114 Piracetam effects on global complexities of spontaneous multichannel EEG

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parietal lesions cause visual inattention, neglect, mislocalisation and misaiming to targets in contralateral space. These characteristics suggest that the inferior parietal lobule is responsible for specifying in visual coordinates the parameters of the movements which would be required to bring eye or arm onto a target. The main output from the inferior parietal lobule passes not to other parts of the cerebral cortex, but to the cerebellum via the pontine nuclei. Hence cerebellar lesions impair the ability to recalibrate the parameters of movements programs to adapt to changing circumstances.

111 HOW DOES THE BRAIN COORDINATE HANDS FOR UNIFIED ACTIONS?

of Psychophysiology

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fine accuracy control of the reach; this control is delegated to the arm and hand.

113 PATTERNS OF INTERLIMB COORDINATION: CONSTRAINTS IN BIMANUAL MOVEMENT

Stephan P. Swinnen’, Natalia Dounskaia’,‘, Hedwig Bogaerts’ and Suy Ellen’ ‘Motor Control Laboratory, Dep. of Kinesiology, K.U. Leuven ‘Institute of Control Sciences, Russian Academy of Sciences, Moscow

THE TWO

Mario Wesindanger Department of Neurology, University of Bern, Switzerland Several experiments are described that provides some indication of how the brain controls what each hand does during unified actions.

112 COORDINATION AMONG BODY SEGMENTS DURING REACH-TO-GRASP MOVEMENTS ASSISTED BY THE TRUNK George E. Stelmach, Rachael Seidler and Jinsung Wang Arizona State University, Tempe, AZ. USA Several experiments are reported that examined the coordination among the body segments during reach-to-grasp movements, which involves grasping by the hand and reaching by the arm and trunk In one experiment, it was found that with different combinations of body segments used to deliver the reach to an object, the temporal and spatial kinematic parameters related to the grasp aperture remained invariant. In second experiment where temporal constraints were placed on the reach, a similar pattern of results were observed. The striking feature of these data were how the motor system reduced variability across segments such that the variability was reduced as the components became more distal. Regression analysis revealed that arm movement was more correlated with the hand movement under high temporal constraints while. the trunk was more correlated with the hand for the unconstrained condition. Together these experiments suggest that their exist a hierarchy of motor control process in which the reach and grasp components are governed by independent neuromotor synergies. Furthermore, the neuromotor synergy that governs the transport component is independent of the synergy that governs the grasp component, it can be superimposed without affecting the other synergy. In that way the motor control process that determines the grasp compo nent can keep the kinematic properties of the grasp formation invariant regardless of the body segments involved. Finally, these data suggest that the trunk does not participate in the

Even though humans produce a variety of bimanual tasks in which each hand uniquely contributes to accomplishment of goal-directed behavior, basic interlimb coordination constraints often limit the production of new tasks. More specifically, features of one task become evident in the other task, or vice versa. The study of these processes is particularly informative about the organizational procedures used by the CNS to deal with the production of such complex movements. Potential movement parameter candidates that serve as a medium for the expression of such constraints will be discussed, e.g., amplitude, force, and movement direction. In view of substantial evidence that many CNS centers are involved in the specification of movement direction (the population coding hypothesis) and that directional specifications are subject to interhemispheric transfer through callosal connections, particular emphasis will be placed on limitations in the simultaneous specification of different directions for both limbs. The present findings will be discussed within the framework of a combination of an egocentric and allocentric coordinate system in which the patterns of directional interaction between the upper limbs can be accounted for most parsimoniously, and whereby the former coordinate system plays a more predominant role than the latter.

SYMPOSIUM 20: Nonlinear Aspects of Brain Function: Clinical Application

114 PIRACETAM EFFECTS ON GLOBAL TIES OF SPONTANEOUS MULTICHANNEL

COMPLEXIEEG

I. Kondakor*, D. Lehmann, C.M. Michel, J. Wackermann, T. Koenig, K. Kochi and R.D. Pascual-Marqui The KEY institute for Brain-Mind Research, Department of Psychiatry, University of Zurich, Switzerland; Department of Neurology, University Medical School of P&s, Hungary Global complexity of 47-channel resting human electroencephalogram (EEG) was studied after intake of a single dose of nootropic drug (piracetam, Nootropil”, UCB Pharma) for 13 healthy volunteers. Four treatment levels were used: 2.4g, 4.8g, 9.6g piracetam and placebo. Brain electric activity was assessed through Global OMEGA Complexity (GOC), as

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quantitative measure of complexity of the trajectory of EEG map series in state space. For statistics the medians of GOC of the four treatment levels were used. GOC decreased from placebo (median GOC: 5.621 to groups with drug (median GOCs: 4.80 (2.4 g piracetam); 5.07 (4.8 g); 4.73 (9.6 g)>. A Friedman’s ANOVA (N = 13, K = 4) showed significant overall result (x2 = 11.5, df = 3, p < 0.01). Post-hoc paired Wilcoxon tests showed significant decreases from placebo to all of the treatment levels with drug. Our study indicates single dose effects of piracetam on spontaneous EEG map series. The drug is already effective by the lowest treatment level. Lower value of GOC can be interpreted as a lower number of independent parallel processes of the brain.

115 NONLINEAR BRAIN DYNAMICS: WORKING MEMORY PERFORMANCE AND THE POINT-DIMENSION MEASURE

Sammer Gebhard Inst. of Psychology 1, University of Hamburg, Von-Melle-Park 11, D-20146 Hamburg, Germany

Recently, non-linear EEG-dynamic measures were shown to vary with memory load. The point correlation dimension, which is a non-linear measure of the dimensional complexity of the EEG, is known also to work with locally non-stationary signals. This is of interest, if an EEG-times series is expected to be stationary only within sub-stages because of processingrelated factors. In this study both non-linear and linear analyses were applied to the EEG, which was recorded from 6 healthy subjects performing Corsi block tapping. Frequently, this test is used for clinical examination of the non-verbal memoryspan. A computerised version of the Corsi-task was used: 9,,cubes“ were presented using 39 different templates; memory set-sizes were 4,5 and 6 cubes; tapping was done via the pointer device (position reset at the start of each trial); subjects performed 30 trials x 3 set sizes + 10 baseline trials (5 cubes in one line, requiring just one fixed tapping sequence - left to right) = 100 single trials. For correctly performed trials both the point-correlation dimension and the spectral power were computed from the EEG (tapping-sequences) as dependent variables. Response times (tapping) were taken as behavioural measures. Compared to the baseline recordings the dimensional complexity decreased at all locations under the memory load conditions. Theta-power increased at right-frontal locations with increased mental load. Response latencies were longer with higher memory load indicating memory search during tapping. Problems related to the non-linear analysis will be discussed.

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116 CHANGES IN THE DIMENSIONAL COMPLEXITY OF THE EEG AND ERPs CAUSED BY CORTICAL AND SUBCORTICAL STROKE M. Molnar’, J. Sagi-Osman’, 2. Nagy’, J. Kenez3 and S. Horvath3 ‘Institute for Psychology, Hungarian Academy of Sciences, Budapest, Hungary ‘National Stroke Center, Budapest, Hungary 3MAV Hospital, Budapest, Hungary The use of mathematical methods based on chaos theory allow the quantitative assessment of the predominantly nonlinear features of brain electrical activity, not accessible to conventional electrophysiological analysis. The main objective of the present study was to compare the efficacy of these two methodologies in the analysis of EEG in stroke patients. The EEG and auditory ERPs were recorded by 32 electrodes (eyes closed, eyes open and video watching conditions) and in different paradigms in which the P3 ERP wave appeared. The point correlation dimension (PD2, calculated from 80 see long epochs) was used to determine the dimensional complexity of the EEG. The scalp distribution of the PD2 and that of frequency spectra were mapped. 13 normal subjects and 14 stroke patients (unilateral partial or complete middle cerebral artery occlusion1 were investigated. Typical cases are presented. In the normal population the scalp distribution of the PD2 and that of frequency spectra were symmetrical in all conditions.‘A marked asymmetry was found in stroke irrespective of whether it involved subcortical (basal ganglia), or both cortical and subcortical (temporoparietal regions, hippocampus, amygdala, insula, putamen) structures with low PD2 values ipsilateral to the stroke. In all cases there was but only partial overlap between the low dimensional area and that characterized by slow frequencies. The results of dimensional analyses to indicate pathology were more consistent, i.e. less dependent on recording conditions than those based on the investigation of frequency spectra. Unilateral lesion of the basal ganglia, hippocampus and amygdala caused ipsilateral disappearence of the P3 wave. It is suggested that non-linear methods, compared to traditional spectral analysis, may in cases be more accurate to localize brain pathology.

117 ELECIROCORTICAL CONCOMITANTS OF EMOTIONAL PROCESSING AND PERSONALITY IN THE LIGHT OF NON-LINEAR DYNAMICS SYSTEM THEORY: AN EEG INVESTIGATION L. Aftanas Psychophysiology Laboratory, RAMS, Novosibirsk, Russia

Institute

of Physiology

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The application of non-linear system theory to the EEG has been shown to evidence information beyond that provided by