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Annual meeting of the Bulgarian society of EEG, EMG and clinical neurophysiology
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Electroencephalography and Clinical Neurophysiology, 1981, 52: 76P--82P Elsevier/North-Holland Scientific Publishers, Ltd.
Society proceedings ANNUAL MEETING OF THE BULGARIAN NEUROPHYSIOLOGY
SOCIETY OF EEG, EMG AND CLINICAL
Sofia, February 28, 1981
Secretary: Dr. N. NIKOEVSKI 1st Neurological Clinic, Medical Academy, str. G. Sofiiski 1, Sofia 1431 (Bulgaria) (Accepted for publication: July 14, 1981)
1. A microprocessor system for EEG a n a l y s i s . - I. Dascalov, M. Matveev, C. Levkov, R. Arnaudova and M. Nikolova (Sofia) A system for the analysis of the spontaneous EEG was built, using a 6800 microprocessor with 8k RAM and 8k EPROM. Two or 4 channels are simultaneously digitized at a frequency of 250 Hz. Durations and amplitudes of the successive EEG waves of 10 sec epochs are measured, and histograms are obtained and stored. Cumulative histograms from four 10 sec epochs are printed out, simulating frequency quasispectra in the 0--50 Hz range at 2 Hz intervals. The raw 'spectra' are previously smoothed using the simple Hamming algorithm. The frequency resolution, being limited by the digitizing frequency, has been improved in the high-frequency region by computing the channel contents through interpolation as well as by the smoothing algorithm.
2. Inhibitory extracranial stimulation. -- D. Tchavdarov (Sofia) In a group of 24 epileptics with frequent subclinical paroxysmal activity in the EEG, 125 extracranial electrical stimulations were performed. The results may be summarized as follows: without c h a n g e s 14; changes in the background a c t i v i t y - 34; intensified paroxysmal a c t i v i t y - 23; inhibition of the paroxysmal a c t i v i t y - 54. The effects depend on the size of the electrode, their place and relation, as well as electrical parameters. The effect on the EEG is 3--4 times the duration of each stimulation. By changing the position of the electrodes it is possible to elicit activating or inhibitory effects. The results are compared with those of subcortical stimulation and the suggested mechanisms of electrosleep.
3. VEP and plasma level of anticonvulsants. -- D. Tchavdarov (Sofia) The most important EEG control of seizures during carbamazepine treatment of 54 out of 130 patients was misleading because of increased focal abnormalities and EEG aggravation. In 43 of the 54 patients the amplitudes of the VEP after-discharges were abolished during treatment with carbamazepine. In 28 epileptics from this group the amplitude of wave 78--94 msec on the side of the focus decreased significantly. These findings correlate with the plasma levels of carbamazepine.
4. Polarity histogram in the analysis of evoked potential (EP) v a r i a b i l i t y . - D. Dalbokova (Sofia), I. Drews, M. Pietschmann, P. Ullsperger and H.-G. Gille (Berlin, G.D.R.) An experimental study was carried out to evaluate how much the variations in amplitude of the average EP (AEP) components, estimated by the t test, correspond to the variability in the frequency of occurrence (from the polarity histogram), estimated by the ×2 test. EPs from Cz (10/20 system) in a discriminative task with 'soft' and l o u d ' tones presented in a Bernoulli sequence were recorded. A control situation, i.e., stimulus presentation while the subject was reading a book, was also included. For each subject the two situations were presented according to the experimental design of Berenblut (1964) to separate the direct effect of the situation from the first residual effect and the time effect on the amplitude and the frequency of the EP components. The analysis of variance for the N100 and P300 parameters showed that the task had significant effect only on the P300 parameters, while the data for N 100 were not so con-
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BU L GAR I AN EEG/EMG SOCIETY
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sistent. The differences in the parameters of N100 and P300 between each combination of control and task situations were assessed for each subject separately. Totally, in 89% of all comparisons significant differences in the amplitude as well as in the frequency of occurrence of P300 were found. This suggests that the polarity histogram, together with the AEP wave form, provide a quick estimate of the individual EP variability.
post-caloric nystagmus was very useful in cases with overt vestibular response asymmetry. The amplitude of AERs (P1NI and N1P2 components) during the nystagmus was significantly reduced; recovery time was approximately 30 min. The A ER dynamic characteristics in the affected labyrinths were significantly different from those in normal labyrinths. The clinical value of this observation is discussed.
5. On the central mechanisms of vestibular function compensation in a model of delabyrinthization. -H. Kolchev (Sofia)
7. All-night polygraphic investigation in patients with temporal lobe e p i l e p s y . - - A . Alexiev, S. Slavchev and M. Kyuchukov (Sofia)
The temporal characteristics of behavioural and electrophysiological (EEG, ENG, AERs, VEPs, ERA) shifts were investigated in chronic cats following unilateral destruction of the vestibular end-organ by means of mono-iodine acetic acid. The initial signs of vertibular nystagmus appeared 27--35 rain after acid application ; at the 24th hour it was well expressed, gradually disappearing after 72 h. Tonal stimulation (1000 Hz, 60 dB SPL, ISI 2 sec) revealed amplitude augmentation of the P1N1 and NIP2 components between the 45th and 120th rain, followed by progressive reduction of A E R amplitude and disappearance after the 24th hour. Conversely, VEP amplitude significantly increased after the 150th min. The central compensation of the peripheral vestibular dysfunction, based on the corrective influences of visual somaesthetic analysers, most likely takes place in the initial 2--3 days, after which the mechanisms of 'vestibular accommodation' (Mittermayer, Pfaltz and Kammath) are triggered, i.e., compensatory influences of the intact labyrinth, interrelation effects at the level of primary vestibular nuclei and pathways in the brain stem.
Nine patients with temporal lobe epilepsy were polygraphically investigated for two consecutive nights (one phantom) each. The patients had been under Tegretol treatment for at least 30 days. In 4 of the patients investigated, generalized paroxysms of sharp and slow waves were found in the first or second stage of NREM sleep. No focal paroxysmal discharges were registered in any of the patients investigated.
6. Correlation between the parameters of caloricprovoked nystagmus and cerebral electrical activity in patients with otoneurological syndromes. -H. Kolchev and J. Wassileva (Sofia) The effects of cold water (20°C, 100 ml, 10 sec) and warm water (40 O C, 100 ml, 10 sec) vestibular provocation on EEG, ENG, ECG and AERs in 77 patients with peripheral, combined and central otoneurological syndromes were investigated. Seventy-five percent of the patients with unilateral post-caloric hypo- or hyper-reflexia revealed non-paroxysmal EEG abnormalities (single spikes or sharp waves, polymorphic slow waves) in the hemisphere ipsilateral to the damaged labyrinth. The evaluation of the angular velocity dynamics of
8. EEG investigations in acute disturbances of cerebral c i r c u l a t i o n . - - A . Alexiev and M. Memov (Sofia) Fifteen patients with acute disturbances of cerebral circulation were investigated by EEG immediately after hospitalization. The EEG was repeated 90-120 min after i.v. administration of 500 ml 10% solution of mannitol. Another EEG investigation was performed 4--5 days later, after daily i.v. administration of at least 1500 ml 10% mannitol solution during this period. After the EEG investigation, 40 mg Lasix were administered i.m. in 3 of the patients, and 2 h later the EEG was repeated. The results show that administration of 10% mannitol solution reduces the slow waves in the EEG and tends to localize them just over the ischaemic region. The EEG performed 4--5 days later shows a certain elevation of the slow waves, as well as a tendency towards their more diffuse distribution. The administration of Lasix in 3 of the patients did not lead to any significant EEG changes.
9. The epileptic state in acute disturbances of cerebral c i r c u l a t i o n . - M. Rasheva, E. Stamenov and P. Todorova (Sofia) The dynamics of the electrical activity of the brain have been studied in 20 patients in epileptic status (13 Jacksonian and 7 generalized), during the acute
78P stage o f t h e cerebral stroke. Grave c h a n g e s d u r i n g t h e i n t e r i c t a l p e r i o d were registered, c h a r a c t e r i z e d b y diffuse slow wave activity in 13 of t h e cases. In 5 pat i e n t s m o d e r a t e diffuse c h a n g e s were o b s e r v e d a n d in o n l y 2 p a t i e n t s were t h e y slight. It has b e e n established t h a t slowing a n d decrease o f a m p l i t u d e in r e p e a t e d e x a m i n a t i o n is a b a d p r o g n o s t i c sign for t h e o u t c o m e of t h e disease. Signs o f e p i l e p t i c activity in E E G s were f o u n d in 65% of t h e p a t i e n t s . It h a s b e e n p o i n t e d o u t t h a t t h e d i s t u r b a n c e s in t h e electrical activity o f t h e b r a i n registered d u r i n g t h e seizure p e r i o d h a v e n o special c h a r a c t e r i s t i c s . I n t h e i n t e r i c t a l p e r i o d t h e grave diffuse changes w i t h a general disturbance of cerebral electrogenesis and domination of t h e processes o f i n h i b i t i o n , are a relatively f r e q u e n t E E G o c c u r r e n c e , w h i c h is a result o f t h e epileptic s t a t u s as well as o f t h e a c u t e d i s t u r b a n c e of t h e cerebral c i r c u l a t i o n .
10. D y n a m i c s o f t h e electrical a c t i v i t y o f the brain in cerebellar h a e m o r r h a g e . - M. R a s h e v a , E. S t a m e n o v , P. T o d o r o v a a n d S. A v r a m o v {Sofia) T h e c h a n g e s in t h e electrical activity o f t h e b r a i n have b e e n s t u d i e d in 6 p a t i e n t s w i t h cerebellar h a e m o r r h a g e - - 5 m e n a n d 1 w o m a n aged a b o u t 62 years, a f t e r p a t h o - a n a t o m i c a l v e r i f i c a t i o n . All cases were in a d e e p l y c o m a t o s e s t a t e a n d in 5 o f t h e m p r o l o n g e d artificial v e n t i l a t i o n was p e r f o r m e d , w h i c h also gave a n o p p o r t u n i t y t o s t u d y t h e d y n a m i c s of t h e electrical activity of t h e b r a i n for l o n g p e r i o d s of t i m e . In t o t a l t h e r e were 22 E E G r e c o r d s , a n a l y s e d visually a n d b y m e a n s of a f r e q u e n c y - a m p l i t u d e analyser. High voltage d e l t a waves d o m i n a t e d in all cases against a b a c k g r o u n d o f grave generalized c h a n g e s , d e m o n s t r a t e d b y general d i s o r g a n i z a t i o n a n d slowness o f t h e electrical a c t i v i t y , m o r e clearly e x p r e s s e d in t h e c e r e b r a l h e m i s p h e r e c o n t r a l a t e r a l t o t h e cerebellar h a e m o r r h a g e . In 4 o f t h e cases f r o n t a l i n t e r m i t t e n t r h y t h m i c d e l t a a c t i v i t y ( F I R D A ) was o b s e r v e d , w h i c h d i s a p p e a r e d in l a t e r stages parallel w i t h t h e d e t e r i o r a t i o n o f t h e clinical process. T h e possible p a t h o g e n e t i c m e c h a n i s m s o f t h e o b s e r v e d c h a n g e s o f t h e bioelectrical activity were discussed a n d t h e i m p o r t a n c e o f t h e E E G for t h e d e t e r m i n a t i o n o f t h e t o p i c a l diagnosis was p o i n t e d o u t .
11. C h a n g e s in t h e electrical a c t i v i t y o f t h e brain in t h a l a m i c h a e m o r r h a g e . - E. S t a m e n o v , M. Rasheva, P. T o d o r o v a a n d S. A v r a m o v {Sofia) T h e electrical activity of t h e b r a i n d u r i n g t h e a c u t e stage o f t h a l a m i c h a e m o r r h a g e has b e e n e x a m i n e d in 11 p a t i e n t s . T h r e e t y p e s o f E E G c h a n g e have b e e n d e t e r m i n e d : diffuse c h a n g e s w i t h d i f f e r e n t degrees
SOCIETY PROCEEDINGS of m a n i f e s t a t i o n , c h a r a c t e r i z e d b y slowness and lack o f r e a c t i v i t y to f u n c t i o n a l tests in 4 p a t i e n t s ; diffuse changes w i t h an i n t e r h e m i s p h e r i c a s y m m e t r y w i t h a graver d i s t u r b a n c e o f electrogenesis ipsilateral t o t h e h a e m o r r h a g e in t w o p a t i e n t s ; diffuse changes w i t h an i n t e r h e m i s p h e r i c a s y m m e t r y a n d e v i d e n c e o f a focus of p a t h o l o g i c a l activity in 5 cases. All t h e p a t i e n t s w h o h a d diffuse changes w i t h o u t a s y m m e t r y h a d grave qualitative d i s t u r b a n c e s o f c o n s c i o u s n e s s , while t h e p a t i e n t s w i t h i n t e r h e m i s p h e r i c a s y m m e t r y in t h e E E G were c o n s c i o u s or s o m n o l e n t . E E G d a t a in s o m e of t h e cases suggest t h e great p r o b a b i l i t y t h a t t h e focus o f slow wave activity reflects t h e d a m a g e to deep brain structures. The EEG patho-anatomical c o m p a r i s o n s s h o w t h a t besides t h e c h a r a c t e r i s t i c diffuse d i s t u r b a n c e s in cerebral electrogenesis, s o m e o t h e r changes were o b s e r v e d in t h e E E G s in t h e a c u t e stage o f t h e t h a l a m i c h a e m o r r h a g e , reflecting n o t o n l y t h e gravity of t h e s t r o k e process b u t also s h o w ing t h e u n e q u a l i n v o l v e m e n t o f t h e t h a l a m i c nuclei a n d a d j a c e n t s t r u c t u r e s in t h e p a t h o l o g i c a l process.
12. E p i l e p t i c seizures in t h e a c u t e stage o f e m b o l i c s t r o k e . - - M . R a s h e v a (Sofia) E p i l e p t i c seizures ( J a c k s o n i a n and generalized) have b e e n o b s e r v e d in 10.1% (33 o u t of 3 2 8 ) o f pat i e n t s d u r i n g t h e a c u t e stage of e m b o l i c s t r o k e . T h e seizures were t h e initial m a n i f e s t a t i o n of t h e disease in h a l f of t h e cases. P a t h o l o g i c - a n a t o m i c v e r i f i c a t i o n in all t h e p a t i e n t s revealed t h a t t h e cerebral c o r t e x was involved t o d i f f e r e n t degrees in t h e i n f a r c t i o n . Diffuse changes in t h e E E G h a v e b e e n o b s e r v e d , m a n i f e s t e d in a r e d u c t i o n o f a l p h a r h y t h m and d o m i n a t i o n o f t h e t a a n d d e l t a activity, m a i n l y ipsilateral to t h e i n f a r c t i o n . Grave diffuse changes were f o u n d p a r t i c u l a r l y in t h e cases w i t h generalized seizures a n d t h e i r p r e s e n c e was a bad p r o g n o s t i c sign for t h e outc o m e o f t h e disease. S h a r p waves, spikes, spikes a n d stow waves, local or generalized p a r o x y s m a l activity, were registered in 57.1% of t h e p a t i e n t s . A n activity of this t y p e was f o u n d m o r e f r e q u e n t l y in t h e pat i e n t s w i t h J a c k s o n i a n seizures a n d its p r e s e n c e h a d n o b a d p r o g n o s t i c m e a n i n g . I t has b e e n p o i n t e d o u t t h a t t h e focus o f slow wave activity c o r r e s p o n d s t o t h e l o c a l i z a t i o n o f t h e i n f a r c t , while t h e changes o f a n e p i l e p t i c c h a r a c t e r are o b s e r v e d in a d j a c e n t zones, s o m e t i m e s in t h e c o n t r a l a t e r a l h e m i s p h e r e or bilaterally. Possible p a t h o g e n e t i c m e c h a n i s m s for t h e occ u r r e n c e o f t h e epileptic seizures were discussed, as well as t h e c h a n g e s in t h e electrical activity o f t h e b r a i n in t h e a c u t e stage o f t h e e m b o l i c s t r o k e .
BULGARIAN EEG/EMG SOCIETY 13. EEG investigations of women with Stein-Leventhai s y n d r o m e . - A. Shterev, D. Daskalov and S. D o k u m o v (Sofia) EEG e x a m i n a t i o n s were p e r f o r m e d in 46 patients with Stein-Leventhal s y n d r o m e after clinical, l a b o r a t o r y , radiological, operative and histological verification. No patient disclosed anamnestic or clinical data of organic cerebral disorder. In 20 of the cases EEGs were p e r f o r m e d before and after cuneif o r m resection of the ovaries. EEGs were recorded f r o m bipolar longitudinal derivations at rest, after h y p e r v e n t i l a t i o n and after p h o t i c stimulation. N o r m a l E E G s were disclosed in 9 of the 46 patiens investigated. Out of the 37 w o m e n with abnormal EEGs, 20 revealed slight diffuse, 15 m o d e r a t e , and one severe, disorders. Subcortical alterations were estimated in 15 of the patients in c o n n e c t i o n with diffuse changes. No statistically significant changes were disclosed in either diffuse or subcortical alterations after ovarian c u n e i f o r m resection. With the exception of one patient, the 9 cases with normal E E G findings disclosed a corpus l u t e u m in the ovaries. The deviations in the EEGs were discussed as primary functional changes or as secondary alterations o f the subcortical structures due to a primary endocrine disorder.
14. Mean values and c o m p a r i s o n of s o m e rheogTaphic p a r a m e t e r s . - S. Merdjanova and Ch. Merdjanov (Sofia) A f r o n t o - m a s t o i d r h e o e n c e p h a l o g r a m and a longitudinal rheogram of the leg in the area of the calf were carried o u t in 411 subjects aged 20--45 years. The mean values of 10 parameters were d e t e r m i n e d for the two rheograms: a m p l i t u d e of systolic and diastolic waves, dicrotic and diastolic indices, absolute and relative values of the anacrotic and systolic parts, p a r a m e t e r 'anacrotic part:catacrotic p a r t ' and the time for spreading of the pulse wave. In addition, relations b e t w e e n the identical rheographic parameters in the t w o e x a m i n e d areas were calculated.
15. Changes of some quantitative h a e m o d y n a m i c cerebral parameters under physiotherapeutic influences. -- Ch. Merdjanov, S. Merdjanova and N. Tsolov (Sofia) The authors have f o l l o w e d the changes of the hemispheral b l o o d flow (D. H a d j i e v ) a n d the cerebral circulation t i m e (J. J a c q u i and collaborators), determ i n e d f r o m the fronto-mastoid r h e o e n c e p h a l o g r a m after application of the following 5 p h y s i o t h e r a p e u t i c factors: electrical currrent with ultra high frequency,
79P microwaves, electrophoresis, diadynamic current and ultrasound. The hemispheric b l o o d flow was 373.3 ± 5.9 m l / m i n before the physical influence (n = 407). This p a r a m e t e r increased significantly after the ultra high f r e q u e n c y current ( o l i g o t h e r m i c dose) and after microwaves (20 W) applied in the area of the head and the calf of the leg. The circulation t i m e decreased significantly after the aforesaid t w o factors and after nasal electrophoresis. The relative part of the cerebral blood flow from the m i n u t e v o l u m e o f the heart increased after the physical influence.
16. S o m e correlations between the neurological, psychoneurological and E E G s y m p t o m s in children with speech disorders in MBD. -- R. Raychev, N. Rasheva and M. Vulcheva (Sofia) The p r o b l e m of the interrelations between the clinical variant s y n d r o m e s included in the 'children with MBD' group and the s y m p t o m s of brain disturbances established in the clinical, neurological and EEG investigations, is c o n t i n u o u s l y discussed. In 241 children, b e t w e e n 5 and 9 years of age, with speech disorders (alalia, dyslalia and stuttering, dysgraphia and dyslexia), the following investigations were p e r f o r m e d : neurological consultation, neuropsychic e x a m i n a t i o n by means of a special test-set after A.R. Luria, IQ d e t e r m i n a t i o n after Binet-Simon-Terman-Manova, routine EEG e x a m i n a t i o n with functional tests for stimulation in the visual analysis. In 94 of the children, focal neurological signs ( ' s o f t ' focal signs) were established. Besides the speech disorders, the neurological investigations d e t e c t e d : visuospatial disorders in 84 children, disturbed praxis of posture in 107 children and of dynamic praxis in 101. A c c o r d i n g to E E G changes the patients were divided in t w o groups: with diffuse changes -- 94 patients (of the generally delayed or i m m a t u r e for the age type); with focal E E G changes -- 147 children (with focal c h a r a c t e r i s t i c s - high voltage sharp waves, spikes and complexes). The focal distribution in the hemisphere areas was: t e m p o r o - p a r i e t a l - 37.4%, temporo-parieto-occipital -- 34.7%, t e m p o r a l -- 21.1%, frontop a r i e t o - t e m p o r a l - 6.8%. In almost all individually analyzed s y n d r o m e s of speech disorders, this focal distribution was preserved. In the children with combined speech disorders (dyslalia, dysgraphia and dyslexia) the highest focal percentage was established in the temporo-parieto-occipital area (54.51%). The changes in the left hemisphere p r e d o m i n a t e d . C o m p l e x e x a m i n a t i o n of children with MBD revealed various s y m p t o m s of CNS lesions, which correlated a m o n g themselves and were m o s t p r o b a b l y at the b o t t o m of the observed speech disorders. These basic disturbances were n o t elucidated aetiologically, but t h e y were m o s t probably expressions of perinatal pathology.
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SOCIETY PROCEEDINGS
17. Paroxysmal E E G activity in children with m e n t a l retardation. - - D. Mintchev, M. A p o s t o l o v a and D. A p o s t o l o v (Plovdiv) The electrical activity o f the brains of 156 children with mental r e t a r d a t i o n was studied. The children a t t e n d e d special schools. The following E E G changes were registered: normal in 59 cases (37.82%), diffuse in 36 (23.08%), local in 7 (4.49%), low voltage in 23 (14.74%) and p a r o x y s m a l (epileptiform) activity in 31 (19.87%) cases. The children with brain damage and p a r o x y s m a l activity were considered to be disposed to developing s y m p t o m a t i c epilepsy. A n t i c o n vulsive prophylaxis is discussed.
18. On t h e possibility o f objectifying brightness disc o m f o r t . -- S. Slavchev (Varna) and N. Angelov
(Razgrad) The t e r m 'brightness d i s c o m f o r t ' includes the influence of unsuitable light sources on man, causing unpleasant e m o t i o n s like awkwardness, tenseness and irritation. The aetiological and p a t h o g e n e t i c basis of brightness d i s c o m f o r t , as well as its quantitative objectivization and m e a s u r e m e n t have been a m a t t e r for c o n t i n u e d a r g u m e n t and discussion. A possibility o f objectifying d i s c o m f o r t is proposed. Its quantitative values are calculated by the m e t h o d o f Epaneshnikov, using t h e values o f the reaction t i m e (measured in a light c h a m b e r for 8 discomfort levels), as well as in a p r o d u c t i o n plant using the values o f limited t i m e for a simple o p t i c o - m o t o r reaction, t i m e c o n s u m e d and errors in L a n d o l t ' s correction test, n u m b e r of errors and c o n s u m e d t i m e in the test for ocular fatigue, carried o u t with Pirkovsky's apparatus, the percentage subjectification of the workers asked a b o u t high and low spirits in the respective d i s c o m f o r t situations, as well as by studying the visibility values after Darkshlevitch. The e x p e r i m e n t a l results p o i n t to an o p t i m a l disc o m f o r t range of 25--30 d i s c o m f o r t units (after Epaneshnikov) which, in our opinion, objectifies the c o m f o r t - d i s c o m f o r t limit, subjectified by the existing m e t h o d s o f quantitative objectivization of d i s c o m f o r t (Guth, E p a n e s h n i k o v et al.).
19. C o m p a r a t i v e studies o f low and m e d i u m freq u e n c y currents for e l e c t r o s t i m u l a t i o n o f nondenervated muscles. - - S. Bankov (Sofia)
C o m p a r a t i v e studies were c o n d u c t e d with the purpose of finding the o p t i m a l current for electrostimulation o f n o n - d e n e r v a t e d muscles - - a current producing a sufficiently strong c o n t r a c t i o n with m i n i m a l
sensory stimulation. The subjective feeling o f the current was r e c o r d e d during antigravity e l b o w flexion up to 90 °, p r o d u c e d by e l e c t r o s t i m u l a t i o n o f the biceps muscle in the arm. In a series of 121 persons, divided into 5 groups, a comparative study was carried o u t on the effect o f m e d i u m f r e q u e n c y (5000 Hz) currents, m o d u l a t e d at 50 Hz, m o n o - and bipolar, with varying depths of m o d u l a t i o n , or d u r a t i o n of the m o d u l a t i o n trend, as well as with different shapes of cycles, basic f r e q u e n c y and different shapes of the m o d u l a t i o n trend. In studies with variation o f the current parameters outlined above the following o p t i m a l characteristics were established: basic f r e q u e n c y 5000 Hz with bipolar rectangular cycles, m o d u l a t e d at 60 Hz in trends with duration 2 msec and rectangular shape. This current was referred to by the t e r m ' m e d i u m freq u e n c y m o d u l a t e d impulse current'. A special portable battery-fed e l e c t r o s t i m u l a t o r was c o n s t r u c t e d for this particular current. In a series of 51 persons, using the same m e t h o d of study, the above-described current was c o m p a r e d with the l o w - f r e q u e n c y current ' D i n a t r o n ' , recently widely r e c o m m e n d e d as a means of painless electrostimulation. The results show that the ' m e d i u m freq u e n c y m o d u l a t e d i m p u l s e ' current was better tolerated for e l e c t r o s t i m u l a t i o n of ion-denervated muscles t h a n the ' D i n a t r o n ' current.
20. Galvanic versus alternating current in electroderm o m e t r i c diagnosis o f sensory deficit in peripheral nerve lesions to t h e hand. -- S. Bankov (Sofia) There is disagreement on t h e q u e s t i o n which current - - galvanic or alternating - - is m o r e suitable for skin e l e c t r o c o n d u c t i v i t y investigation as a test for s u d o m o t o r activity or sensory deficit in peripheral nerve injuries o f the hand. Comparative studies were carried o u t in a series of 20 patients with media n and ulnar nerve lesions at 376 sites o n the volar aspect of b o t h hands (the pulps of all 5 fingers, toruli tactiles, thenar and hypothenar). Skin e l e c t r o c o n d u c t i v i t y was e x a m i n e d using galvanic and alternating currents (50, 400 and 1200 Hz). A battery e l e c t r o d e r m o m e t e r , as well as selected parameters of the currents m e n t i o n e d above, were e m p l o y e d with a view to obtaining a c o m p a r a b l e basis f r o m the electrical v i e w p o i n t for measuring the individual current. It was established that skin e l e c t r o c o n d u c t i v i t y in denervated zones s h o w e d lowest values w h e n measured with galvanic current, n e x t the values for alternating current 50 Hz (twice higher), 400 Hz (3 times higher) and 1200 Hz (6 times higher). The discrimin a t o r y capacity (ratios b e t w e e n skin e l e c t r o c o n d u c -
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tivity values for d e n e r v a t e d a n d s y m m e t r i c h e a l t h y skin z o n e s ) was o p t i m a l w i t h galvanic c u r r e n t : it was 3 t i m e s greater t h a n w i t h a l t e r n a t i n g c u r r e n t a t 50 Hz, 8 t i m e s greater t h a n at 4 0 0 Hz a n d 11 t i m e s greater t h a n at 1 2 0 0 Hz. T h e results s h o w t h a t changes in p o s t - d e n e r v a t i o n a l skin e l e c t r o c o n d u c t i v i t y are m o s t m a r k e d in its ohmic component. Galvanic current reflects most a d e q u a t e l y t h e s e changes.
t h e rising variability b e c a m e spindle-like, s h o w i n g m o r e r h y t h m i c p a t t e r n in s o m e c o n d i t i o n s . It is a s s u m e d t h a t a t s o m e i n t e r i m p u l s e intervals t h e a l p h a motoneurone receives m o r e c o h e r e n t a c t i v a t i o n t h r o u g h its d i f f e r e n t i n p u t s .
21. S e n s o r y a c t i o n p o t e n t i a l a n d s e n s o r y c o n d u c t i o n v e l o c i t y o f the median n e r v e - - t h e i r role in carpal' t u n n e l syndrome diagnosis. -- R. Popov and E. Stoyanova (Sofia)
T h e e x p e r i m e n t s were p e r f o r m e d w i t h 6 t r a i n e d s u b j e c t s w h o h a d t o a c t i v a t e t h e m o t o r u n i t s (MUs) in o n e a n d t h e s a m e muscle. O n e o f t h e MUs was k e p t in s t e a d y - s t a t e firing, t h e o t h e r o n e was s w i t c h e d o n a n d off. T h e first a n d last i m p u l s e s o f t h e s e s h o r t series were used t o s h o w t h e t i m e r e l a t i o n b e t w e e n b o t h i m p u l s e sequences. T h e delay a n d t h e a n t i c i p a t i o n o f t h e s e i m p u l s e s were m e a s u r e d w i t h r e s p e c t t o t h e n e i g h b o u r i n g i m p u l s e s o f t h e parallel MU. It was s h o w n t h a t t h e t i m e axis was i n t e r s e c t e d at p r e f e r r e d a n d n o n - p r e f e r r e d intervals a f t e r a n i m p u l s e in t h e c o n t i n u o u s l y active MU. T h e first a n d last i m p u l s e s o f t h e s h o r t series in t h e s e c o n d M U a p p e a r e d w i t h diff e r e n t p r o b a b i l i t y in t h e s e intervals. T h e c o i n c i d e n c e o f i m p u l s e s was l o w e r t h a n m a t h e m a t i c a l l y e x p e c t e d . W i t h i n 3 0 - - 7 0 m s e c a f t e r a n i m p u l s e in t h e c o n t i n u o u s l y firing M U t h e r e was a n a l t e r n a t i o n o f t h e p r o b a b i l i t y for a p p e a r a n c e o f t h e first impulse only, w h e r e a s for t h e last impulse e v e n t s w e n t m o r e s m o o t h l y . T h e s e facts are used as a basis for t h e e x p l a n a t i o n o f t h e t h r e s h o l d f l u c t u a t i o n o f MUs.
I n a t o t a l series o f 250 p a t i e n t s w i t h 391 s y m p t o m a t i c h a n d s , w h e r e t h e clinical diagnosis was carpal t u n n e l s y n d r o m e , c o n f i r m e d t h r o u g h E M G studies, c h a n g e s in s e n s o r y c o n d u c t i o n v e l o c i t y o f t h e m e d i a n n e r v e in t h e w r i s t - t h i r d finger r e g i o n were d e m o n strated. I n 1 1 6 s y m p t o m a t i c h a n d s s e n s o r y c o n d u c t i o n v e l o c i t y was d e l a y e d b e l o w 4 5 - - 4 0 m / s e c , in 173 b e l o w 40 m / s e c . In 102 h a n d s n o s e n s o r y n e r v e a c t i o n p o t e n t i a l was registered. Distal m o t o r l a t e n c y o f n. m e d i a n u s was f o u n d t o be u n a l t e r e d in 101 h a n d s - - b e l o w 4.5 msec. P r o l o n g e d distal m o t o r l a t e n c y against t h e b a c k g r o u n d o f u n c h a n g e d s e n s o r y c o n d u c t i o n v e l o c i t y o f t h e m e d i a n nerve was r e c o r d e d in n o n e o f t h e cases. E M G e v i d e n c e o f d e n e r v a t i o n o f m.m. a b d u c t u s pollicis brevis a n d o p p o n e n s pollicis was e s t a b l i s h e d in a c o m p a r a t i v e l y small n u m b e r of s y m p t o m a t i c h a n d s (64). I n all symptomatic hands sensory conduction velocity of t h e u l n a r n e r v e in t h e w r i s t - f i f t h finger r e g i o n was unchanged. The sensitivity of the electrodiagnostic a s s e s s m e n t in discovering t h e carpal t u n n e l s y n d r o m e was a u g m e n t e d u p o n c o m p a r i n g s e n s o r y c o n d u c t i o n v e l o c i t y a l o n g t h e m e d i a n a n d u l n a r nerves in t h e wrist-ring finger z o n e .
22. V a r i a b i l i t y o f t h e i n t e r i m p u l s e intervals o f t h e m o t o r u n i t firing d u r i n g v o l u n t a r y a c t i v a t i o n . Y.T. S h a p k o v ( L e n i n g r a d , U.S.S.R.) a n d D. Kosaroy (Sofia) T h e single m o t o r u n i t a c t i v i t y in m. b i c e p s b r a c h i i was i n v e s t i g a t e d in 20 h e a l t h y subjects. T h e leading o f f w i t h small surface skin e l e c t r o d e s was a m p l i f i e d b y a 3 - c h a n n e l 'Disa' e l e c t r o m y o g r a p h . T h e s u b j e c t s were t r a i n e d t o a c t i v a t e t h e i r m o t o r u n i t s (MUs) in l o n g series o f i m p u l s e s w i t h s p o n t a n e o u s f r e q u e n c y of firing. T h e m e a n intervals in successive series varied. T h e rise o f t h e v a r i a t i o n o f t h e intervals w e n t n o t s m o o t h l y b u t at s o m e m e a n values it was smaller t h a n at s o m e l o w e r values o f t h e m e a n . So t h e p i c t u r e of
23. V o l u n t a r y c o n t r o l o f t w o m o t o r u n i t s in o n e h u m a n muscle. - - D. Kosarov a n d L. C h r i s t o v a (Sofia)
24. E l e c t r o m y o g r a p h i c studies o f p o s t i n s u l t spasticity. - - N. Nikoevski (Sofia) T h e r e p o r t generalizes t h e results f r o m t h e investig a t i o n o f t h e value o f t h e H/M ratio, H/M r a t i o w i t h J e n d r a s s i k m a n o e u v r e , A / M ratio, a n d t h e e f f e c t o f v i b r a t i o n at 1 0 0 c/sec o n t h e H reflex in m o n o p o l a r E M G r e g i s t r a t i o n in a large g r o u p o f 60 p a t i e n t s w i t h p o s t i n s u l t spasticity - - f r o m slight u p t o p r o n o u n c e d - - c o m p a r e d w i t h t h e c o n t r o l groups. A n e v a l u a t i o n is given o f t h e possibilities o f q u a n t i t a t i o n o f t h e degree of c h a n g e of t h e muscle t o n e . T h e values o f t h e H / M ratio, e x p r e s s e d w i t h t h e a r i t h m e t i c m e a n a n d s t a n d a r d d e v i a t i o n , are very significant in t h e g r o u p s c o m p a r e d (a spastic w i t h a n o n - p a r e t i c leg a n d a spastic leg w i t h a h e a l t h y o n e in t h e same age g r o u p - P < 0.001; of the H/M ratio with Jendrassik m a n o e u v r e - - P < 0.01, a n d o f t h e A / M r a t i o - - P < 0.02). A n a c c o u n t is given o f t h e peculiar i n f l u e n c e o f v i b r a t i o n at 1 0 0 c/sec o n t h e H reflex o f a spastic muscle, w h i c h c a n serve t o evaluate its degree.
82P 25. Correlation b e t w e e n t h e reaction t i m e and t h e a m p l i t u d e changes o f the H reflex evoked in a muscle o f t h e contralateral leg in simple reaction t i m e task c o n d i t i o n s . - - Tz. T z e k o v (Varna) The correlation b e t w e e n the r e a c t i o n t i m e and the a m p l i t u d e changes of the H reflex evoked in m. gastrocnemius lateralis of the contralateral leg to the m o t o r response in conditions of a simple reaction t i m e task is studied. A c c o r d i n g to f o r m e r instructions, the subjects answered with m a x i m a l speed to a light signal f r o m a flash lamp t h r o u g h a red filter, lifting the right heel f r o m the floor. U n d e r these conditions, m. gastrocnemius lateralis dextri is one o f the agonists of the v o l u n t a r y m o v e m e n t . The H reflex was evoked in m. gastrocnemius lateralis sinistri, i.e., f r o m the leg contralateral to the m o t o r response. The r e a c t i o n time of the right leg m o t o r response was c o m p a r e d w i t h the a m p l i t u d e changes of the H reflex in the left gastrocnemius (an H reflex was evoked for each light signal). T h e characteristic correlation b e t w e e n the reaction t i m e and the a m p l i t u d e changes of the H reflex of the ipsilateral leg was measured under the same conditions. These results provide a basis for the a s s u m p t i o n t h a t in simple r e a c t i o n t i m e task c o n d i t i o n s there exists a certain specific preparation o f the muscle agonists to t h e f o r t h c o m i n g m o v e m e n t , which is connected with the f u l f i l m e n t o f the task.
SOCIETY PROCEEDINGS 26. I n f l u e n c e o f s i m u l t a n e o u s vestibular and optical
stimulation o n h u m a n muscle activity. - - V . Dam i a n o v a and Y. Toshev (Sofia) The purpose o f the w o r k is to investigate the influence o f simultaneous vestibular and optical stimulation on the bioelectrical activity (BEA) of s o m e muscles o f the h u m a n arm. The e x p e r i m e n t s consist in: optical stimulation o f the eye with white light; e l e c t r o s t i m u l a t i o n of the vestibular system; simultaneous vestibular and optical stimulation with white light; simultaneous vestibular and optical stimulation with red light. Each e x p e r i m e n t was carried o u t as follows: the muscles were relaxed in advance; the muscles were active in advance. B E A was measured with bipolar surface electrodes. The left and right flexors and the right e x t e n s o r o f the fingers were investigated. The results showed that muscle activity increased under optical stimulation and especially under vestibular stimulation. Simultaneous vestibular and optical stimulation with white light resulted in m o r e flexor activity than optical stimulation with red light. In each e x p e r i m e n t BEA of the preliminarily relaxed muscles was greater t h a n the B E A of the preliminarily active muscles.
Electroencephalography and Clinical Neurophysiology, 1981, 52: 76P--82P Elsevier/North-Holland Scientific Publishers, Ltd.
Society proceedings ANNUAL MEETING OF THE BULGARIAN NEUROPHYSIOLOGY
SOCIETY OF EEG, EMG AND CLINICAL
Sofia, February 28, 1981
Secretary: Dr. N. NIKOEVSKI 1st Neurological Clinic, Medical Academy, str. G. Sofiiski 1, Sofia 1431 (Bulgaria) (Accepted for publication: July 14, 1981)
1. A microprocessor system for EEG a n a l y s i s . - I. Dascalov, M. Matveev, C. Levkov, R. Arnaudova and M. Nikolova (Sofia) A system for the analysis of the spontaneous EEG was built, using a 6800 microprocessor with 8k RAM and 8k EPROM. Two or 4 channels are simultaneously digitized at a frequency of 250 Hz. Durations and amplitudes of the successive EEG waves of 10 sec epochs are measured, and histograms are obtained and stored. Cumulative histograms from four 10 sec epochs are printed out, simulating frequency quasispectra in the 0--50 Hz range at 2 Hz intervals. The raw 'spectra' are previously smoothed using the simple Hamming algorithm. The frequency resolution, being limited by the digitizing frequency, has been improved in the high-frequency region by computing the channel contents through interpolation as well as by the smoothing algorithm.
2. Inhibitory extracranial stimulation. -- D. Tchavdarov (Sofia) In a group of 24 epileptics with frequent subclinical paroxysmal activity in the EEG, 125 extracranial electrical stimulations were performed. The results may be summarized as follows: without c h a n g e s 14; changes in the background a c t i v i t y - 34; intensified paroxysmal a c t i v i t y - 23; inhibition of the paroxysmal a c t i v i t y - 54. The effects depend on the size of the electrode, their place and relation, as well as electrical parameters. The effect on the EEG is 3--4 times the duration of each stimulation. By changing the position of the electrodes it is possible to elicit activating or inhibitory effects. The results are compared with those of subcortical stimulation and the suggested mechanisms of electrosleep.
3. VEP and plasma level of anticonvulsants. -- D. Tchavdarov (Sofia) The most important EEG control of seizures during carbamazepine treatment of 54 out of 130 patients was misleading because of increased focal abnormalities and EEG aggravation. In 43 of the 54 patients the amplitudes of the VEP after-discharges were abolished during treatment with carbamazepine. In 28 epileptics from this group the amplitude of wave 78--94 msec on the side of the focus decreased significantly. These findings correlate with the plasma levels of carbamazepine.
4. Polarity histogram in the analysis of evoked potential (EP) v a r i a b i l i t y . - D. Dalbokova (Sofia), I. Drews, M. Pietschmann, P. Ullsperger and H.-G. Gille (Berlin, G.D.R.) An experimental study was carried out to evaluate how much the variations in amplitude of the average EP (AEP) components, estimated by the t test, correspond to the variability in the frequency of occurrence (from the polarity histogram), estimated by the ×2 test. EPs from Cz (10/20 system) in a discriminative task with 'soft' and l o u d ' tones presented in a Bernoulli sequence were recorded. A control situation, i.e., stimulus presentation while the subject was reading a book, was also included. For each subject the two situations were presented according to the experimental design of Berenblut (1964) to separate the direct effect of the situation from the first residual effect and the time effect on the amplitude and the frequency of the EP components. The analysis of variance for the N100 and P300 parameters showed that the task had significant effect only on the P300 parameters, while the data for N 100 were not so con-
0013-4649/81/0000--0000/$02.50 © 1981 Elsevier/North-Holland Scientific Publishers, Ltd.
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sistent. The differences in the parameters of N100 and P300 between each combination of control and task situations were assessed for each subject separately. Totally, in 89% of all comparisons significant differences in the amplitude as well as in the frequency of occurrence of P300 were found. This suggests that the polarity histogram, together with the AEP wave form, provide a quick estimate of the individual EP variability.
post-caloric nystagmus was very useful in cases with overt vestibular response asymmetry. The amplitude of AERs (P1NI and N1P2 components) during the nystagmus was significantly reduced; recovery time was approximately 30 min. The A ER dynamic characteristics in the affected labyrinths were significantly different from those in normal labyrinths. The clinical value of this observation is discussed.
5. On the central mechanisms of vestibular function compensation in a model of delabyrinthization. -H. Kolchev (Sofia)
7. All-night polygraphic investigation in patients with temporal lobe e p i l e p s y . - - A . Alexiev, S. Slavchev and M. Kyuchukov (Sofia)
The temporal characteristics of behavioural and electrophysiological (EEG, ENG, AERs, VEPs, ERA) shifts were investigated in chronic cats following unilateral destruction of the vestibular end-organ by means of mono-iodine acetic acid. The initial signs of vertibular nystagmus appeared 27--35 rain after acid application ; at the 24th hour it was well expressed, gradually disappearing after 72 h. Tonal stimulation (1000 Hz, 60 dB SPL, ISI 2 sec) revealed amplitude augmentation of the P1N1 and NIP2 components between the 45th and 120th rain, followed by progressive reduction of A E R amplitude and disappearance after the 24th hour. Conversely, VEP amplitude significantly increased after the 150th min. The central compensation of the peripheral vestibular dysfunction, based on the corrective influences of visual somaesthetic analysers, most likely takes place in the initial 2--3 days, after which the mechanisms of 'vestibular accommodation' (Mittermayer, Pfaltz and Kammath) are triggered, i.e., compensatory influences of the intact labyrinth, interrelation effects at the level of primary vestibular nuclei and pathways in the brain stem.
Nine patients with temporal lobe epilepsy were polygraphically investigated for two consecutive nights (one phantom) each. The patients had been under Tegretol treatment for at least 30 days. In 4 of the patients investigated, generalized paroxysms of sharp and slow waves were found in the first or second stage of NREM sleep. No focal paroxysmal discharges were registered in any of the patients investigated.
6. Correlation between the parameters of caloricprovoked nystagmus and cerebral electrical activity in patients with otoneurological syndromes. -H. Kolchev and J. Wassileva (Sofia) The effects of cold water (20°C, 100 ml, 10 sec) and warm water (40 O C, 100 ml, 10 sec) vestibular provocation on EEG, ENG, ECG and AERs in 77 patients with peripheral, combined and central otoneurological syndromes were investigated. Seventy-five percent of the patients with unilateral post-caloric hypo- or hyper-reflexia revealed non-paroxysmal EEG abnormalities (single spikes or sharp waves, polymorphic slow waves) in the hemisphere ipsilateral to the damaged labyrinth. The evaluation of the angular velocity dynamics of
8. EEG investigations in acute disturbances of cerebral c i r c u l a t i o n . - - A . Alexiev and M. Memov (Sofia) Fifteen patients with acute disturbances of cerebral circulation were investigated by EEG immediately after hospitalization. The EEG was repeated 90-120 min after i.v. administration of 500 ml 10% solution of mannitol. Another EEG investigation was performed 4--5 days later, after daily i.v. administration of at least 1500 ml 10% mannitol solution during this period. After the EEG investigation, 40 mg Lasix were administered i.m. in 3 of the patients, and 2 h later the EEG was repeated. The results show that administration of 10% mannitol solution reduces the slow waves in the EEG and tends to localize them just over the ischaemic region. The EEG performed 4--5 days later shows a certain elevation of the slow waves, as well as a tendency towards their more diffuse distribution. The administration of Lasix in 3 of the patients did not lead to any significant EEG changes.
9. The epileptic state in acute disturbances of cerebral c i r c u l a t i o n . - M. Rasheva, E. Stamenov and P. Todorova (Sofia) The dynamics of the electrical activity of the brain have been studied in 20 patients in epileptic status (13 Jacksonian and 7 generalized), during the acute
78P stage o f t h e cerebral stroke. Grave c h a n g e s d u r i n g t h e i n t e r i c t a l p e r i o d were registered, c h a r a c t e r i z e d b y diffuse slow wave activity in 13 of t h e cases. In 5 pat i e n t s m o d e r a t e diffuse c h a n g e s were o b s e r v e d a n d in o n l y 2 p a t i e n t s were t h e y slight. It has b e e n established t h a t slowing a n d decrease o f a m p l i t u d e in r e p e a t e d e x a m i n a t i o n is a b a d p r o g n o s t i c sign for t h e o u t c o m e of t h e disease. Signs o f e p i l e p t i c activity in E E G s were f o u n d in 65% of t h e p a t i e n t s . It h a s b e e n p o i n t e d o u t t h a t t h e d i s t u r b a n c e s in t h e electrical activity o f t h e b r a i n registered d u r i n g t h e seizure p e r i o d h a v e n o special c h a r a c t e r i s t i c s . I n t h e i n t e r i c t a l p e r i o d t h e grave diffuse changes w i t h a general disturbance of cerebral electrogenesis and domination of t h e processes o f i n h i b i t i o n , are a relatively f r e q u e n t E E G o c c u r r e n c e , w h i c h is a result o f t h e epileptic s t a t u s as well as o f t h e a c u t e d i s t u r b a n c e of t h e cerebral c i r c u l a t i o n .
10. D y n a m i c s o f t h e electrical a c t i v i t y o f the brain in cerebellar h a e m o r r h a g e . - M. R a s h e v a , E. S t a m e n o v , P. T o d o r o v a a n d S. A v r a m o v {Sofia) T h e c h a n g e s in t h e electrical activity o f t h e b r a i n have b e e n s t u d i e d in 6 p a t i e n t s w i t h cerebellar h a e m o r r h a g e - - 5 m e n a n d 1 w o m a n aged a b o u t 62 years, a f t e r p a t h o - a n a t o m i c a l v e r i f i c a t i o n . All cases were in a d e e p l y c o m a t o s e s t a t e a n d in 5 o f t h e m p r o l o n g e d artificial v e n t i l a t i o n was p e r f o r m e d , w h i c h also gave a n o p p o r t u n i t y t o s t u d y t h e d y n a m i c s of t h e electrical activity of t h e b r a i n for l o n g p e r i o d s of t i m e . In t o t a l t h e r e were 22 E E G r e c o r d s , a n a l y s e d visually a n d b y m e a n s of a f r e q u e n c y - a m p l i t u d e analyser. High voltage d e l t a waves d o m i n a t e d in all cases against a b a c k g r o u n d o f grave generalized c h a n g e s , d e m o n s t r a t e d b y general d i s o r g a n i z a t i o n a n d slowness o f t h e electrical a c t i v i t y , m o r e clearly e x p r e s s e d in t h e c e r e b r a l h e m i s p h e r e c o n t r a l a t e r a l t o t h e cerebellar h a e m o r r h a g e . In 4 o f t h e cases f r o n t a l i n t e r m i t t e n t r h y t h m i c d e l t a a c t i v i t y ( F I R D A ) was o b s e r v e d , w h i c h d i s a p p e a r e d in l a t e r stages parallel w i t h t h e d e t e r i o r a t i o n o f t h e clinical process. T h e possible p a t h o g e n e t i c m e c h a n i s m s o f t h e o b s e r v e d c h a n g e s o f t h e bioelectrical activity were discussed a n d t h e i m p o r t a n c e o f t h e E E G for t h e d e t e r m i n a t i o n o f t h e t o p i c a l diagnosis was p o i n t e d o u t .
11. C h a n g e s in t h e electrical a c t i v i t y o f t h e brain in t h a l a m i c h a e m o r r h a g e . - E. S t a m e n o v , M. Rasheva, P. T o d o r o v a a n d S. A v r a m o v {Sofia) T h e electrical activity of t h e b r a i n d u r i n g t h e a c u t e stage o f t h a l a m i c h a e m o r r h a g e has b e e n e x a m i n e d in 11 p a t i e n t s . T h r e e t y p e s o f E E G c h a n g e have b e e n d e t e r m i n e d : diffuse c h a n g e s w i t h d i f f e r e n t degrees
SOCIETY PROCEEDINGS of m a n i f e s t a t i o n , c h a r a c t e r i z e d b y slowness and lack o f r e a c t i v i t y to f u n c t i o n a l tests in 4 p a t i e n t s ; diffuse changes w i t h an i n t e r h e m i s p h e r i c a s y m m e t r y w i t h a graver d i s t u r b a n c e o f electrogenesis ipsilateral t o t h e h a e m o r r h a g e in t w o p a t i e n t s ; diffuse changes w i t h an i n t e r h e m i s p h e r i c a s y m m e t r y a n d e v i d e n c e o f a focus of p a t h o l o g i c a l activity in 5 cases. All t h e p a t i e n t s w h o h a d diffuse changes w i t h o u t a s y m m e t r y h a d grave qualitative d i s t u r b a n c e s o f c o n s c i o u s n e s s , while t h e p a t i e n t s w i t h i n t e r h e m i s p h e r i c a s y m m e t r y in t h e E E G were c o n s c i o u s or s o m n o l e n t . E E G d a t a in s o m e of t h e cases suggest t h e great p r o b a b i l i t y t h a t t h e focus o f slow wave activity reflects t h e d a m a g e to deep brain structures. The EEG patho-anatomical c o m p a r i s o n s s h o w t h a t besides t h e c h a r a c t e r i s t i c diffuse d i s t u r b a n c e s in cerebral electrogenesis, s o m e o t h e r changes were o b s e r v e d in t h e E E G s in t h e a c u t e stage o f t h e t h a l a m i c h a e m o r r h a g e , reflecting n o t o n l y t h e gravity of t h e s t r o k e process b u t also s h o w ing t h e u n e q u a l i n v o l v e m e n t o f t h e t h a l a m i c nuclei a n d a d j a c e n t s t r u c t u r e s in t h e p a t h o l o g i c a l process.
12. E p i l e p t i c seizures in t h e a c u t e stage o f e m b o l i c s t r o k e . - - M . R a s h e v a (Sofia) E p i l e p t i c seizures ( J a c k s o n i a n and generalized) have b e e n o b s e r v e d in 10.1% (33 o u t of 3 2 8 ) o f pat i e n t s d u r i n g t h e a c u t e stage of e m b o l i c s t r o k e . T h e seizures were t h e initial m a n i f e s t a t i o n of t h e disease in h a l f of t h e cases. P a t h o l o g i c - a n a t o m i c v e r i f i c a t i o n in all t h e p a t i e n t s revealed t h a t t h e cerebral c o r t e x was involved t o d i f f e r e n t degrees in t h e i n f a r c t i o n . Diffuse changes in t h e E E G h a v e b e e n o b s e r v e d , m a n i f e s t e d in a r e d u c t i o n o f a l p h a r h y t h m and d o m i n a t i o n o f t h e t a a n d d e l t a activity, m a i n l y ipsilateral to t h e i n f a r c t i o n . Grave diffuse changes were f o u n d p a r t i c u l a r l y in t h e cases w i t h generalized seizures a n d t h e i r p r e s e n c e was a bad p r o g n o s t i c sign for t h e outc o m e o f t h e disease. S h a r p waves, spikes, spikes a n d stow waves, local or generalized p a r o x y s m a l activity, were registered in 57.1% of t h e p a t i e n t s . A n activity of this t y p e was f o u n d m o r e f r e q u e n t l y in t h e pat i e n t s w i t h J a c k s o n i a n seizures a n d its p r e s e n c e h a d n o b a d p r o g n o s t i c m e a n i n g . I t has b e e n p o i n t e d o u t t h a t t h e focus o f slow wave activity c o r r e s p o n d s t o t h e l o c a l i z a t i o n o f t h e i n f a r c t , while t h e changes o f a n e p i l e p t i c c h a r a c t e r are o b s e r v e d in a d j a c e n t zones, s o m e t i m e s in t h e c o n t r a l a t e r a l h e m i s p h e r e or bilaterally. Possible p a t h o g e n e t i c m e c h a n i s m s for t h e occ u r r e n c e o f t h e epileptic seizures were discussed, as well as t h e c h a n g e s in t h e electrical activity o f t h e b r a i n in t h e a c u t e stage o f t h e e m b o l i c s t r o k e .
BULGARIAN EEG/EMG SOCIETY 13. EEG investigations of women with Stein-Leventhai s y n d r o m e . - A. Shterev, D. Daskalov and S. D o k u m o v (Sofia) EEG e x a m i n a t i o n s were p e r f o r m e d in 46 patients with Stein-Leventhal s y n d r o m e after clinical, l a b o r a t o r y , radiological, operative and histological verification. No patient disclosed anamnestic or clinical data of organic cerebral disorder. In 20 of the cases EEGs were p e r f o r m e d before and after cuneif o r m resection of the ovaries. EEGs were recorded f r o m bipolar longitudinal derivations at rest, after h y p e r v e n t i l a t i o n and after p h o t i c stimulation. N o r m a l E E G s were disclosed in 9 of the 46 patiens investigated. Out of the 37 w o m e n with abnormal EEGs, 20 revealed slight diffuse, 15 m o d e r a t e , and one severe, disorders. Subcortical alterations were estimated in 15 of the patients in c o n n e c t i o n with diffuse changes. No statistically significant changes were disclosed in either diffuse or subcortical alterations after ovarian c u n e i f o r m resection. With the exception of one patient, the 9 cases with normal E E G findings disclosed a corpus l u t e u m in the ovaries. The deviations in the EEGs were discussed as primary functional changes or as secondary alterations o f the subcortical structures due to a primary endocrine disorder.
14. Mean values and c o m p a r i s o n of s o m e rheogTaphic p a r a m e t e r s . - S. Merdjanova and Ch. Merdjanov (Sofia) A f r o n t o - m a s t o i d r h e o e n c e p h a l o g r a m and a longitudinal rheogram of the leg in the area of the calf were carried o u t in 411 subjects aged 20--45 years. The mean values of 10 parameters were d e t e r m i n e d for the two rheograms: a m p l i t u d e of systolic and diastolic waves, dicrotic and diastolic indices, absolute and relative values of the anacrotic and systolic parts, p a r a m e t e r 'anacrotic part:catacrotic p a r t ' and the time for spreading of the pulse wave. In addition, relations b e t w e e n the identical rheographic parameters in the t w o e x a m i n e d areas were calculated.
15. Changes of some quantitative h a e m o d y n a m i c cerebral parameters under physiotherapeutic influences. -- Ch. Merdjanov, S. Merdjanova and N. Tsolov (Sofia) The authors have f o l l o w e d the changes of the hemispheral b l o o d flow (D. H a d j i e v ) a n d the cerebral circulation t i m e (J. J a c q u i and collaborators), determ i n e d f r o m the fronto-mastoid r h e o e n c e p h a l o g r a m after application of the following 5 p h y s i o t h e r a p e u t i c factors: electrical currrent with ultra high frequency,
79P microwaves, electrophoresis, diadynamic current and ultrasound. The hemispheric b l o o d flow was 373.3 ± 5.9 m l / m i n before the physical influence (n = 407). This p a r a m e t e r increased significantly after the ultra high f r e q u e n c y current ( o l i g o t h e r m i c dose) and after microwaves (20 W) applied in the area of the head and the calf of the leg. The circulation t i m e decreased significantly after the aforesaid t w o factors and after nasal electrophoresis. The relative part of the cerebral blood flow from the m i n u t e v o l u m e o f the heart increased after the physical influence.
16. S o m e correlations between the neurological, psychoneurological and E E G s y m p t o m s in children with speech disorders in MBD. -- R. Raychev, N. Rasheva and M. Vulcheva (Sofia) The p r o b l e m of the interrelations between the clinical variant s y n d r o m e s included in the 'children with MBD' group and the s y m p t o m s of brain disturbances established in the clinical, neurological and EEG investigations, is c o n t i n u o u s l y discussed. In 241 children, b e t w e e n 5 and 9 years of age, with speech disorders (alalia, dyslalia and stuttering, dysgraphia and dyslexia), the following investigations were p e r f o r m e d : neurological consultation, neuropsychic e x a m i n a t i o n by means of a special test-set after A.R. Luria, IQ d e t e r m i n a t i o n after Binet-Simon-Terman-Manova, routine EEG e x a m i n a t i o n with functional tests for stimulation in the visual analysis. In 94 of the children, focal neurological signs ( ' s o f t ' focal signs) were established. Besides the speech disorders, the neurological investigations d e t e c t e d : visuospatial disorders in 84 children, disturbed praxis of posture in 107 children and of dynamic praxis in 101. A c c o r d i n g to E E G changes the patients were divided in t w o groups: with diffuse changes -- 94 patients (of the generally delayed or i m m a t u r e for the age type); with focal E E G changes -- 147 children (with focal c h a r a c t e r i s t i c s - high voltage sharp waves, spikes and complexes). The focal distribution in the hemisphere areas was: t e m p o r o - p a r i e t a l - 37.4%, temporo-parieto-occipital -- 34.7%, t e m p o r a l -- 21.1%, frontop a r i e t o - t e m p o r a l - 6.8%. In almost all individually analyzed s y n d r o m e s of speech disorders, this focal distribution was preserved. In the children with combined speech disorders (dyslalia, dysgraphia and dyslexia) the highest focal percentage was established in the temporo-parieto-occipital area (54.51%). The changes in the left hemisphere p r e d o m i n a t e d . C o m p l e x e x a m i n a t i o n of children with MBD revealed various s y m p t o m s of CNS lesions, which correlated a m o n g themselves and were m o s t p r o b a b l y at the b o t t o m of the observed speech disorders. These basic disturbances were n o t elucidated aetiologically, but t h e y were m o s t probably expressions of perinatal pathology.
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SOCIETY PROCEEDINGS
17. Paroxysmal E E G activity in children with m e n t a l retardation. - - D. Mintchev, M. A p o s t o l o v a and D. A p o s t o l o v (Plovdiv) The electrical activity o f the brains of 156 children with mental r e t a r d a t i o n was studied. The children a t t e n d e d special schools. The following E E G changes were registered: normal in 59 cases (37.82%), diffuse in 36 (23.08%), local in 7 (4.49%), low voltage in 23 (14.74%) and p a r o x y s m a l (epileptiform) activity in 31 (19.87%) cases. The children with brain damage and p a r o x y s m a l activity were considered to be disposed to developing s y m p t o m a t i c epilepsy. A n t i c o n vulsive prophylaxis is discussed.
18. On t h e possibility o f objectifying brightness disc o m f o r t . -- S. Slavchev (Varna) and N. Angelov
(Razgrad) The t e r m 'brightness d i s c o m f o r t ' includes the influence of unsuitable light sources on man, causing unpleasant e m o t i o n s like awkwardness, tenseness and irritation. The aetiological and p a t h o g e n e t i c basis of brightness d i s c o m f o r t , as well as its quantitative objectivization and m e a s u r e m e n t have been a m a t t e r for c o n t i n u e d a r g u m e n t and discussion. A possibility o f objectifying d i s c o m f o r t is proposed. Its quantitative values are calculated by the m e t h o d o f Epaneshnikov, using t h e values o f the reaction t i m e (measured in a light c h a m b e r for 8 discomfort levels), as well as in a p r o d u c t i o n plant using the values o f limited t i m e for a simple o p t i c o - m o t o r reaction, t i m e c o n s u m e d and errors in L a n d o l t ' s correction test, n u m b e r of errors and c o n s u m e d t i m e in the test for ocular fatigue, carried o u t with Pirkovsky's apparatus, the percentage subjectification of the workers asked a b o u t high and low spirits in the respective d i s c o m f o r t situations, as well as by studying the visibility values after Darkshlevitch. The e x p e r i m e n t a l results p o i n t to an o p t i m a l disc o m f o r t range of 25--30 d i s c o m f o r t units (after Epaneshnikov) which, in our opinion, objectifies the c o m f o r t - d i s c o m f o r t limit, subjectified by the existing m e t h o d s o f quantitative objectivization of d i s c o m f o r t (Guth, E p a n e s h n i k o v et al.).
19. C o m p a r a t i v e studies o f low and m e d i u m freq u e n c y currents for e l e c t r o s t i m u l a t i o n o f nondenervated muscles. - - S. Bankov (Sofia)
C o m p a r a t i v e studies were c o n d u c t e d with the purpose of finding the o p t i m a l current for electrostimulation o f n o n - d e n e r v a t e d muscles - - a current producing a sufficiently strong c o n t r a c t i o n with m i n i m a l
sensory stimulation. The subjective feeling o f the current was r e c o r d e d during antigravity e l b o w flexion up to 90 °, p r o d u c e d by e l e c t r o s t i m u l a t i o n o f the biceps muscle in the arm. In a series of 121 persons, divided into 5 groups, a comparative study was carried o u t on the effect o f m e d i u m f r e q u e n c y (5000 Hz) currents, m o d u l a t e d at 50 Hz, m o n o - and bipolar, with varying depths of m o d u l a t i o n , or d u r a t i o n of the m o d u l a t i o n trend, as well as with different shapes of cycles, basic f r e q u e n c y and different shapes of the m o d u l a t i o n trend. In studies with variation o f the current parameters outlined above the following o p t i m a l characteristics were established: basic f r e q u e n c y 5000 Hz with bipolar rectangular cycles, m o d u l a t e d at 60 Hz in trends with duration 2 msec and rectangular shape. This current was referred to by the t e r m ' m e d i u m freq u e n c y m o d u l a t e d impulse current'. A special portable battery-fed e l e c t r o s t i m u l a t o r was c o n s t r u c t e d for this particular current. In a series of 51 persons, using the same m e t h o d of study, the above-described current was c o m p a r e d with the l o w - f r e q u e n c y current ' D i n a t r o n ' , recently widely r e c o m m e n d e d as a means of painless electrostimulation. The results show that the ' m e d i u m freq u e n c y m o d u l a t e d i m p u l s e ' current was better tolerated for e l e c t r o s t i m u l a t i o n of ion-denervated muscles t h a n the ' D i n a t r o n ' current.
20. Galvanic versus alternating current in electroderm o m e t r i c diagnosis o f sensory deficit in peripheral nerve lesions to t h e hand. -- S. Bankov (Sofia) There is disagreement on t h e q u e s t i o n which current - - galvanic or alternating - - is m o r e suitable for skin e l e c t r o c o n d u c t i v i t y investigation as a test for s u d o m o t o r activity or sensory deficit in peripheral nerve injuries o f the hand. Comparative studies were carried o u t in a series of 20 patients with media n and ulnar nerve lesions at 376 sites o n the volar aspect of b o t h hands (the pulps of all 5 fingers, toruli tactiles, thenar and hypothenar). Skin e l e c t r o c o n d u c t i v i t y was e x a m i n e d using galvanic and alternating currents (50, 400 and 1200 Hz). A battery e l e c t r o d e r m o m e t e r , as well as selected parameters of the currents m e n t i o n e d above, were e m p l o y e d with a view to obtaining a c o m p a r a b l e basis f r o m the electrical v i e w p o i n t for measuring the individual current. It was established that skin e l e c t r o c o n d u c t i v i t y in denervated zones s h o w e d lowest values w h e n measured with galvanic current, n e x t the values for alternating current 50 Hz (twice higher), 400 Hz (3 times higher) and 1200 Hz (6 times higher). The discrimin a t o r y capacity (ratios b e t w e e n skin e l e c t r o c o n d u c -
BULGARIAN EEG/EMG SOCIETY
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tivity values for d e n e r v a t e d a n d s y m m e t r i c h e a l t h y skin z o n e s ) was o p t i m a l w i t h galvanic c u r r e n t : it was 3 t i m e s greater t h a n w i t h a l t e r n a t i n g c u r r e n t a t 50 Hz, 8 t i m e s greater t h a n at 4 0 0 Hz a n d 11 t i m e s greater t h a n at 1 2 0 0 Hz. T h e results s h o w t h a t changes in p o s t - d e n e r v a t i o n a l skin e l e c t r o c o n d u c t i v i t y are m o s t m a r k e d in its ohmic component. Galvanic current reflects most a d e q u a t e l y t h e s e changes.
t h e rising variability b e c a m e spindle-like, s h o w i n g m o r e r h y t h m i c p a t t e r n in s o m e c o n d i t i o n s . It is a s s u m e d t h a t a t s o m e i n t e r i m p u l s e intervals t h e a l p h a motoneurone receives m o r e c o h e r e n t a c t i v a t i o n t h r o u g h its d i f f e r e n t i n p u t s .
21. S e n s o r y a c t i o n p o t e n t i a l a n d s e n s o r y c o n d u c t i o n v e l o c i t y o f the median n e r v e - - t h e i r role in carpal' t u n n e l syndrome diagnosis. -- R. Popov and E. Stoyanova (Sofia)
T h e e x p e r i m e n t s were p e r f o r m e d w i t h 6 t r a i n e d s u b j e c t s w h o h a d t o a c t i v a t e t h e m o t o r u n i t s (MUs) in o n e a n d t h e s a m e muscle. O n e o f t h e MUs was k e p t in s t e a d y - s t a t e firing, t h e o t h e r o n e was s w i t c h e d o n a n d off. T h e first a n d last i m p u l s e s o f t h e s e s h o r t series were used t o s h o w t h e t i m e r e l a t i o n b e t w e e n b o t h i m p u l s e sequences. T h e delay a n d t h e a n t i c i p a t i o n o f t h e s e i m p u l s e s were m e a s u r e d w i t h r e s p e c t t o t h e n e i g h b o u r i n g i m p u l s e s o f t h e parallel MU. It was s h o w n t h a t t h e t i m e axis was i n t e r s e c t e d at p r e f e r r e d a n d n o n - p r e f e r r e d intervals a f t e r a n i m p u l s e in t h e c o n t i n u o u s l y active MU. T h e first a n d last i m p u l s e s o f t h e s h o r t series in t h e s e c o n d M U a p p e a r e d w i t h diff e r e n t p r o b a b i l i t y in t h e s e intervals. T h e c o i n c i d e n c e o f i m p u l s e s was l o w e r t h a n m a t h e m a t i c a l l y e x p e c t e d . W i t h i n 3 0 - - 7 0 m s e c a f t e r a n i m p u l s e in t h e c o n t i n u o u s l y firing M U t h e r e was a n a l t e r n a t i o n o f t h e p r o b a b i l i t y for a p p e a r a n c e o f t h e first impulse only, w h e r e a s for t h e last impulse e v e n t s w e n t m o r e s m o o t h l y . T h e s e facts are used as a basis for t h e e x p l a n a t i o n o f t h e t h r e s h o l d f l u c t u a t i o n o f MUs.
I n a t o t a l series o f 250 p a t i e n t s w i t h 391 s y m p t o m a t i c h a n d s , w h e r e t h e clinical diagnosis was carpal t u n n e l s y n d r o m e , c o n f i r m e d t h r o u g h E M G studies, c h a n g e s in s e n s o r y c o n d u c t i o n v e l o c i t y o f t h e m e d i a n n e r v e in t h e w r i s t - t h i r d finger r e g i o n were d e m o n strated. I n 1 1 6 s y m p t o m a t i c h a n d s s e n s o r y c o n d u c t i o n v e l o c i t y was d e l a y e d b e l o w 4 5 - - 4 0 m / s e c , in 173 b e l o w 40 m / s e c . In 102 h a n d s n o s e n s o r y n e r v e a c t i o n p o t e n t i a l was registered. Distal m o t o r l a t e n c y o f n. m e d i a n u s was f o u n d t o be u n a l t e r e d in 101 h a n d s - - b e l o w 4.5 msec. P r o l o n g e d distal m o t o r l a t e n c y against t h e b a c k g r o u n d o f u n c h a n g e d s e n s o r y c o n d u c t i o n v e l o c i t y o f t h e m e d i a n nerve was r e c o r d e d in n o n e o f t h e cases. E M G e v i d e n c e o f d e n e r v a t i o n o f m.m. a b d u c t u s pollicis brevis a n d o p p o n e n s pollicis was e s t a b l i s h e d in a c o m p a r a t i v e l y small n u m b e r of s y m p t o m a t i c h a n d s (64). I n all symptomatic hands sensory conduction velocity of t h e u l n a r n e r v e in t h e w r i s t - f i f t h finger r e g i o n was unchanged. The sensitivity of the electrodiagnostic a s s e s s m e n t in discovering t h e carpal t u n n e l s y n d r o m e was a u g m e n t e d u p o n c o m p a r i n g s e n s o r y c o n d u c t i o n v e l o c i t y a l o n g t h e m e d i a n a n d u l n a r nerves in t h e wrist-ring finger z o n e .
22. V a r i a b i l i t y o f t h e i n t e r i m p u l s e intervals o f t h e m o t o r u n i t firing d u r i n g v o l u n t a r y a c t i v a t i o n . Y.T. S h a p k o v ( L e n i n g r a d , U.S.S.R.) a n d D. Kosaroy (Sofia) T h e single m o t o r u n i t a c t i v i t y in m. b i c e p s b r a c h i i was i n v e s t i g a t e d in 20 h e a l t h y subjects. T h e leading o f f w i t h small surface skin e l e c t r o d e s was a m p l i f i e d b y a 3 - c h a n n e l 'Disa' e l e c t r o m y o g r a p h . T h e s u b j e c t s were t r a i n e d t o a c t i v a t e t h e i r m o t o r u n i t s (MUs) in l o n g series o f i m p u l s e s w i t h s p o n t a n e o u s f r e q u e n c y of firing. T h e m e a n intervals in successive series varied. T h e rise o f t h e v a r i a t i o n o f t h e intervals w e n t n o t s m o o t h l y b u t at s o m e m e a n values it was smaller t h a n at s o m e l o w e r values o f t h e m e a n . So t h e p i c t u r e of
23. V o l u n t a r y c o n t r o l o f t w o m o t o r u n i t s in o n e h u m a n muscle. - - D. Kosarov a n d L. C h r i s t o v a (Sofia)
24. E l e c t r o m y o g r a p h i c studies o f p o s t i n s u l t spasticity. - - N. Nikoevski (Sofia) T h e r e p o r t generalizes t h e results f r o m t h e investig a t i o n o f t h e value o f t h e H/M ratio, H/M r a t i o w i t h J e n d r a s s i k m a n o e u v r e , A / M ratio, a n d t h e e f f e c t o f v i b r a t i o n at 1 0 0 c/sec o n t h e H reflex in m o n o p o l a r E M G r e g i s t r a t i o n in a large g r o u p o f 60 p a t i e n t s w i t h p o s t i n s u l t spasticity - - f r o m slight u p t o p r o n o u n c e d - - c o m p a r e d w i t h t h e c o n t r o l groups. A n e v a l u a t i o n is given o f t h e possibilities o f q u a n t i t a t i o n o f t h e degree of c h a n g e of t h e muscle t o n e . T h e values o f t h e H / M ratio, e x p r e s s e d w i t h t h e a r i t h m e t i c m e a n a n d s t a n d a r d d e v i a t i o n , are very significant in t h e g r o u p s c o m p a r e d (a spastic w i t h a n o n - p a r e t i c leg a n d a spastic leg w i t h a h e a l t h y o n e in t h e same age g r o u p - P < 0.001; of the H/M ratio with Jendrassik m a n o e u v r e - - P < 0.01, a n d o f t h e A / M r a t i o - - P < 0.02). A n a c c o u n t is given o f t h e peculiar i n f l u e n c e o f v i b r a t i o n at 1 0 0 c/sec o n t h e H reflex o f a spastic muscle, w h i c h c a n serve t o evaluate its degree.
82P 25. Correlation b e t w e e n t h e reaction t i m e and t h e a m p l i t u d e changes o f the H reflex evoked in a muscle o f t h e contralateral leg in simple reaction t i m e task c o n d i t i o n s . - - Tz. T z e k o v (Varna) The correlation b e t w e e n the r e a c t i o n t i m e and the a m p l i t u d e changes of the H reflex evoked in m. gastrocnemius lateralis of the contralateral leg to the m o t o r response in conditions of a simple reaction t i m e task is studied. A c c o r d i n g to f o r m e r instructions, the subjects answered with m a x i m a l speed to a light signal f r o m a flash lamp t h r o u g h a red filter, lifting the right heel f r o m the floor. U n d e r these conditions, m. gastrocnemius lateralis dextri is one o f the agonists of the v o l u n t a r y m o v e m e n t . The H reflex was evoked in m. gastrocnemius lateralis sinistri, i.e., f r o m the leg contralateral to the m o t o r response. The r e a c t i o n time of the right leg m o t o r response was c o m p a r e d w i t h the a m p l i t u d e changes of the H reflex in the left gastrocnemius (an H reflex was evoked for each light signal). T h e characteristic correlation b e t w e e n the reaction t i m e and the a m p l i t u d e changes of the H reflex of the ipsilateral leg was measured under the same conditions. These results provide a basis for the a s s u m p t i o n t h a t in simple r e a c t i o n t i m e task c o n d i t i o n s there exists a certain specific preparation o f the muscle agonists to t h e f o r t h c o m i n g m o v e m e n t , which is connected with the f u l f i l m e n t o f the task.
SOCIETY PROCEEDINGS 26. I n f l u e n c e o f s i m u l t a n e o u s vestibular and optical
stimulation o n h u m a n muscle activity. - - V . Dam i a n o v a and Y. Toshev (Sofia) The purpose o f the w o r k is to investigate the influence o f simultaneous vestibular and optical stimulation on the bioelectrical activity (BEA) of s o m e muscles o f the h u m a n arm. The e x p e r i m e n t s consist in: optical stimulation o f the eye with white light; e l e c t r o s t i m u l a t i o n of the vestibular system; simultaneous vestibular and optical stimulation with white light; simultaneous vestibular and optical stimulation with red light. Each e x p e r i m e n t was carried o u t as follows: the muscles were relaxed in advance; the muscles were active in advance. B E A was measured with bipolar surface electrodes. The left and right flexors and the right e x t e n s o r o f the fingers were investigated. The results showed that muscle activity increased under optical stimulation and especially under vestibular stimulation. Simultaneous vestibular and optical stimulation with white light resulted in m o r e flexor activity than optical stimulation with red light. In each e x p e r i m e n t BEA of the preliminarily relaxed muscles was greater t h a n the B E A of the preliminarily active muscles.