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Biomedical subjects

W Lutzenberger

Publications and source records attributed to W Lutzenberger.

At least 19 recordsLinked to original sources
PubMed1999

Frontal brain asymmetry as a biological substrate of emotions in patients with panic disorders.

BACKGROUND: Right frontal hemisphere activation, as indicated by reduced frontal alpha amplitude, seems to represent activation of an avoidance-withdrawal system and seems to be associated with negative emotions. Since patients with panic disorder are characterized by both negative emotions and avoidance-withdrawal behavior, we expected them to show greater right than left frontal hemisphere activation. METHODS: Spontaneous electroencephalography was recorded from the left and right frontal and parietal scalp regions of 23 patients with panic disorder patients without a diagnosis of depression and from 25 healthy control participants during the following conditions: rest, confrontation with neutral, panic-relevant, anxiety-relevant but panic-irrelevant, or anxiety-irrelevant but emotionally relevant stimuli, and performance of a motor task. Their emotional state during these conditions was assessed by the Self-Assessment Manikin. RESULTS: In patients with panic disorders, there were asymmetries in frontal hemisphere activation during resting phases and when confronted with anxiety-relevant stimuli. Their right frontal alpha power was significantly decreased compared with the left, while control participants did not show frontal brain asymmetry during these phases. There was no frontal brain asymmetry when patients observed an emotionally neutral picture or performed a motor task. Under these conditions, left and right frontal hemisphere alpha activation of patients with panic disorder and healthy participants were comparable. CONCLUSIONS: These data support the hypothesis that patients with panic disorder are characterized by greater activation of a right frontal avoidance-withdrawal system in negatively valenced situations. The findings are interpreted as biological evidence for a disturbed cortical processing in patients with panic disorder.

Adult↗
PubMed1999

Hemispheric lateralization of the neural encoding of temporal speech features: a whole-head magnetencephalography study.

Using a passive oddball design (randomized series of standard [frequent] and deviant [rare] stimuli), the present study investigated the neural encoding of syllables differing in a duration parameter (/da/ = short-lag voice onset time [VOT], /ta/ = long-lag VOT) by means of whole-head magnetencephalography (MEG). Dipolar activities at the level of the supratemporal planes allowed to explain the evoked magnetic fields. The N1m/P2m-complex (magnetic equivalent to the N /P2-wave of the electroencephalogram) in response to standard stimuli showed bilateral symmetric distribution. Furthermore, the latency of P2m significantly depended on VOT. Finally, the mismatch response to the deviant /da/-syllables-which represent in German a very frequent word (English: 'here' or 'there')- evolved significantly earlier in the left hemisphere as compared to the right side. In conclusion, processing speed may be an important aspect of the hemispheric specialization of language.

Adult↗
PubMed1998

The cortical somatotopic map and phantom phenomena in subjects with congenital limb atrophy and traumatic amputees with phantom limb pain.

The extent of the cortical somatotopic map and its relationship to phantom phenomena was tested in five subjects with congenital absence of an upper limb, four traumatic amputees with phantom limb pain and five healthy controls. Cortical maps of the first and fifth digit of the intact hand, the lower lip and the first toe (bilaterally) were obtained using neuroelectric source imaging. The subjects with congenital upper limb atrophy showed symmetric positions of the left and right side of the lower lip and the first toe, whereas the traumatic amputees with pain showed a significant shift (about 2.4 cm) of the cortical representation of the lower lip towards the hand region contralateral to the amputation side but no shift for the toe representation. In healthy controls, no significant hemispheric differences between the cortical representation of the digits, lower lip or first toe were found. Phantom phenomena were absent in the congenital but extensive in the traumatic amputees. These data confirm the assumption that congenital absence of a limb does not lead to cortical reorganization or phantom limbs whereas traumatic amputations that are accompanied by phantom limb pain show shifts of the cortical areas adjacent to the amputation zone towards the representation of the deafferented body part.

Adult↗
PubMed1997

Effects of regional anesthesia on phantom limb pain are mirrored in changes in cortical reorganization.

The causes underlying phantom limb pain are still unknown. Recent studies on the consequences of nervous system damage in animals and humans reported substantial reorganization of primary somatosensory cortex subsequent to amputation, and one study showed that cortical reorganization is positively correlated with phantom limb pain. This paper examined the hypothesis of a functional relationship between cortical reorganization and phantom limb pain. Neuroelectric source imaging was used to determine changes in cortical reorganization in somatosensory cortex after anesthesia of an amputation stump produced by brachial plexus blockade in six phantom limb pain patients and four pain-free amputees. Three of six phantom limb subjects experienced a virtual elimination of current phantom pain attributable to anesthesia (mean change: 3.8 on an 11-point scale; Z = -1.83; p < 0.05) that was mirrored by a very rapid elimination of cortical reorganization in somatosensory cortex (change = 19.8 mm; t(2) = 5.60; p < 0.05). Cortical reorganization remained unchanged (mean change = 1.6 mm) in three phantom limb pain amputees whose pain was not reduced by brachial plexus blockade and in the phantom pain-free amputation controls. These findings suggest that cortical reorganization and phantom limb pain might have a causal relationship. Methods designed to alter cortical reorganization should be examined for their efficacy in the treatment of phantom limb pain.

Adult↗
PubMed1997

Enhanced dimensional complexity of the EEG during memory for personal pain in chronic pain patients.

Associative connections between cortical cell assemblies representing pain-related memories should be stronger and more extensive in subjects with chronic pain. To test this hypothesis, the dimensional complexity of the electroencephalograph (EEG) was examined during the actual experience as well as during memory for pain. Nine chronic pain patients and nine matched healthy controls participated in the study. During acute pain induction, acute pain recall, personal stress and pain recall, the EEG was recorded from 15 scalp sites. Non-linear analysis, based on the theory of deterministic chaos, revealed higher and more widespread EEG complexity in the patients compared to the healthy controls only during the recall of the personal pain scene. The personal stress scene was rated equally aversive but did not induce more EEG complexity. These more extensive and more readily accessible pain memories may be instrumental for the persistence of chronic pain.

Adult↗
PubMed1997

Fractal dimensions of short EEG time series in humans.

Fractal dimensions has been proposed as a useful measure for the characterisation of electrophysiological time series. But one of the problems of this approach, is the difficulty to record time series long enough of determine the 'real' fractal dimension. Nevertheless it is possible to calculate fractal dimensions for very short data-segments. Using time series of different length it is possible to show, that there is a monotoneous relation between fractal dimension and the number of data-points. This relation could be further interpreted with the help of an extrapolation scheme. In addition this effect is also seen with surrogate data, generated from that signal. We conclude that it is feasible to use fractal dimension as a tool to characterise the complexity for short electroencephalographic (EEG) time series, but it is not possible to decide whether the brain is a chaotic system or not.

Electroencephalography↗
PubMed1997

Increased duration and altered topography of EEG microstates during cognitive tasks in chronic schizophrenia.

The surface EEGs of 32 medicated chronic schizophrenic patients, 12 unmedicated chronic schizophrenics and 35 matched healthy controls were analyzed by adaptive segmentation of continuous EEG during a rest condition, a mental arithmetic task, and a CNV paradigm. Results indicate increased duration of brain microstates in both unmedicated and medicated schizophrenics as well as reduced topographic variability. These findings did not vary across the different tasks. Comparing different cognitive tasks, schizophrenics and controls alike showed task-related changes of electric field topography, of EEG microstate duration and of the number of very short microstates (single-peak segments). However, the topography of the microstates during the tasks differed significantly in both medicated and unmedicated schizophenics from that of controls. Age, sex and educational levels did not influence these findings. Neuroleptic medication correlated negatively with microstate duration in a dose-dependent way. There was an inverse relationship between topographic variability and negative symptoms as well as BPRS scores. It is concluded that the temporo-spatial characteristics of brain electric activity indicate an impoverished array of functional modes and enhanced stability of brain electrical microstates in schizophrenia.

Adult↗
PubMed1997

EEG alpha dynamics as viewed from EEG dimension dynamics.

EEG alpha power covaries with changes in visual input and with changes in other aspects of cortical processing. We present an synopsis of three experiments that demonstrate these effects. A concurrent analysis of the EEG dimension indicates that the dynamics of EEG alpha may result from at least two different mechanisms.

Adolescent↗
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

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

Fractal dimension of sustained vowel productions in neurological dysphonias: an acoustic and electroglottographic analysis.

In order to investigate whether nonlinear methods of signal analysis provide a measure of phonatory irregularities in neurogenic voice disorders, the present study computed the fractal dimension (D) both of the electroglottographic (EGG) and the acoustic signal of sustained vowel productions obtained from patients with Parkinson's disease (PD) and cerebellar atrophy (CA). Compared with normal speakers, the female PD group as well as the male and female CA patients showed an increased dimension (D) of the EGG. The dimensional complexity of the acoustic signal largely depended on vowel type. Furthermore, the dimension of the acoustic signal was reduced in male PD patients as compared to the respective controls.

Brain↗
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

Enhanced dynamic complexity in the human EEG during creative thinking.

This study shows that divergent thinking, considered the general process underlying creative production, can be distinguished from convergent, analytical thought based on the dimensional complexity of ongoing electroencephalographic (EEG) activity. EEG complexity over the central and posterior cortex was higher while subjects solved tasks of divergent than convergent thinking, and also higher than during mental relaxation. Over the frontal cortex, EEG complexity was comparable during divergent thinking and mental relaxation, but reduced during convergent thinking. Results indicate that the basic process underlying the generation of novel ideas expresses itself in a strong increase in the EEG's complexity, reflecting higher degrees of freedom in the competitive interactions among cortical neuron assemblies. Frontocortical EEG complexity being comparable with that during mental relaxation, speaks for a loosened attentional control during creative thinking.

Adult↗
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

Abnormal topography of EEG microstates in Gilles de la Tourette syndrome.

Quantitative analysis of scalp EEGs was performed on 13 patients with Gilles de la Tourette syndrome (GTS) and 25 matched controls. The analysis method was adaptive segmentation, which describes the topography and sequence of brain electric fields in continuous EEG. The GTS patients showed an abnormal increase in fields with a right-frontal/left-posterior configuration. The GTS patient's EEGs did not differ from normal controls in the average duration of the brain electric microstates, field stability and EEG carrier frequency. To find out whether the abnormal activity is similar to movement-related activity a simple and a complex motor task were performed. Both tasks led to distinct changes of brain electric activity, but not to an increase in right-frontal-/left-posterior-oriented patterns. Motor-related activity was contrasted with two auditory tasks. We conclude that GTS patient's EEG show abnormal topographic patterns of brain electric activity. Unlike other psychiatric disorders, the temporal descriptors of the EEG aspects are unaffected. The abnormal EEG patterns in GTS patients are not similar to those elicited by simple or complex movements; thus, the presence of abnormally facilitated, near-threshold motor activity in GTS patients seems not a likely explanation.

Adult↗
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↗