Biomedical subjects

N Birbaumer

Publications and source records attributed to N Birbaumer.

At least 37 records · Page 2Linked to original sources

PubMed2003

[EEG-based communication--a new concept for rehabilitative support in patients with severe motor impairment].

This paper describes a paralyzed patient diagnosed with severe infantile cerebral palsy, trained over a period of several months to use an EEG-based brain-computer interface (BCI) for verbal communication. The patient learned to "produce" two distinct EEG patterns by mental imagery and to use this skill for BCI-controlled spelling. The EEG feedback training was conducted at a clinic for Assisted Communications, supervised from a distant laboratory with the help of a telemonitoring system. As a function of training sessions significant learning progress was found, resulting in an average accuracy level of 70% correct responses for letter selection. At present, "copy spelling" can be performed with a rate of approximately one letter per minute. The proposed communication device, the "Virtual Keyboard", may improve actual levels of communication ability in completely paralyzed patients. "Telemonitoring-assisted" training facilitates clinical application in a larger number of patients.

Action Potentials↗

PubMed2003

Predictors of successful self control during brain-computer communication.

OBJECTIVES: Direct brain-computer communication uses self regulation of brain potentials to select letters, words, or symbols from a computer menu to re-establish communication in severely paralysed patients. However, not all healthy subjects, or all paralysed patients acquire the skill to self regulate their brain potentials, and predictors of successful learning have not been found yet. Predictors are particularly important, because only successful self regulation will in the end lead to efficient brain-computer communication. This study investigates the question whether initial performance in the self regulation of slow cortical potentials of the brain (SCPs) may be positively correlated to later performance and could thus be used as a predictor. METHODS: Five severely paralysed patients diagnosed with amyotrophic lateral sclerosis were trained to produce SCP amplitudes of negative and positive polarity by means of visual feedback and operant conditioning strategies. Performance was measured as percentage of correct SCP amplitude shifts. To determine the relation between initial and later performance in SCP self regulation, Spearman's rank correlations were calculated between maximum and mean performance at the beginning of training (runs 1-30) and mean performance at two later time points (runs 64-93 and 162-191). RESULTS: Spearman's rank correlations revealed a significant relation between maximum and mean performance in runs 1-30 and mean performance in runs 64-93 (r= 0.9 and 1.0) and maximum and mean performance in runs 1-30 and mean performance in runs 162-191 (r=1.0 and 1.0). CONCLUSIONS: Initial performance in the self regulation of SCP is positively correlated with later performance in severely paralysed patients, and thus represents a useful predictor for efficient brain-computer communication.

Adult↗

PubMed2002

A non-invasive communication device for the paralyzed.

An EEG-based communication system has been developed to re-establish communication in severely paralyzed patients who operate the device by generating shifts of their slow cortical potentials. Training to gain control over slow cortical potentials was based on visual feedback and operant conditioning strategies. The vertical movement of a graphic signal on a computer screen informs the patients about the course of their slow cortical potential amplitude. Positive slow cortical potential shifts move the cursor up, negative shifts move it down. These shifts are then translated into binary responses. When a patient has achieved reliable control over his/her slow cortical potential shifts, these responses can be used to select or reject items presented at the bottom of the screen. As learning processes and applications differ considerably between patients, the present paper describes the data from one patient with amyotrophic lateral sclerosis. After about three months of training, this patient gained stable, near-perfect control over his slow cortical potentials. This skill enabled him to operate a specially designed program to communicate messages to his caregivers.

Adult↗

PubMed2001

Event-related beta desynchronization indicates timing of response selection in a delayed-response paradigm in humans.

Voluntary movements are preceded by event-related desynchronization (ERD) of alpha and beta activity. The present study used magnetoencephalography to investigate the relationship between motor preparation and the time course of beta ERD in a delayed response paradigm. Depending on the task, the required response (left or right finger lifting) was cued either spatially by the lateralization of a sound at trial onset, or verbally by the content of a midline auditory event. Beta ERD appeared over sensorimotor regions contralaterally to the response side about 200 ms earlier for the spatial than the verbal cue task. This suggests a close relationship between the latency of beta ERD onset and the duration of cognitive processes involved in selecting a motor response.

Acoustic Stimulation↗

PubMed2001

Phantom limb pain.

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Electric Stimulation↗

PubMed2001

Early activation of the primary somatosensory cortex without conscious awareness of somatosensory stimuli in tumor patients.

The primary sensory cortex has usually been regarded as a necessary step in the information processing stream leading to conscious awareness. Recently, it has been proposed that that higher order associative areas rather than the primary sensory areas are the neural basis of conscious perception. In two patients with tumors near the central region we recorded magnetic somatosensory evoked fields. Magnetic source imaging revealed early (40 ms) neural activation in primary somatosensory cortex and absence of later (>60 ms) neural activation in the primary and associative areas in these patients. None of the patients showed conscious awareness of somatosensory stimuli applied to the corresponding body site although the first component of the evoked field was within normal limits. The time course of the magnetic responses and additional evidence on intensity ratings of somatosensory stimuli suggest that early activity in the primary somatosensory cortex is not sufficient for conscious experience to emerge.

Adult↗

PubMed2001

Reorganization of motor and somatosensory cortex in upper extremity amputees with phantom limb pain.

Phantom limb pain (PLP) in amputees is associated with reorganizational changes in the somatosensory system. To investigate the relationship between somatosensory and motor reorganization and phantom limb pain, we used focal transcranial magnetic stimulation (TMS) of the motor cortex and neuroelectric source imaging of the somatosensory cortex (SI) in patients with and without phantom limb pain. For transcranial magnetic stimulation, recordings were made bilaterally from the biceps brachii, zygomaticus, and depressor labii inferioris muscles. Neuroelectric source imaging of the EEG was obtained after somatosensory stimulation of the skin overlying face and hand. Patients with phantom limb pain had larger motor-evoked potentials from the biceps brachii, and the map of outputs was larger for muscles on the amputated side compared with the intact side. The optimal scalp positions for stimulation of the zygomaticus and depressor labii inferioris muscles were displaced significantly more medially (toward the missing hand representation) in patients with phantom limb pain only. Neuroelectric source imaging revealed a similar medial displacement of the dipole center for face stimulation in patients with phantom limb pain. There was a high correlation between the magnitude of the shift of the cortical representation of the mouth into the hand area in motor and somatosensory cortex and phantom limb pain. These results show enhanced plasticity in both the motor and somatosensory domains in amputees with phantom limb pain.

Adult↗

PubMed2001

Brain potentials in human patients with extremely severe diffuse brain damage.

To test higher cortical functions of neurological patients, oddball tasks are often used in which a frequent and a rare stimulus are randomly presented and a P3 brain wave is recorded to the rare stimulus. We examined 33 patients with extremely severe brain injury. Three oddball conditions were used: with two sine tones (ST), with two complex tones (CT) and with vowels 'o' and 'i'. Across all patients, CT elicited P3 more often than ST, and the occurrence of the P3 after vowels was intermediate. However, among patients who showed a distinct P3 wave, its amplitude in the subgroup with traumatic brain injury was larger to vowels than to CT. In patients with non-traumatic etiology, CT and vowels elicited a P3 of a nearly equal amplitude. Stimuli of sufficient complexity should be used when the P3 technique is applied for assessment of cortical functions in severely impaired patients.

Adolescent↗

PubMed2001

The effect of opioids on phantom limb pain and cortical reorganization.

The efficacy of oral retarded morphine sulphate (MST) was tested against placebo in a double-blind crossover design in 12 patients with phantom limb pain after unilateral leg or arm amputation. Two counterbalanced treatment phases of 4 weeks each were initiated with an intravenous test infusion of MST or Placebo. The titration phase was 2 weeks. The dose of MST was titrated to at least 70 mg/day and at highest 300 mg/day. Pain intensity was assessed hourly on visual analog scales during a 4-week treatment-free phase, both treatment phases and at two follow-ups (6 and 12 months). Reorganization of somatosensory cortex, electric perception and pain thresholds as well as selective attention were measured pre- and post-treatment. A significant pain reduction was found during MST but not during placebo. A clinically relevant response to MST (pain reduction of more than 50%) was evident in 42%, a partial response (pain reduction of 25-50%) in 8% of the patients. Neuromagnetic source imaging of three patients showed initial evidence for reduced cortical reorganization under MST concurrent with the reduction in pain intensity. Perception and pain thresholds were not significantly altered whereas attention was significantly lower under MST. Thus, opioids show efficacy in the treatment of phantom limb pain and may potentially influence also cortical reorganization. These data need to be replicated in larger patient samples.

Adult↗

PubMed2001

Cerebral activation during anal and rectal stimulation.

While the rectum is innervated by visceral afferents, the anal canal is innervated by the somatosensory pudendal nerve. The representation of these two central domains of intestinal sensations in the human brain is largely unknown. Nonpainful pneumatic stimulation of the anal canal and the distal rectum using event-related functional magnetic resonance imaging (fMRI) was performed in eight healthy subjects. Subjective scaling of sensations revealed no differences in unpleasantness and pain during both stimuli. Both types of stimuli revealed fMRI activation in secondary somatosensory, insula, cingular gyrus, left inferior parietal, and right orbitofrontal cortex. Anal stimulation resulted in additional activation of primary sensory and motor cortex, supplementary motor area, and left cerebellum. We concluded that viscerorectal and somatosensory anal stimulation predominantly differ in their primary sensory activation and additional activation in motor areas. This motor response following aversive somatosensory stimuli may be caused by a reflexive avoidance reaction which is not observed after the more diffuse experienced visceral stimulation.

Adult↗

PubMed2001

[Neural networks and pain processing. New insights from imaging techniques].

Imaging techniques with high spatial and temporal resolution (PET,fMRI, MEG) provide detailed information about the brains' processing of pain. Structures detected by these techniques are not understood as pain centers but as nodal points of a dynamic network which is influenced by physiological and psychological input. Imaging techniques can be used for the investigation of different pain components. The neuronal network that encodes sensory-discriminative information consists of the primary and secondary somatosensory cortex which receive input from lateral thalamic nuclei. Information for the affective pain component reach the anterior cingulate cortex, insula and prefrontal cortex via medial thalamic nuclei. Until now only little is known about cortical structures mediating the cognitive pain component. In chronic pain the cortical and subcortical processing of nociceptive input is presumably modified. Reorganization in the primary somatosensory cortex is presented as an example of neuronal plasticity induced by chronic pain.

Animals↗

PubMed2001

Investigation of brain dynamics in Parkinson's disease by methods derived from nonlinear dynamics.

EEGs were recorded from patients in early stages of Parkinson's disease (17 patients, 9 females) and healthy controls (12 subjects, 8 females) during rest and during execution/imagining of a complex motor task. The prediction that Parkinson's disease patients compared to controls would show more complex brain dynamics during performance of a complex motor task and imagination of the movements was confirmed by methods derived from nonlinear dynamics. In the resting state, analysis of correlation dimension of EEG time series revealed only slight topographical differences between the groups. During performance of a complex motor task, however, data from Parkinson's disease patients showed higher dimensionality than data from controls, indicating more complex EEG time series. The same difference was found when subjects did not perform any motor movements but imagined the complex movements they had just performed. The data are consistent with the hypothesis that the disturbances in Parkinson's disease result in the recruitment of superfluous cortical networks due to failed inhibition of alternative motor programs in the striatum and thus increase the complexity of cortical representation in motor conditions.

Aged↗

PubMed2001

The distribution of mislocalizations across fingers demonstrates training-induced neuroplastic changes in somatosensory cortex.

The somatosensory system has been shown to alter its cortical activation patterns in reaction to changes in the attended sensory input to certain body parts. Whether these modifications in the functional organization of the somatosensory cortex of humans also result in perceptual changes has rarely been investigated. Here we used near-threshold tactile stimuli to the center of the fingertips to evoke mislocalizations to fingers other than the stimulated. In healthy untrained subjects, the distribution of the mislocalizations from each of the fingers was different from a distribution expected if the subjects were purely guessing the position of the stimulus. The digits next to the stimulated one receive a higher number of mislocalizations than digits further away from the stimulated digits. This decrease can be accounted for by digit-overlapping receptive fields in combination with the sequential representation of the digits in the primary somatosensory cortex. In a second experiment subjects received 20 h of simultaneous stimulation of the left thumb and little finger in the context of a perceptual task. For both hands, the distribution of mislocalization from these fingers was analyzed at the beginning and the end of the training. For the left hand, the number of assigned mislocalizations to the most distant neighbor digit (i.e., the simultaneously stimulated digit in the training) increased while the number of mislocalizations toward the direct neighboring digit decreased with the training. This change did not occur in the untrained right hand, or in the untrained subjects. We conclude that the distribution of mislocalization to fingers other than the stimulated can be used to investigate perceptual changes paralleling training-induced modifications in the activation patterns of the somatosensory cortex.

Adult↗

PubMed2001

[Cortical reorganization and pain. Empirical findings and therapeutic implication using the example of phantom pain].

The neuroscientific research of the past years has shown that extensive plastic change occurs in the adult human brain. The functional reorganization of the somatosensory and motor maps related to phantom limb pain is described. Subsequent to deafferentation amputees with phantom limb pain show a shift of neighbouring representation zones into the deafferented zone of the somatosensory and motor cortex that can be detected with noninvasive neuroimaging methods. This reorganization of the sensory and motor maps is not found in painfree amputees and persons with congenital loss of a limb. We discuss a model of the development of phantom limb pain that incorporates both peripheral and central factors and assigns an important role to chronic pain before the amputation. The modulation of plasticity and phantom limb pain by anesthesiological interventions is described and the results of preemptive analgesia for the prevention of phantom limb pain are discussed. Opioid treatment and behaviorally relevant stimulation are effective means to eliminate phantom limb pain and cortical somatosensory pain memories.

Humans↗

PubMed2001

Self-initiation of EEG-based communication in paralyzed patients.

OBJECTIVES: Severely paralyzed patients could learn to voluntarily generate slow cortical potential (SCP) shifts in their electroencephalogram and to use these signals to operate a communication device. To enhance the patients' autonomy, the present study describes the development of a permanently available communication system that can be turned on and off by locked-in patients without external assistance. A skill necessary for turning the system on is the ability to regulate one's slow potentials in the absence of continuous feedback. METHODS: A stepwise learning approach was employed to train two paralyzed patients to regulate their SCPs without continuous feedback. Elements of the original communication system were gradually removed and elements of the new stand-by mode were introduced. RESULTS: At the end of the learning procedure, both patients achieved correct response rates of above 84% in training sessions without continuous feedback. This skill enabled them to turn the communication device on and off without assistance from others. CONCLUSIONS: These findings suggest that severely paralyzed individuals can learn to operate an EEG-based communication device autonomously.

Adult↗

PubMed2001

Treatment of phantom limb pain with combined EMG and thermal biofeedback: a case report.

Phantom pain is a frequent consequence of the amputation of an extremity and causes considerable discomfort and disruption of daily activities. This study describes a patient with extreme phantom limb pain following amputation of the right upper limb. The treatment consisted of 6 sessions of EMG biofeedback followed by 6 sessions of temperature biofeedback. The patient did not use a prosthesis and had not received previous treatment for chronic pain. Results demonstrated complete elimination of phantom limb pain after treatment, which was maintained at a 3- and 12-month follow-up. Pain relief covaried with increase in skin temperature at stump and perceptual telescoping (retraction of phantom limb into stump).

Aged↗

PubMed2001

Brain-computer communication: unlocking the locked in.

With the increasing efficiency of life-support systems and better intensive care, more patients survive severe injuries of the brain and spinal cord. Many of these patients experience locked-in syndrome: The active mind is locked in a paralyzed body. Consequently, communication is extremely restricted or impossible. A muscle-independent communication channel overcomes this problem and is realized through a brain-computer interface, a direct connection between brain and computer. The number of technically elaborated brain-computer interfaces is in contrast with the number of systems used in the daily life of locked-in patients. It is hypothesized that a profound knowledge and consideration of psychological principles are necessary to make brain-computer interfaces feasible for locked-in patients.

Brain↗

PubMed2001

Modification of slow cortical potentials in patients with refractory epilepsy: a controlled outcome study.

PURPOSE: To compare self-regulation of low-frequency EEG components (slow cortical potentials, SCPs) with other methods of seizure control for patients with drug-refractory partial epilepsy and to separate the real anticonvulsive effect from placebo effects. METHODS: Results of a treatment program of SCP self-regulation (experimental group) are compared with two groups of patients, one of which learned self-control of respiratory parameters (end-tidal CO2 and respiration rate: RES group); the other received medication with new anticonvulsive drugs (AEDs) in combination with psychosocial counseling (MED group). Clinical, cognitive, behavioral, and personality measures were assessed before and after treatment. In addition, to control for placebo responses, patients repeatedly estimated their beliefs in the efficiency of the respective treatment, their satisfaction and expectations, and the quality of the relationship with their therapists. RESULTS: SCP and MED groups showed a significant decrease of seizure frequency, but the RES group did not. Clear positive changes in the sociopsychological adjustment were obtained in all three groups, with the maximal improvement being attained in the RES group. CONCLUSIONS: All kinds of therapy result in considerable improvement of patients' emotional state, which may in part be due to potential placebo effects: however, this improvement is not related to the quality of the therapeutic effect proper (i.e., seizure reduction). Traditional double-blind control group designs are inappropriate for behavioral interventions or treatments with psychoactive pharmacologic drugs. Rather, specific tests can be developed to control the placebo effect and to separate it from the genuine therapeutic effects.

Adolescent↗