to comparison with outstanding features of complexity systems, including nonlinear determinism, self-organization, coevolution, and disequilibrium conditions for change and growth. Examples are used throughout to illustrate inferred processes called cascading, multisubjectivity, and asynchronous change processes. Therapist role indications are in the direction of implementing the group's own processes of creating change, at close range in the sessions.

Group Processes↗
PubMed2001

Mathematical modeling of the aging processes and the mechanisms of mortality: paramount role of heterogeneity.

Main problems of modeling the link between aging processes and mechanisms of mortality are addressed. Various applications of Gompertz's law, which allowed to formulate some fruitful hypotheses on the field, are reviewed. Some pitfalls occurring in its applications are also discussed using a model built on purpose to overcome these difficulties. The role played by heterogeneity emerges as the common cause of some relevant failure in using Gompertz's law and the necessary key ingredient of any model aimed to interpret the link between aging and mortality correctly. Though a number of problems are related to inter-individual variability, the search for their solution can lead to an intriguing approach to the study of aging and mortality. Living beings can be considered as complex systems and their age-related changes can be described at the light of complex system theory.

Aging↗
PubMed1986

Fetal and neonatal origins of being a person and belonging to the world.

The complexity of the psycho-biological development of the individual in his surroundings is described according to the General Systems Theory. Biological data derived from the observation of fetal and neonatal motor development show that movement is a modular function and that genetic, epigenetic and learned repertoires of modules can be distinguished. A systemic hierarchy grows into a structure in which the mind appears to be a function of biological functions. The findings strongly support the notion of autonomous initiative in the individual who appears to be the protagonist of the building up of his personal identity and of his belonging to the world. The core of this individual autonomy and relationship with the human partners is described as "the secret". This creative autonomy is the drive for growth in the emotional and also in the cognitive dimensions. The child casts his taxonomic net on the surroundings. This net, allowing him to attain new contexts, is given initially by epigenetic paragons. Early cognitive development and learning are seen as the result of metaphoric freedom. In a systemic developmental model the qualitative gain due to the attainment of new acquisition contexts gives the phenomenon a punctate feature.

Child↗
PubMed1996

Accuracy of telemetry signals in the post-implantation monitoring of electrograms sensed by pacemakers.

Monitoring of electrograms (EGMs) sensed by pacemakers (PMs) during their lifetime is the utmost importance, since changes of these signals, due to modifications of the electrode-myocardial interface may occur compromising the proper functioning of the PM. Since after implantation these intracardiac signals are accessible only by means of a telemetry system, it is necessary to ascertain how faithfully the telemetric signals reproduce the direct ones. To this aim we devised an accurate method, based on linear system theory, which allows the estimation of the transfer function of the PM-telemetry system and the comparison of a set of time and frequency domain parameters (wave amplitude, slew rate, frequency at the spectrum peak and bandwidth) computed on both direct and telemetric signals. To overcome the problem that these two signals cannot be recorded simultaneously, an appropriate model of the input and output signals of the PM-telemetry system and of their interrelationship was identified. This model relies on a set of reasonable assumptions about the nature of the direct signal (supposed to have a fixed morphology within a predefined analysis window) and of noise sources corrupting both the direct and telemetric signals. Owing to the involvement of deterministic and stochastic signals, the theory of quasi-stationary signals was employed to obtain the system transfer function. To test our method, direct and telemetric recordings were performed on 12 patients with atrial sensing carrying Medtronic Pacemakers (Mod Elite 7077/7086, programmer Mod 9760) with unipolar steroid eluting leads (Medtronic Capsure 4523). The results we obtained demonstrate that the specific system considered acts as a low-pass filter with a -3 dB frequency at about 90 Hz this ensures that the telemetric signal contains almost all the information of the direct one and can be used to monitor the changes of the signals sensed by the PM.

Aged↗
PubMedDate not supplied

Homeostasis: a framework for integrating the life sciences.

Nurse education curricula continue to emphasize the holistic nature of health and ill-health. As a concept, holism recognizes that the interactions between a person and his/her environment are significant factors in shaping the individual, and important determinants of wellbeing. Psychosocial interactions as a basis for health now figure prominently in nursing curricula. In contrast, the applied biological sciences have increasingly become marginalized, yet knowledge of the biological construct of the individual, and an understanding of how it is influenced by psychosocial interactions, are also necessary if holistic care is the aim. Nursing models attempt to reinforce holistic principles, but the integrative nature of health and illness needs to be established before their application. This article proposes that the concept of homeostasis, and its relationship to systems theory, provides a workable framework for teaching the basis of health, and so forms a foundation for the application of nursing theory and nursing models.

Biological Science Disciplines↗
PubMed1994

Topography of alpha and theta oscillatory responses upon auditory and visual stimuli in humans.

Brain resonance phenomena and induced rhythms in the brain recently gained importance in electroencephalographic, magnetoencephalographic and cellular studies (Başar and Bullock 1992). It was hypothesized that evoked potentials are superpositions of induced rhythms caused by resonance phenomena in neural populations (Başar et al. 1992). According to Başar (1972), such resonance phenomena are reflected in the main peaks of the amplitude frequency characteristics computed from EEG responses. The present study is based on a frequency domain approach for the evaluation of topography- and modality-dependent properties of oscillatory brain responses. EEG and evoked potentials were recorded from vertex, parietal and occipital scalp locations in 24 volunteers. Two combined methods were applied: (1) amplitude frequency characteristics were computed from the transient evoked responses, and (2) frequency components of the transient responses were obtained by adaptive digital filtering. Our main goal was to investigate theta (4-7 Hz) and alpha (8-15 Hz) response components. (1) Amplitude frequency characteristics. Auditory stimuli elicited theta-alpha compound responses in the 4-11 Hz frequency band (e.g. typical peaking frequency around 7 Hz for vertex recordings). Visual stimuli elicited alpha responses (e.g. typical peaking frequency for vertex recordings around 9-12 Hz). Frequency maxima for visual stimuli thus had main peaks at higher frequency values than frequency maxima for auditory stimuli. (2) Digital filtering confirmed these results: for vertex recordings, theta vs. alpha response amplitudes were 9 muV vs 6 muV for auditory stimuli and 5 muV vs 5 muV for visual stimuli, thus confirming a shift towards higher frequencies, i.e. a more prominent contribution of the alpha range, in the case of visual stimulation. We hypothesize that these properties might reflect site- and modality-specific features of stimulus encoding in the brain in which resonance properties of neuron populations are involved. Furthermore we emphasize the utility of the systems theory approach for a better understanding of brain function by means of EPs.

Biological Clocks↗
PubMed1979

Developments in family treatment of schizophrenia.

For the treatment of families of schizophrenics the following issues are discussed: (1) Is there any evidence that families cause schizophrenia? (2) Is it useful to consider the family as a system? (3) What is the aim of family therapy? (4) Does family therapy work for any kind of family? (5) Does family therapy work for families of schizophrenics? The conclusion is reached that systems theory can be applied successfully to some families when the patient suffers from certain conditions.

Family Therapy↗
PubMed1987

[New paradigms in human sciences].

In this paper, the author describes the jump of paradigm in Human Sciences the conceptual model introduced by G. Bateson implies inasmuch as it shifts emphasis from the analysis of facts to formal organization of reality, and defines 'mental' as a concept which comprehends an organism with relation to its surroundings. The author reviews the main ideas Bateson extracted from both the systems theory and cybernetics in order to outline his 'ecology of human mind'. The complexity of psychosocial processes, however, requires no such mechanical models--i.e. 'less mechanical' ones--to explain time as a continuum in which changes in human systems occur, for instance. Thus, systems dynamics and recursivity models including a multiplicity of feedback loops contribute with some useful constructs. Finally, some ideas developed within 'hard sciences', applied to Social Sciences to integrate the complexity of the goals are also discussed.

Humans↗