Biomedical subjects

N Birbaumer

Publications and source records attributed to N Birbaumer.

At least 145 records · Page 8Linked to original sources

PubMed1994

Words and pseudowords elicit distinct patterns of 30-Hz EEG responses in humans.

Meaningful words, such as moon, and physically similar but meaningless pseudowords, such as noom, were presented visually in a lexical decision task. The EEG was recorded from 17 scalp electrodes. Significant differences between both stimulus classes were observed in evoked spectral responses of the 'gamma-band' approximately 30 Hz. A hemisphere by wordness interaction demonstrated that 30-Hz spectral power over the left hemisphere was reduced after pseudowords only. These results indicate that gamma-band responses reflect the different cognitive processes induced by words and pseudowords. A possible explanation is the following. Synchronous activation of large cortical cell assemblies takes place after word presentation but not after presentation of pseudowords.

Brain↗

PubMed1994

Central effects of baroreceptor activation in humans: attenuation of skeletal reflexes and pain perception.

Activating the arterial baroreceptors blunts pain sensation and produces other forms of central nervous system inhibition in animals. These effects may be important to blood pressure regulation but have not been rigorously verified in humans. We describe (i) a noninvasive behaviorally unbiased method for baroreceptor stimulation and (ii) the application of this method to measurement of baroreceptor-mediated attenuation of pain perception and of the Achilles tendon reflex. The findings are relevant to basic mechanisms of blood pressure stabilization and cardiovascular reactivity and may also have implications for noncompliance with antihypertensive medications and for the pathophysiology of essential hypertension.

Achilles Tendon↗

PubMed1994

Slow cortical potential biofeedback and the startle reflex.

The negativity of slow cortical potentials (SCP) of the surface EEG is a measure of brain excitability, correlating with motor and cognitive preparation. Self-control of SCP positivity has been shown to reduce seizure activity. Following SCP biofeedback from a central EEG electrode position, subjects gained bidirectional control over their SCP. The current study used a modified feedback methodology, and found a positive relationship between negativity and magnitude of EMG startle response (a measure of cortical and subcortical arousal, particularly aversive response disposition). Greater success in SCP differentiation was associated with self-report of less relaxation during negativity training.

Adult↗

PubMed1994

Positive shifts of event-related potentials: a state of cortical disfacilitation as reflected by the startle reflex probe.

Cortical positivity as measured by slow event-related potentials is assumed to represent a decreased excitability of cortical networks and suppression of their behavioral-cognitive output. The blink reflex probe is a commonly used defensive electromyographic response whose amplitude was shown to be modulated by emotional and attentional orientation. It was used here as an indicator of cortico-subcortical excitation. In study 1, 33 healthy subjects took part in a continuous performance test (CPT). Event-related potentials were recorded from 15 standard scalp locations. Acoustic startling noise bursts were delivered during conditions that required either performance of prepared motor responses (Go), inhibition of prepared motor responses (NoGo), or had no motor significance (Irrelevant condition). During the NoGo condition, EEG surface potentials showed a widespread P300-like positivity with a central maximum. Startle responses were inhibited during the NoGo condition as compared to the Irrelevant condition. In study 2 (21 subjects) the same format was used, except that the startle reflex was elicited visually. Startle reflexes again showed smaller magnitude during the NoGo condition, which evoked larger positivity at central sites in comparison to the Irrelevant condition. The relationship between positivity in the EEG and inhibited startle responses is in line with the hypothesis that positive EEG shifts reflect a state of cortical disfacilitation.

Acoustic Stimulation↗

PubMed1994

Behavioral treatment of scoliosis and kyphosis.

A behavioral treatment of scoliosis and kyphosis was tested with 27 adolescent patients (19 scoliosis, eight kyphosis patients) to determine in which cases the conspicuous and restraining brace treatment could be replaced. In 22 compliant patients, posture biofeedback (PB) was highly effective compared to five non-compliant patients. Biologically more mature scoliosis patients (menarche at the beginning of treatment) seemed to profit more from PB. With kyphosis patients the PB treatment resulted in rapid straightening of the spine and removal of structural deformities of Scheuermann's disease. PB may serve as an unobtrusive yet effective treatment alternative for both juvenile scoliosis and kyphosis.

Adolescent↗

PubMed1994

Mapping P300 waves onto inhibition: Go/No-Go discrimination.

Subjects viewed letters presented at 2 sec intervals and prepared a fast button press whenever an "O" appeared. If the next letter was an "X" the button press was executed (Go signal), but if the letter was a non-X character (T, H, Z) suppression of the response was required (No-Go cue). No-Go signals elicited a P300-like wave that was larger at central and frontal scalp sites contralateral to the prepared movement, compared to P300s elicited by Go cues which were symmetric about the sagittal midline and dominant at parietal sites. Subtraction of preparatory CNVs from the No-Go P300 did not remove differences in scalp topography, or reduce the amplitude of the No-Go P300 to that seen following control letters that required perceptual identification but did not call for suppression of prepared motor responses. Principal components analysis identified a middle positive wave following X-alone control stimuli whose topography resembled the No-Go P300. These findings suggest that the source of augmented No-Go P300s is a generator involved with sensorimotor inhibition. We discuss the mechanism of P300 waves and evidence linking these waves with inhibition in other task arrangements.

Adult↗

PubMed1994

Neurophysiological differences between perception and imagery.

The present study was designed to examine brain activity underlying mental imagery is conceptualized as behavior guided by internal representation only, the activity of the prefrontal lobes was assumed to be a measure of differentiation of imagery from perception. Twenty-one subjects were requested to observe and imagine a swinging pendulum and to touch and imagine a coshball in separate trials. The EEG was recorded from 15 standard electrode sites and analyzed with (1) traditional alpha power and (2) an estimation of dimensional complexity (a measure derived from nonlinear dynamics). Both EEG measures revealed expected object-related differences during perception as well as during imagery. The visual pendulum showed relative to the tactile coshball increased dimensional complexity and less alpha power at parietal and frontal sites. However, only the EEG dimension supported the main hypothesis: Imagery resulted in increased prefrontal dimensional complexity in comparison to perception independent of the modality of the image. In contrast, for alpha power the difference between imagery and perception was due to stimulus modality.

Adolescent↗

PubMed1994

Brain potentials during mental arithmetic: effects of extensive practice and problem difficulty.

Recent behavioral investigations indicate that the processes underlying mental arithmetic change systematically with practice from deliberate, conscious calculation to automatic, direct retrieval of answers from memory [Bourne, L.E.Jr. and Rickard, T.C., Mental calculation: The development of a cognitive skill, Paper presented at the Interamerican Congress of Psychology, San Jose, Costa Rica, 1991: Psychol. Rev., 95 (1988) 492-527]. Results reviewed by Moscovitch and Winocur [In: The handbook of aging and cognition, Erlbaum, Hillsdale, NJ, 1992, pp. 315-372] suggest that consciously controlled processes are more dependent on frontal lobe function than are automatic processes. It is appropriate, therefore to determine whether transitions in the locus of primary brain activity occur with practice on mental calculation. In this experiment, we examine the relationship between characteristics of event-related brain potentials (ERPs) and mental arithmetic. Single-digit mental multiplication problems varying in difficulty (problem size) were used, and subjects were trained on these problems for four sessions. Problem-size and practice effects were reliably found in behavioral measures (RT). The ERP was characterized by a pronounced late positivity after task presentation followed by a slow wave, and a negativity during response indication. These components responded differentially to the practice and problem-size manipulations. Practice mainly affected topography of the amplitude of positivity and offset latency of slow wave, and problem-size mainly offset latency of slow wave and pre-response negativity. Fronto-central positivity diminished from session to session, and the focus of positivity centered finally at centro-parietal regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Category-specific semantic impairment in Alzheimer's disease and temporal lobe dysfunction: a comparative study.

In this paper we report an in-depth case study of a patient suffering from Alzheimer's disease who presented with a category-specific disorder relating to processing of knowledge about animate objects in the presence of spared knowledge of inanimate objects. Impairments appeared not only in a confrontation naming task but also on a range of visual knowledge tasks, such as drawing from memory or part-whole matching. The pattern of impairment was compared to that shown by a post-encephalitic patient who manifested a well-documented category-specific deficit for animate objects. Both patients' performance was compatible with an interpretation in terms of impairment at the level of the structural description of objects within the semantic system, as general encyclopaedic knowledge was largely preserved. Temporal lobe damage may be the cause of memory breakdown in both patients.

Adult↗

PubMed1994

Effects of PRES baroreceptor stimulation on thermal and mechanical pain threshold in borderline hypertensives and normotensives.

Prior studies have noted a pain relieving effect of baroreceptor stimulation and of higher tonic blood pressure in animals and humans. The present study used a new technique for the controlled, noninvasive stimulation of human carotid baroreceptors (PRES). PRES baroreceptor manipulation was delivered to both normotensive subjects (n = 11) and medication-free labile hypertensive subjects (n = 10) during both thermal and mechanical pain. Consistent with prior research, hypertensives had a higher threshold for thermal pain than did normotensives. PRES baroreceptor manipulation had no significant effect on thermal pain threshold for either group. For the mechanical pain model, the opposite results were obtained; group pain thresholds did not differ, but there was a significant PRES baroreceptor stimulation effect of increasing pain threshold for both groups. Results are discussed in terms of specific features of the stimuli, dampening of pain in hypertensives, and adaptation to pain.

Adult↗

PubMed1994

Chaos and physiology: deterministic chaos in excitable cell assemblies.

In this review we examined the emerging science of deterministic chaos (nonlinear systems theory) and its application to selected physiological systems. Although many of the popular images of fractals represent fascination and beauty that by analogy corresponds to nature as we see it, the question remains as to its ultimate meaning for physiological processes. It was our intent to help clarify this somewhat popular, somewhat obscure area of nonlinear dynamics in the context of an ever-changing procedural base. We examined not only the basic concepts of chaos, but also its applications ranging from observations in single cells to the complexity of the EEG. We have not suggested that nonlinear dynamics will answer all of our questions; however, we did attempt to illustrate ways in which this approach may help us to answer new questions and to rearticulate old ones. Chaos is revolutionary in that the overall approach requires us to adopt a different frame of reference which, at times, may move us away from previous concerns and methods of data analysis. In sections I-IV, we summarized the nonlinear dynamics approach and described its application to physiology and neural systems. First, we presented a general overview of the application of nonlinear dynamical techniques to neural systems. We discussed the manner in which even apparently simple deterministic systems can behave in an unpredictable manner. Second, we described the principles of nonlinear dynamical systems including the derived analytical techniques. We now see a variety of procedures for delineating whether frenetic chaotic behavior results from a nonlinear dynamical system with a few degrees of freedom, or whether it is caused by an infinite number of variables, i.e., noise. Third, we approached the applications of nonlinear procedures to the cardiovascular systems and to the neurosciences. In terms of time series, we described initial studies which applied the now "traditional" measures of dimensionality (e.g., based on the algorithm by Grassberger and Procaccia) and information change (e.g., Lyapunov exponents). Examples include our own work and that of Pritchard et al., demonstrating that the dynamics of neural mass activity reflect psychopathological states. Today, however, the trend has expanded to include the use of surrogate data and statistical null hypotheses testing to examine whether a given time series can be considered different from that of white or colored noise (cf. Ref. 262). One of the most important potential applications is that of quantifying changes in nonlinear dynamics to predict future states of the system.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1994

Sensory effects of baroreceptor activation and perceived stress together predict long-term blood pressure elevations.

Activating the arterial baroreceptors in animals has been shown to blunt pain sensation and provide other forms of central nervous system inhibition. This study tested the hypothesis that, among human subjects, a tonic increase in blood pressure (BP) could be a learned response to environmental stressors among subjects in whom the baroreceptor inhibitory mechanism is active. In a sample of 96 healthy, normotensive men and women, amount of pain-reduction produced by baroreceptor stimulation predicted an increase in resting BP 20 months later: the increase was proportional to self-assessed daily life stress. Among the subjects reporting the greatest amount of stress, the pain inhibition effect accounted for more than 80% of the BP variance. These results support the hypothesis that the reduction in perceived stress produced by baroreceptor stimulation may reward learned increases in BP.

Journal Article↗

PubMed1993

Comparison of a mechanized version of the 'König' reaction and a fluorescence polarization immunoassay for the determination of nicotine metabolites in urine.

Smoking can be detected by the determination of cotinine in urine. We compared the performance of an automated modification of the 'König' reaction adapted to a centrifugal analyzer with an automated commercial fluorescence polarization immunoassay (TDX system). In the latter assay, cotinine, as the primary metabolite of nicotine, can be measured with high specificity. In contrast, the 'König' reaction also detects nicotine metabolites other than cotinine by a group colour reaction. Analysis speed of the 'König' reaction was about 66 samples/h with a detection limit 2 S.D. above the mean value of urine samples of non-smokers. Analysis speed of the TDX system was 41 samples/h. The coefficient of variation (C.V.) of both methods in smokers' urine was 8.6% ('König' reaction) vs. 3.4% (TDX system) in the high range and 16.4% vs. 9.5% in the low range. In a controlled, prospective study recruiting 86 cigarette-smoking volunteers, 83.7% were correctly classified as being smokers by both systems, 13.9% were classified as smokers by the 'König' reaction only and 2.4% were misclassified as non-smokers by both systems. Thus, the sensitivity of the 'König' reaction seems to be higher than in the TDX system (97.6% vs. 83.7%). Of 33 non-smoking individuals, 81.8% were correctly classified as non-smokers by both systems, 18.2 were misclassified as smokers by the 'König' reaction and no person was misclassified by the fluorescence polarization immunoassay. Thus, the specificity of the TDX system seems to be higher than that of the 'König' reaction (100% vs. 81.8%). We conclude that both systems are applicable to detect individuals who smoke regularly by simple urine testing. The higher specificity of the TDX system is outweighed by the higher sensitivity of the 'König' reaction at much lower cost.

Autoanalysis↗

PubMed1993

Self-regulation of slow cortical potentials in psychiatric patients: alcohol dependency.

Ten unmediated alcohol-dependent male inpatients participated in a Slow Cortical Potential (SCP) self-regulation task utilizing biofeedback and instrumental conditioning. These patients were hospitalized for treatment of alcohol dependency after chronic abuse of alcoholic beverages. Somatic withdrawal symptomatology had occurred recently and the patients were free of any withdrawal symptoms of the autonomic nervous system. Immediately after hospitalization patients were unable to control their SCPs without the reinforcement of immediate feedback across 4 sessions. Seven patients participated in a fifth session an average of 4 months later. Six out of these 7 patients had not had a relapse at the follow-up. In the fifth session these patients were immediately able to differentiate between the required negativity and negativity suppression, whereas the seventh patient, who had relapsed, was unable to control his brain potentials successfully. Results are further evidence that some of the frontocortical dysfunctions in alcohol-dependent patients are reversible. This could covary with a morphological restitution of the cortex.

Adult↗

PubMed1993

Effects of smoking on thermal pain threshold in deprived and minimally-deprived habitual smokers.

This study examined the antinociceptive effects of smoking in nine habitual smokers under deprived (12 h) and minimally-deprived (< 30 min) conditions. Pain threshold for thermal stimuli, heart rate, blood pressure and ratings of mood, arousal, dominance and well-being were assessed before and after smoking a cigarette. Over-all, smoking affected all measured variables in the expected direction, leading to increased physiological activity, elevated pain threshold and improved mood. However, most of these effects depended on the deprivation status of the subjects, such that smoking after deprivation increased pain threshold whereas smoking after minimal deprivation did not. Pain threshold before smoking was the same for both groups. Deprived subjects had lower pre-smoke diastolic blood pressure, heart rate, and arousal levels, which rose to equal minimally-deprived subjects' scores after smoking.

Adult↗

PubMed1993

Assessment of pain-related cognitions in chronic pain patients.

The construction of the Pain-Related Self Statements Scale (PRSS) and the Pain-Related Control Scale (PRCS) is described. The PRSS assesses situation-specific aspects of patients' cognitive coping with pain, while the PRCS measures general attitudes towards pain. The reliability and validity of these scales were determined in a sample of 120 chronic pain patients suffering from various rheumatic disorders, 213 patients who suffered from chronic back pain, 44 patients with temporomandibular pain and dysfunction and 38 healthy controls. The analysis of the PRSS yielded two scales termed 'Catastrophizing' and 'Coping'; the PRSC consists of the subscales 'Helplessness' and 'Resourcefulness'. All four subscales were demonstrated to be valid and sensitive to change, and they are closely related to pain intensity and interference from pain experiences.

Adaptation, Psychological↗

PubMed1993

Hypochondriacal attitudes, pain sensitivity, and attentional bias.

The relation between hypochondriacal attitudes, thermal pain threshold, and attentional bias toward pain was examined in a non-clinical population (N = 28). Attentional bias was operationalized with a concentration-performance test, which subjects performed while connected to a pain stimulator. Subjects were informed that they would receive a painful stimulus during the second part of the test, while the first part was introduced as pain-free. The pain stimulus was never applied during the test phase. The expectancy of a forthcoming pain stimulus reduced the performance of high hypochondriacal subjects in both parts of the test. Low hypochondriacal subjects, on the other hand, displayed significantly better performance in the first, pain-free compared to the second, pain-related part of the test. Thermal pain thresholds were assessed at four measuring sites (thenar, neck, collar-bone, abdomen), but no relations with hypochondriasis sum scores and locus of pain stimulation were found. A stepwise multiple regression of pain threshold by individual Illness Attitude Scales (IAS) led to 66% of the variance being explained by the scales 'concern about pain', 'worry about illness', and 'disease phobia'. Results are discussed in terms of amplifying somatic style, preoccupation with or attentional bias toward bodily symptoms, and experimental induction of a hypochondriacal state.

Adult↗

PubMed1993

Memory performance and area-specific self-regulation of slow cortical potentials: dual-task interference.

We examined the effect of area-specific feedback for slow potentials on sensorimotor and memory performance under single and dual-task conditions. Subjects observed a memory set for 400 ms and then determined 5 s later whether a target letter had been contained in the original presentation (Sternberg task). After one session of Sternberg-only training, feedback training was added for production of negative and positive slow potentials area-specifically at Fz, Cz or Pz during the 5-s interval separating the memory set and target probes. Addition of the feedback task resulted in an increase in Sternberg response latency and errors which was followed by gradual recovery over five dual-task sessions (recovery not complete for the error measure). Subjects successfully regulated their slow potentials, but only in an area-nonspecific fashion, even though area-specific control was observed in an earlier study under a feedback-only condition. Sternberg performance did not depend on whether slow potential negativity or positivity was produced. These findings indicate that competition between tasks was a more important determinant of performance than was modulation of dendritic polarization by feedback-induced slow potentials.

Adult↗