Scalp topography of mono- and binocularly evoked potentials: generators

s59 B-1.04 EFFECTS OF A NEW ANTISPASTIC DRUG (DS 103-282) ON DYNAMIC MOTOR CAPACITY AND PASSIVE RESISTANCE IN PATIENTS WITH SPASTIC PARESIS. A. Mirtensson and E. Knutsson (Stockholm,Sweden) To evaluate the effects of a new antispastic drua. 5-Chloro-4-(2-imidazolin-2-vl-amino)-2,1, 3-benzothiadiazole hydrochloride,-on spastics reflexes and motor performance, clinical examinations were supplemented with determinations of torque in isokinetic voluntary and passive movements at different speeds (30, 60 and 120 The antispastic drug was given in deg/sec). oral doses successively increased to a maximal tolerated level or up to 32 mg/day (average 25 In the 10 patients studied, quantimglday). tative estimations of drug effects were made after medication for two weeks at the final Movements tested were knee extendose level. sion and flexion, foot plantar and dorsal flexion in one leg. The mean torque in voluntary movements at maximal effort increased in 16 and decreased in 4 movements at slow speed (30 deg/sec). At fast speed (120 deg/sec), it increased in 19 movements and decreased in 1 movement. In slow movements, spastic resistance increased in 3 and decreased in 18 movements. Commonly, the increase in voluntary strength was larger than the reduction in passive resistance. Four patients experienced an improved walking capacity. B-I.02 COMPUTER ANALYSIS OF VOLUNTARY AND PASSIVE SPEED-CONTROLLED MOVEMENTS IN MAN. L. Gransberg and E. Knutsson (Stockholm, Sweden) A system for the analysis of passive resistance, muscle force and EMG activity during joint movements in man has been designed for the study of motor disorders. It facilitates differentiation of prime-mover dysfunction and restraint due to contracture, spastic reflexes and excessive coactivation of antagonists. The examination procedure is preprogrammed for movement control and interactive data acquisition and processing. Movements are controlled by an isokinetic dynamometer (Cybex 11, Lumex Inc.) that inhibits motion above a preset speed set by the computer. Torque, angular displacement and surface EMG are recorded throughout the movement. Records are taken in repeated series of voluntary and passive equal movements at selected speeds. .Average torque, with correction for the force of qravitv, and averaqe EMG activity from antagonistic muscle groups-are calculated. For the different angular positions within the movement, the results are displayed in graphs and tables for immediate assessment of range of movement and dynamic strength and how these parameters are related to movement speed, restraint due to contracture, spastic reflexes and antagonist coactivation. The information obtained is used in decisions on

therapy and training therapeutic effects.

and in evaluation

of

B-9.08 SCALP TOPOGRAPHY OF MONO- AND BINOCULARLY EVOKED POTENTIALS: GENERATORS. D. Lehmann, E. Adachi-Usama and F. Zafiridis (Zurich, Switzerland) The scalp topography of average potentials evoked by monocular vs. binocular 2/set checkerboard reversal stimulation (150 field, lo checks) was examined in 15 normal volunteers. Data from a midline row of 6 or 9 electrodes (from 2.5 cm below the inion to 7.5 or 15 cm above the inion and an anterior electrode at 30% nasioninion) were collected. Latency of the evoked occipitally positive component around 100 msec was defined as time of maximal potential difference (response amplitude) within a time window of 30 msec between any two of the utilized electrodes, a reference-free determination. Profiles of the instantaneous voltages along the electrode row were plotted at the latency of maximal response amplitude, and compared for upper and lower hemiretinal mono- and binocular stimulation. Across subjects, upper hemiretinal stimuli showed a significantly more anterior location for binocular than for monocular potentials. Lower hemiretinal stimulation caused significantly different results, i.e. a tendency to more posterior locations for binocular than monocular potentials. These differing locations of evoked maximal responses for monocular vs binocular stimuli indicate different neural generator populations for the potentials. The more anterior location for binocular than monocular upper hemiretinal and the tendency to a more posterior location for binocular than monocular lower hemiretinal stimuli suggest generators in the extrastriate regions. B-9.03 MAPPING OF EVOKED POTENTIAL FIELDS: REFERENCE-FREE DETERMINATION OF COMPONENT LATENCY AND LOCATION. D. Lehmann and W. Skrandies (Zurich, Switzerland) Evoked potential data recorded simultaneously from many scalp points (48) are conveniently displayed as time series of isoootential contour maps. -The configuration of a map is not influenced by the chosen reference. Times of maximal response strength (latency of evoked potential components) reflect maximal activities of circumscribed-neural populations. In order to determine these times of maximal activity in an unbiased approach, the root of the mean of the squares of all possible potential differences (N*(N-1)/2) between the utilized N scalp electrodes is computed for each map. This value is called "field power". Plotted over time, field power is high when the mapped distribution shows a prominent peak, and low during times of unpronounced field relief. The map at maximal field power is then searched for the location of