Application of chaos theory to biology and medicine

The application of “chaos theory” to the physical and chemical sciences has resolved some long-standing problems, such as how to calculate a turbulent event in fluid dynamics or how to quantify the pathway of a molecule during Brownian motion. Biology and medicine also have unresolved problems, such as how to predict the occurrence of lethal arrhythmias or epileptic seizures. The quantification of a chaotic system, such as the nervous system, can occur by calculating the correlation dimension (D2) of a sample of the data that the system generates. For biological systems, the point correlation dimension (PD2) has an advantage in that it does not presume stationarity of the data, as the D2 algorithm must, and thus can track the transient non-stationarities that occur when the systems changes state. Such non-stationarities arise during normal functioning (e.g., during an event-related potential) or in pathology (e.g., in epilepsy or cardiac arrhythmogenesis). When stochastic analyses, such as the standard deviation or power spectrum, are performed on the same data they often have a reduced sensitivity and specifity compared to the dimensional measures. For example, a reduced standard deviation of heartbeat intervals can predict increased mortality in a group of cardiac subjects, each of which has a reduced standard deviation, but it cannot specify which individuals will or will not manifest lethal arrhythmogenesis; in contrast, the PD2 of the very same data can specify which patients will manifest sudden death. The explanation for the greater sensitivity and specificity of the dimensional measures is that they aredeterministic, and thus are moreaccurate in quantifying the time-series. This accuracy appears to be significant in detecting pathology in biological systems, and thus the use of deterministic measures may lead to breakthroughs in the diagnosis and treatment of some medical disorders.     

the chaos theory of careers

The Chaos Theory of Careers (CTC; Pryor & Bright, 2011) construes both individuals and the contexts in which they develop their careers in terms of complex dynamical systems. Such systems perpetually operate under influences of stability and change both internally and in relation to each other. The CTC introduces new concepts to account for previously neglected phenomena. The CTC was formulated to address identified shortcomings in existing career theory. Early theories had positive aspects but were partial, segmental, too rational, too individual focused, and divorced from much counseling practice. The authors found attempts at converging the theories unconvincing.     

Application of chaos theory to a model biological system: Evidence of self-organization in the intrinsic cardiac nervous system

The neural organization that determines the specific beat-to-beat pattern of cardiac behavior is expected to be demonstrated in the independent regulation of the RR intervals (chronotropy) and the corresponding QT subintervals (inotropy), as the former defines the rate of contraction and the latter has a linear negative correlation with the peak pressure inside the contracting ventricular muscles. The neurons of the isolated cardiac nervous system, many of which are located in the fat-pads of the heart, exhibit the same types of mechanical and chemical receptors and the same types of cholinergic and noradrenergic effectors as those found in the neural superstructure. In the surgically isolated and perfused rabbit heart we studied the responses of the QT and RR intervals evoked by block of coronary blood flow. We found that if we separated each RR cycle into QT and RR-QT components, then the dynamics of variation for each subinterval series often had the same fractional number of degrees of freedom (i.e., chaotic dimensions), a finding which suggests they are both regulated by the same underlying system. The ischemia/anoxia evoked transient dimensional increases and separations between the two subinterval series that, after the temporary divergence, reconverged to having the same lower value. The dimensional fluctuations occurred repeatedly and preceded or coincided with alterations in the magnitude and sign of the slope of QT vs RR-QT. We interpret the dimensional fluctuations of the two subinterval series as correlates of adaptation-dependent self-organization and reorganization in the underlying intrinsic cardiac nervous system during accumulating ischemia/anoxia. Such attempts at functional reorganization in this simple neurocardiac system may explain the transient dimensional changes in the RR intervals that precedes by 24 hrs the occurrences of fatal ventricular fibrillation in high-risk cardiac patients.     

Young children''s naive theory of biology

This article aimed at investigating the nature of young children's naive theory of biology by reviewing a large number of studies conducted in our laboratories. More specifically, we tried to answer the following five critical questions. What components does young children's knowledge system for biological phenomena (or naive biology) have? What functions does it have in children's lives? How is it acquired in ontogenesis? How does its early version change as children grow older? Is it universal across cultures and through history? We propose that young children's biological knowledge system has at least three components, that is, knowledge needed to specify the target objects of biology, ways of inferring attributes or behaviors of biological kinds, and a non-intentional causal explanatory framework, and that these three constitute a form of biology, which is adaptive in children's lives. We also claim that the core of naive biology is acquired based on specific cognitive constraints as well as the general mechanism of personification and the resultant vitalistic causality, but it is differently instantiated and elaborated through activity-based experiences in the surrounding culture.     

Anthropology and the theory of medicine

Instead of presupposing reality as the “realists” do, a genetic theory of knowledge attempts to understand scientific knowledge through the psychological origins of both the concepts, and the operations on which these concepts are based. Adopting the viewpoint of genetic epistemology, the envisaged theory of medicine will have to perform a threefold task: (1) A revision and reformulation of the psycho-physical problem and the development of a model for the living body; (2) A revision of our views concerning the relationship between humans and the inanimate and animate environment; and (3) The development of a concept for the construction of individual reality and its consequences for the patient-physician relationship.     

Application of holland's theory to a nonprofessional occupation

The authors, using the recently developed Position Classification Inventory (PCI; G. Gottfredson & J. L. Holland, 1991), examined male and female perceptions of a nonprofessional occupation. Results suggest that the PCI shows promise as a method of classifying occupations according to J. L. Holland's (1997) theory.     

Causality in medicine: Towards a theory and terminology

One of the cornerstones of modern medicine is the search for what causes diseases to develop. A conception of multifactorial disease causes has emerged over the years. Theories of disease causation, however, have not quite been developed in accordance with this view. It is the purpose of this paper to provide a fundamental explication of aspects of causation relevant for discussing causes of disease. The first part of the analysis will discuss discrimination between singular and general causality. Singular causality, as in the specific patient, is a relation between a concrete sequence of causally linked events. General causation, e.g. as in disease etiology, means various categories of causal relations between event types. The paper introduces the concept of a reference case serving as a source for causal inference, reaching beyond the concept of general causality. The second part of the analysis provides exemplification of a theory of causation suitable for discussing singular causation. The chain of events that induce a disease state can be identified as effective causal complexes, each complex composed of nonredundant components, which separately contribute to the effect of the complex, without the individual component being necessary or sufficient in itself to produce the effect. In the third part of the analysis the theory is elaborated further. Causes, defined as nonredundant components, can furthermore be differentiated according to their avoidability, according to theories about human error or by the potential of eradication. Multifactorial models of disease creates a need for systematic approaches to causal factors. The paper proposes a taxonomical terminology that serves this purpose.     

Application of variable criterion theory to choice reaction time

A theory of choice reaction time ICRT is presented which is based on a variable criterion model assuming the decision criterion to be normally distributed. The theory provides functions of time describing the growth of component processes following stimulus onset. For correct responses, these processes are sensory and associative strength. For errors, the processes are sensory strength, generalized associative strength, and associative inhibition. A model for separating the effects of these processes from that of response competition is presented. The theory describes, with great accuracy, the CRT distributions of correct responses and errors, not only for the experiment for which it was derived, but also for a second experiment in which the criterion was experimentally manipulated. It accounts for the basic facts of the speed-accuracy tradeoff, not only with respect to the two experiments with different speed requirements, but also with respect to the variation of speed over trials within each experiment. While derived from group data, the theory also describes the performance of individual subjects. The mean and variability of the criterion distribution and the ability to utilize associative inhibition are identified as the major sources of individual differences. Methodological problems involved in the scaling analysis of group data are also discussed.     

Action theory as a source for philosophy of medicine

The article tries to demonstrate how the tools and perspectives of action theory may be used in philosophy of medicine and medical ethics. In the first part, some concepts and principles of action theory are reconstructed and used to sketch a view of medicine as a ‘science of actions’. The second part is a contribution to the discussion on medical ethics in the same issue of this journal and consists in a detailed analysis of the main arguments and critical remarks from the point of view of action theory.     

Application of the sensory-tonic theory of perception to figural after-effect

Current theoretical positions concerned with figural after-effects were criticized for their inadequacy in accounting for figural after-effects data and for their failure to link these phenomena with other perceptual phenomena in any systematic fashion. On the basis of the relative broadness of Gibson's early formulation, it was decided to adapt a similar adaptation theory, the sensory-tonic field theory of perception, to figural after-effect displacements. Appropriate hypotheses were stated and predictions made. These were tested and confirmed. It was concluded that although the success of the theory is limited, there appears to be hope for its extension.