Movement Disorders Vol. 4, No. 1, 1989, pp 97-104 0 1989 Movement Disorder Society

Abstracts of the Symposium on High Technology in the Quantitation of Movement Disorders

Sponsored by the Movement Disorder Society

Held in Jersusalem, Israel, on June 5, 1988

Supported by educational grants from Sandoz Phamaceuticals, U.S.A.; Schering AG,

Organizing Committee: J. Jankovic (Houston), A, E. Lang (Toronto), S. Fahn (New York)

HIGH TECHNOLOGY IN THE QUANTITATION OF MOVEMENT DISORDERS. Mark Hallett, M.D., (Human Motor Control Section, MNB, NINCDS, National Institutes of Health, Bethesda, Maryland, U.S.A.). Quantification of movement disorders can be useful for both evaluation of therapy and

evaluation of progressive disease. In clinical and research practice today, most of the quantitative studies done are subjective functional scales or objective clinical signs. Ex- amples of subjective functional scales are those that include estimates of abilities in activ- ities of daily living and parts of the traditional physical examination. Videotaping would be an aid in this type of assessment. Examples of clinical signs with objective measurement include number of button presses in a fixed period of time and amount of time needed to walk a fixed distance. As knowledge grows in this area, there should be a shift to objective assessment of pathophysiology because this should be the most direct measure of the disease process and of the efficacy of therapy. An example of physiological quantification is in the analysis of the speed of movement. The time taken to complete specified move- ment tasks can be an easily quantified clinical sign. As the first step in approaching the pathophysiology , the time from a triggering stimulus to the completion of movement should be divided into the reaction time, from stimulus to initiation of movement, and the move- ment time, from initiation to completion of movement. Movement time, at least in Parkin- son’s disease, has been better related to the clinical assessment of bradykinesia, and there is some understanding of the pathophysiology of slowed movement times, both with sim- ple, single joint movement and more complex, simultaneous and sequential movements.

Methods of electrophysiologic assessment include electromyography (EMG) of the mus- cles involved in the movement disorder, correlation of the electroencephalography (EEG) simultaneous with the abnormal EMG, reflexes, and kinematic analysis (including accel- erometry) and kinetic analysis of the movements. There has also been some use of spe- cialized types of event-related potentials for quantification, for example, in assessing level of dopaminergic activity. Some of these studies can be done with routine EEG, EMG, or evoked-potential equipment; other require more sophisticated equipment including com- puters. Real “high technology” including magnetic resonance imaging and positron emis- sion tomography scanning are currently most useful in establishing diagnoses, but certainly can quantify the amount of anatomic pathology.

Examples of where quantification can be useful in current clinical practice include tremor, muscle tone, and sway during standing.

F.R.G.; Merck Sharp & Dohme, U.S.A.; and Ambulatory Monitoring, U.S.A.

QUANTITATION OF CEREBELLAR DYSMETRIA USING A THREE-DIMENSIONAL MOTION ANALYSIS SYSTEM. R. G. Lee (Department of Clinical Neurosciences, Uni- versity of Calgary, Calgary, Canada).

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Quantitative kinematics of limb movements requires a system that will provide an acu- rate record of movement for several limb segments with high resolution in both the spatial and temporal domains. Several commerical systems capable of accomplishing this are now available. This report will describe our initial experience using a WATSMART motion analysis system to analyze reaching movements in patients with cerebellar incoordination.

Infrared-emitting diodes were attached to the tip of the index finger, the wrist, the elbow, and the shoulder. From a starting position with the arm at the side and the elbow flexed to No, subjects were required to move the finger tip to a target located at shoulder height and arms length in front of them. This task required -90" of flexion at the shoulder and simultaneous extension at the elbow joint. Two infrared cameras recorded the position of each diode at a rate of 2001s. The results were converted into three-dimensional coordinates that were used to generate plots of movement path, velocity, and joint angles.

In normal subjects, movement at the shoulder and elbow is coupled so that the finger tip follows a consistent straight line path to the target with little variation from trial to trial regardless of the speed of the movement. In the cerebellar patients the movement paths were irregular and highly variable from trial to trial. Part of the reason for this could be seen in the joint angle plots, which revealed uncoupling of the normal precise relationship between elbow angle and shoulder angle. Often the shoulder began to flex well before any extension occurred at the elbow. In addition the symmetrical bell-shaped velocity profiles that are a feature of normal movements of this type were distorted in the cerebellar pa- tients. In many cases there was more than one velocity peak, or peak velocity occurred at different times in different limb segments.

Our preliminary experience suggests that this system will be a powerful tool to analyze the kinematics of multijoint limb movements in patients with cerebellar dysfunctions and other movement disorders.

24-H TREMOR RECORDING METHOD AND ADVANTAGES. M. Bacher, E. Scholz, and J. Dichgans (Department of Neurology, University of Tubingen, Tubingen, F.R.G.).

We have designed a method for tremor recording based on surface electromyography (EMG). It was our aim to use this method in clinical practice. Therefore, only standard equipment is used. Data are recorded continuously on a small, battery operated, four- channel, Medilog recorder (a standard device for electroencephalographic recordings). Data are evaluated offline on a PDPll/44. Implementation of the software on a standard PC is possible. Starting and stopping of the tape replay on an Oxford PMD12 system and A/D-conversion are controlled by the program. Signal quality is controlled via a predefined amplitude range. Low-frequency artifacts are eliminated by means of a digital FIR filter. EMG modulation is extracted by squaring, lowpass filtering (FIR filter), and linearizing the signal. Power spectra are calculated for periods of 5.12 s each. Three consecutive spectra are averaged. Tremor occurrence, tremor frequency, and tremor intensity (signal-to-noise ratio of dominant peak) are extracted from each spectrum.

The main advantages of the method are: (a) Data recording is easy. Data evaluation is fully atuomatic (no additional checks are necessary). (b) Patients are not disturbed or handicapped by the recording procedure. (c) Data recording is not restricted to a labora- tory. The method can be used in outpatients. (d) Tremor occurrence can be quantified. (e) Tremor intensity (distribution, average and maximum) can be measured under everyday conditions. (f) All relevant tremor parameters (occurrence, frequency, and intensity) are given with a time resolution of 15.36 s over a period of 24 h, if desired. (g) Diurnal variations (e.g., due to on and off phases) can be quantified.

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BIOMECHANICAL ASSESSMENT OF GAIT AND UPPER EXTREMITY MOVEMENTS IN PARKINSON’S DISEASE. K. R. Campbell, M. D. Grabiner, P. J. Sweeney, and M. R. Hanson (Cleveland Clinic, Cleveland, Ohio, U.S.A.).

Techniques have been developed to assess mechanical and neuromuscular variables that delineate deviations from normalcy in Parkinson’s patients during movement tasks involv- ing gait and selected upper extremity motions. A state-of-the-art high-speed videography system has been employed in conjunction with force platforms and telemetered electro- myography (EMG) to assess locomotion deficits in parkinsonism. During gait analysis a set of 25 passive retroreflective markers are placed on body segments. The three-dimensional (3D) motion of these markers is then tracked by the videography system and subsequently analyzed to determine the 3D kinematics of gait. Synchronously recorded analog data from force platforms and EMGs from bilateral pairs of lower extremity musculature are em- ployed to analyze kinetic and neuromuscular mechanisms. EMG profiles for each subject are determined as ensemble averages of linear envelopes from 10 gait cycles computed from full wave rectified and low-pass digitally filtered (3-Hz cutoff) EMGs. These profiles are then averaged across the parkinsonian population. Upper-extemity motion is assessed using the high speed videography system. A single retroreflective marker is placed on the distal phalanx of the third digit to track motion in frontal and sagittal plane tasks. Frontal plane tasks involve drawing straight horizontal and vertical lines as well as tracing a circular pattern. The sagittal plane task involves planar motion around an obstacle. Move- ment data is obtained unilaterally at an acquisition rate of 200 Hz. These results are subsequently analyzed for spectral content and smoothness of motion, employing the time derivative of acceleration, jerk. The variables analyzed in these tests provide quantitative measures of movement disorders in the lower extremity during gait and in the upper extremity. These variables are then employed to statistically identify: deviations from normal populations, the time course of movement disorders in Parkinson’s disease, and the effects of various interventions on movement deficits in parkinsonism.

ELECTROPHYSIOLOGICAL ASSESSMENT OF MOTOR DISABILITY IN PARKINSON

Ray L. Watts, M.D., Alan Freeman, M.D., Allen Mandir, B.S.E.E., J. Claude Hemphill 111, B.S., Brian Hirschfield, B.S., Erwin B. Montgomery, Jr., M.D. (Emory University School of Medicine, Atlanta, Georgia, and Washington University School of Medicine, St. Louis, Missouri, U.S.A.).

We are employing electrophysiological techniques to objectively study motor disability in Parkinson’s disease (PD) patients before and after autologous adrenal-caudate trans- plantation. We assess tremorhnvoluntary movements, reaction time (RT; a measure of premovement neural processing), movement time (MT; the phsyiological correlate of bradykinesia), and rigidity preoperatively and at 3, 6, 12, and 24 months postoperatively. Using electromyographic (EMG) and accelerometric recording techniques, in conjunction with videotaped application of modified Columbia and Unified PD Rating Scales and plasma L-Dopa levels during an “all-day” study, we measure the amount of tremor andor involuntary movement (dystonia or dyskinesia) during the patient’s best (“on”) and worst (“off ’) functional status. By correlating these electrophysiological and clinical measures with the plasma L-Dopa levels we produce a dose-response curve for comparison with later studies postoperatively. We measure RT and MT in the millisecond range using a visually instructed wrist flexiodextension paradigm that is computer controlled. Rigidity at the

DISEASE PATIENTS UNDERGOING ADRENAL-CAUDATE TRANSPLANTATION.

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elbow is quantified using a computer-controlled torque motor system that yields a single, reproducible number that represents the stiffness of muscles acting at the elbow. Video- taped clinical functional status and plasma L-Dopa levels are determined in conjunction with these studies as well.

Preliminary data from patient 1 (male; age 48 years; stage IV off medications) preoper- atively and at 3 months postoperatively reveal a 40-50% reduction in the clinical disability score and frequency/duration of dystonic spasms when “off.” His preoperative RT (time from “go” signal to onset of agonist EMG) and MT (time from onset of movement to achievement of a final target) were significantly prolonged compared with age-matched controls (patient 1 RT 285+/-47 ms and MT 418+/-28; control RT 171 +/-23 and MT 239+/-26; p < .001). At 3 months postoperative, movement parameters were improved

Results at 3 and 6 months postoperative on the six patients who have undergone surgery (RT 194+/-46 and MT 348+/- 15).

thus far will be presented.

OBJECTIVE METHODS FOR THE ASSESSMENT OF MOTOR PERFORMANCE DUR- ING ARM MOVEMENTS IN BASAL GANGLIA DISORDERS. T. Flash, R. Inzelberg, S. Edleman, and A. D. Korczyn (Department of Applied Mathematics, Weizmann Institute of Science, Rehovot, Department of Neurology, Tel-Aviv Medical Center, and Depart- ment of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv, Israel).

Recently, mathematical models were formulated that were shown to predict both the qualitative features and quantitative details observed experimentally in arm and handwrit- ing movements performed by normal subjects in the horizontal plane (1). Based on these models, the aim of the present study is to develop objective methods of identifying and quantifying motor deficits in Parkinson’s disease (PD) and other basal ganglia disorders. Using dynamic optimization theory, coordination was modeled mathematically by defining an objective function, a measure of performance for any possible movement. The objective function was the magnitude of hand jerk (rate of change of acceleration) intergrated over the entire movement duration. This is equivalent to assuming that a major goal of motor coordination is the production of the smoothest possible movement of the hand. The measured movements confirmed the following predictions of the model: unconstrained reaching movements are roughly straight with bell-shaped speed profiles, curved motions are composed of low-curvature segments joined by curvature maxima; at points of high curvature the tangential velocity is reduced; the duration of the segments are roughly equal. The dynamic optimization paradigm has been recently extended to model all types of trajectories occumng in handwritten characters. The trajectories are assumed to be planned as series of simple strokes that are then concatenated to form the entire variety of character shapes. For each stroke, in turn, arm kinematics can be modeled assuming snap (time derivative of jerk) minimization and based on a small number of parameters such as the directions of motion and hand locations at the stroke end-points. The above mathe- matical models permit both analysis and synthesis of intact motor behavior. They, there- fore, served as a basis for assessing the nature and degree of motor deficits in PD and idiopathic torsion dystonia patients. Control and patient arm and handwriting trajectories were recorded and numerical estimates of the degree of fit of the movements to those predicted by the model were obtained by calculating correlation indices of hand positions and velocities. The application of these methods to the analysis of straight and curved movements in PD and idiopathic torsion dystonia patients will be described.

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1 . Flash T, Hogan N. The coordination of arm movements: an experimentally confirmed mathemat- ical model. J Neurosci 1985;5:1688-703.

OPTOELECTRONIC MOVEMENT ANALYSIS TESTS QUANTLFYING PARKINSONIAN DISSOLUTION OF COMPLEX MOVEMENTS. G. Steq, P. Ingvarsson, U. Norrsell, and B. Johnels (Department of Neurology, Sahlgren Hospital, Goteborg, Sweden).

The dissolution of complex movements in Parkinson's disease has gained increasing interest. Until recently, however, no methods have been available for movement analysis in the freely moving human. We will describe an optoelectronic camera system recording the three-dimensional space coordinates of 6-12 infrared-light-emitting diodes fastened on the body segments and movement tasks designed to permit analysis of the coordination of postural, locomotor, and manual acts in goal-directed movements. The task of lifting an object from the floor forward to a shelf on 1.5-m horizontal and vertical distance aims to test the coordination of postural erection, gait, and goal-directed placing. Postural and bimanual coordination is analyzed when the patient facing the camera grasps an object on the floor on one side and places it on a shelf on the other side. Sensorimotor integration is tested when the patient is requested to grasp, move, and place the object repeatedly between two independently moving platforms. The results are discussed as tentative ex- pressions of a reduced capacity of simultaneous motor program coordination in Parkin- son's disease.

QUANTITATION OF INVOLUNTARY MOVEMENTS WITH SURFACE ELECTROMY- OGRAFWY. Nobuo Yanagisawa and Takao Hashimoto Department of Medicine (Neu- rology), Shinshu University School of Medicine, Matsumoto, Japan].

Involuntary movements caused by disorders of the central nervous system are expres- sions of excitation of motoneurons innervating the involved muscles, whose electromyog- raphy (EMG) furnishes information on the quality and quantity of movements and may contribute to evaluating movement disorders on a physiological basis. EMG was recorded with Ag-AgC1 disk electrodes bipolarly, rectified and integrated. The amount of integrated action potentials were converted into sequential pulses, which were fed into a pulse counter. The EMG amount, thus calculated, corresponds well to force (torque) generated by the muscle in tonic voluntary contraction of extremity muscles. For evaluation of phasic burst discharges appearing repeatedly, which are observed in tremor, chorea, or ballism, the power spectrum of intervals of successive peaks in smoothed curve of integrated EMG was calculated in addition to the total amount of EMG over a limited time. As for condi- tions of recording, interelectrode distance of 3.5-4.0 cm and time constant with amplifiers of -0.005 s were appropriate. Differences in the site of electrode placement within 1 cm did not produce a crucial difference in EMG amount when exmained in extremity, forehead, and submental regions. Records on different dates resulted in larger variations in the amount of EMG when tested with 2040% of maximal voluntary contraction. Differences in amount for continuous contraction for 30 s were from 5 to 16% in facial or extremity muscles. The pattern of phasic discharges of EMG in involuntary movement showed ex- cellent reproducibility. Examples of quantification of involuntary movements with this method will be presented in the evaluation of the effects of neuropeptides on dyskinesia.

KINEMATIC AND ELECTROMYOGRAPHIC ANALYSIS OF BALLISTIC PERFOR- MANCE IN PATENTS WITH PARKINSON'S DISEASE. F. Benvenuti, A. Baroni, S. Bandinelli, M. L. Lunardelli, M. A. Mencarelli, and T. Pantaleo (Geriatric Department,

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I.N.R.C.A., National Research Institute, and Department of Physiological Sciences, University of Florence, Italy).

Ballistic movements have been operationally defined as the movements performed “as rapidly and accurately as possible” in a step-tracking task. In normal subjects they are characterized by a triphasic electromyographic (EMG) pattern of activation of the agonist and antagonist muscles. The sequence consists of an initial burst of activity in the agonist muscle, followed by a burst of activity in the antagonist and finally by a small, not constant, second agonist burst. This EMG pattern is present both in young and elderly normal subjects, although the latter show a reduced mean velocity accompanied by a reduced duration of the first agonist burst. On the other hand, it has been shown that patients with Parkinson’s disease display alterations of the EMG patterns underlying ballistic perfor- mance.

The effects of some antiparkinsonism drugs, such as L-Dopa, bromocriptine, lisuride, and L-deprenyl, were investigated in patients with Parkinson’s disease. Patients were as- sessed clinically and evaluated further by studying some kinematic and EMG variables of fast arm abduction movements performed in a step-tracking task. Surface EMG activity was recorded from the posterior fibers of the deltoid muscle (agonist) and from the pec- toralis major muscle (antagonist). EMG signals are also full-wave rectified and “integrated” (leaky integrator, time constant 20 ms). A close parallelism was found be- tween the severity of bradykinesia and the severity of the alterations of the kinematic and EMG variables of ballistic movements. Results indicate that the analysis of ballistic motor performance may be a useful tool in pathophysiological and pharmacological research on Parkinson’s disease.

This method has recently been proved to be valuable in the objective assessment of flunarizine-induced parkinsonism and recovery after drug withdrawal.

COMPUTER QUANTIFICATION OF THE SLOW EYE MOVEMENTS. Kyota Adki, Ph.D. and Natsue Shimizu, M.D. (Department of Information Science, Faculty of Engineering, Utsunomiya University, Utsunomiya-shi, and Department of Medicine, Ichihara Hos- pital, Teikyo University School of Medicine, Ichihara-shi, Japan).

For the evaluation of voluntary and involuntary movements, the quantification of the velocity of movements is useful. This paper proposes a method for obtaining the velocity of the slow eye movements such as slow phase of nystagmus and pursuit eye movement with a number of noises and more than 200,OOO data. The horizontal and vertical eye movements were recorded by DC-EOG or oculotracker using a high speed TV system. The method is implemented using C language. The program can be executed on a personal computer or a workstation. In our experiment, data were converted into the digital signals at the sampling rate of 6.7 ms. Slow eye movement was characterized by no change of direction during a certain period of time and no large change in speed during 140 ms. At the first step, the noise signal, defined as a large change in speed during a very short period, was removed. Then, the speed of eye movements were calculated by change in eye position during 100 ms. At the second step, the average velocity of eye movements for 8 s before and after an eye speed datum was calculated and the datum that was off the average was removed. Thus, small noise signals were taken away. Finally, data of velocity were aver- aged at every certain period and were printed out in value and in graph. Using this method, we can have reliable data of spontaneous nystagmus and pursuit eye movements. The

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method can be widely applied to an analysis of slow movements such as chorea and voluntary arm movements.

COMPUTERIZED EVALUATION OF SIDE ACCENTUATION OF DIADOCHOKINETIC MOVEMENTS. P. H. Kraus, P. Klotz, B. Keck, and H. Przuntek (Department of Neu- rology, University of Bochum, and Department of Neurology, University of Wiirzburg, F.R.G.).

Using a computer-aided examination of diadochokinesia (fast-alternating pronation and supination) we estimated phase and phase shift between left and right hand for healthy controls as well as differences of frequency and amplitude between both sides. We com- pared the values for simultaneous oscillation with those of the single-handed tasks. The pattern of rotation was found to be quite sinusoidal. In patients with parkinsonism and ataxia we found shape of the oscillation to look more

like a triangle in the first case whereas in ataxia it looked like a saw tooth in a typical manner. Furthermore, oscillation was markedly more irregular in parkinsonism and some patients showed fast motion with a very low amplitude.

Most patients who had movement disorders showed clear side-accentuated symptoms. Regarding this we found high correlation between clinical and computer-aided examina- tion.

In some patients (including one patient with spasmodic torticollis) clinical diadochoki- nesia appeared to be normal but the computer-aided simultaneous test frequency of the left and right hand showed a small difference (phase shift); obviously coordination between left and right was disturbed. As in the rest of our battery of tests using technical equipment we found side accentuation to be a useful additional parameter for identiiication of motor disturbance.

MECHANICAL, AND ELECTROMYOGRAPHIC ANALYSIS OF MUSCULAR RIGIDITY IN PARKINSON’S DISEASE. M. D. Grabiner, K. R. Campbell, P. J. Sweeney, and M. R. Hanson (Cleveland Clinic, Cleveland, Ohio, U.S.A.).

A technique is proposed that quantifies the bioelectric and contractile responses of skeletal muscle to passive lengthening, which can be used to assess muscular rigidity and spasticity associated with Parkinson’s disease. An isokinetic dynamometer has been inte- grated with electromyographic (EMG) instrumentation. The dynamometer permits upper or lower extremities to be passively moved through a range of motion at a predetermined and angular velocity. The available range of isokinetic velocities in the passive mode is from 10 to 12O”ls. Surface EMG is used to generate temporal and amplitude excitation profiles of the joint system agonists and antagonists. Up to eight EMG signals may be digitized and appended to the files containing torque, position, and velocity data from the dynamometer. A typical assessment for rigidity of the knee joint includes placing EMG electrodes over the superficial components of the quadriceps femoris and hamstrings mus- cles. After subject positioning and stabilization in the dynamometer the knee joint is pas- sively extended and flexed. The subject is instructed to “not interfere” with the passive motion. The passive resistance of the anatomical system to the motion of the dynamometer is measured in terms of magnitude (in torque units) and location and duration (in terms of angular position of the knee). The EMG signals from the agonisvantagonist system are recorded simultaneously, and subsequently analyzed with respect to the magnitudes and

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durations of excitation, the angular positions of the knee joint at which these excitations occur, the relationship between excitation and involuntary knee joint torque, and syner- gistic patterns of the agonist/antagonist system. The clinical value of this type of assess- ment is the quantification of the progression of rigidity and spasticity in Parkinson's disease and the effects of various interventions, which then provide a statistically defined time course record.

QUANTITATIVE EVALUATION OF INTERDEPENDENCE OF MOTOR UNIT DIS- CHARGES IN TREMOR. A. W. Wiegner and M. M. Wierzbicka (Massachusetts Gen- eral Hospital and Harvard Medical School, Boston, Massachusetts, U.S.A.).

The analysis of interdependence of firing times of motor units simultaneously recorded from one muscle is of prime importance in studies of tremor. A new synchronization index (SI) is proposed for quantitative evaluation of motor unit behavior in tremor. Previously introduced similar indices (see, for example, Sears and Stagg, 1976, J Physiol263:357-381) were applied to data from recordings, which resulted in large mean bin counts in the cross-correlation histogram. Such long recordings are usually made in studies using anes- thetized animals but are technically impractical in recordings of motor units in humans, in particular during tremor. The new index is useful for mean bin counts as low as 10. A further advantage of our index is that it covers the whole range of possible motor unit behavior: it is not limited to the detection of short-term synchronization characterized by a narrow (3-4 ms) peak in the cross-correlation histogram, such as might be observed in phsyiological tremor, but can also be used to evaluate the degree of synchronization of motor unit firng in larger-amplitude tremors in which broader (20-80 ms), flatter peaks appear in the cross-correlation histogram.

The SI is defined as the ratio of excess bin counts under the peak (in comparison to mean bin count outside the peak area) to the total number of counts in the cross-correlation histogram. (Wiegner and Wierzbicka, 1987, J Neurosci Methods 22: 125-13 1). Mathemat- ical formulas are derived for the critical values of SI (if SI > critical value, peak is statis- tically significant) at a chosen level of statistical significance in terms of three parameters: number of bins, number of bin counts, and width of histogram peak expressed in number of bins. In addition, a table of critical values of the SI at several levels of statistical significance has been calculated.

We have used the SI to quantify motor with synchronization during physiological and enhanced physiological tremor measured at the wrist in humans.

Movement Disorders, Vol. 4, No. I , 1989