Biomedical subjects

Manuel Schabus

Publications and source records attributed to Manuel Schabus.

7 recordsLinked to original sources

PubMed2006

Brain response to one's own name in vegetative state, minimally conscious state, and locked-in syndrome.

BACKGROUND: A major challenge in the management of severely brain-injured patients with altered states of consciousness is to estimate their residual perception of the environment. OBJECTIVE: To investigate the integrity of detection of one's own name in patients in a behaviorally well-documented vegetative state (VS), patients in a minimally conscious state (MCS), and patients with locked-in syndrome. DESIGN: We recorded the auditory evoked potentials to the patient's own name and to 7 other equiprobable first names in 15 brain-damaged patients. RESULTS: A P3 component was observed in response to the patient's name in all patients with locked-in syndrome, in all MCS patients, and in 3 of 5 patients in a VS. P3 latency was significantly (P<.05) delayed for MCS and VS patients compared with healthy volunteers. CONCLUSIONS: These results suggest that partially preserved semantic processing could be observed in noncommunicative brain-damaged patients, notably for the detection of salient stimuli, such as the subject's own name. This function seems delayed in MCS and (if present) in VS patients. More important, a P3 response does not necessarily reflect conscious perception and cannot be used to differentiate VS from MCS patients.

Acoustic Stimulation↗

PubMed2006

How should functional imaging of patients with disorders of consciousness contribute to their clinical rehabilitation needs?

PURPOSE OF REVIEW: We discuss the problems of evidence-based neurorehabilitation in disorders of consciousness, and recent functional neuroimaging data obtained in the vegetative state and minimally conscious state. RECENT FINDINGS: Published data are insufficient to make recommendations for or against any of the neurorehabilitative treatments in vegetative state and minimally conscious state patients. Electrophysiological and functional imaging studies have been shown to be useful in measuring residual brain function in noncommunicative brain-damaged patients. Despite the fact that such studies could in principle allow an objective quantification of the putative cerebral effect of rehabilitative treatment in the vegetative state and minimally conscious state, they have so far not been used in this context. SUMMARY: Without controlled studies and careful patient selection criteria it will not be possible to evaluate the potential of therapeutic interventions in disorders of consciousness. There also is a need to elucidate the neurophysiological effects of such treatments. Integration of multimodal neuroimaging techniques should eventually improve our ability to disentangle differences in outcome on the basis of underlying mechanisms and better guide our therapeutic options in the challenging patient populations encountered following severe acute brain damage.

Brain↗

PubMed2005

Increasing individual upper alpha power by neurofeedback improves cognitive performance in human subjects.

The hypothesis was tested of whether neurofeedback training (NFT)--applied in order to increase upper alpha but decrease theta power--is capable of increasing cognitive performance. A mental rotation task was performed before and after upper alpha and theta NFT. Only those subjects who were able to increase their upper alpha power (responders) performed better on mental rotations after NFT. Training success (extent of NFT-induced increase in upper alpha power) was positively correlated with the improvement in cognitive performance. Furthermore, the EEG of NFT responders showed a significant increase in reference upper alpha power (i.e. in a time interval preceding mental rotation). This is in line with studies showing that increased upper alpha power in a prestimulus (reference) interval is related to good cognitive performance.

Adult↗

PubMed2005

Fronto-parietal EEG coherence in theta and upper alpha reflect central executive functions of working memory.

For human working memory the neural correlates of the phonological loop and the visuospatial sketch pad are well explored. In contrast, less is known about central executive processes. Neuroimaging studies suggest that central executive processes are related to a complex fronto-parietal network. In the present study we investigate the question whether varying demands on central executive processes are reflected by differences in coherent activity between and within a fronto-parietal network. We calculated coherence during a visuospatial working memory task. Under an easy executive condition subjects had to mentally imagine previously studied abstract patterns, whereas in the difficult condition, subjects had to mentally manipulate these patterns. The results indicate the involvement of prefrontal areas in executive functions reflected by a decrease of anterior upper alpha short-range connectivity and a parallel increase of fronto-parietal long-range coherence mirroring activation of a fronto-parietal network.

Adult↗

PubMed2004

Sleep spindles and their significance for declarative memory consolidation.

STUDY OBJECTIVES: Functional significance of stage 2 sleep spindle activity for declarative memory consolidation. DESIGN: Randomized, within-subject, multicenter. SETTING: Weekly sleep laboratory visits, actigraphy, and sleep diary (4 weeks). PARTICIPANTS: Twenty-four healthy subjects (12 men) aged between 20 and 30 years. INTERVENTIONS: Declarative memory task or nonlearning control task before sleep. MEASUREMENT AND RESULTS: This study measured spindle activity during stage 2 sleep following a (declarative) word-pair association task as compared to a control task. Participants performed a cued recall in the evening after learning (160 word pairs) as well as in the subsequent morning after 8 hours of undisturbed sleep with full polysomnography. Overnight change in the number of recalled words, but not absolute memory performance, correlated significantly with increased spindle activity during the experimental night (r24 = .63, P < .01). Time spent in each sleep stage could not account for this relationship. CONCLUSION: A growing body of evidence supports the active role of sleep for information reprocessing. Whereas past research focused mainly on the distinct rapid eye movement and slow-wave sleep, these results indicate that increased sleep stage 2 spindle activity is related to an increase in recall performance and, thus, may reflect memory consolidation.

Adult↗

PubMed2004

Theta coupling in the human electroencephalogram during a working memory task.

The role of coupling between prefrontal and temporo-parietal brain areas within the theta frequency range of the human electroencephalogram was explored in a working memory task. During encoding of visual information higher theta amplitudes were observed in the right compared to the left hemisphere. Retrieval of visuospatial and verbal information elicited a more bilateral activation pattern. These effects were accompanied by theta coupling between dorsolateral prefrontal and right posterior temporal electrode sites during encoding. During retrieval prefrontal and bilateral temporo-parietal brain areas were coupled. These results support the idea of working memory functions being dependent on distributed prefrontal-temporal networks.

Acoustic Stimulation↗

PubMed2004

Phase-locked alpha and theta oscillations generate the P1-N1 complex and are related to memory performance.

An oscillatory phase resetting model is presented and data are reported which indicate that early components of the event-related potential are due to the superposition of evoked oscillations. The following hypotheses were tested and could be confirmed: (i) theta and alpha show a significant increase in phase locking during the time window of the P1 and N1 as compared to a prestimulus reference, (ii) the dynamics of event-related changes in evoked theta and alpha power obey the same principles as are known from event-related de-/synchronization research, and (iii) latency measures of the P1-N1 complex are negatively correlated with individual alpha frequency. In addition, we have found that theta phase locking is larger during encoding than recognition and that good memory performers show a larger increase in theta and alpha phase locking during recognition in the time window of the N1. Our general conclusion is that the P1-N1 complex is generated primarily by evoked alpha and theta oscillations reflecting the synchronous activation of a working- and semantic memory system.

Adult↗