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PubMed1978

Seed germination as a thermobiological problem.

Thermal effects on seed germination are considered through the changes brought about by temperature in the germination capacity, in the germination rate, and in the distribution of the relative frequency of germination along the incubation times. A number of questions of general thermobiological interest are thus raised, entailing the need of an analysis of the temperature dependence of the seed germination rate. A treatment of these rates by the activation-energy approach cannot be general, for their Arrhenius plots are not always linear. Moreover, it is shown that any process displaying a temperature optimum (as happens in the germination of most seed species) cannot follow one of the fundamental tenets of the collision rate theory. The need of a theoretical treatment stressing the essential role of the partition of energy within the seed system has led to an anlysis using the absolute reaction rate theory. New experimental prospects for the physiology of seed germination are thus raised, concerning the meaning of the temperature cardinal points, the growth pattern of the embryo in germinating seeds, the dual effect of protein thermodenaturation, the effects of high hydrostatic pressures, and a whole pharmacological line of work. The cybernetic counterpart of the thermodynamic view of seed germination appears in the study of the distribution of the relative frequency of germination along the isothermal incubation time. In some species of seeds the thermal communication between the environment and the seed growth effector can be shown to proceed by molecular collisions at all germination isotherms. In the seeds of Dolichos biflorus this communication through random thermal noise prevails only at temperatures close to both extreme limits of germination. Both in this species and in Calotropis procera there is a temperature range (encompassing the optimum) within which a temperature signal is superimposed upon the gaussian noise. An interpretation is proposed according to which the temperature signal is transduced in a protein-conformation code.

Protein Denaturation↗
PubMedDate not supplied

Patterns of covert speech behavior and phonetic coding.

In previous research a discriminative relationship has been established between patterns of covert speech behavior and the phonemic system when processing continuous linguistic material. The goal of the present research was to be more analytic and pinpoint covert neuromuscular speech patterns when one processes specific instances of phonemes. Electromyographic (EMG) recording indicated that the lips are significantly active when visually processing the letter "P"(an instance of bilabial material), but not when processing the letter "T" or a nonlinguistic control (C) stimulus. Similarly, the tongue is significantly active when processing the letter "T" (an instance of lingual-alveolar material), but not when processing the letters "P" or "C". It is concluded that the speech musculature covertly responds systematically as a function of class of phoneme being processed. These results accord with our model that semantic processing ("understanding") occurs when the speech (and other) musculature interacts with linguistic regions of the brain. In the interactions phonetic coding is generated and transmitted through neuromuscular circuits that have cybernetic characteristics.

Afferent Pathways↗
PubMedDate not supplied

How is linguistic memory accessed? A psychophysiological approach.

The role of "subvocalization" during language comprehension, especially reading, is examined. Four arguments against it having a role in accessing memory are erroneous because 1) its latency is much shorter than is conventionally stated; 2) rate of visual information processing is erroneously estimated by failing to distinguish between reading and scanning; 3) covert speech does not disappear in the competent language performer; and 4) the argument that subvocalization is an epiphenomenon is irrelevant. Rather, data support the generalization that covert speech is present during all cognitive functioning and that its specific topography is discriminatively related to the class of phoneme being processed. It is thus inferred that during cognition the speech musculature generates a phonetic code that may function to access linguistic memory. However, since there are also numerous other psychophysiologic events associated with covert speech, a multichannel processing system is hypothesized wherein speech, visual, and kinesthetic modalities interact with the brain. Illustrations are given of how this accessing model is compatible with existing holographic and feature analyzer models of memory. Data are presented that illustrate how phonetically encoded neuromuscular events can be directly measured through psychophysiologic methods. It is hypothesized that cognitive processes are generated when cybernetic neuromuscular circuits selectively interact. Consequently, all components of these neuromuscular circuits serve a function during cognition so that a role for "subvocalization" (a muscular component) cannot be ruled out in an apriori manner.

Electromyography↗
PubMed1997

[Psychosomatic aspects of chronic pain].

This paper gives a report on the current views of psychosomatic theories on chronic pain. Based on Melzack's and Wall's "gate-control theory", Freud's ideas on hysteric neurosis, and Engel's "pain-prone patient" the unidirectional nociceptive model of pain is replaced by a cybernetic system of biopsycho-social etiology. The psychodynamic theories of pain-proneness, the narcissistic mechanism in the etiology of pain, the mechanism of conversion, states of psychovegetative tension and processes of learning are presented. In addition the impact of gain from illness, life-events, coping, the doctors behavior and the comorbidity of affective disorders on pain syndromes becoming chronic is pointed out. As an example the multifactorial etiology of chronic low back pain is demonstrated.

Conversion Disorder↗
PubMed2002

A model of the cerebellar pathways applied to the control of a single-joint robot arm actuated by McKibben artificial muscles.

This article describes an expanded version of a previously proposed motor control scheme, based on rules for combining sensory and motor signals within the central nervous system. Classical control elements of the previous cybernetic circuit were replaced by artificial neural network modules having an architecture based on the connectivity of the cerebellar cortex, and whose functioning is regulated by reinforcement learning. The resulting model was then applied to the motion control of a mechanical, single-joint robot arm actuated by two McKibben artificial muscles. Various biologically plausible learning schemes were studied using both simulations and experiments. After learning, the model was able to accurately pilot the movements of the robot arm, both in velocity and position.

Arm↗
PubMed1996

Computation of inverse dynamics for the control of movements.

Accuracy of movements requires that the central nervous system computes approximate inverse functions of the mechanical functions of limb articulations. In vertebrates, this is known to be achieved within the cerebellar pathways, and also in the cerebral cortex of primates. A cybernetic circuit achieving this computation allows accurate simulation of fast movements of the eye or forearm. It is consistent with anatomy, and with the classical view of the cerebellum as permanently supervised by the inferior olive. The inferior olive detects over-or under-shoots of movements, and the resulting climbing fiber activity corrects ongoing movements, regulates the function of cerebellar cortex and nuclei, and sets the gains of the sensorimotor reactions.

Cerebellum↗
PubMed2006

The question of questions: what is a gene? Comments on Rolston and Griffiths & Stotz.

If the question "What is a gene?'' proves to be worth asking it must be able to elicit an answer which both recognizes and address the reasons why the concept of the gene ever seemed to be something worth getting excited about in the first place as well analyzing and evaluating the latest develops in the molecular biology of DNA. Each of the preceding papers fails to do one of these and suffers the consequences. Where Rolston responds to the apparent failure of molecular biology to make good on the desideratum of the classical gene by veering off into fanciful talk about "cybernetic genes,'' Griffiths and Stotz lose themselves in the molecular fine print and forget to ask themselves why "genes'' should be of any special interest anyway.

Animals↗
PubMed1986

Latency of eye movement and other REM sleep parameters in bipolar depression.

Parameters of rapid eye movement (REM) sleep were measured in 10 endogenous bipolar depressive drug-free patients and in healthy subjects. A significant reduction of eye movement latency and larger standard deviations in the values for activity and density of eye movement were found in the depressed patients. The method applied in this study, embodying an aspect of cybernetic theory in pattern recognition, proved very useful for the elaboration of the biological data.

Adult↗
PubMed1992

Feedback control of limb stiffness and scaled phase invariance properties of skilled high-speed arm flexion movements of a loaded manipulator.

In this and a previous experiment it has been observed that subjects produce innervation patterns (EMG) that are load specific, i.e., they produce concentration patterns for movements made with inertial loads and triphasic patterns for movements made with elastic loads. The protocol of these experiments prevented any adaptive responses to the load changes, therefore, it was assumed that pattern matching to load type was a real time updating response of the peripheral feedback systems. This updating response was assumed to be a mechanism for fine tuning the muscle torque by regulation of the mechanical impedance (stiffness) of the limb. Using a standard equation of motion, it was shown that the velocity is equal to the ratio of the muscle torque to the mechanical impedance. Substitution of this ratio for the ordinate of the scaled phase diagrams was then suggested as a real time updating mechanism to account for the scaled phase invariance recorded in this experiment and in the experiment reported by Ruitenbeek, J.C., Biol. Cybernetics 51 (1984) 11-20.

Biomechanical Phenomena↗
PubMed1980

Multichannel analysis of intracellular control and intercellular transfer of molecules.

The metabolic regulation and exchanges within intracellular organelles or a cell cluster are studied by multichannel microfluorometry and microinjection of metabolites or tracers. The determination of structure-function relationships relies on the retrieval of cells after microfluorometry, for subsequent morphological evaluation. Rate constants of coenzyme reduction-reoxidation were deduced from a mathematical model of NAD(P) in equilibrium with NAD(P)H transients due to microinjection of metabolites into cultured cells belonging to a variety of normal or malignant lines. Nuclear and cytoplasmic sites operate synchronously or not, depending upon metabolic demand or pathological alterations. Intercellular transit times are determined for tracers and metabolites. Within cell clusters 'communicating territories' are described, which can show metabolically a multicellular integrated state. Microfluorometry in conjunction with ultrastructural and other studies can be used to develop a cybernetic model of the living cell, also yielding dynamic models of cooperative and regulatory interactions between different kinds of specialised cells within a cell cluster.

Animals↗
PubMed1991

Spatial organization of nonlinear interactions in form perception.

We examined the perception of structure in a family of visual textures whose second-order correlation structure is flat. These textures were generated by two-dimensional recursion rules, in a manner which extends the construction of Julesz, Gilbert and Victor (1978; Biological Cybernetics, 31, 137-140). Textures generated by some recursion rules elicited a visually salient percept of structure, while textures generated by other recursion rules did not. Textures whose statistical structure was visually salient produced evoked responses which differed from the response evoked by completely random textures. The size of this VEP difference correlated well with psychophysical measures. Since the textures were constructed to have identical global spatial frequency spectra, models for the extraction of visual structure must be essentially nonlinear. Models based on symmetry, information content, or simple spatial extent (but not pattern) of correlation fail to explain the observed results. Models based on the cooperative interaction of pairs of nonlinear subunits provide a reasonable qualitative account of the findings. The critical model features are (i) the presence of multiple nonlinear subunits, and (ii) a second nonlinearity, such as a threshold, at the stage of combination of subunit signals.

Adult↗
PubMed1994

Probabilistic analysis of human supervised learning and classification.

Probabilistic classification techniques based on Bayesian decision theory are used to analyze human supervised learning and classification. The procedure rests on the assumption that human classification behaviour is based on internal feature states which can be linked to physical feature vectors (corresponding to the system input). In the present approach, this relationship is modeled in terms of additive stochastic error signals. The corresponding random variables describe the additional degrees of bias and variance introduced by the (perceptual) process of internal feature measurement. Estimates of internal feature states are obtained by least-squares minimization. Structure and dimensionality of the resulting internal representation are displayed by plotting the configuration of internal class means, or virtual prototypes. Their temporal evolution reflects the dynamic properties of the learning process. The use of the procedure is demonstrated by analyzing the results of two experiments. First, it is shown that Minimum Distance Classifiers, such as used by Caelli, Rentschler and Scheidler [(1987) Biological Cybernetics, 57, 233-240], are suboptimal in predicting human performance. Second, it is found that extrafoveal learning is much slower than foveal learning and that extrafoveal pattern representations are severely distorted. The latter distortions reveal the existence of limitations for the generalization of supervised learning over space.

Adult↗
PubMedDate not supplied

DIABETEX decision module 2--calculation of insulin dose proposals and situation recognition by means of classifiers.

Current research in the field of medical decision making tries to represent and to analyse complex, uncertain and complicated situations. The first version of DIABETEX, which is a decision support system for the treatment of diabetic out-patients, accepts the challenge to overcome these difficulties. It includes a network of rules on the basis of known glucose-insulin relationships under different situations. The insulin dose for type I diabetic patients is suggested accordingly. In this, the application of special cybernetic methods offers the chance to overcome complexity, uncertainty, fuzzyness and incompleteness of data. Two methods of classification are presented to complete the DIABETEX decision unit: (1) the Bayes' classification is used in the calculation of insulin doses for type I diabetic patients on multiple subcutaneous insulin injections considering the basis-bolus concept; (2) fuzzy classification is employed in separating 'normal diabetic days' from days with information on special situations such as exercise, illness, menstruation on the one side, from stress, hypoglycaemia etc. on the other.

Bayes Theorem↗
PubMed1996

A unifying hypothesis for acetylcholine release.

Mediatophore is the only nerve terminal membrane protein known to translocate acetylcholine upon calcium action. It is localized at the active zone. In this review we attempted to describe its role in relation to the vesicular and membrane protein complexes that are formed at the active zone. The model pictures a possible set of sequential steps that lead to exocytosis. The smallest quantal events are attributed to mediatophore opening momentarily, while synaptic vesicles synchronize release by controlling the calcium microdomain. A clear distinction is made between sub-quantal ACh release preserved after Botulinum toxin action, and exocytosis of vesicular contents. A cybernetic model for release and exocytosis related to protein interactions is presented for future works.

Acetylcholine↗
PubMed1990

A foundation for physiology.

From a study of the literature on the Philosophy of Physiology it became clear that a crisis exists. This crisis was studied by means of a classification of philosophical views. Two main categories, namely Positivistic and Transcendentalistic, frameworks of thought were used. Under the Positivistic category such models as radical materialistic, mechanistic and cybernetic were placed. Under the Transcendentalistic category were classified holistic, humanistic, mystic and eastern ideas. Paradoxic ideas were discussed. None of the frameworks of thought supply a good foundation for Physiology. A liberating foundation for Physiology is proposed. A model of man as a personal unity in a created environment is described. This model does not contain either the contradictions nor polarizations of the positivistic versus transcendentalistic frameworks of thought.

Humans↗
PubMed2004

Plasma renin activity levels in hypertensive persons: their wide range and lack of suppression in diabetic and in most elderly patients.

BACKGROUND: The renin-angiotensin system (RAS) maintains hemodynamic integrity by modulating both volume and vasoconstriction through a cybernetic feedback control mechanism. In addition, angiotensin II, the active component of the RAS, can be vasculotoxic and, in hypertensive individuals, is associated with increased cardiovascular morbidity and mortality. The objective of this study was to determine the distribution and determinants of plasma renin activity (PRA) in a representative sample of hypertensive persons. METHODS: We systematically measured PRA in 4170 untreated participants in a systematic work site-based, hypertension treatment program. RESULTS: In this multiethnic employed population, patients were classified as follows: low renin, <0.65 ng/mL/h (30% of the sample); medium renin, 0.66 to 4.5 mg/mL/h (60%); or high renin, >4.5 ng/mL/h (10%). Low renin patients were more likely to be African American, female, and slightly older. However, the majority of women and African American individuals were not low renin. The 469 diabetic subjects distributed across renin categories, as did the group as a whole. CONCLUSIONS: This systematic study of PRA in a large community sample of hypertensive patients reveals a wide distribution of activity level, with identifiable differences according to ethnicity, age, and sex but not diabetic status. However, these demographic differences were more quantitative than qualitative and do not provide a useful basis for estimation of the activity of the RAS. Instead, in hypertensive subjects, direct measurement of PRA is necessary, both for prognosis and for guiding hypertensive therapy.

Age Factors↗
PubMedDate not supplied

What is signal and what is noise in the brain?

The response of a cortical neuron to a stimulus can show a very large variability when repeatedly stimulated by exactly the same stimulus. This has been quantified in terms of inter-spike-interval (ISI) statistics by several researchers (e.g., [Softky, W., Koch, C., 1993. The highly irregular firing of cortical cells is inconsistent with temporal integration of random EPSPs. J. Neurosci. 13(1), 334-350.]). The common view is that this variability reflects noisy information processing based on redundant representation in large neuron populations. This view has been challenged by the idea that the apparent noise inherent in brain activity that is not strictly related or temporally coupled to the experiment could be functionally significant. In this work we examine the ISI statistics and discuss these views in a recently published model of interacting cortical areas [Knoblauch, A., Palm, G., 2002. Scene segmentation by spike synchronization in reciprocally connected visual areas. I. Local effects of cortical feedback. Biol. Cybernet. 87(3), 151-167.]. From the results of further single neuron simulations we can isolate temporally modulated synaptic input as a main contributor for high ISI variability in our model and possibly in real neurons. In contrast to alternative mechanisms, our model suggests a function of the temporal modulations for short-term binding and segmentation of figures from background. Moreover, we show that temporally modulated inputs lead to ISI statistics which fit better to the neurophysiological data than alternative mechanisms.

Action Potentials↗