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PubMed1989

Cybernetic model of psychophysiologic pathways: II. Consciousness of tension and kinesthesia.

This paper describes a series of experiments directed toward the following questions: a) do signals from musculotendinous receptors reach consciousness?, and b) does feed-forward information of muscular force and expected extent of voluntary movement exist? To answer these questions, data from voluntary compression of springs and strain-gauge have been analyzed in healthy young subjects. By successive elimination of information from other sources, it was possible to verify that receptors in muscles and tendons do signal movement magnitude and muscular tension to the cerebral cortex, and that this information does reach consciousness. There also exists a feed-forward mechanism signalling parameters of voluntary contraction. However, it is unclear whether peripheral, subcortical or intracortical loops are directly involved.

Biofeedback, Psychology↗
PubMed1988

A prospective study of the predictive value of electroencephalographic abnormalities for epileptic loss of consciousness.

Patients referred to a neurology clinic with their first episode of loss of consciousness were studied prospectively in order to clarify the positive predictive value of an epileptic EEG for establishing an epileptic cause of the loss of consciousness. The clinical diagnosis was categorised as epileptic or non-epileptic. The EEG was reported as epileptic or non-epileptic, but abnormal or normal, according to recognised criteria. Patients were followed for a period ranging from 1 to 18 months to assess the accuracy of the original diagnosis. A total of 38 patients were available for analysis. Thirteen patients had a clinical diagnosis of epilepsy and 25 patients had a non-epileptic diagnosis. Five patients with an epileptic history had an epileptic EEG and 2 patients with a non-epileptic history had an epileptic EEG. Non-epileptic EEG abnormalities were present in a further 4 patients with a non-epileptic history. Follow-up was achieved for 53% of patients and in none of these was the final diagnosis different from the initial one. The positive predictive value of an epileptic EEG for a diagnosis of epilepsy was 71%, and the negative predictive value of a normal EEG for a diagnosis of non-epilepsy was 74%. The positive predictive value for any abnormality in the EEG for a diagnosis of epilepsy was 45%, and the negative predictive value of an absence of any abnormality in the EEG for a diagnosis of non-epilepsy was 70%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Changes in central hemodynamics during experimental septic shock in conscious rats.

This study describes the hemodynamic, metabolic, and respiratory effects of a 4-h continuous intravenous infusion of live Escherichia coli bacteria (10(9)/h) in conscious, unrestrained rats. The early response to bacterial infusion was moderate hypotension and a marked and sustained increase in heart rate and respiratory rate. During later stages of bacteria infusion a marked decrease in stroke volume and cardiac output was observed, while total peripheral resistance increased. Arterial blood gas measurements showed an early primary respiratory alkalosis, while later stages of bacteria infusion were accompanied by progressive development of metabolic acidosis. This small-sized animal shock model may be useful for further studies, particularly since conscious rats were used to avoid the influence of anesthesia upon the development of septic shock.

Animals↗
PubMed1987

Multiple memory systems and consciousness.

This Introduction to the Special Issue on Human Memory discusses some of the recent and current developments in the study of human memory from the neuropsychological perspective. A problem of considerable current interest, that of multiple memory systems, is a problem in classification. Much of the evidence for it is derived from clinical and experimental observations of dissociations between performances in memory tasks. The distinction between short-term and long-term memory is considered as an example of classification by dissociation. Current conceptualizations of multiple long-term memory systems are reviewed from the vantage point that distinguishes among three major kinds of memory--episodic, semantic, and procedural. These systems are briefly described and compared, and current views concerning the relation between them are discussed. The role of consciousness in memory is raised against the backdrop of the suggestion that it may be necessary to differentiate among several kinds of consciousness.

Consciousness↗
PubMedDate not supplied

Relation between the aortic pressure and the cardiac cycle in different neurovegetative conditions in the conscious dog.

The relation between mean aortic pressure (mAoP) and the duration of cardiac cycle (C) has been studied in resting conscious dogs in normal condition (n), after vagal blockade (vb), after sympathetic blockade (sb), and after combined blockade of the two systems (sb+vb). The relation has been found to be negative in all conditions. The different conditions are clearly differentiated by the slope of the relation between mAoP/C (= kPa/s = mW/ml) and C. The hypothesis is put forward that the balance between sympathetic and parasympathetic activities on the heart and the vessels produces the best compromise between the pump function of the heart and the afterload, in relation to the actual behavioural situation, in conscious animals.

Animals↗
PubMed1985

The electroencephalogram in altered states of consciousness.

The EEG can be very helpful in the evaluation of patients with altered states of consciousness. Diffuse slowing of background rhythms and the presence of triphasic waves suggests metabolic dysfunction, particularly hepatic. Generalized fast activity may be seen in patients with a drug intoxication. Abnormalities, such as PLEDs or focal continual PDA, support a diagnosis of supratentorial lesion, whereas a normal appearing EEG in a comatose patient suggests a brain-stem lesion. In addition, the EEG may reveal that the alteration in consciousness is due to continual epileptic activity without motor manifestations (nonconvulsive status) that had not been suspected. As indicated, certain patterns have prognostic implications. However, as these patterns are not specific for a single etiology, the EEG is of most help when the cause is known. For example, burst suppression or a diffuse alpha pattern coma can be seen in either hypoxia or a drug intoxication. With hypoxia, these patterns carry an extremely poor prognosis for useful recovery, whereas complete recovery is often seen in cases secondary to drug ingestion. As a more extreme example, a patient whose EEG shows ECS secondary to drug intoxication may recover but will not if the ECS is due to hypoxia or severe head trauma. If the etiology of the encephalopathy is unknown, then sequential records are needed for prognosis.

Adolescent↗
PubMed1985

"Memory of the future": an essay on the temporal organization of conscious awareness.

The classical tripartite concept of time divided into past/present/future components, has been applied to the analysis of the functional cerebral substrate of conscious awareness. Attempts have been made to localize and to separate the neuronal machineries which are responsible for the experience of a past, a present, and a future. One's experience of a past is obviously related to one's memories. Memory mechanisms (in the conventional sense) have a well known functional relation to superficial and deep parts of the temporal lobe. Some such mechanisms presumably have a more widespread distribution. The experience of a present or a "Now-situation" is mediated by the sensory input. This input also exerts a role for conscious awareness of an inner Now-situation, independent of current afferent impulses, as shown by numerous observations on sensory deprivation. The main discussion is devoted to the experience of a future. Evidence is summarized that the frontal/prefrontal cortex handles the temporal organization of behaviour and cognition, and that the same structures house the action programs or plans for future behaviour and cognition. As these programs can be retained and recalled, they might be termed "memories of the future". It is suggested that they form the basis for anticipation and expectation as well as for the short and long-term planning of a goal-directed behavioural and cognitive repertoire. This repertoire for future use is based upon experiences of past events and the awareness of a Now-situation, and it is continuously rehearsed and optimized. Lesions or dysfunctions of the frontal/prefrontal cortex give rise to states characterized by a "loss of future", with consequent indifference, inactivity, lack of ambition, and inability to foresee the consequences of one's future behaviour. It is concluded that the prefrontal cortex is responsible for the temporal organization of behaviour and cognition due to its seemingly specific capacity to handle serial information and to extract causal relations from such information. Possibly the serial action programs which are stored in the prefrontal cortex are also used by the brain as templates for extracting meaningful (serial) information from the enormous, mainly non-serial, random, sensory noise to which the brain is constantly exposed. Without a "memory of the future" such an extraction cannot take place.

Awareness↗
PubMed1977

[Experimental examination on the development of altered states of consciousness by autogenic training in comparison to sensory deprivation].

In a sample of 32 trainees of autogenic training the alterations of the state of consciousness during the exercises were recorded by means of a questionnaire (APZ). To check the influence of acoustic stimulation the subjects were exposed to various sounds by headphone. The data were compared with the results of an experiment with sensory deprivation. A significant correspondence was found between the altered states of consciousness through sensory deprivation and autogenic training under usual low stimulus condition. According to these results autogenic training can be understood as a technique of self-induced sensory deprivation.

Acoustic Stimulation↗
PubMedDate not supplied

Cardiovascular and respiratory effects of beta-endorphin in anesthetized and conscious rats.

This study deals with the effects of beta-endorphin on blood pressure, heart rate, and respiratory frequency in anesthetized and conscious rats after both peripheral and central administration. Intravenous injection of beta-endorphin (40 and 160 micrograms/kg) in urethane-anesthetized rats resulted in a prolonged decrease in blood pressure, which, after the higher dose, was accompanied by bradycardia. In the pentobarbitone-anesthetized animals the same doses of beta-endorphin caused a small rise in blood pressure without affecting heart rate. No effect on respiratory frequency was observed. In urethane-anesthetized rats with hemorrhagic shock intravenous naloxone elicited a small pressor effect. Intracerebroventricular injection (i.c.v.) of beta-endorphin (40 micrograms/rat) in urethane-anesthetized rats resulted in severe respiratory depression and death. With lower doses there was a decrease in all parameters studied without ensuing death. Respiratory depression was even more pronounced in pentobarbitone-anesthetized rats, occurring with much lower doses of the peptide than in the urethane-anesthetized animals. beta-endorphin in the dose of 0.6 micrograms/rat still reduced respiratory frequency as well as heart rate without affecting blood pressure. Naloxone pretreatment antagonized the respiratory depression and death, while the decrease in heart rate was diminished. In conscious rats 10 microgram/rat, i.c.v., of beta-endorphin resulted in a decrease in heart rate and blood pressure without affecting respiratory frequency. It is concluded that beta-endorphin, or related opioid peptides, may be involved in cardiovascular and respiratory regulation. The effects of beta-endorphin, however, are markedly modified by the anesthetic agent used.

Animals↗
PubMed1982

Brain stimulation in the study of neuronal functions for conscious sensory experiences.

Some features of cerebral neuronal functions that are uniquely related to generation of conscious sensory responses, have been discovered. Included are two temporal factors: (1) Substantial delays, of up to about 0.5 sec, before achieving cerebral "neuronal adequacy" appear to be required for eliciting a sensory experience. This includes the demonstration that a cortical stimulus (C) can retroactively modify a skin (S)-induced sensation even when C stimulus begins up to 500 msec after S stimulus. (2) However, there appears to be a subjective referral of the experience back to the time of the cortical primary evoked response to S; subjectively the skin sensation would thus appear to have no delay. Stimuli that are inadequate for eliciting conscious sensory experience can nevertheless evoke considerable neuronal activity, including that represented in direct cortical responses or in primary (early) components of evoked potentials. Virtually all the qualities of somatic sensation (except pain) can be elicited by stimuli at post-central gyrus, when intensities of suitable trains of pulses are kept down to liminal levels. Some additional implications, for the manner in which mental and neural events are related, are discussed.

Arousal↗
PubMed1983

[Dream interpretation: theory of the "psychological apparatus" as initial consciousness theory in Freud's metapsychology].

In the "Interpretation of Dreams" (1900 a) Freud presents for the first time a purely psychologically founded theory of psychic functioning, in the centre of which stands the model of the "psychic apparatus". In the detailed reconstruction of the statements of the "Interpretation" the present study tries to elaborate the meaning of "consciousness" within a psychology of the unconscious, in order to transfer--with reference to the early writings of J.-P. Sartre--the critique of Freudian unconscious to the level of the underlying conception of consciousness.

Arousal↗
PubMed1983

Effects of acetylcholine on large and small coronary arteries in conscious dogs.

The effects of acetylcholine, 10 microgram/kg i.v., were examined in nine conscious dogs on measurements of left ventricular pressure, dP/dt, aortic pressure, heart rate, coronary blood flow, left circumflex external coronary arterial diameter, arterial and coronary sinus O2 content and calculations of late diastolic coronary resistance and left circumflex internal coronary cross-sectional area. In conscious dogs in the absence of autonomic blockade, acetylcholine induced a rapid, transient response characterized by hypotension and peak increases in coronary blood flow (+135 +/- 14%) and coronary sinus O2 content (+5.0 +/- 0.5 volume percent) and decreases in late diastolic coronary resistance (-65 +/- 3%). The peak large coronary arterial effects were observed 60 sec later at a time when arterial pressure, left ventricular end-diastolic pressure, left ventricular dP/dt and heart rate were not significantly different from control. At this time, large coronary cross-sectional area was increased by 36 +/- 4%, whereas late diastolic coronary resistance was not significantly different from control. Beta adrenergic or combined alpha and beta adrenergic receptor blockade did not alter the responses significantly. However, the effects were abolished by muscarinic blockade with atropine methylbromide, 0.1 mg/kg. Thus, acetylcholine dilates large coronary arteries as well as coronary resistance vessels. These effects are independent of metabolic and adrenergic mechanisms, and are mediated by muscarinic receptors, inasmuch as the effects are abolished by prior muscarinic receptor blockade.

Acetylcholine↗
PubMed1980

[A system for biological pressure telemetry in conscious animals (author's transl)].

Cardiovascular studies on conscious laboratory animals are required for an accurate assessment in drug evaluations. However, attempts to define pharmacological significance of an agent in conscious and unrestrained animals have been limited by the techniques available for recording the cardiovascular parameters. We designed a system which can be applied to record biological pressure, such as the blood pressure, using a miniature FM-FM radio-transmitter and a receiver demodulator. The transmitter consists of a differential amplifier capable of an input signal up to 3 X 10(6) times, voltage controlled oscillator which triggers a 2-5 volts range and 76-90 MHz transmitting oscillator. The transmitter requires a 5.6 V mercury battery. Earphone output of a commercial FM radio-receiver serves for signals to the demodulator. The demodulator is based on the phase locked loop principle and is equipped with an independent output for instantaneous wave recording and the mean of this recording. Transmitting distance of the system may depend on the receiver, however, in most instances, the distance is over 39 meters, in an open field. Accuracy of the telemetering data is dependent on discharge characteristics of the mercury battery. After discharging 5%, the full capacity of the cell gives a sufficient zero stability and accurate pressure measurements.

Animals↗
PubMed1980

[A procedure for recording electroretinogram (ERG) in conscious monkeys, and effects of some drugs (author's transl)].

Stable ERG was successfully recorded using a contact lens-type electrode in conscious cynomolgus monkeys restrained in a monkey-chair with a specially devised head-holder. After adaptation to darkness, single photostimulation evoked ERG consisting of an initial negative wave (a-wave), followed by a positive wave superimposed with oscillatory potentials (b-wave), and a late positive (c-wave). The former two waves were clearly recorded but c-wave was often mixed with artifacts probably due to eye movements. Amplitudes and peak latencies of a- and b-waves increased in progression of dark adaptation and attained to maximum within 20 min. The optimal intensity of photostimulus and time-constant for recording stable a- and b-waves with intermediate amplitudes were found to be 2 joule and 0.1 sec, respectively. The amplitudes and peak latencies (mean +/- s.d.) of a- and b-waves obtained by these conditions were 163.3 +/- 44.9 and 437.0 +/-37.9 microV, and 17.3 +/- 0.5 and 53.5 +/- 3.2 msec, respectively. These waves were reproducible within 25% variations change in a-wave: pentobarbital increased the amplitude of b-wave, whereas ketamine reduced this amplitude. A 3-day treatment with 1,5-di(p-aminophenoxy)pentane (200 mg/kg/day, p.o.), a retinal toxic and behavioral signs of visual dysfunction. Histological abnormality of the retina was also detected. The results indicate that this technique is useful for recording ERG in order to evaluate the effect of chronically treated drugs on visual perception in conscious monkeys.

Adaptation, Ocular↗
PubMed1981

The effect of hyperbaric oxygen on infarct size in the conscious animal.

The effect of hyperbaric oxygen (HBO) on infarct size associated with myocardial infarction remains uncertain. Accordingly, the present study was performed in 46 conscious dogs with experimental infarction to determine the effect of HBO on enzymatic estimates of infarct size. Since HBO may affect plasma creatine kinase (CK) release or disappearance, parameters used to calculate enzymatic estimates of infarct size from plasma CK, we assessed infarct size by directly measuring myocardial CK depletion. Twenty-three animals were given HBO (2 atm of pressure) for 3 h immediately after coronary occlusion and results of infarct size compared to those in 23 dogs with occlusion who remained in room air. In 10 other animals CK release was measured after coronary occlusion in 5 controls and compared to 5 treated. In 5 normal animals the CK disappearance rate of purified canine CK was determined before and after HBO. Infarct size was determined 24 h after coronary occlusion and in the treated animals averaged 25.4 +/- 1.3% of LV (mean +/- SEM), and being similar to controls (26.7 +/- 1.4, P greater than 0.25). The plasma CK disappearance rate before and after HBO was the same being 0.0072 +/- 0.0022 (min-1) and 0.0073 +/- 0.0021, respectively. Total CK released into the plasma was also the same in treated and controls (2232 +/- 210 IU and 2011 +/- 232), as was the ratio of CK released to that depleted from the myocardium (0.15 +/- 2% vs 0.15 +/- 3%). Our results indicate: (1) HBO does not reduce infarct size produced experimentally in the conscious dog; (2) HBO does not affect CK release or disappearance; and (3) estimates of infarct size by plasma CK remain valid despite administration of HBO.

Animals↗
PubMed1981

[Compressed spectral EEG analysis in patients with consciousness disorders complicating stroke].

In 26 patients with stroke accompanied by consciousness disorders, 48 monitoring recordings of compressed spectral array of EEG were performed by means of computerised real-time fast Fourier transformation of initial EEG with digital assay of total spectral power and percentage of frequency components in the brain hemispheres. Bilateral increase in the total spectral power and in slow-wave spectral components correlated with diffuse alterations in the initial EEG. 3 types of spectrograms were distinguished in accordance with the degree of consciousness disorders. Possibilities and prospects for application of the new method in patients with stroke are discussed.

Adult↗
PubMedDate not supplied

[Consciousness and evoked cerebral cortical electrical activity].

The analysis of the late positive wave (component P300) of an averaged evoked potential, recorded to visual stimuli in different experimental situations has shown that local activation of the cerebral cortex during conscious experience (Pavlovian "light spot") is of a dynamic nature and is determined by signal significance of stimuli and predominant voluntary activity. In cases when it is necessary to decide on the choice of reaction anterior areas of neocortex are activated. If the function of perception is dominating the local activation essentially occurs in corresponding cortical area at which the perceived stimulus is timed. The cortico-thalamo-cortical mechanism of focused attention and its role in providing for conscious human experience is discussed.

Association↗
PubMed1980

Hemorrhage and regional renal blood flow in the conscious dog.

The effects of hemorrhage on renal blood flow and the extent to which the responses are modulated by prostaglandins were investigated in 23 conscious, splenectomized dogs. Renal blood flows were measured with radioactive microspheres injected into the left atrium. The renal cortex was divided into four layers for studies of regional flow distribution. Sequential hemorrhage of 10 ml/kg, 20 ml/kg, and 30 ml/kg was performed in six dogs. Total renal blood flow did not change at 10 ml/kg or 20 ml/kg blood loss, but at 30 ml/kg, when mean aortic pressure fell by 41 +/- 9 (SE) mm Hg, there was a reduction in total renal flow from 6.09 +/- 1.04 to 3.00 +/- 0.74 ml/min/gm (P < 0.01). No redistribution in renal cortical blood flow occurred at any level of hemorrhage. Meclofenamate--5.0 mg/kg IV--a prostaglandin synthetase inhibitor, induced vasoconstriction without redistribution of cortical flow. When 10 ml/kg blood loss with subsequent reinfusion was studied before and after meclofenamate in nine normal dogs and two dogs with bilateral adrenalectomy and unilateral renal denervation, neither total nor regional renal flow were altered further. Thus, in conscious dogs, hemorrhage has no effect on total renal blood flow until blood volume is reduced by approximately 3% of body weight and renal cortical blood flow is not redistributed. In addition, an inhibitor of prostaglandin synthetase does not influence the renovascular response to hemorrhagic stress, although it increases renal vascular resistance at rest.

Adrenalectomy↗

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