Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CYBERNETICS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMedDate not supplied

The function of 'brain waves': a cybernetic model of electroencephalography.

Electroencephalograms recorded from sleeping subjects are reinterpreted, from first principles, to explain the relationship between the observed wave-forms and cerebral processes. The manifestations of narcolepsy, namely, sleep paralysis, hypnopompic hallucinations and cataplexy are consistent with a hypothesis that the disorder is the result of entrainment of cerebral waves, causing almost instantaneous descent into a REM sleep state.

Cataplexy↗
PubMed1990

Functional assessment of control systems for cybernetic elbow prostheses--Part II: Application of the technique.

This paper (Part II of II) presents application of the technique described in Part I to functional assessment of two myoelectric elbow-prosthesis controllers: the controller implemented in the Boston Elbow, a state-of-the-art elbow prosthesis, and a proposed control scheme that, to a crude degree, mimics control of the intact elbow. Assessment of the controllers was achieved by evaluating an amputee subject's functional capability as he performed a constrained motion task with a prosthesis that implemented each control scheme. Evaluation of the amputee's capability was accomplished off line using sampled values of his myoelectric activity, his limb kinematics, and the interface forces at the constraint. Superior performance was observed with the proposed scheme. Namely, the subject exhibited better synergy among his elbow and shoulder muscles. Furthermore, when using the proposed controller, he exhibited some natural patterns of muscle coordination.

Amputation, Surgical↗
PubMed2004

Are depressive persons capable of describing changes in their reactions without being able to explain them? A proof of a cybernetic hypothesis of depression.

BACKGROUND: Many studies on the autobiographical memory and the explanation of reasons for success and failure proved that persons suffering from major depression tend to overgeneralize. This study examines the hypothesis that changes of reactions caused by a depressive disorder can be described by the affected persons but not explained. SAMPLE AND METHODS: Persons suffering from major depression and persons with posttraumatic stress disorder or disturbance of accommodation with depressive mood (= reactive form of a depressive disorder) were presented with a list of modalities (behaviour, emotional and physical reactions) characteristic for depression. They were asked to identify modalities applicable to them and to describe and explain them. Their responses were analysed using a content analysis and assigned to the categories description and explanation. RESULTS: Persons with a major depression tended to use explanations or evaluations rather than descriptions for their depression-related modalities. Those persons suffering from a reactive form of depressive disorder tended to prefer evaluations. CONCLUSION: These results support the assumption that states of depression cause general descriptions of depression-relevant behaviour. The specific characteristics that have been perceived confirm the general concepts, which however make the patient prone to the respective selective perceptions. Persons suffering from a reactive form of depressive mood cannot be assumed to have this tendency of self-affirmation. Their depressive state may be maintained by perseverating general pessimistic schemes. LIMITATIONS: It must however be conceded that it was not possible to control the physical comorbidity methodically and to take its effects into consideration, even though only persons without serious illnesses were included in the samples. This study did not verify whether other clinical groups, like patients suffering from anxiety, show the same patterns of explaining and describing their problems. It should furthermore be reviewed how other actions, e.g. positive ones, are represented by depressive persons.

Adult↗
PubMed1998

Hierarchical and cybernetic nature of biologic systems and their relevance to homeostatic adaptation to low-level exposures to oxidative stress-inducing agents.

During evolution in an aerobic environment, multicellular organisms survived by adaptive responses to both the endogenous oxidative metabolism in the cells of the organism and the chemicals and low-level radiation to which they had been exposed. The defense repertoire exists at all levels of the biological hierarchy--from the molecular and biochemical level to the cellular and tissue level to the organ and organ system level. Cells contain preventive antioxidants to suppress oxidative damage to membranes. Cells also contain proteins and DNA; built-in redundancies for damaged molecules and organelles; tightly coupled redox systems; pools of reductants; antioxidants; DNA repair mechanisms and sensitive sensor molecules such as nuclear factor kappa beta; and signal transduction mechanisms affecting both transcription and post-translational modification of proteins needed to cope with oxidative stress. The biologic consequences of the low-level radiation that exceeds the background level of oxidative damage could be necrosis or apoptosis, cell proliferation, or cell differentiation. These effects are triggered by oxidative stress-induced signal transduction mechanisms--an epigenetic, not genotoxic, process. If the end points of cell proliferation, differentiation, or cell death are not seen at frequencies above background levels in an organism, it is unlikely that low-level radiation would play a role in the multistep processes of chronic diseases such as cancer. The mechanism linked to homeostatic regulation of proliferation and adaptive functions in a multicellular organism could provide protection of any one cell receiving deposited energy by the radiation tract through the sharing of reductants and by triggering apoptosis of target stem cells. Examples of the role of gap junctional intercellular communication in the adaptive response of cells and the bystander effect illustrate how the interaction of cells can modulate the effect of radiation on the single cell.

Adaptation, Physiological↗
PubMed1992

[How do occlusion disorder and stress influence cybernetic masticatory control?].

Chewing forces were registered and compared in three subjects under normal conditions as well as in presence of occlusal interferences, and under stress. Biting force, blood pressure, and concentration of blood catecholamines were measured. Psychic stress was induced by demanding reactions on a test machine. In the presence of occlusal interferences, no significant increase in biting force was recorded. However, the biochemical analysis documented that biting forces appeared to be no longer under local control, but, increased up to 600% when the level of stress was raised. This study confirms the importance of stress as an etiologic factor in masticatory dysfunction.

Adult↗
PubMed1990

[Studies on the cybernetic aspects of occlusal splint therapy].

This study was focussed on the effects of changes in interocclusal clearance on the activity of oral muscles. Two types of occlusal splints were incorporated in 20 subjects without TMJ-syndrome. Their muscle reactions were recorded electromyographically in the masseter muscle. The results show 5 groups of muscle reaction correlated with the mean postural face height. The changed height of the postural position has a significant influence on the control pattern of the masticatory system.

Adult↗
PubMed1990

Functional assessment of control systems for cybernetic elbow prostheses--Part I: Description of the technique.

This paper (Part I of II) presents a novel control scheme with which an amputee commands an elbow prosthesis using myoelectric activity. By mimicking some important characteristics of the intact neuromuscular system, the proposed controller attempts to make the prosthesis respond as the natural elbow to both voluntary commands from the amputee and applied moments from the environment. Also presented is the description of a novel experiment for functionally assessing elbow prosthesis controllers. The experimental design calls for an amputee to perform a constrained motion task while operating a prosthesis capable of implementing a wide variety of controllers. Due to the nature of the constraint, the task emphasizes the prosthesis response to both inputs: voluntary commands and external moments. Application of the experiment to assessment of the proposed control scheme and the control scheme used in a state-of-the-art prosthesis is presented in Part II.

Amputation, Surgical↗