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Biomedical subjects

N Birbaumer

Publications and source records attributed to N Birbaumer.

At least 109 records · Page 6Linked to original sources
PubMed1997

High-frequency brain activity: its possible role in attention, perception and language processing.

Coherent high-frequency neuronal activity has been proposed as a physiological indicator of perceptual and higher cognitive processes. Some of these processes can only be investigated in humans and the use of non-invasive recording techniques appears to be a prerequisite for investigating their physiological substrate in the healthy human brain. After addressing methodological issues in the non-invasive recording of high-frequency responses, we summarize studies indicating co-occurrence of neuronal synchrony of single cells exhibiting rhythmic activity at high frequencies, oscillations in the local field potential and dynamics in high frequencies recorded using high-resolution electroencephalography (EEG) and magnetoencephalography (MEG). We then review EEG and MEG studies of attention, perception, and language processing in humans indicating that dynamics in the high-frequency range > 20 Hz reflect specific cognitive processes. Types of high-frequency (HF) activity can be distinguished according to their latency after stimulus onset, stimulus-locking, cortical topography and frequency. There appears to be a systematic relationship between specific cognitive processes and types of HF activity. The findings are related to recent theories about the generation of HF activity and their possible role in binding of stimulus features. Dynamics of HF cortical activity reflecting higher cognitive processes can be accounted for based on the assumption that the elements of cognitive processing, e.g. visual objects and words, are organized in the brain as distributed neuronal assemblies with defined cortical topographies generating well-timed spatio-temporal activity patterns.

Arousal↗
PubMed1997

The relationship of phantom limb pain to other phantom limb phenomena in upper extremity amputees.

In thirty-two unilateral upper extremity amputees with and without phantom limb pain, various phantom limb phenomena were investigated. In general, the incidence of non-painful phantom limb sensations was higher in patients with phantom limb pain than in pain-free amputees. Kinesthetic and kinetic phantom limb sensations were reported more frequently than exteroceptive cutaneous sensations. There was a significant positive correlation between phantom limb pain and stump pain. Patients more frequently assigned sensory than affective pain qualities to their phantom limb pain, whereas no differences between pain qualities were observed for stump pain. No support was found for a relationship between the presence of telescoping (i.e., shrinkage of the phantom limb) and phantom limb pain. These findings point to central as well as to peripheral factors contributing to phantom limb pain.

Adult↗
PubMed1997

A new method for self-regulation of slow cortical potentials in a timed paradigm.

A new method of slow cortical potential (SCP) biofeedback is described, in which subjects were presented with a sequence of two alternating tones. Subjects learned to adjust their SCPs with the 4-s rhythm of presented tones by producing directed SCP changes only in certain inter-tone intervals. Specifically, they learned to simultaneously produce two EEG signals: 1) positive or negative SCP shift at vertex, and 2) SCP asymmetry between the right and the left central area. After one training session, 13 healthy participants were able to differentiate significantly between the negativity and the positivity conditions; this differentiation was achieved within less than 300 ms after the discriminative signal, i.e. much faster than in previous studies employing traditional SCP biofeedback technique. However, these participants did not produce a significant hemispheric asymmetry in the first session. In the second experiment, five subjects participated in prolonged training (6 to 17 sessions). Highly significant control of SCP asymmetry over the precentral cortex was attained in four out of five participants. Advantages and disadvantages of the new method as compared with the "classical" SCP biofeedback technique are discussed.

Adolescent↗
PubMed1997

Behavioral and neurophysiological evidence for altered processing of anxiety-related words in panic disorder.

Body-related and nonsomatic words were presented tachistoscopically to 15 panic patients and 15 healthy controls at each participant's threshold for correctly identifying 50% of neutral words. Behavioral (proportion of words correctly recognized) and electrocortical (event-related brain potentials [ERPs]) measures were registered. Panic patients recognized more body-related than nonsomatic words, and body-related as compared with nonsomatic words elicited, in these patients, significantly larger P300 amplitudes and enhanced positive slow waves (600 to 800 ms after stimulus presentation). In healthy controls, the number of correct recognized words and the ERPs were not differentially affected by the 2 word types. These results are grossly consistent with cognitive models of panic disorders, assuming that certain bodily sensation are perceived and processed in an affective manner that differentiates panic patients from healthy controls.

Adult↗
PubMed1997

Cerebral processing of words and the development of chronic pain.

The processing of pain-related, body-related, and neutral words was assessed in individuals with prechronic pain and matched healthy controls. Integrated surface electromyogram, heart rate, skin conductance level, and visual event-related potentials from 11 electrode sites were recorded during the presentation of three word types at perception threshold. Startle responses were recorded from words presented above perception threshold. The patient and control groups did not differ in recognition performance. Pain-related words evoked an enhanced early component (N100) of the visual event-related potential only in the prechronic pain group. In both groups the late slow wave and the startle response were enhanced for body- and pain-related words compared with those for neutral words. All word types elicited larger late positivities in the prechronic pain group and in the right compared with the left hemisphere. These data suggest differential cortical processing of pain-related material in persons at a prechronic pain stage.

Adult↗
PubMed1997

Probe P3 and blinks: two measures of affective startle modulation.

Two concurrent measures of the evoked startle response, the elicited blink reflex and the event-related potential, were measured while individuals viewed pictures that varied in pleasure and arousal. Replicating previous findings, the blink response was modulated by picture pleasantness, with larger reflexes elicited in the context of viewing unpleasant versus pleasant pictures. However, the probe P3 was primarily modulated by picture arousal, with smaller P3 responses elicited when viewing affective (pleasant or unpleasant) than when viewing neutral pictures. Both modulatory effects were sustained for probes presented in a subsequent picture imagery period. These data suggest that two measurable responses to the same startle probe are differentially modified by emotional context, with blink magnitude varying with pleasure and probe P3 varying with stimulus arousal.

Adult↗
PubMed1997

[What are you doing when you are doing nothing? ERP components without a cognitive task].

Two experiments, an "active" and a "passive" oddball-paradigm (1. phase) with visual and auditive stimuli were performed. In both, two stimuli with a probability of 0.7/0.3 were presented. The oddball-sequence was replaced in the 2. phase without knowledge of the subjects by a sequence, in which only targets were presented. One group of the subjects has got an active task (counting the rare stimulus), the other group was told to view the stimuli passively. The rare stimulus in the oddball-sequence evoked a larger parietal P3, the auditive stimulation additionally a larger fronto-central N1 and the visual stimulation a larger central P2. The non-expected change into the 2. phase resulted in a reverse of the ERP-lateralization between 150-300 ms: Before the change of the probability the amplitudes were more negative left than right, thereafter more negative right than left. All components and effects in the active task maintained without task, but they decreased. The differences were larger with the visual stimuli. These results suggest, that the passive paradigm could be applied to patients with motoric deficits. From a theoretical point of view these results lead to certain difficulties in the interpretation of the functional importance of the P3. It can be explained better by the context-closure theory (Desmedt, 1980; Verleger, 1988) than by the context-updating theory (Donchin, 1981).

Adult↗
PubMed1996

Self-regulation of interhemispheric asymmetry in humans.

Five healthy right-handed subjects learned to control hemispheric asymmetry with biofeedback of the amplitude difference of slow cortical potentials between the left and the right precentral areas. Six training sessions were conducted with subject I, 12 sessions with subjects II and III, and 14 sessions, with subjects IV and V. Performance of four out of five subjects improved continuously as a function of sessions. Towards the end of training, these subjects demonstrated highly significant differentiation between conditions where right versus left precentral negativity was required. In subject V, no improvement was observed after 14 training sessions. The data indicate that most subjects can learn to self-generate fast electroencephalograph (EEG) differences between the left and the right sensorimotor cortical regions.

Adolescent↗
PubMed1996

Slow potentials, event-related potentials, "gamma-band" activity, and motor responses during aversive conditioning in humans.

We examined slow potentials, transient event-related potentials, and oscillatory-like responses in the electroencephalogram during aversive conditioning in humans, in order to determine what is happening in the neocortex when behavioral adaptations are learned. Pictures of an angry and a happy human face served as reinforced (CS+) and unreinforced (CS-) conditioned stimuli, respectively, in one group, and either the reversed condition or two discriminably different neutral faces in two other groups (total n = 48 subjects). The unconditioned stimulus (US) was intracutaneous shock delivered to the left hand 5 s after CS+ onset. The electroencephalographic (EEG) activity was recorded from Fz, Cz, Pz, C3, and C4, electromyographic (EMG) activity from bilateral forearm and corrugator muscles, and skin conductance from the right hand. During acquisition a negative slow potential developed after CS+ (not CS-), which was more pronounced when a neutral face served as CS+. Early (iCNV, initial contingent negative variation) and late (tCNV, terminal contingent negative variation) components of the slow-potential response were positively related to the magnitude of conditioned EMG responses. Differentiation of tCNV was larger when neutral faces signaled the US; iCNV persisted during extinction when a happy face served as CS+. Late-occurring event-related potentials (ERPs) elicited by the US diminished over conditioning, whereas short-latency US components and ERPs elicited by CS events did not. Fourier analysis revealed oscillatory ("gamma-band") activity between 30 and 40 Hz, which persisted up to 3 s after US delivery and diminished as conditioning progressed. Our findings indicate that learning is expressed in neocortical structures at the earliest stages of conditioning. The functional roles of the three types of EEG response in learning are discussed.

Adult↗
PubMed1996

Loss of tolerance to morphine after a change in route of administration: control of within-session tolerance by interoceptive conditioned stimuli.

Tolerance to morphine analgesia (tail-immersion test) was examined after manipulation of two aspects of a tolerance test: 1) the route of drug administration and 2) the time interval between the test dosing and the tolerance test. The intravenous (IV) and intraperitoneal (IP) routes were used, together with a novel test for tolerance in which the test morphine was infused IV just 2 min before measuring the opiate effect. The first experiment validated this test as an assay for tolerance by examining the log dose-response (LDR) curve changes produced by daily IP injection with 0, 20 or 200 mg/kg morphine; the IV test confirmed the expected parallel shift to the right and flattening of the LDR curve. In the second experiment, all rats of two groups were injected once daily for 3 weeks with 20 mg/kg morphine and with saline except that one group received the morphine IV (and saline IP), the other morphine IP (saline IV). The results indicated route-specific tolerance. On a test using 20 mg/kg given IV morphine, tolerance was significantly greater in rats treated with IV morphine than in those treated IP. However, a larger effect on tolerance was produced by a pretest application of 5 mg/kg morphine 30 min before the actual tolerance test. This manipulation was designed to "prime" short-term, adaptive processes hypothesized to occur within a normal tolerance test session as morphine is taking effect. The tolerance on the test increased (equivalent to 2 to 3 fold shift in the LDR curve) when the pretest morphine was given with the same route as the chronic morphine, regardless of treatment group. It was concluded that opiate tolerance may be modulated by conditioned stimuli produced by morphine acting through different routes. These interoceptive cues appear to modulate rapidly acquired and short-lived adaptive processes taking place within a given test session.

Analgesics, Opioid↗
PubMed1996

High-frequency cortical responses reflect lexical processing: an MEG study.

Meaningful words and matched pseudowords, such as moon vs. noom, are of equal perceptual complexity, but invoke different cognitive processes. To investigate high-frequency cortical responses to these stimuli, biomagnetic signals were recorded simultaneously over both hemispheres of right-handed individuals listening to words and pseudowords. Consistent with earlier EEG studies, evoked spectral responses recorded from the left hemisphere revealed depression of spectral power in the low gamma band (around 30 Hz) after pseudowords but not after words. Similar differences between stimulus categories were present in the beta range. These results indicate that distinct patterns of high-frequency cortical responses correspond to the different cognitive processes invoked by words and pseudowords. It is hypothesized that differential high-frequency cortical responses signal the activation or activation failure of distributed Hebbian cell assemblies representing words and other elements of cognitive processing.

Adult↗
PubMed1996

P3 and contingent negative variation in Parkinson's disease.

Patients with idiopathic Parkinson's syndrome, most of them in early stages of the disease, and matched healthy controls participated in a continuous performance task while their EEGs were recorded from 15 electrodes. During preparation of movements, a contingent negative variation (CNV) maximal at central and posterior sites was visible. This CNV was reduced in the patient population. A large P3-like positive deflection occurred after go and no-go stimuli that called for execution (go) or suppression (no-go) of a button press. Compared to healthy controls, the positive wave in Parkinson patients was significantly reduced after go stimuli and maximally attenuated when no-go stimuli had indicated to suppress the motor response. In contrast, P3 amplitudes after irrelevant "ignore' stimuli was not significantly reduced in the patients. These results are interpreted in the framework of a model of striatal function postulating (i) that populations of cortical and striatal neurons form distributed functional units (Hebbian cell assemblies), and (ii) that mutual inhibition between such cortico-striatal cell assemblies is mediated by the neostriatum, the forebrain structure primarily affected in Parkinson's disease.

Behavior↗
PubMed1996

Evidence for a change in neural processing in phantom limb pain patients.

The present study was designed to investigate differences in neural processing of pain-related semantic information in amputees with and without chronic phantom limb pain and healthy controls. One-hundred-and-twenty words (40 neutral, 40 body-related, 40 pain-related) were presented in pseudorandom order to probe group differences in the perception of pain-related information. Visual evoked potentials (VEP) to the words were recorded from 11 scalp locations, EMG was measured at the stump and the contralateral side and bilaterally from the M. corrugator. In addition, heart rate and skin conductance responses were obtained. Both early and late VEP components were altered. Pain-free amputees showed a reduced N100 amplitude compared to phantom limb pain patients and healthy controls whereas the phantom limb pain patients displayed a significantly enhanced late positivity (500-800 msec after word onset). VEP components were unaffected by word type. The peripheral EMG responses were significantly different among the groups: phantom limb pain patients showed larger EMG reactions on the stump than on the contralateral side, whereas pain-free amputees showed the opposite effect. The data suggest an enhanced central and peripheral processing of visual stimuli in phantom limb pain patients.

Adult↗
PubMed1996

Age increases brain complexity.

This study investigated age-related changes in the human brain function using both traditional EEG analysis (power spectra) and the correlational dimension, a measure reflecting the complexity of EEG dynamics and, probably, the complexity of neurophysiological processes generating the EEG. Assuming that the accumulation of individual experience is determined by the formation of functionally related groups of neurons showing a repetitive synchronous activation (cell assemblies), an increase in the number of such independently oscillating cortical cell assemblies can be expected, despite a decline of some metabolic and memory functions with normal ageing. Thus, the "wisdom of old age' may find its neurophysiological basis in greater complexity of brain dynamics compared to young ages. The experimental hypothesis was that EEG dimension steadily increases with age. In order to test this hypothesis the resting EEGs of 5 age groups from 7 to 60 were analysed. The results confirm the hypothesis: after a jump in the brain dynamics complexity during puberty a linear increase with age is observed. During maturation (7-25 years), the maximum gain in complexity occurs over the frontal associative cortex.

Adolescent↗
PubMed1996

Self-regulation of slow cortical potentials in epilepsy: a retrial with analysis of influencing factors.

Twenty sessions of biofeedback training were carried out with 12 drug-resistant patients with focal epilepsy who learned to produce either negative or positive shifts of their slow cortical potentials (SCPs) at vertex. Feedback trials were interspersed with transfer trials in which only a discriminative stimulus (signalizing whether positivity or negativity was required) was presented, without feedback signal. Patients were able to differentiate significantly between the conditions of cortical positivity and cortical negativity, with larger differentiation scores being obtained in feedback trials than in transfer trials. The amplitude of positivity generated in the positivity condition increased linearly across sessions both in feedback and in transfer trials. The largest negativity was produced in the 5th session; after this, more transient negativities were generated, whose amplitude decreased towards the end of trial. The mean severity of seizures, estimated as the frequency of seizures weighted by their subjective 'strength', decreased significantly after training as compared to the pre-training phase. The data suggest that (1) patients could learn to achieve a state of cortical disfacilitation and (2) with progressed learning, they became less motivated for (or afraid of) producing considerable negative shifts, since extensive negativity may reflect cortical over-excitation and therefore be associated with early signs of seizures. The inability of producing cortical negativity is however not necessarily a bad predictor.

Adult↗
PubMed1996

Semantic memory impairment in Alzheimer's disease.

The present study investigated semantic memory and the presence of category-specific impairments in patients with dementia of the Alzheimer's type (DAT). Patients in advanced stages of Parkinson's disease (PD) and matched control subjects served as comparison groups. Semantic memory was assessed by a range of verbal and visual tasks and by direct and indirect memory tests. The DAT patients showed severe deficits on all semantic knowledge tasks. Performance was poorer on animate relative to inanimate items, on naming with and without cues, and on semantic knowledge probes, indicating a category-specific knowledge loss on these tasks. Indirect memory tests yielded significantly better preservation of knowledge compared to the traditional semantic memory tasks. Analyses of the nature of the semantic breakdown in DAT suggested combined storage and access deficits and a disturbance of the structural description and phonological output systems.

Aged↗
PubMed1996

Startle reflex and emotion modulation impairment after a right amygdala lesion.

In the present study, startle responses during resting states as well as during the presentation of a set of emotive slides were recorded from a 32-year-old male patient with a rare localized lesion of the right amygdala. The startle reflex is a response modulated by affective states: it has been reliably used in the literature to measure the aversiveness of emotive stimuli. The animal literature has shown that the circuit of this reflex is directly influenced by amygdala projections. The startle responses of the patient were compared with those of eight age-matched normal subjects. The patient's startle amplitudes showed an overall impaired response and an inhibited reflex contralateral to the lesion. In addition, he failed to show the typical startle potentiation induced by an aversive emotive background. The data confirm, in the human, previous results from the literature in other species on amygdala involvement in startle and emotional responses. Furthermore, the observation of the importance of the right amygdala in the modulation of emotion is consistent with the hypothesis of right hemisphere specialization for aversive emotions. The results are discussed in the context of the literature on human amygdala lesions.

Adult↗