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Biomedical subjects

Niels Birbaumer

Publications and source records attributed to Niels Birbaumer.

At least 73 records · Page 4Linked to original sources
PubMed2003

Brain areas activated in fMRI during self-regulation of slow cortical potentials (SCPs).

In humans, surface-negative slow cortical potentials (SCPs) originating in the apical dendritic layers of the neocortex reflect synchronized depolarization of large groups of neuronal assemblies. They are recorded during states of behavioural or cognitive preparation and during motivational states of apprehension and fear. Surface positive SCPs are thought to indicate reduction of cortical excitation of the underlying neural networks and appear during behavioural inhibition and motivational inertia (e.g. satiety). SCPs at the cortical surface constitute summated population activity of local field potentials (LFPs). SCPs and LFPs may share identical neural substrates. In this study the relationship between negative and positive SCPs and changes in the BOLD signal of the fMRI were examined in ten subjects who were trained to successfully self-regulate their SCPs. FMRI revealed that the generation of negativity (increased cortical excitation) was accompanied by widespread activation in central, pre-frontal, and parietal brain regions as well as the basal ganglia. Positivity (decreased cortical excitation) was associated with widespread deactivations in several cortical sites as well as some activation, primarily in frontal and parietal structures as well as insula and putamen. Regression analyses revealed that cortical positivity was predicted with high accuracy by pallidum and putamen activation and supplementary motor area (SMA) and motor cortex deactivation, while differentiation between cortical negativity and positivity was revealed primarily in parahippocampal regions. These data suggest that negative and positive electrocortical potential shifts in the EEG are related to distinct differences in cerebral activation detected by fMRI and support animal studies showing parallel activations in fMRI and neuroelectric recordings.

Adult↗
PubMed2003

A brief and unobtrusive instrument to detect simulation and exaggeration in patients with whiplash syndrome.

The objective of this study was to develop and test a brief and unobtrusive instrument to detect exaggeration and simulation in whiplash syndrome. The instrument consists of eight scenarios with ten response options that have to be ordered according to how easy a behavior is to perform. Twenty-five simulating and 25 non-simulating patients with whiplash syndrome of grades 2 and 3 according to the Quebec Task Force classification as well as 25 simulating and 25 non-simulating controls completed the instrument. In a cross-validation study 20 controls and 20 patients participated. Malingering and exaggeration scores were determined for each subject and patient. The scores were summed up and compared across malingering and exaggerating subjects and controls and cut-off values were determined to classify the patients. T-tests and a discriminant analysis were used to determine classification accuracy. The instrument correctly identified 94% of the simulators and 84% of the exaggerators in both samples. This brief and unobtrusive instrument can detect exaggeration and simulation in whiplash syndrome.

Adult↗
PubMed2003

Effects of hydration and hyperventilation on cortical complexity.

The effects of hydration and hyperventilation on cortical complexity were investigated in a sample of 19 healthy volunteers in a double-blind placebo design using magnetoencephalographic recordings. The subjects were asked to abstain from the intake of liquids 18 h before the study. Spontaneous magnetoencephalograms (MEG) were recorded before and after drinking 750 ml water (WAT group: nine subjects) or saline solution (SAL group: ten subjects) with eyes closed and open and during hyperventilation (HV) with eyes open. The MEG data were analysed using both linear (spectral power) and non-linear (pointwise dimension and largest Lyapunov exponent) algorithms. The prediction that intake of water, because of induced cell swelling, will lead to an increased synchronization and a decreased complexity of the spontaneous MEG during hyperventilation was confirmed. Hyperventilation following the drinking condition produced an increase in all power spectra with a stronger increase of delta and theta power after drinking of water. This synchronization of spontaneous MEG is accompanied by a general significant decrease of cortical complexity, especially after water drinking. Moreover, cortical complexity was inversely related to delta and theta power and partly also to alpha power. The SAL and WAT groups showed different relations between alpha power and dimensional complexity during HV: whereas in the SAL group the correlations between these measures became more negative during HV, they reversed in the WAT group to become positive. The synchronizing effect of hyperventilation, leading to a decrease of cortical complexity, is related in the SAL group to delta, theta and alpha power, whereas in the WAT group only delta and theta activity contribute to a reduction of cortical complexity.

Adult↗
PubMed2003

Conscious perception of brain states: mental strategies for brain-computer communication.

Direct brain-computer communication utilises self-regulation of brain potentials to select letters, words or symbols from a computer menu. In this study a completely paralysed (locked-in) patient learnt to produce slow cortical potential (SCP) shifts to operate a binary spelling device. After hundreds of training sessions he gave a detailed description of his mental strategies for self-regulation. His cognitive strategies matched with the electrocortical changes perfectly. Thus he produced a contingent negative variation (CNV) with images of preparation such as an arrow being drawn on a bow. To produce a positive potential shift he imagined the arrow shooting up from the bow. To suppress potential shifts he tried to stop thinking. The study demonstrates that patients become sensitive for their brain states with increasing self-regulation practice. The use of conscious cognitive strategies may, however, be incompatible with the complete automatization of the self-regulation skill.

Amyotrophic Lateral Sclerosis↗
PubMed2003

Combining MEG and MRI with neuronavigation for treatment of an epileptiform spike focus in the precentral region: a technical case report.

BACKGROUND: Epileptic foci are often located in the vicinity but not necessarily within the boundaries of intra-axial brain tumors. Resection of these tumors is based on two major goals: first, maximizing tumor removal without provoking new neurologic deficits, and second, minimizing epileptic seizure activity. Magnetic source imaging (MSI) depicts the generators of magnetic fields overlaid on individual magnetic resonance (MR) images. Established application areas are lesions located adjacent to or partly within the sensory and motor cortex, or in the depth of the brain, necessitating a surgical approach through functionally highly relevant cortical regions. Magnetoencephalography (MEG) is also applicable for epileptiform spike foci recording during interictal activity. CASE DESCRIPTION: A patient with a recurrent glioma close to the Rolandic cortex scheduled for epilepsy and tumor surgery was investigated with MSI. The MSI data showed an epileptiform spike focus outside the tumor boundaries. The resulting MSI images were integrated into our neuronavigation system. This procedure allowed for the preoperative identification of the sensory and motor cortex, the precise localization of the epileptiform spike focus, and careful planning of the surgical procedure. In this case, we were able to safely resect the recurrent tumor and the epileptiform spike focus under general anesthesia using MSI-based neuronavigational guidance but no conventional intraoperative mapping techniques. CONCLUSION: Magnetic source imaging can be a valuable, noninvasive method for planning and performing tumor resections in high-risk brain regions, especially if an epileptiform spike focus has to be localized and included into the resection strategy.

Brain Neoplasms↗
PubMed2003

Gender differences in response to pictures of nudes: a magnetoencephalographic study.

The magnetic equivalent of the contingent negative variation (CMV) and visual evoked magnetic fields (VEF) in anticipation of pictures of opposite-sex nude, same-sex nude, and neutral photographs has been recorded with whole-head MEG in 12 males and 12 females. Subjective ratings of valence indicated a strong gender effect. While females rated both male and female nudes as neutral, males rated male nudes similar to neutrals but female nudes received higher scores of pleasantness. Gender differences were also found for ratings of picture-induced arousal. While females rated male and female nudes as equally arousing, males attributed more arousal to opposite-sex nudes. The CMV instead revealed, for both male and female participants, higher amplitudes for opposite-sex nudes. VEF in response to nudes revealed two components with mean latencies of 126 and 203 ms. The amplitude of the first component was stronger in males than in females, and only in males the magnetic activity was increased in response to male and female nudes compared to neutral pictures. For the second component the mean magnetic activity was higher in response to nudes than to neutral contents for both male and female participants. The results are discussed in terms of an evolutionary view of sexual selection, which predicts a greater response in male subjects to stimuli relevant for mate choice.

Adult↗
PubMed2003

Complexity of visual stimuli and non-linear EEG dynamics in humans.

The effects of stimulus complexity on the nonlinear electrical brain (EEG) dynamics were investigated in a sample of 24 healthy volunteers. Stimuli used were either a single mechanical low-friction pendulum with a periodic movement (temporal frequency about 1 Hz) or a double-pendulum with a chaotic movement, which were observed for 2-3 min in each case. The prediction that a more complex visual stimulus (double-pendulum) increases the dimensional complexity of brain activity as compared to a simple visual stimulus (single-pendulum), was confirmed by determination of pointwise correlation dimension. Further, there was a significant decrease of alpha power in the double-pendulum compared to a single-pendulum condition. Moreover, a correlation analysis showed a positive correlation between EEG complexity and beta power over the whole cortex in the single- and, above all, in the double-pendulum condition, and also a positive correlation between dimensional complexity and alpha power in the double-pendulum condition only, particularly in the brain regions responsible for the 'bottom-up' sustained attention processes.

Adult↗
PubMed2003

Electrocortical and behavioral effects of chronic immobility on word processing.

Neuroelectrical and subjective effects of chronic motor deficits (severe immobility) on word processing were explored. A total of ten artificially ventilated patients with end-stage amyotrophic lateral sclerosis (ALS), seven patients with tetraplegia due to a high spinal cord injury (SCI), and nine matched controls were examined. Both ALS and SCI patients were almost completely paralyzed; eye, head, and face movements were intact in SCI but not in ALS patients. Event-related brain potentials (ERPs) were recorded during presentation of verbs with strong motor-action associations and nouns with strong visual associations. Subjects estimated the subjective strength of motor and visual associations for each word using a scale from 0 to 5. No between-group difference was found for subjectively rated motor associations. All patients reported much stronger visual associations for both nouns and verbs than healthy subjects. ERPs to both word classes revealed a left occipital negativity in SCI patients at a latency of 200-300 ms, and a marked decrease of the slow positive wave in the interval of 300-800 ms in the two patient groups. Both psychophysical and electrophysiological data suggest compensatory activation of visual information processing areas in severely paralyzed patients. The more pronounced effects in the SCI group as compared with the ALS group may be attributed to somatosensory deafferentation in SCI patients, while the sensory inflow in ALS remains relatively intact.

Adult↗
PubMed2003

Event-related brain potentials in a patient with akinetic mutism.

The clinical pattern of complete akinetic mutism (AM) was observed in a patient with a bilateral infarction of the anterior cerebral arteries extending to the rostral cingulate cortex and the supplementary motor areas. Since the patient was unable to produce any overt response, event-related brain potentials (ERPs) were used to obtain information about cortical processing of stimuli. Oddball tasks with simple acoustical stimuli and semantic categories were used. Verbal processing was further assessed by comparing event-related potentials to words compatible versus incompatible to the semantic context. Although the pattern of cortical responses was abnormal, differential responses were clearly obtained to semantically different word classes. Thus, the hypothesis about cortical non-responsivity of AM patients, drawn from several previous reports, was not supported. An ERP examination in AM patients can deliver information about their mental state, provided that the stimuli and tasks possess a wide range of informational complexity and motivational value.

Akinetic Mutism↗
PubMed2003

Physiological self-regulation of regional brain activity using real-time functional magnetic resonance imaging (fMRI): methodology and exemplary data.

A brain-computer interface (BCI) based on real-time functional magnetic resonance imaging (fMRI) is presented which allows human subjects to observe and control changes of their own blood oxygen level-dependent (BOLD) response. This BCI performs data preprocessing (including linear trend removal, 3D motion correction) and statistical analysis on-line. Local BOLD signals are continuously fed back to the subject in the magnetic resonance scanner with a delay of less than 2 s from image acquisition. The mean signal of a region of interest is plotted as a time-series superimposed on color-coded stripes which indicate the task, i.e., to increase or decrease the BOLD signal. We exemplify the presented BCI with one volunteer intending to control the signal of the rostral-ventral and dorsal part of the anterior cingulate cortex (ACC). The subject achieved significant changes of local BOLD responses as revealed by region of interest analysis and statistical parametric maps. The percent signal change increased across fMRI-feedback sessions suggesting a learning effect with training. This methodology of fMRI-feedback can assess voluntary control of circumscribed brain areas. As a further extension, behavioral effects of local self-regulation become accessible as a new field of research.

Adult↗
PubMed2003

Dynamics of gamma-band activity in human magnetoencephalogram during auditory pattern working memory.

Both electrophysiological research in animals and human brain imaging studies have suggested that, similar to the visual system, separate cortical ventral "what" and dorsal "where" processing streams may also exist in the auditory domain. Recently we have shown enhanced gamma-band activity (GBA) over posterior parietal cortex belonging to the putative auditory dorsal pathway during a sound location working memory task. Using a similar methodological approach, the present study assessed whether GBA would be increased over auditory ventral stream areas during an auditory pattern memory task. Whole-head magnetoencephalogram was recorded from N = 12 subjects while they performed a working memory task requiring same-different judgments about pairs of syllables S1 and S2 presented with 0.8-s delays. S1 and S2 could differ either in voice onset time or in formant structure. This was compared with a control task involving the detection of possible spatial displacements in the background sound presented instead of S2. Under the memory condition, induced GBA was enhanced over left inferior frontal/anterior temporal regions during the delay phase and in response to S2 and over prefrontal cortex at the end of the delay period. gamma-Band coherence between left frontotemporal and prefrontal sensors was increased throughout the delay period of the memory task. In summary, the memorization of syllables was associated with synchronously oscillating networks both in frontotemporal cortex, supporting a role of these areas as parts of the putative auditory ventral stream, and in prefrontal, possible executive regions. Moreover, corticocortical connectivity was increased between these structures.

Acoustic Stimulation↗
PubMed2003

Task-specific plasticity of somatosensory cortex in patients with writer's cramp.

Focal dystonias such as writer's cramp are characterized by muscular cramps that accompany the execution of specific motor tasks. Until now, the pathophysiology of focal dystonia remains incompletely understood. Recent studies suggest that the development of writer's cramp is related to abnormal organization of primary somatosensory cortex (SI), which in turn leads to impaired motor function. To explore contributions of SI on mechanisms of task specificity in focal dystonia, we investigated dynamic alterations in the functional organization of SI as well as sensory-motor gating for rest, left- and right-handed writing and brushing in writer's cramp patients and healthy controls. The functional organization of somatosensory cortex was assessed by neuromagnetic source imaging (151 channel whole-head MEG). In accordance with previous reports, distances between cortical representations of thumb and little finger of the affected hand were smaller in patients compared to healthy subjects. However, similar to healthy controls, patients showed normal modulation of the functional organization of SI as induced by the execution of different motor tasks. Both in the control subjects and patients, cortical distances between representations of thumb and little finger increased when writing and brushing compared to the resting condition. Although, cramps only occured during writing, no differences in the organization of SI were seen among motor tasks. Our data suggest that despite alterations in the organization of primary somatosensory cortex in writer's cramp, the capability of SI to adapt dynamically to different tasks is not impaired.

Adult↗
PubMed2003

A brain-computer interface (BCI) for the locked-in: comparison of different EEG classifications for the thought translation device.

OBJECTIVE: The Thought Translation Device (TTD) for brain-computer interaction was developed to enable totally paralyzed patients to communicate. Patients learn to regulate slow cortical potentials (SCPs) voluntarily with feedback training to select letters. This study reports the comparison of different methods of electroencephalographic (EEG) analysis to improve spelling accuracy with the TTD on a data set of 6,650 trials of a severely paralyzed patient. METHODS: Selections of letters occurred by exceeding a certain SCP amplitude threshold. To enhance the patient's control of an additional event-related cortical potential, a filter with two filter characteristics ('mixed filter') was developed and applied on-line. To improve performance off-line the criterion for threshold-related decisions was varied. Different types of discriminant analysis were applied to the EEG data set as well as on wavelet transformed EEG data. RESULTS: The mixed filter condition increased the patients' performance on-line compared to the SCP filter alone. A threshold, based on the ratio between required selections and rejections, resulted in a further improvement off-line. Discriminant analysis of both time-series SCP data and wavelet transformed data increased the patient's correct response rate off-line. CONCLUSIONS: It is possible to communicate with event-related potentials using the mixed filter feedback method. As wavelet transformed data cannot be fed back on-line before the end of a trial, they are applicable only if immediate feedback is not necessary for a brain-computer interface (BCI). For future BCIs, wavelet transformed data should serve for BCIs without immediate feedback. A stepwise wavelet transformation would even allow immediate feedback.

Communication Devices for People with Disabilities↗
PubMed2003

Neurofeedback treatment for attention-deficit/hyperactivity disorder in children: a comparison with methylphenidate.

Clinical trials have suggested that neurofeedback may be efficient in treating attention-deficit/hyperactivity disorder (ADHD). We compared the effects of a 3-month electroencephalographic feedback program providing reinforcement contingent on the production of cortical sensorimotor rhythm (12-15 Hz) and betal activity (15-18 Hz) with stimulant medication. Participants were N = 34 children aged 8-12 years, 22 of which were assigned to the neurofeedback group and 12 to the methylphenidate group according to their parents' preference. Both neurofeedback and methylphenidate were associated with improvements on all subscales of the Test of Variables of Attention, and on the speed and accuracy measures of the d2 Attention Endurance Test. Furthermore, behaviors related to the disorder were rated as significantly reduced in both groups by both teachers and parents on the IOWA-Conners Behavior Rating Scale. These findings suggest that neurofeedback was efficient in improving some of the behavioral concomitants of ADHD in children whose parents favored a nonpharmacological treatment.

Attention Deficit Disorder with Hyperactivity↗
PubMed2003

Perception and production of biological movement in patients with early periventricular brain lesions.

Recent neuroimaging and psychophysical findings suggest that perception and production of human body motion share a common representational network. In the present study, we address the issue of whether early disorders in production of biological movement correspond to impairment in biological motion perception. By using the simultaneous masking paradigm, we examined visual sensitivity to biological motion in adolescents (aged 13-16 years) who were born very preterm (at 27-33 gestational weeks). In a confidence rating procedure, the presence of a point-light walking figure embedded in a moving mask was judged. The participants differed in their locomotion ability, ranging from normal to a complete walking disability exhibiting signs of leg-dominated bilateral spastic cerebral palsy (BS-CP) caused by periventricular leukomalacia (PVL). Irrespective of an ability to produce movement, patients with a similar extent of PVL in the parieto-occipital complex exhibit nearly the same sensitivity to biological motion. Sensitivity correlates negatively with the extent of PVL over the parieto-occipital complex, whereas neither the severity of motor disorder nor the severity of pyramidal tract affection relate significantly to the sensitivity index. The data suggest that perception of biological motion is not substantially affected by an observer's early restrictions in body movement. Instead, the findings favour the assumption that the common network for perception and production of biological motion might be inherent for the brain. Motor experience per se does not appear to be necessary for the visual analysis of human movement.

Adolescent↗
PubMed2003

Motor learning elicited by voluntary drive.

Motor training consisting of voluntary movements leads to performance improvements and results in characteristic reorganizational changes in the motor cortex. It has been proposed that repetition of passively elicited movements could also lead to improvements in motor performance. In this study, we compared behavioural gains, changes in functional MRI (fMRI) activation in the contralateral primary motor cortex (cM1) and in motor cortex excitability measured with transcranial magnetic stimulation (TMS) after a 30 min training period of either voluntarily (active) or passively (passive) induced wrist movements, when alertness and kinematic aspects of training were controlled. During active training, subjects were instructed to perform voluntary wrist flexion-extension movements of a specified duration (target window 174-186 ms) in an articulated splint. Passive training consisted of wrist flexion- extension movements elicited by a torque motor, of the same amplitude and duration range as in the active task. fMRI activation and TMS parameters of motor cortex excitability were measured before and after each training type. Motor performance, measured as the number of movements that hit the target window duration, was significantly better after active than after passive training. Both active and passive movements performed during fMRI measurements activated cM1. Active training led to more prominent increases in (i) fMRI activation of cM1; (ii) recruitment curves (TMS); and (iii) intracortical facilitation (TMS) than passive training. Therefore, a short period of active motor training is more effective than passive motor training in eliciting performance improvements and cortical reorganization. This result is consistent with the concept of a pivotal role for voluntary drive in motor learning and neurorehabilitation.

Adult↗