Showing papers by "Werner Lutzenberger published in 2000"
TL;DR: Both mismatch dipole latencies at the supratemporal plane and gamma-band activity in posterior parietotemporal areas suggested a right hemisphere engagement in the processing of bidirectional sound-source shifts, in contrast, left-hemisphere regions responded predominantly to contralateral events.
Abstract: Cortical processing of change in direction of a perceived sound source was investigated in 12 human subjects using whole-head magnetoencephalography. The German word "da" was presented either with or without 0.7 msec interaural time delays to create the impression of right- or left-lateralized or midline sources, respectively. Midline stimuli served as standards, and lateralized stimuli served as deviants in a mismatch paradigm. Two symmetrically linked dipoles fitted to the mismatch fields showed stronger moments in the hemisphere contralateral to the side of the deviant. The right dipole displayed equal latencies to both left and right deviants, whereas left dipole latencies were longer for ipsilateral than contralateral deviants. Frequency analysis between 20-70 Hz and statistical probability mapping revealed increased induced gamma-band activity at 53+/-2.5 Hz to both types of deviants. Right deviants elicited spectral amplitude enhancements in this frequency range, peaking at latencies of 160 and 240 msec. These effects were localized bilaterally over the angular gyri and posterior temporal regions. Coherence analysis suggested the existence of two separate interhemispheric networks. For left-lateralized deviants, both spectral amplitude enhancements at 110 and 220 msec and coherence increases were restricted to the right hemisphere. In conclusion, both mismatch dipole latencies at the supratemporal plane and gamma-band activity in posterior parietotemporal areas suggested a right hemisphere engagement in the processing of bidirectional sound-source shifts. In contrast, left-hemisphere regions responded predominantly to contralateral events. These findings may help to elucidate phenomena such as unilateral auditory neglect.
181 citations
TL;DR: Gender differences in DCx suggested faster cerebral maturation in girls over late adolescence, and relationships between DCx and spectral power varied as a function of tasks and scalp locations, suggesting that these EEG measures can reflect different aspects of cortical functioning.
Abstract: Dimensional complexity (DCx) is an EEG measure derived from nonlinear systems theory that can be indicative of the global dynamical complexity of electrocortical activity. This study examined developmental changes in DCx, as well as the effects of cognitive tasks, gender, and brain topography, and compared DCx with traditional spectral power measures. EEG was recorded in three groups of children at mean age of 7.5 (n = 37), 13.8 (n = 42), and 16.4 (n = 56) years at rest and during the performance of verbal and spatial cognitive tasks. DCx measured both at rest and during tasks increased with age. Specific effects of brain topography, condition, and gender became stronger with age, suggesting an increase in structural and functional differentiation of the cortex. Hemispheric asymmetry of DCx recorded during tasks also increased with age, with the task-induced DCx reduction being stronger in the left hemisphere. Gender differences in DCx suggested faster cerebral maturation in girls over late adolescence. Relationships between DCx and spectral power varied as a function of tasks and scalp locations, suggesting that these EEG measures can reflect different aspects of cortical functioning.
66 citations
TL;DR: Evidence is provided that speech-relevant acoustic features differentially affect evoked magnetic fields as early as the M50 component, which could reflect an ongoing monitoring process whereas the M100 component is bound to more specific operations such as detection of signal periodicity.
Abstract: Voiced and unvoiced sounds, characterized by a periodic or aperiodic acoustic structure, respectively, represent two basic information-bearing elements of the speech signal Using whole-head magnetencephalography (MEG), magnetic fields (M50/M 100) in response to synthetic vowel-like as well as noise-like signals matched in spectral envelope were recorded in 20 subjects Aperiodic events gave rise to increased M50 concomitant with reduced M100 activity as compared to their periodic cognates Attention toward the auditory channel enhanced the effects of signal periodicity These data provide first evidence that speech-relevant acoustic features differentially affect evoked magnetic fields as early as the M50 component Conceivably, the M50 field reflects an ongoing monitoring process whereas the M100 component is bound to more specific operations such as detection of signal periodicity
41 citations
TL;DR: For instance, the authors found that during binaural stimulus presentation attention toward target events resulted in a significantly enhanced mismatch field (MMNm, magnetic analogue to the mismatch negativity) over the left as compared to the right hemisphere.
39 citations
TL;DR: Oscillatory MEG activity in 12 normal adults during a self-paced, complex sequence of finger movements and a simple finger opposition task paced externally by tactile stimuli revealed enhanced non-phase-locked spectral amplitudes in the 22-28 Hz range over bilateral frontal cortex duringSelf-paced as compared to externally cued finger movements.
32 citations
TL;DR: Both fast, contralaterally dominant location mismatch responses and facilitated detection of auditory spatial deviance in the right hemifield are suggested.
Abstract: Magnetoencephalography (MEG) was used to compare mismatch responses between hemispheres to changes in sound-source direction. Sixteen adults listened passively to two types of complex non-language sounds presented in separate blocks with midline standards and right- and left-lateralized deviants. Mismatch dipole amplitudes were larger contra- than ipsilaterally to the deviants. Both hemispheres processed right deviants simultaneously, whereas to left deviants, the left dipole peaked 20 ms later than the right dipole. A second experiment using the same standards but midline spectral deviants showed no interhemispheric differences. Here mismatch latencies were about 60 ms longer than in the location mismatch experiment. This suggested both fast, contralaterally dominant location mismatch responses and facilitated detection of auditory spatial deviance in the right hemifield.
31 citations
TL;DR: In this 25-year-old man who had traumatically lost digits II to V (DII-V) on his right hand, magnetoencephalographic source imaging is used to document the recovery of somatosensory cortical responses after tactile stimulation at four sites on the replanted digits and indicates cortical reorganization caused by altered peripheral input.
Abstract: ✓ Functional recovery after digit-to-hand replantation depends on the interaction of various factors. In addition to peripheral mechanisms, cortical and subcortical reorganization of digit representation may play a substantial role in the recovery process. However, cortical processes during the first months after replantation are not well understood. In this 25-year-old man who had traumatically lost digits II to V (DII—V) on his right hand, the authors used magnetoencephalographic source imaging to document the recovery of somatosensory cortical responses after tactile stimulation at four sites on the replanted digits. Successful replantation of DIV and DV was accomplished at the original position of DIII and DIV with mixed innervation. Cortical evoked fields could be recorded starting from the 10th week after digit-to-hand replantation. Initially, signals from all sites showed decreased amplitudes and prolonged latencies. In the subsequent six recordings obtained between the 12th and 55th week postrepla...
21 citations
TL;DR: Recorded mismatch fields provide first neurophysiological evidence that the integration of acoustic stimulus elements into a coherent syllable representation constitutes a distinct stage of left-hemisphere speech sound encoding.
Abstract: Simultaneous experience of the same stimulus events in two distinct phenomenological modes is referred to as duplex perception (DP). The most widely investigated DP paradigm decomposes the formant pattern of the stop consonant‐vowel (CV) syllables /ga/ and /da/ into two complementary portions: the isolated transient of the third formant (‘‘chirp’’) and the remaining sound structure (‘‘base’’). Presentation of the two syllable components to opposite ears results in the perception, first, of the chirp and, second, the fused CV syllable. In order to further elucidate the mechanisms underlying DP, the present study recorded mismatch fields in response to a series of dichotically applied base and chirp components using whole‐head magnetencephalography (MEG). This magnetic analog to mismatch negativity is considered a correlate of early cognitive stimulus representation. (a) Under a visual distraction task, the preattentive mismatch fields were stronger in response to contralateral deviants and lateralized to t...
5 citations
TL;DR: The Magnetenzephalographie (MEG) ermoglicht in Kombination with the Magnet Resonance Resonance Tomography (MRT) the Lokalisation and funktionelle Charakterisierung der Zentralregion.
Abstract: Die Magnetenzephalographie (MEG) ermoglicht in Kombination mit der Magnetresonanztomographie (MRT) die Lokalisation und funktionelle Charakterisierung der Zentralregion. Aufgrund des grosen apparativen und zeitlichen Aufwandes konnte sich dieses Verfahren bisher in der neurochirurgischen Routine nicht durchsetzen. Ziel der hier vorgestellten Arbeit war daher die Entwicklung eines Protokolls, welches die Integration funktioneller MEG-Daten in die Planung und Durchfuhrung von neurochirurgischen Operationen als Routinemethode ermoglicht.
3 citations
01 Jan 2000