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Biomedical subjects

N Birbaumer

Publications and source records attributed to N Birbaumer.

At least 37 records · Page 2Linked to original sources
PubMed1986

Slow brain potentials and the "tunnel effect".

The present study investigated electrocortical concomitants of the "tunnel effect." The tunnel effect refers to the following perceptual phenomenon: if a continuously moving object disappears behind a shield ("enters a tunnel") the observer has the impression that the same object continues to move with the time point of reappearance usually being underestimated. In the present study, an object moved across a tv-screen for 6 s; it either disappeared behind a shield (tunnel condition), disappeared at once (explosion condition), or remained visible until the end of its trajectory (control condition). Subjects had to press a button whenever they believed that the object had arrived at its trajectory's end. The object's flight was accompanied by a continuously rising slow negative shift of the EEG that resembled the contingent negative variation (CNV). Either type of object disappearance produced a positive-going potential that may reflect brain processes associated with memory rehearsal and/or time estimation. A late P300-like positivity was prominent under tunnel conditions only. Response latency was shorter under disappearance than under control conditions. The positive deflection is discussed as sign of amodal brain processing (memory rehearsal and/or time estimation). The P300-like wave elicited by the object's disappearance activates these memory representations. Based on these considerations, an attempt was made to interpret the premature motor responses, which are commonly observed for tunnel conditions but not for other time estimation tasks.

Brain↗
PubMed1985

An ACTH 4-9 analog impairs selective attention in man.

Male adults were tested in a dichotic listening task, providing electrophysiological measures of selective attention. Subjects were tested twice, 60 min after oral administration of either 40 mg of ACTH 4-9 analog, or placebo. Averaged auditory evoked potentials (AEPs) to tone pips when attended and when unattended, EEG spectra, heart rate and blood pressure, and behavioral performance were measured during task performance. ACTH 4-9 analog treatment impaired selective attention as indicated a) by a diminished difference between evoked potential waveforms to attended and to unattended tone pips, b) by an impaired behavioral signal detection performance. Furthermore, frontal EEG theta activity slowed down after ACTH 4-9 analog. With time on task, however, there was no decay, but an improvement of selective attention after peptide administration. Differences in attention could not be due to concurrent changes in general cortical and autonomic arousal as indicated by EEG alpha activity, blood pressure and heart rate. Since separate analyses of the AEPs revealed an increased processing of the unattended tone pips in the ACTH 4-9 analog sessions the impaired selective attention under ACTH 4-9 analog may be described as an inability to suppress processing of irrelevant or distracting stimuli.

Adolescent↗
PubMed1985

Removal of ocular artifacts from the EEG--a biophysical approach to the EOG.

The present paper describes the propagation of ocular potentials across the scalp on a biophysical basis. It is concluded that 3 EOG derivations (two for EEG records along the midline) are generally necessary to account for ocular disturbances in the EEG. The inadequacy of many methods suggested for EOG artifact control may be due to the false assumption that just one EOG derivation provides enough information to remove ocular potentials from any EEG recording along the mid(-sagittal) line. A comparison of compensation with one or with two EOG derivations is described for a data set of slow brain potentials. A frequency dependence of the ocular influence cannot be neglected, if fast and slow EOG activities have to be removed. The present considerations should allow a more theoretically based decision of the EOG correction method necessary for a certain data set.

Biophysical Phenomena↗
PubMed1985

Asymmetry of brain potentials related to sensorimotor tasks.

The present study investigates the hemispheric specificity of event-related (ERP) and slow potentials (SP) of the brain during preparation and performance of sensorimotor (haptic) tasks. Tasks were selected which have been assumed to be processed primarily by only one brain hemisphere. ERPs, SPs and spontaneous EEGs were obtained from both hemispheres (C3-C4, P3-P4) and from Fz and Cz in a constant foreperiod (6 s) paradigm. Warning and task stimuli comprised up to four tactile stimuli, applied to index and middle finger of each hand. To maximize lateralized processing, the right-hand task required counting, the left hand task pattern matching. Components of the ERP (N1, P3, SW) and of SPs show task-dependent lateral asymmetry with the larger amplitudes contralateral to the preparing and responding hand. Results confirm hemisphere-specific processing of the tactile tasks but quantification as indicated by ERP amplitudes show considerable activity in both hemispheres. The SP-distribution rather reflects task-specific preparation than general alertness or orienting.

Adult↗
PubMed1985

Behavioral method for the treatment of idiopathic scoliosis.

Idiopathic scoliosis was treated by an automated portable posture-training device that incorporated precise behavioral principles and enabled therapeutic training to be given in the patients' normal environment throughout the entire day. Twenty-one patient-years of training were completed with a group of 12 adolescent girls selected as being imminently likely to require a brace because of the way their spinal curves had been progressing. As an alternative to conventional brace therapy, patients found the posture-training device considerably less physically restraining and more cosmetically acceptable. Most patients wore it 23 hr per day for at least 1 year and adapted well to the constant physical and psychological presence of the instrument. For 10 patients, the outcome was entirely successful; they were discharged from this pilot study as satisfactorily corrected. Progression of the scoliotic curve was arrested; in fact, there was an average slight improvement in the Cobb angle (a measure of spinal curvature) as measured by x-ray radiography.

Adolescent↗
PubMed1984

Operant control of EEG and event-related and slow brain potentials.

Research on operant control of brain potentials is reviewed. From single-unit firing and spontaneous EEG activity to event-related potentials such as sensory and pain evoked potentials, and slow potential shifts, most of the aspects of electrical brain activity have been investigated. Results produced by conditioning of spontaneous EEG oscillations (alpha and theta) dampened the early enthusiasm: e.g., no increase above baseline levels could be achieved and no reliable behavioral effects became manifest. Evidence accumulates, however, that operant conditioning of the sensorimotor rhythm (12-15 Hz) may lead to successful self-regulation and that epileptic patients may profit from the training. First steps in the conditioning of brainstem, as well as pain evoked potentials suggest that self-regulation of EPs can be achieved by adequate biofeedback procedures. If some of the observed behavioral effects prove to be stable, the therapeutic usefulness seems to be within reach. A comparable progress has been achieved for the operant control of slow potentials (DC-shifts across seconds). Biofeedback procedures have been used successfully as a scientific tool to achieve systematic variations on a psychological level and to record psychological covariations. This method may provide insights into the behavioral meaning of electrical brain activity.

Biofeedback, Psychology↗
PubMed1983

Evaluation of contingencies and conditional probabilities. A psychophysiological approach to anhedonia.

Slow brain potentials, evoked potentials and autonomic responses were investigated in anhedonic subjects and controls. The distribution of physical anhedonia (PA) scores from different samples (students, soldiers, schizophrenics, depressives) is compared. Within a S1-S2 reaction time paradigm, an additional, S2-similar stimulus was introduced during the anticipation interval in 50% of trials (pseudorandom). Subjects had to press the button only to the S2. The additional stimulus (AS) elicits a distinct positive deflection. Anhedonics show larger pre-AS negativity and less reduction in negativity after the S2 (PINV) than controls. The slow wave to S1 as well as the pre-AS negativity vary with the conditional probability of the AS, but to a lesser extent in anhedonics. Anhedonics provide more preparatory negativity prior to and following ambiguous or difficult discrimination tasks, but at the frontal site. Results may suggest impaired contingency evaluation in anhedonic subjects.

Adolescent↗
PubMed1983

Distractability under the influence of an ACTH 4-9 derivative.

Event-related brain potentials, autonomic responses, and response latency under distraction conditions served to investigate the effects of an ACTH 4-9 derivative (ORG 2766) on attention. Male volunteers (45) received either 40 mg ORG 2766 or placebo in a double-blind setting. Two-stimulus trials with acoustic warning signal (S1) and acoustic S2 which had to be interrupted by immediate button press, preceded trials with distraction during the warning interval in 50% of the trials. A final period without distraction served to test for rebound effects. A reduction in early CNV was found in placebo subjects under distraction, while subjects under ORG 2766 showed no reduced early negativity, but increased late negativity under this condition. Peptide subjects differed from controls in evoked potential components, showing enhanced N1 and P3 amplitudes. Activity in the alpha band was elevated. Postexperimental systolic blood pressure was raised by 15 mm Hg under ORG 2766. Results are in agreement with previous findings and suggest ORG 2766 effects on distraction resistance and attention fixation.

Adrenocorticotropic Hormone↗
PubMed1982

EEG and slow brain potentials during anticipation and control of painful stimulation.

Cerebral responses in anticipation of painful stimulation and while coping with it were investigated in a "fakir" and 12 male volunteers. Experiment 1 consisted of 3 periods of 40 trials each. During period 1, subjects heart one of two acoustic warning stimuli of 6 sec duration signalling that either an aversive noise or a neutral tone would be presented at S1 offset. During period 2, subjects were asked to use any technique for coping with pain that they had ever found to be successful. During period 3, the neutral S2 was presented simultaneously with a weak electric shock and the aversive noise was presented simultaneously with a strong, painful shock, again under pain copying instructions. EEG activity within the theta band increased in anticipation of aversive events. Theta peak was most prominent in the fakir's EEG. A negative slow potential shift during the S1-82 interval was generally more pronounced in anticipation of the aversive events that the neutral ones, even though no overt motor response was required. Negativity tended to increase across the three periods, opposite to the usually observed diminution. In Experiment 2, all subjects self-administered 21 strong shock-noise presentations. The fakir again showed more theta power and more pronounced EEG negativity after stimulus delivery compared with control subjects. Contrary to the controls, self-administration of shocks evoked a larger skin conductance response in the fakir than warned external application.

Adult↗
PubMed1980

Biofeedback of slow cortical potentials. I.

An experiment was performed to investigate the self-regulation of slow cortical potentials (SCP) found in a previous study (Elbert et al. 1979). Seventeen subjects received continuous visual feedback of their actual cortical shift perceptible as a rocket moving across a TV-screen during intervals of 6 sec; subjects had to direct the rocket into one of two goals representing more or less cortical negativity, depending on the pitch of two signal tones. Within two identical experimental sessions feedback trials alternated with test trials without feedback. Highly significant differences of SCP between the two required polarities were demonstrated. The most pronounced differences were observed during test trials without feedback of the second session in which a positive shift below baseline level occurred when positivity (or less negativity) was required.

Adult↗
PubMed1980

Biofeedback of slow cortical potentials. II. Analysis of single event-related slow potentials by time series analysis.

A single trial analysis of slow cortical potentials treating the EEG as a time series was developed. The method was applied to data resulting from an experiment on self-regulation of slow cortical potentials (SCP). Parametric models of the EEG were developed on the basis of autoregressive filter models and a two-component model of SCP (during 6 sec intervals), taking into account ocular influences as a further parameter. Results from different models were compared with each other and with results of averaging SCP data. For the present data time series analysis and traditional analysis provided qualitatively equal results, but fewer trials were necessary for analysis in the single trial approach and more detailed structures of the data became evident. If the EEG was filtered above 5 Hz it could be described by an autoregressive filter model of low order. Ocular influences were estimated as too small in a non-filtered EEG compared to the filtered EEG.

Biofeedback, Psychology↗