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Mental practice in stroke patients: EEG changes and pre-requisites for the use of MEG
Abstracts 7th IOP Scientific Meeting /International
Mental practice in stroke patients: EEG changes and pre-requisites for the use of MEG T. Weiss a, E. Hansen a, L. Beyer a, F. Merten b, C. Nichelmann *, R. Rost a, C. Zippel ‘, a Friedrich Schiller University, Institute of Physiology, D-07740 Jena, Germany, b Clinic of Internal Medicine and Rehabilitation, D-13125 Berlin, Germany In healthy subjects mental practice is known to improve motor performance. It is also known to be accompanied by a higher central nervous activity, Since such effects seem to be desirable for rehabilitation, we investigated the possibility of detecting changes in the central nervous activity by means of EEG mapping in stroke patients, and whether these changes were similar to those observed in healthy subjects. 2.5 hemiplegic patients (14 left-sided, 11 right-sided) who underwent specific post-stroke rehabilitation treatment were requested to perform a simple arm movement sequence. In the following mental practice period the patients were requested to imagine the same sequence without any real movement. EEG background activity was recorded during rest and imagination periods. After the calculation of z-transformed power values within the theta, alpha, and beta-l band, differences between rest and imagination periods were evaluated on significance. Stroke patients show significant decreases in theta, alpha, and beta-l power during mental practice in comparison to the rest period. These changes are similar to those obtained in healthy subjects. Theta power decreases in central, parietal, and occipital leads. Central alpha power diminishes only in some patients during imagination of the contralatera1 arm. This phenomenon as well as the decrease in beta-l power in central derivation were also obtained during real motor performance and might indicate an activation of the sensorimotor cortex. In accordance with the hypothesis of internal feedback mechanisms, this activation is a necessary prerequisite for motor learning during mental practice. In order to use MEG and EEG registration in future experiments we investigated some prerequisites for their simultaneous use (e.g., ten types of electrodes, localisation errors for MRI, and MEG).
Use of dynamic psychophysiology M. Winkler, NC, USA
systems
and chaos
Universit)’ of North
Carolina,
theory
in
Asheville,
Dynamic systems have become a rapidly expanding field of research to which mathematicians and physicists have made important contributions. This paradigm, often referred to as chaos theory, has become a powerful tool for understanding chaotic weather patterns and studying com-
Journal of Psychophysiology 18 (1994) 87-159
157
plex ecological systems. Although dynamic systems have received less attention in psychophysiology than in some other fields, it presents a modelling strategy that allows for the description of complex and unpredictable activity in various biological systems. Instead of structural concepts, dynamic systems concern terms such as “attractors,” “bifurcations,” ” phase portraits,” etc. These topological representations allow for the interpretation of dynamic interactive variables, whereas current linear measurements in psychophysiological research have no ready way of interpreting highly complex features of systems organization. The utility of chaos theory in psychophysiology will be illustrated in this presentation through research we have conducted in (1) the human nasal cycle, and (2) human mood cycles. “Phase portraits” will be presented to illustrate the utility of this paradigm in describing and understanding these complex activities.
Sensory memory for virtual pitch I. Winkler a, M. Tervaniemi b, R. NIltlnen b, a Institute for Psychology, Hungarian Academy of Sciences, Budapest, Hungary, b Cognitive Psychophysiology, University of Helsinki, Helsinki, Finland The first phase of information processing converts raw sensory data into percepts. For example, in the auditory modality, pitch is extracted on the basis of the spectral cues. The pitch of a simple tone burst corresponds to its frequency (spectral pitch). When harmonics of the same base frequency are added together the perceived pitch matches that of the fundamental harmonic (virtual pitch). If the base frequency is not present in such a sound the resulting pitch still corresponds to that of the missing fundamental. The present study was aimed at determining whether pitch is extracted before or after sensory information is coded in the auditory sensory memory. An event-related brain potential (ERP) component, termed the mismatch negativity (MMN), has been shown to index traces in the auditory sensory memory. MMN is elicited by infrequent changes (deviants) in an otherwise homogeneous series of auditory stimuli (standards). It reflects the deviation of the incoming stimulus from the trace of the previous repetitive stimuli. If only a few features are kept constant in the auditory stream stimuli deviation in those features also elicit an MMN. In the present study, ten harmonic structures with the fundamental frequency being omitted were equiprobably intermixed with each other. Nine of them had been constructed using 300 Hz as the missing fundamental frequency whereas the tenth had 600 Hz for the base. The only feature in which deviants differed from the rest of the stimuli was the virtual pitch. In separate experiments, two different stimulus durations (150 and 500 msec) were applied. Simple
Mental practice in stroke patients: EEG changes and pre-requisites for the use of MEG T. Weiss a, E. Hansen a, L. Beyer a, F. Merten b, C. Nichelmann *, R. Rost a, C. Zippel ‘, a Friedrich Schiller University, Institute of Physiology, D-07740 Jena, Germany, b Clinic of Internal Medicine and Rehabilitation, D-13125 Berlin, Germany In healthy subjects mental practice is known to improve motor performance. It is also known to be accompanied by a higher central nervous activity, Since such effects seem to be desirable for rehabilitation, we investigated the possibility of detecting changes in the central nervous activity by means of EEG mapping in stroke patients, and whether these changes were similar to those observed in healthy subjects. 2.5 hemiplegic patients (14 left-sided, 11 right-sided) who underwent specific post-stroke rehabilitation treatment were requested to perform a simple arm movement sequence. In the following mental practice period the patients were requested to imagine the same sequence without any real movement. EEG background activity was recorded during rest and imagination periods. After the calculation of z-transformed power values within the theta, alpha, and beta-l band, differences between rest and imagination periods were evaluated on significance. Stroke patients show significant decreases in theta, alpha, and beta-l power during mental practice in comparison to the rest period. These changes are similar to those obtained in healthy subjects. Theta power decreases in central, parietal, and occipital leads. Central alpha power diminishes only in some patients during imagination of the contralatera1 arm. This phenomenon as well as the decrease in beta-l power in central derivation were also obtained during real motor performance and might indicate an activation of the sensorimotor cortex. In accordance with the hypothesis of internal feedback mechanisms, this activation is a necessary prerequisite for motor learning during mental practice. In order to use MEG and EEG registration in future experiments we investigated some prerequisites for their simultaneous use (e.g., ten types of electrodes, localisation errors for MRI, and MEG).
Use of dynamic psychophysiology M. Winkler, NC, USA
systems
and chaos
Universit)’ of North
Carolina,
theory
in
Asheville,
Dynamic systems have become a rapidly expanding field of research to which mathematicians and physicists have made important contributions. This paradigm, often referred to as chaos theory, has become a powerful tool for understanding chaotic weather patterns and studying com-
Journal of Psychophysiology 18 (1994) 87-159
157
plex ecological systems. Although dynamic systems have received less attention in psychophysiology than in some other fields, it presents a modelling strategy that allows for the description of complex and unpredictable activity in various biological systems. Instead of structural concepts, dynamic systems concern terms such as “attractors,” “bifurcations,” ” phase portraits,” etc. These topological representations allow for the interpretation of dynamic interactive variables, whereas current linear measurements in psychophysiological research have no ready way of interpreting highly complex features of systems organization. The utility of chaos theory in psychophysiology will be illustrated in this presentation through research we have conducted in (1) the human nasal cycle, and (2) human mood cycles. “Phase portraits” will be presented to illustrate the utility of this paradigm in describing and understanding these complex activities.
Sensory memory for virtual pitch I. Winkler a, M. Tervaniemi b, R. NIltlnen b, a Institute for Psychology, Hungarian Academy of Sciences, Budapest, Hungary, b Cognitive Psychophysiology, University of Helsinki, Helsinki, Finland The first phase of information processing converts raw sensory data into percepts. For example, in the auditory modality, pitch is extracted on the basis of the spectral cues. The pitch of a simple tone burst corresponds to its frequency (spectral pitch). When harmonics of the same base frequency are added together the perceived pitch matches that of the fundamental harmonic (virtual pitch). If the base frequency is not present in such a sound the resulting pitch still corresponds to that of the missing fundamental. The present study was aimed at determining whether pitch is extracted before or after sensory information is coded in the auditory sensory memory. An event-related brain potential (ERP) component, termed the mismatch negativity (MMN), has been shown to index traces in the auditory sensory memory. MMN is elicited by infrequent changes (deviants) in an otherwise homogeneous series of auditory stimuli (standards). It reflects the deviation of the incoming stimulus from the trace of the previous repetitive stimuli. If only a few features are kept constant in the auditory stream stimuli deviation in those features also elicit an MMN. In the present study, ten harmonic structures with the fundamental frequency being omitted were equiprobably intermixed with each other. Nine of them had been constructed using 300 Hz as the missing fundamental frequency whereas the tenth had 600 Hz for the base. The only feature in which deviants differed from the rest of the stimuli was the virtual pitch. In separate experiments, two different stimulus durations (150 and 500 msec) were applied. Simple