- Email: [email protected]
Annual meeting of the Bulgarian EEG society
Electroencephalography and Clinical Neurophysiology, 1977, 4 2 : 5 8 4 - - 5 9 1
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© E l s e v i e r / N o r t h - H o l l a n d Scientific Publishers, Ltd. Society ANNUAL
proceedings MEETING
OF THE
BULGARIAN
EEG SOCIETY
Sofia, J a n u a r y 1 6 - 1 7 , 1 9 7 6
Secretary: G. V L A D I M I R O V A Institute o f Pediatrics, 11 D. Nestorov Str., Sofia 1606 (Bulgaria)
1. D e p e n d e n c e o f t h e r e a c t i o n t i m e a n d o f t h e cont i n g e n t negative v a r i a t i o n o n t h e c o m p l e x i t y o f the task and the degree o f vigilance. - - A. Atsev, T. G a v r i l e n k o , T. Mazgaleva, B. Kolev a n d A. S h m a rov (Sofia). T h r e e d a y t i m e a n d five n i g h t o n e - h o u r e x p e r i m e n tal sessions were p e r f o r m e d w i t h seven h e a l t h y y o u n g male subjects. S e q u e n c e s o f four variants of t h e signals were a p p l i e d : with intervals of 1, 2 or 3 sec b e t w e e n the w a r n i n g (Sl-click) a n d t h e i m p e r a t i v e (S2-flash) signals or o n l y with S t . S i m u l t a n e o u s recordings o f EEG, EOG, ECG a n d GS were m a d e . A n increase of the average R T a n d of the average a m p l i t u d e of CNV were o b s e r v e d u p o n t r a n s i t i o n f r o m i n d e p e n d e n t to m i x e d series o f signals, which is a t t r i b u t e d to t h e c o m p l i c a t i o n of t h e task. On t h e o t h e r h a n d , in t h e n i g h t e x p e r i m e n t s w i t h a series of m i x e d signals, a l o w e r i n g o f t h e a m p l i t u d e o f t h e averaged C N V was o b s e r v e d , p r e d o m i n a n t l y after m i d n i g h t . A l t h o u g h t h e R T d y n a m i c s in t h e night e x p e r i m e n t s m a n i f e s t e d c o n s i d e r a b l e individual differences, the general t e n d e n c y was also t o w a r d s an increase of the average RT, w i t h increased m e a n standard deviation. The significance o f selective a t t e n t i o n , of vigilance a n d o f phasic a n d t o n i c arousal, are discussed in c o n d i t i o n s o f c o m p l i c a t i o n o f t h e task a n d d u r i n g n i g h t tests.
2. V a r i a n t s of positive and negative feedback on the basis o f EMG a n d p a t h o l o g i c a l reflex activity. -- S. B a y k u s h e v (Plovdiv). T h e p r o b l e m of e x t e r i o r i z e d f e e d b a c k l o o p s as a m e a n s o f a d d i t i o n a l biological c o n t r o l a n d m o t o r corr e c t i o n is s t u d i e d . T h e bioelectrical activity in 36 p a t i e n t s w i t h c e n t r a l m o t o r d i s t u r b a n c e s was transf o r m e d into electrical s t i m u l a t i o n . This was achieved b y triggering the s t i m u l a t o r b y a c t i o n p o t e n t i a l s a b o v e a p r e d e t e r m i n e d level. Electrical s t i m u l a t i o n was applied t o t h e c u t a n e o u s r e c e p t o r fields of reflexes w i t h e x i t a t o r y or i n h i b i t o r y effects. In this m a n n e r a new f e e d b a c k l o o p was f o r m e d .
Positive f e e d b a c k was f o r m e d in p a t i e n t s w i t h postictal h e m i p a r e s e s in t w o variants: (1) o n t h e basis of flexor s y n r e f l e x i a (defensive w i t h d r a w a l reflex); (2) o n the basis of e x t e n s o r s y n r e f l e x i a in t h e paretic limb. In b o t h cases the s y n r e f l e x i a was a c t i v a t e d b y EMG c o r r e s p o n d i n g to t h e v o l u n t a r y c o n t r a c t i o n of a paretic group. I m p r o v e m e n t in the bioelectrical activity was achieved. In this m a n n e r t h e a c t i v a t i o n a n d s u p p r e s s i o n of t h e circuit b e c a m e f u n c t i o n s of t h e v o l u n t a r y m o t o r activity of t h e p a t i e n t , i.e., t h e nervous s y s t e m of t h e p a t i e n t r e m a i n e d t h e c e n t r e o f c o n t r o l archieved t h r o u g h t h e n e w c o r r e c t i v e loop. Negative f e e d b a c k was also f o r m e d in t w o varia n t s : (1) in torticollis, the bioelectrical activity of t h e h y p e r k i n e s i s was t r a n s f o r m e d i n t o electrical stimulat i o n applied to a c u t a n e o u s i n h i b i t o r y field o n t h e edge of the m a n d i b l e ; i n h i b i t i o n of t h e h y p e r k i n e s i s was achieved, h o w e v e r , w i t h s u b s e q u e n t h a b i t u a t i o n ; (2) in the case o f e x t e n s o r spasticity, bioelectrical activity c o r r e s p o n d i n g to t h e clonus o f t h e f o o t was applied to a c u t a n e o u s r e c e p t o r field of f l e x o r synreflexia. T h e i n h i b i t o r y c o m p o n e n t s o f t h e l a t t e r were used to suppress t h e activity of t h e e x t e n s o r s .
3. Visual e v o k e d p o t e n t i a l s in p a t i e n t s w i t h cortical d y s t r o p h y . - - B. Blazhev (Sofia). Visual e v o k e d p o t e n t i a l s were studied f r o m t w o b r o t h e r s w i t h Spiegel--Vogt cortical d y s t r o p h y a n d f r o m t h e i r p a r e n t s . T h e diagnosis of t h e t w o p a t i e n t s was d e t e r m i n e d a f t e r clinical e x a m i n a t i o n i n c l u d i n g b i o p s y o f t h e f r o n t a l c o r t e x . T h e p a r e n t s had n o c o m p l a i n t s or established diseases. T h e t w o p a t i e n t s were aged 16 a n d 22, t h e p a r e n t s 42 a n d 37. A mic r o e l e c t r o r e t i n o g r a m a n d c o n s i d e r a b l y r e d u c e d visual a c u i t y a n d p i g m e n t a r y d e g e n e r a t i o n of t h e r e t i n a were f o u n d in b o t h p a t i e n t s . T h e VEPs in t h e t w o p a t i e n t s revealed considerable d i s r u p t i o n o f f r o m , with a b s e n c e o f t h e early components, reduced amplitude a n d increased l a t e n c y of t h e late c o m p o n e n t s c o m p a r e d w i t h h e a l t h y s u b j e c t s f o r m t h e c o n t r o l g r o u p and t h e p a r e n t s . In t h e p a r e n t s t h e r e were n o d e v i a t i o n s in t h e
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BULGARIAN EEG SOCIETY VEPs c o m p a r e d w i t h t h e c o n t r o l g r o u p of h e a l t h y subjects.
4. Visual e v o k e d p o t e n t i a l s in patients w i t h intracranial g r o w t h s . - B. Blazhev (Sofia). Visual e v o k e d p o t e n t i a l s were s t u d i e d in 20 h e a l t h y s u b j e c t s ( c o n t r o l g r o u p ) a n d 21 p a t i e n t s with i n t r a c r a n i a l g r o w t h s : 17 p a t i e n t s w i t h t u m o u r s , t w o patients with optico-chiasmal arachnoiditis, one p a t i e n t with an abscess a n d o n e p a t i e n t w i t h a cyst. An o p e r a t i v e or a n a t o m i c a l v e r i f i c a t i o n of t h e diagnosis was p e r f o r m e d in 19 p a t i e n t s . In the p a t i e n t s w i t h t u m o u r s t h e r e was an increase in t h e a m p l i t u d e a n d l a t e n c y of t h e VEPs, b o t h in t h e a f f e c t e d a n d in t h e u n a f f e c t e d h e m i s p h e r e s c o m p a r e d w i t h t h e sub-" jects in t h e c o n t r o l g r o u p (p ~< 0 . 0 5 ) a n d significant i n t r a h e m i s p h e r i c a s y m m e t r y , w i t h greater l a t e n c y a n d smaller a m p l i t u d e in the a f f e c t e d h e m i s p h e r e . Considerable a s y m m e t r y of t h e e v o k e d r e s p o n s e s was also f o u n d in t h e p a t i e n t s with abscess a n d cyst. T h e t w o p a t i e n t s w i t h o p t i c o - c h i a s m a l a r a c h n o i d i t i s s h o w e d an increase in t h e l a t e n c y a n d a decrease in the amplit u d e of t h e VEPs. VEPs can be m u c h m o r e i n f o r m a t i v e in s o m e cases t h a n t h e basic E E G w h e n d e t e r m i n i n g t h e a f f e c t e d h e m i s p h e r e a n d t h e l o c a t i o n of t h e lesion.
5. All-night p o l y g r a p h i c studies o f patients r h e u m a t i c e p i l e p s y . - - D. Daskalov (Sofia).
with
F o u r t e e n p a t i e n t s (nine female a n d five m a l e ) aged 2 2 - - 4 9 (average age 3 6 ) were e x a m i n e d clinically a n d by o n e all-night E E G ( c o m b i n e d w i t h EMG, E O G a n d E C G ) in o r d e r to s t u d y t h e n i g h t d y n a m i c s of the sleep~activated e p i l e p t o g e n i c focus. T h e p a t i e n t s h a d a h i s t o r y of various r h e u m a t i c diseases d u r i n g childh o o d , c o m p l i c a t e d in all cases b y h e a r t disease. Rare n o c t u r n a l epileptic seizures a p p e a r e d in all p a t i e n t s a f t e r t h e age of 21. M o r e o v e r , n i n e p a t i e n t s also m a n ifested focal seizures, p r e d o m i n a n t l y t e m p o r a l . In half of t h e p a t i e n t s t h e seizures o c c u r r e d m o r e t h a n five years a f t e r t h e h e a r t disease. T h e diurnal E E G d u r i n g w a k e f u l n e s s was n o r m a l in five p a t i e n t s a n d in n i n e p a t i e n t s it s h o w e d diffuse c h a n g e s , m a i n l y slight. No f o c u s or bilaterally s y n c h r o n o u s p a r o x y s m s were f o u n d in a n y p a t i e n t i m m e d i a t e l y b e f o r e t h e n i g h t test. T h e all-night E E G revealed f r o n t o - t e m p o r a l foci in eight p a t i e n t s . T h e foci were seen m o s t o f t e n d u r i n g t h e s e c o n d N R E M phase. During R E M t h e foci were i n h i b i t e d in all p a t i e n t s e x c e p t one. It was f o u n d t h a t d u r i n g the s a m e sleep phase t h e f o c u s was a c t i v a t e d to d i f f e r e n t degrees in t h e initial, m i d d l e a n d final periods of t h e night. T w o m a x i m a o f focal a c t i v a t i o n
b e c a m e o u t l i n e d -- a t t h e b e g i n n i n g a n d at t h e e n d o f t h e night. During the m i d d l e p e r i o d o f t h e n i g h t t h e focus was c o m p l e t e l y or p a r t l y suppressed. In conclusion, a c t i v a t i o n of t h e focus did n o t d e p e n d o n l y o n t h e N R E M a n d R E M phases, b u t also o n the three periods o f t h e n i g h t (initial, m i d d l e a n d final).
6. Changes in the s p o n t a n e o u s and e v o k e d activity in different brain structures after administration o f stimulants. - - V. D i m o v a and D. Tchavdarov (Sofia). In e x p e r i m e n t s o n cats a s t u d y was m a d e of t h e e f f e c t of l i t h i u m , a m p h e t a m i n e a n d c e n t r o p h e n o x i n e o n the s p o n t a n e o u s a n d e v o k e d electrical activity of the somatosensory cortex, the ascending activating reticular s y s t e m , t h a l a m u s and h y p o t h a l a m u s . U n d e r t h e e f f e c t o f l i t h i u m , t h e cortical activity b e c a m e m o r e regular, with m o d e r a t e increase in a m p l i t u d e . F a s t e r waves a n d r h y t h m s a p p e a r e d 1 h after the a d m i n i s t r a t i o n of l i t h i u m , and after t h e s e c o n d h o u r the c o r t i c o g r a m a p p r o a c h e d t h e initial activity. T h e changes in t h e t h a l a m u s a n d h y p o t h a l a m u s were analogous, b u t t h e y a p p e a r e d later. Initially the activity of t h e reticular s t r u c t u r e s was faster, f o l l o w e d b y a delay a f t e r t h e first h o u r . S t i m u l a t i o n of n u c l e u s ischiadicus c h a n g e d t h e r e s p o n s e s of t h e c o r t e x a n d the deep s t r u c t u r e s in l a t e n c y a n d c o n f i g u r a t i o n of the c o m p o n e n t s . A m p h e t a m i n e d e s y n c h r o n i z e t h e activity of the c o r t e x a n d reticular s t r u c t u r e s and resulted in high voltage slow waves in t h e t h a l a m u s . E l e c t r o s t i m u l a tion o f t h e reticular s t r u c t u r e s while r e c o r d i n g f r o m the s o m a t o s e n s o r y c o r t e x was a c c o m p a n i e d by t h e a p p e a r a n c e of a c h a r a c t e r i s t i c slow negative c o m p o nent. A f t e r c e n t r o p h e n o x i n e slow waves p r e d o m i n a t e d initially in t h e c o r t e x , t r a n s f o r m e d i n t o regular alphalike activity, w i t h parallel slight d e s y n c h r o n i z a t i o n of t h e reticular s t r u c t u r e s .
7. C h a n g e s in C N V in d r o w s i n e s s induced b y m o n o t o n o u s noise. - - E. Dincheva and N. Tsaneva (Sofia). T h e CNV was studied in t h e classical p a r a d i g m : S 1-1.5 sec--S2--MR in seven t r a i n e d subjects. E E G activity was r e c o r d e d f r o m v e r t e x / m a s t o i d d e r i v a t i o n s w i t h a 6 sec time c o n s t a n t . A f t e r r e c o r d i n g c o n t r o l data a s t a t e o f m o n o t o m y was achieved by a p p l y i n g c o n t i n u o u s w h i t e noise w i t h 65 d B i n t e n s i t y . T h e a m p l i t u d e values of t h e s u m m a t e d C N V were m e a s u r e d at intervals of 200 msec. A p r o b a b i l i t y analysis o f t h e R T was p e r f o r m e d and a p o w e r s p e c t r u m o f the basic E E G activity was c o m p u t e d . In t h e c o n t r o l r e c o r d s t h e r e was a positive correla-
BULGARIAN EEG SOCIETY R e c o r d i n g o f t h e b a c k g r o u n d E E G a c t i v i t y was foll o w e d b y n o n - r h y t h m i c light stimuli (flash-~eries) a n d b y series r e q u i r i n g a rapid m o t o r r e s p o n s e a f t e r t h e stimulus. A significant increase in t h e n u m b e r o f slow waves ( t h e t a a n d d e l t a ) was f o u n d at t h e e n d o f t h e w o r k i n g day. T h e evoked p o t e n t i a l s t o flash w i t h motor r e s p o n s e m a n i f e s t an increase o f P200 a n d N160 c o m p a r e d w i t h EPs to flashes alone. T h e a m p l i t u d e of the e v o k e d p o t e n t i a l s decreased significantly at t h e e n d of t h e w o r k i n g d a y , while t h e R T increased. A positive c o r r e l a t i o n was established b e t w e e n t h e degree of a m p l i t u d e r e d u c t i o n o f P200 and t h e increase of t h e RT.
12. E f f e c t o f v o l u n t a r y m u s c l e activity o n the polys y n a p t i c reflexes e v o k e d b y electrical s t i m u l a t i o n o f n. suralis in m a n . - - L. G e r i l o w s k y , A. Gydikov, N. R a d i t c h e v a a n d N. T a n k o v (Sofia). A p o l y s y n a p t i c reflex p o t e n t i a l ( P S R P ) f r o m the muscles o f t h e ipsilateral leg w i t h b r i e f l a t e n c y ( 4 0 - 60 m s e c ) was e v o k e d b y s u p r a t h r e s h o l d electrical s t i m u l a t i o n o f n. suralis b y a series o f 12 pulses w i t h t o t a l d u r a t i o n o f 36 msec a n d 1 msec d u r a t i o n of each pulse. P r e c e d i n g s u p r a t h r e s h o l d s t i m u l a t i o n w i t h a similar series h a d a s t r o n g i n h i b i t o r y effect o n PSRP of t h e ipsilateral leg a n d a slight i n h i b i t o r y e f f e c t o n PSRP o f t h e c o n t r a l a t e r a l leg. P S R P was p o t e n t i a t e d s t r o n g l y in t h e interval 50 msec b e f o r e t h e v o l u n t a r y movement, S t r o n g electrical s t i m u l a t i o n of n. suralis b y a series of 12 pulses for 36 msec or 3 pulses for 10 msec was a c c o m p a n i e d by pain a n d e v o k i n g o f PSRP w i t h 8 0 - - 1 2 0 msec l a t e n c y in t h e muscles o f b o t h legs, as well as in o t h e r muscles of t h e b o d y ( b o t h m. trapezii). P r e l i m i n a r y s u b t h r e s h o l d s t i m u l a t i o n h a d an i n h i b i t o r y e f f e c t in this case as well. Before a n d during t h e v o l u n t a r y m o v e m e n t P S R P s w i t h l o n g l a t e n cies were a b s e n t in the t w o m, trapezii a n d were s t r o n g l y i n h i b i t e d in the leg muscles. T h e significance of t h e o b s e r v e d p h e n o m e n a for t h e r e g u l a t i o n of v o l u n t a r y m o v e m e n t , w h e n t h e m o v e m e n t was m a d e o n the b a c k g r o u n d of stimuli causing d e f e n c e reactions, is discussed.
13. V o l u m e - c o n d u c t e d p o t e n t i a l s o f m o t o r units in m. triceps surae in man. - - A. G y d i k o v , L. Geril o w s k y a n d G. D i m i t r o v (Sofia). T h e w o r k describes s o m e f e a t u r e s of t h e p o t e n t i a l s f r o m individual m o t o r u n i t s (MU) in m. triceps surae in m a n r e c o r d e d w i t h m o n o p o l a r a n d b i p o l a r surface e l e c t r o d e s w i t h a small leading-off area. In t h e distal part o f m. soleus t h e p o t e n t i a l s o r i g i n a t e f r o m pars p o s t e r i o r o f t h e same mLiscle. A b o v e ram. gastrocne-
587 mius lateralis and medialis t h e p o t e n t i a l s can b e l o n g e i t h e r to t h e s e muscles or t o pars p o s t e r i o r o f m. soleus. Very f r e q u e n t l y t h e e n d p l a t e s o f MUs in m. triceps surae are n o t in t h e m i d d l e o f t h e muscle fibres b u t closer t o o n e o f t h e i r ends. MUs in m. triceps surae are s h o r t a n d m a n y o f t h e m are n o t parallel to t h e skin surface. T h e p r o x i m a l MUs e n d s are deep in t h e distal part o f m. soleus, while t h e distal MUs e n d s are in t h e d e p t h o f the t w o ram. gastrocnemii. MUs along t h e edges of t h e distal part of m. soleus have curved fibres. These f e a t u r e s are in a g r e e m e n t w i t h the m o r p h o l o g i c a l data o n t h e l e n g h t a n d p o s i t i o n of t h e muscle fibres. T h e y c o n d i t i o n t h e specificities of shape, a m p l i t u t e a n d p r o p a g a t i o n velocity o f t h e negative m a x i m u m o f t h e p o t e n t i a l s in the volume conductor. 14. C o n d u c t i o n velocity in the m o t o r fibres o f nn. ulnaris, m e d i a n u s , fibularis and tibialis in patients w i t h hemiparesis after cerebral stroke. -- B. I s h p e k o v a (Sofia). C o m p a r i s o n is m a d e b e t w e e n t h e c o n d u c t i o n velocities in t h e p e r i p h e r a l nerves o n t h e paretic a n d o n t h e u n a f f e c t e d sides. It is e s t a b l i s h e d t h a t t h e m e a n c o n d u c t i o n velocity in t h e nerves t e s t e d is sign i f i c a n t l y decreased o n the paretic side (P < 0.001). The d i f f e r e n c e s in t h e m e a n distal t i m e s b e t w e e n u n a f f e c t e d and paretic sides is smaller. A n o t h e r c o m parison shows t h a t t h e c o n d u c t i o n velocity o n t h e h e a l t h y side is significantly lower t h a n in h e a l t h y c o n t r o l subjects, this b e i n g valid for all f o u r nerves. This is an i n t e r e s t i n g fact w h i c h i n d i c a t e s t h a t t h e unilateral a f f e c t i o n of t h e p y r a m i d a l t r a c t is n o t t h e o n l y f a c t o r for t h e decreased c o n d u c t i v i t y .
15. V e c t o r e l e c t r o m y o g r a p h i c studies o f antagonist muscles. - - D. Kosarov (Sofia). T h e so-called " c r o s s e d e l e c t r o d e s " were used for a vector e l e c t r o m y o g r a p h i c s t u d y o f t h e bioelectrical activity of t h e f o l l o w i n g pairs of a n t a g o n i s t muscles: biceps a n d triceps brachii, flexors a n d e x t e n s o r s o f t h e wrist, a b d u c t o r s a n d a d d u c t o r s o f t h e wrist. T h e s t u d y o f t h e biceps-triceps pair allowed e v a l u a t i o n of the e x t e n t o f c o a c t i v a t i o n o f the a n t a g o n i s t in the p e r f o r m a n c e of a m o v e m e n t or o n increasing t h e muscle t e n s i o n t o t h e m a x i m u m . It was f o u n d t h a t c o i n c i d e n c e of impulses f r o m a m o t o r u n i t b e l o n g i n g to each muscle o c c u r s a c c i d e n t a l l y r a t h e r t h a n as a result of s y s t e m i c s y n c h r o n i z a t i o n o f t h e i r impulse activities. In p a t i e n t s w i t h slight h e m i p a r e s i s t h e electrical activity d u r i n g a m o v e m e n t originated f r o m the agonist. In p a t i e n t s w i t h severe h e m i p a r e s i s t h e electrical activity m i g h t originate o n l y in t h e a n t a g o n i s t in a n a t t e m p t e d m o v e m e n t .
588
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A s t u d y was m a d e of t h e muscles o f t h e f o r e a r m in a g o n i s t - a n t a g o n i s t pairs d u r i n g o n e of t h e wrist m o v e m e n t s : flexion, e x t e n s i o n , a b d u c t i o n a n d a d d u c t i o n . T h e relative c o a c t i v a t i o n o f t h e radial a n d u l n a r flexor a n d o f t h e radial a n d u l n a r e x t e n s o r in each m o v e m e n t p e r f o r m e d was s h o w n .
r a t i o of t h e largest a m p l i t u d e d o i n g light a d a p t a t i o n to t h e highest value d u r i n g dark a d a p t a t i o n , was smaller in p a t i e n t s w i t h a h i s t o r y o f cerebral ictus a n d greater o n t h e side of t h e b r a i n lesion. It was n o r m a l in t h e cases in w h i c h n o focal n e u r o l o g i c a l s y m p t o m s were o b s e r v e d .
16. Study o f the motor potential during v o l u n t a r y recurrent movement. -- R. Kristeva (Sofia).
18. Visual a n d auditory evoked potentials during therapeutic electroshocks and e l e c t r o c o n v u l s i v e therapy (ECT). - - Ch. M e r d z h a n o v , L. Peneva, D. Gadjev and D. T c h a v d a r o v (Sofia).
A s t u d y was m a d e o f t h e m o r p h o l o g y of t h e m o tor p o t e n t i a l d u r i n g r e c u r r e n t v o l u n t a r y m o v e m e n t (pressing a b u t t o n ) w i t h i n t h e f r a m e w o r k o f a 1 h e x p e r i m e n t w i t h nine r i g h t - h a n d e d e x p e r i m e n t a l subjects. T h e records were m a d e f r o m C3 a n d f r o m an area 2 c m a b o v e t h e inion. T h e p o t e n t i a l changes prec e d i n g and a c c o m p a n y i n g t h e m o v e m e n t were o b s e r v e d in all nine subjects. In seven of t h e m t h e r e was a r e d u c t i o n in t h e a m p l i t u d e of t h e negativity of t h e m o t o r p o t e n t i a l in t h e course o f t h e e x p e r i m e n t and this r e d u c t i o n m i g h t a m o u n t to disappearance. Positivity o c c u r e d in t w o cases. T h e decrease in t h e negative a m p l i t u d e b e g a n b e t w e e n t h e 8 t h a n d 1 5 t h rain of t h e e x p e r i m e n t . In five o f t h e s u b j e c t s t h e r e was a t e n d e n c y t o w a r d s decreased l a t e n c y of t h e b e g i n n i n g o f negativity. T h e spectral d e n s i t y curve of t h e E E G in t h r e e s u b j e c t s s h o w e d a s h i f t to t h e left of t h e d o m i n a n t f r e q u e n c y b y a b o u t 1 Hz a n d appearance o f periods w i t h low f r e q u e n c y waves. T h e decrease in t h e negative a m p l i t u d e o f t h e motor p o t e n t i a l c o u l d be associated w i t h a r e d u c t i o n of t h e a s c e n d i n g a c t i v a t i n g effects o f t h e reticular form a t i o n as a result o f t h e h a b i t u a t i o n process developing d u r i n g t h e r e c u r r e n t v o l u n t a r y m o v e m e n t .
17. Electrooculographic studies o f patients with hypertonic disease and a t h e r o s c l e r o s i s . - M. Matev, G. Zapryanov and D. Daskalov (Sofia). E l e c t r o o c u l o g r a p b i c studies are m a d e in 25 p a t i e n t s w i t h h y p e r t o n i c disease and atherosclerosis. No focal n e u r o l o g i c a l s y m p t o m s were f o u n d in t e n of t h e cases, t h e r e m a i n i n g cases b e i n g in a post-ictal s t a t e ( n o n - o b t u r a t i n g cerebral s o f t e n i n g ) . T h e t i m e for d a r k r e d u c t i o n (the t i m e necessary to a t t a i n t h e lowest a m p l i t u d e d u r i n g d a r k a d a p t a t i o n ) , t h e absolute r e d u c t i o n (the d i f f e r e n c e b e t w e e n t h e m e a n a m p l i t u d e at t b e 3rd rain a n d t h e average m i n i m u m d e f l e x i o n d u r i n g d a r k a d a p t a t i o n ) a n d t h e relative r e d u c t i o n (the r a t i o o f t h e a b s o l u t e r e d u c t i o n a n d t h e m e a n a m p l i t u d e at t h e 3rd r a i n ) s h o w e d lower average values in t h e p a t i e n t s a f t e r cerebral ictus c o m p a r e d w i t h t h o s e in w h o m n o focal neurological s y m p t o m s were f o u n d . T h e values o f t h e a b o v e indices were l o w e r o n t h e side o f the b r a i n lesion. T h e
Series of 32 r e s p o n s e s (analysis e p o c h 500 m s e c ) to light a n d s o u n d stimuli were averaged 1, 5, 15, 30, 60, 90 a n d 120 m i n after bilateral or unilateral ECT. In t h e first m i n u t e s of t h e p o s t c o n v u l s i v e p e r i o d t h e early c o m p o n e n t s of t h e EP were f o l l o w e d b y a high voltage negative wave with d u r a t i o n of 3 0 0 - - 3 5 0 msec. S m o o t h i n g a n d s i m p l i f i c a t i o n of t h e r e s p o n s e c o n f i g u r a t i o n were o b s e r v e d b e t w e e n t h e 5 t h a n d t h e 3 0 t h m i n w h e n a smaller n u m b e r of high voltage c o m p o n e n t s were r e c o r d e d . R h y t h m i c high voltage oscillations w i t h 8 0 - - 1 0 0 msec l a t e n c y a p p e a r e d b e t w e e n the 6 0 t h a n d t h e 1 2 0 t h min. Individual differences in t h e i n t e n s i t y a n d t i m e - c o u r s e of t h e changes in t h e evoked activity were o b s e r v e d in t h e d i f f e r e n t subjects. U n t i l t h e 1 2 0 t h rain n o t all subjects h a d reverted t o the pre-ECT p a t t e r n of the EPs. Differences in t h e c o n f i g u r a t i o n of t h e evoked p o t e n tials f r o m t h e t w o h e m i s p h e r e s were f o u n d in t h e case of u n i l a t e r a l ECT. T h e average a m p l i t u d e valus o f visual a n d a u d i t o r y r e s p o n s e s were e s t i m a t e d for t h e periods: 0 - - 9 0 msec (A), d e r a b l y higher average increases for B a n d C c o m p a r e d w i t h A; (2) t h e amp l i t u d e changes for A a n d B were u n i d i r e c t i o n a l in m o s t cases and reciprocal in t h e r e m a i n i n g cases. The possible m e c h a n i s m s o f t h e changes in t h e e v o k e d p o t e n t i a l s following bilateral or u n i l a t e r a l E C T are discussed.
19. Neurocybernetic aspects o f cerebral electrogenesis in the postconvulsive state -- Ch. Merdzhanov and M. Gospodinov (Sofia). T h e p o s t c o n v u l s i v e s t a t e is c o n s i d e r e d f r o m t h e standpoint of cybernetics, with determination of the information and autoregulation characteristics of the cerebral electrogenesis. T h e q u a n t i t a t i v e a s s e s s m e n t of t h e l a t t e r ( i r o n t a l a n d occipital region u p to 2 h o u r s a f t e r E C T ) was achieved b y f r e q u e n c y - a m p l i t u d e analysis. T h e i n f o r m a t i o n characteristics were d e t e r m i n e d on the basis of t h e p r o b a b i l i t y o f appearance o f d i f f e r e n t f r e q u e n c y ranges (beta, alpha, theta a n d delta waves). In t h e p o s t c o n v u l s i v e s t a t e t h e t o t a l e n t r o p y (H) was increased while t h e c o e f f i c i e n t o f
BULGARIAN EEG SOCIETY redundancy (R) decreased. The autoregulation characteristics were found on the basis of t h i r d ~ r d e r differential equations describing the dynamics of the average frequencies. The stability reserves were determined with respect to phase and amplitude for the different frequencies of the bioelectrical activity. The largest stability reserve with respect to phase and amplitude was found for the theta waves.
20. Comparative analysis o f t h e variance o f s p o n t a n e ous and e v o k e d EEG-activity. -- I. Mezan, N. Vrabchev and M. Matveev (Sofia).
The problem of dividing the variance of EEG signals into components corresponding to the variance of spontaneous activity and that of evoked potentials is dealt with. The evoked activity was obtained by visual stimulation and data were recorded of the preceding as well as the evoked activity from occipital and parietal derivations. The variance of each epoch and derivation, including spontaneous and evoked activity, was determined with respect to the averaged signal, using a specially developed algorithm for an ensemble of 32 epochs. The hypothesis of differentiation between variances of epochs of spontaneous activity and epochs containing evoked potentials was verified by variance analysis. In order to obtain a better accuracy, the experimental design included three factors. The remaining two were correspondingly the derivations and the experimental repetitions. The variances of the epochs of spontaneous activity and those of evoked potentials proved to be statistically indistinguishable, with a high degree of reliability, which proves the hypothesis that the variance of the epoch with evoked activity is due in a considerable degree to the variance of the spontaneous activity. The recording and treatment of the data were performed by a closed cycle of a laboratory experiment, a minicomputer and its programming included.
21. Motor unit firing pattern during f l e x o r reflex in dogs. -- N. Raditcheva and N. Tankov (Sofia). A study was made of the changes in the transient processes of the momentary frequency of discharge of previously active motor units (MU) in m. gastrocnemius and m. semitendinosus in dogs with flexor reflex elicited by electrical stimulation. Surface selective electrodes were used for recording the activity of the different MUs. Five types of transient process are described, mainly depending on the intensity of stimulation. A lower stimulus intensity led to an increase in the momentary frequency of the discharges of MUs 60 msec after its application, followed by a decrease and later by another increase in the frequency. The
589 strongest stimulation first lowered the frequency of firing of MUs for about 150 msec, then increased the frequency. The mechanisms of recurrent inhibition and the role of some afferent inputs of the flexor reflex are taken into account in the interpretation of these data.
22. E l e c t r o p h y s i o l o g i c a l e x p l o r a t i o n o f the sensory f u n c t i o n o f the sural nerve in diabetic patients. - D. Stanchev and N. Nikoevski (Sofia).
The exploration was carried out with an original electrode constructed in the authors' laboratory. The population comprised 106 diabetic patients (average age 56.6) and 50 healthy subjects (average age 56.9) equally distributed in age and sex, as for the first group. A highly significant disturbance of the sensory function of the sural nerve was found in diabetic patients (P < 0.001). The latency demonstrated considerable variability, which limited its value for diagnosis (59.05%). This shortcoming was compensated considerably if expressed as a velocity (67.61%). The changes in amplitude made it possible to determine objectively the disturbances in the highest percentage of patients (81.8%). An important advantage of the parameter is illustrated by examination of diabetic patients without clinical indications of neuropathy. Recording of the amplitude in these cases made it possible to discover subclinical functional disturbances of the sural nerve in 74.1% of the cases.
23. C o n t r i b u t i o n t o the e l e c t r o p h y s i o l o g i c a l assessm e n t o f m o t o r f u n c t i o n o f peripheral nerves in diabetic patients. - - D. Stancbev and N. Uzunov (Sofia).
The recording of changes in the distal latencies and conduction velocities of excitation is routine practice in the electrophysioiogical tests of the motor function of peripheral nerves in diabetic patients. Recently certain important shortcomings were discovered with respect to early electrodiagnosis. The study of changes in the percentage ratio of the amplitudes of the M responses after proximal and distal stimulation of the peroneal nerve in 30 diabetic patients and 23 healthy subjects permitted and expansion of the diagnostic possibilities of the method by about 20%. The ratio reflects most comprehensively the specific structural and functional disturbances in diabetic neuropathy. Its advantage is that it makes objective the changes in a wider range of the m o t o r fibres, including patients with a less serious clinical form of the complications. The above parameter permits the elimination of the effect of changes in the condition and number of the muscle fibres, of the differences in
590 t h e d e v e l o p m e n t of t h e s u b c u t a n e o u s tissues a n d of d i f f e r e n c e s in t h e e l e c t r o d e s used. Our d a t a e m p h a s i z e t h e a b o v e p a r a m e t e r as t h e m o s t sensitive c r i t e r i o n for t h e o b j e c t i v e assessment of early d i s t u r b a n c e s o f m o t o r f u n c t i o n .
24. H reflex in diabetic patients. -- D. S t a n c h e v , N. U z u n o v and N. Nikoevski (Sofia). Only a few studies o f t h e H reflex b a s e d o n a limited n u m b e r of d i a b e t i c p a t i e n t s are r e p o r t e d in t h e l i t e r a t u r e . T h e r e are n o d a t a o n t h e changes in t h e various e l e c t r o p h y s i o l o g i c a l p a r a m e t e r s o f t h e reflex d e p e n d i n g o n t h e clinical m a n i f e s t a t i o n o f t h e diabetic polyneuropathy. For the purpose experiments were m a d e involving 106 d i a b e t i c p a t i e n t s (average age 5 6 . 6 ) a n d 50 h e a l t h y s u b j e c t s (average age 56.9), equally d i s t r i b u t e d a c c o r d i n g to age a n d sex. Our results revealed a significant d i s t u r b a n c e in t h e funct i o n o f t h e Ia a f f e r e n t fibres in d i a b e t i c p a t i e n t s (P < 0.001). A m a r k e d variability of t h e reflex a m p l i t u d e was e s t a b l i s h e d , causing difficulties o f i n t e r p r e t a t i o n . R e c o r d i n g t h e changes in iatencies m a d e it possible to assess o b j e c t i v e l y t h e d i s t u r b a n c e s in 4 5 . 2 8 % of t h e p a t i e n t . C o m p a r a t i v e clinical a n d e l e c t r o p h y s i o l o g i c a l studies illustrate t h e low value of t h e a b o v e p a r a m e t e r for t h e p u r p o s e s of early diagnosis. T h e e x p l o r a t i o n of t h e H reflex was f o u n d t o b e o f i m p o r t a n c e in t h e cases of a b s e n c e o f a s e n s o r y nerve p o t e n t i a l f r o m t h e sural nerve as the result o f a m o r e p r o n o u n c e d disturb a n c e of s e n s o r y f u n c t i o n . T h e significance of t h e H reflex is also d e t e r m i n e d b y t h e fact t h a t it is the o n l y m e t h o d t o assess t h e c o n d i t i o n o f t h e Ia a f f e r e n t fibres.
25. On the s y n d r o m e of the anterior tibial artery: report o f three cases e x a m i n e d clinically and electromyographically. -- K. Subev, B. Ishpekova and R. Rasher (Sofia). T h e significance o f excessive t e n s i o n of t h e calf muscle a n d local tissue c h a n g e s r e s u l t i n g in c o m p r e s sion of t h e same a r t e r y , as f a c t o r s for t h e a p p e a r a n c e of t h e s y n d r o m e o f t h e a n t e r i o r tibial a r t e r y , are well k n o w n . M u l t i p l e e l e c t r o m y o g r a p h i c tests were perf o r m e d a n d the clinical c o u r s e o f t h e disease was foll o w e d in t h r e e cases for periods of 1--2.5 years. All cases m a n i f e s t e d c o m m o n clinical s y m p t o m s : t e n s i o n o f t h e tibial muscles w i t h p r o b a b l e c o m p r e s s i o n of t h e a n t e r i o r tibial a r t e r y a n d a s u b s e q u e n t i m m e d i a t e d e v e l o p m e n t of paralysis o f t h e ipsilateral p e r o n e a l nerve. A c o m m o n f e a t u r e in t h e e l e c t r o m y o g r a p h i c p a t t e r n was t h e i n d i c a t i o n o f d a m a g e t o t h e d e e p b r a n c h o f t h e p e r o n e a l nerve, very p r o n o u n c e d in all t h r e e cases. T h e a i m o f t h e p r e s e n t w o r k is t o f o c u s
SOCIETY PROCEEDINGS a t t e n t i o n o n a s y n d r o m e n o t so m u c h i n f r e q u e n t as s e l d o m diagnosed. T h e great significance of t h e elect r o m y o g r a p h i c tests for t h e c o r r e c t diagnosis was emphasized.
26. E E G in u n i l a t e r a l a n d bilateral e l e c t r o c o n v u l s i v e therapy (ECT). -- D. T c h a v d a r o v , Ch. M e r d z h a nov, N. Peneva and S. P o p o v (Sofia). C o m p a r a t i v e E E G tests (visual analysis, a m p l i t u d e , period analysis a n d p o w e r s p e c t r a ) were p e r f o r m e d on symmetrical temporo~ecipital and temporo-frontal records in m e n t a l p a t i e n t s after bilateral a n d unilateral e l e c t r o c o n v u l s i v e t h e r a p y (ECT). Slowing of t h e E E G was o b s e r v e d in bilateral E C T ; t h e differences b e t w e e n right a n d left were insignificant w i t h respect t o t h e d o m i n a n t f r e q u e n c y , t h e r e c o v e r y t i m e being d e p e n d e n t t o a large e x t e n t o n t h e o r g a n i z a t i o n o f t h e initial EEG. In t h e cases o f unilateral ECT s o m e s u b j e c t s displayed a bilaterally identical d o m i n a n t f r e q u e n c y and o t h e r s , a n 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 f r e q u e n c y c h a r a c t e r i s t i c s , w h i c h were m o r e f r e q u e n t a f t e r t h e 6 0 t h m i n . The a b n o r m a l m a n i f e s t a t i o n s a n d t h e n u m b e r of slow waves were c o n s i d e r a b l y less p r o n o u n c e d in unilateral ECT t h a n in bilateral ECT. R i g h t h e m i s p h e r e ECT resulted in greater i n t e r h e m i s p h e r i c d i f f e r e n c e s in t h e f r e q u e n c y a m p l i t u d e o r g a n i z a t i o n of t h e activity. No bioelectrical silence was o b s e r v e d a f t e r unilateral ECT. Considerable d i f f e r e n c e s in t h e E E G o r g a n i z a t i o n o f t h e t w o h e m i s p h e r e s were o b s e r v e d for a s h o r t t i m e a f t e r a b s e n c e s caused b y u n i l a t e r a l l y placed e l e c t r o d e s .
27. EEG changes in migraine patients treated with acupuncture. -- R. Tsikalova, M. Tsekova and L. Ivanova (Sofia). This w o r k studies t h e e f f e c t o f a single a c u p u n c ture p r o c e d u r e o n t h e brain activity. In 24 p a t i e n t s suffering f r o m m i g r a i n e EEGs were r e c o r d e d f r o m t h e occipital part of the side a f f e c t e d by t h e h e a d a c h e . An analysis was m a d e o f t h e E E G changes as a result of a c u p u n c t u r e b o t h at rest and after a c t i v a t i o n w i t h 0.25 m g N i t r o m i n t a n d h y p e r v e n t i l a t i o n . (1) At t h e 1 5 t h rain a f t e r t h e needles were placed d e s y n c h r o n i z a t i o n a c c o m p a n y i n g t h e pain r e a c t i o n was o b s e r v e d . R e m o v a l o f t h e needles r e s u l t e d in a tendency towards synchronization of the record with a statistically significant increase in t h e m e a n amplit u d e (P < 0.05). (2) T h e changes in the first a n d last 10 sec of a 1 m i n r e c o r d a f t e r h y p e r v e n t i l a t i o n h a d a phasic course a n d were c h a r a c t e r i z e d b y an initial decrease of t h e average f r e q u e n c y (P < 0.01), f o l l o w e d b y an increase in t h e f r e q u e n c y d u r i n g t h e s e c o n d phase.
B UL GAR I AN EEG SOCIETY The changes had the same dynamics and were more pronounced after acupuncture. (3) The studies of the Nitromint effect showed a statistically significant increase in the average frequency (P < 0.001) and an insignificant decrease in the average amplitude. The changes reached their maximum between the 3rd and 5th min after its administration. The effect of Nitroming was reduced after acupuncture. The results show that acupuncture has an effect on the brain structures. Most probably non-specific mechanisms leading to improvement of the vascular regulation participate in this reaction.
28. Rheoencephalographic studies in post-ictal patients before and after application o f rehabilitation procedures. - - N. Tsolov and S. Merdzhanova (Sofia). Quantitative and qualitative rheoencephalographic studies were performed in 50 patients with cerebral ictus. In most patients the stroke had occurred more than one year previously. The rehabilitating procedures involved regimen, vitamins, passive and active movements for the hemiparetic limbs, massage, kinesitherapy, paraffin applications, partial water iodine baths, etc. Drug therapy was completely excluded. After the end of the procedures there was a slight decrease in the tone of the peripheral and cerebral blood vessels. A drop in the systolic and diastolic blood pressure was found. Both in the "healthy" and in the "affected" hemisphere there was a rise in amplitude of the rheographic wave, a decrease in the relative share of the anacrotic part and dicrotic index with an insignificant increase in the hemispheral blood flow (estimated after the method of D. Hadjiev). All rheoencephalographic changes were more pronounced over the "healthy" hemispheres.
29. Study of m ot o r potentials in pre-school children. - - G. Vladimirova, R. Kristeva and G.M. Gantchev
(Sofia). The motor potentials from C3 (mastoid reference) were investigated in 21 children aged 6 to 6 11/12
591 years w h o were asked to press a button with the right thumb at an arrhythmic rate. T w o series of 100 trials each were averaged with analysis time of 2 sec (1.5 sec before and 0.5 sec after the movement). Type P motor potentials (after Timsit-Berthier et al. 1973) were found in 2 4 % of the children. In the remaining cases in which type N was recorded, it was not always possible to distinguish every component of the motor potential. Thus, the readiness potential could be seen clearly in only 4 7 % of the cases; N2 and P2 were the most frequent components. Comparing the data from both series it could be seen that N2 was the most invariable component of the motor potential at this age.
30. Electrooculographic
studies of Farkinsonian patients. - - G. Zapryanov, M. Matev and D. Daskalov (Sofia).
Electrooculographic studies were made in 32 patients with Parkinsonian syndrome and in a control group of 12 practically healthy subjects. It was found that the absolute drop (the difference between the average amplitude at the 3rd rain and the average m i n i m u m deflection during dark adaptation) showed insignificant differences between the two groups (P > 0.05). The relative drop (the ratio between the absolute drop and the mean amplitude at the 3rd rain) showed almost identical values in Parkinsonians and in healthy subjects, 15.4 and 15.2% respectively (P > 0.05). The rise-time was greatest at 8,80 rain after light adaptation for Parkinsonians, while in the control group it was at 7.40 rain (P < 0.05). The ratio of the largest amplitude during light adaptation to the lowest value during dark adaptation in parkinsonians was 160.8% and 195.4% in the control group. The experiments indicate the existence of certain changes in the functional state of the retina of Parkinsonians.
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© E l s e v i e r / N o r t h - H o l l a n d Scientific Publishers, Ltd. Society ANNUAL
proceedings MEETING
OF THE
BULGARIAN
EEG SOCIETY
Sofia, J a n u a r y 1 6 - 1 7 , 1 9 7 6
Secretary: G. V L A D I M I R O V A Institute o f Pediatrics, 11 D. Nestorov Str., Sofia 1606 (Bulgaria)
1. D e p e n d e n c e o f t h e r e a c t i o n t i m e a n d o f t h e cont i n g e n t negative v a r i a t i o n o n t h e c o m p l e x i t y o f the task and the degree o f vigilance. - - A. Atsev, T. G a v r i l e n k o , T. Mazgaleva, B. Kolev a n d A. S h m a rov (Sofia). T h r e e d a y t i m e a n d five n i g h t o n e - h o u r e x p e r i m e n tal sessions were p e r f o r m e d w i t h seven h e a l t h y y o u n g male subjects. S e q u e n c e s o f four variants of t h e signals were a p p l i e d : with intervals of 1, 2 or 3 sec b e t w e e n the w a r n i n g (Sl-click) a n d t h e i m p e r a t i v e (S2-flash) signals or o n l y with S t . S i m u l t a n e o u s recordings o f EEG, EOG, ECG a n d GS were m a d e . A n increase of the average R T a n d of the average a m p l i t u d e of CNV were o b s e r v e d u p o n t r a n s i t i o n f r o m i n d e p e n d e n t to m i x e d series o f signals, which is a t t r i b u t e d to t h e c o m p l i c a t i o n of t h e task. On t h e o t h e r h a n d , in t h e n i g h t e x p e r i m e n t s w i t h a series of m i x e d signals, a l o w e r i n g o f t h e a m p l i t u d e o f t h e averaged C N V was o b s e r v e d , p r e d o m i n a n t l y after m i d n i g h t . A l t h o u g h t h e R T d y n a m i c s in t h e night e x p e r i m e n t s m a n i f e s t e d c o n s i d e r a b l e individual differences, the general t e n d e n c y was also t o w a r d s an increase of the average RT, w i t h increased m e a n standard deviation. The significance o f selective a t t e n t i o n , of vigilance a n d o f phasic a n d t o n i c arousal, are discussed in c o n d i t i o n s o f c o m p l i c a t i o n o f t h e task a n d d u r i n g n i g h t tests.
2. V a r i a n t s of positive and negative feedback on the basis o f EMG a n d p a t h o l o g i c a l reflex activity. -- S. B a y k u s h e v (Plovdiv). T h e p r o b l e m of e x t e r i o r i z e d f e e d b a c k l o o p s as a m e a n s o f a d d i t i o n a l biological c o n t r o l a n d m o t o r corr e c t i o n is s t u d i e d . T h e bioelectrical activity in 36 p a t i e n t s w i t h c e n t r a l m o t o r d i s t u r b a n c e s was transf o r m e d into electrical s t i m u l a t i o n . This was achieved b y triggering the s t i m u l a t o r b y a c t i o n p o t e n t i a l s a b o v e a p r e d e t e r m i n e d level. Electrical s t i m u l a t i o n was applied t o t h e c u t a n e o u s r e c e p t o r fields of reflexes w i t h e x i t a t o r y or i n h i b i t o r y effects. In this m a n n e r a new f e e d b a c k l o o p was f o r m e d .
Positive f e e d b a c k was f o r m e d in p a t i e n t s w i t h postictal h e m i p a r e s e s in t w o variants: (1) o n t h e basis of flexor s y n r e f l e x i a (defensive w i t h d r a w a l reflex); (2) o n the basis of e x t e n s o r s y n r e f l e x i a in t h e paretic limb. In b o t h cases the s y n r e f l e x i a was a c t i v a t e d b y EMG c o r r e s p o n d i n g to t h e v o l u n t a r y c o n t r a c t i o n of a paretic group. I m p r o v e m e n t in the bioelectrical activity was achieved. In this m a n n e r t h e a c t i v a t i o n a n d s u p p r e s s i o n of t h e circuit b e c a m e f u n c t i o n s of t h e v o l u n t a r y m o t o r activity of t h e p a t i e n t , i.e., t h e nervous s y s t e m of t h e p a t i e n t r e m a i n e d t h e c e n t r e o f c o n t r o l archieved t h r o u g h t h e n e w c o r r e c t i v e loop. Negative f e e d b a c k was also f o r m e d in t w o varia n t s : (1) in torticollis, the bioelectrical activity of t h e h y p e r k i n e s i s was t r a n s f o r m e d i n t o electrical stimulat i o n applied to a c u t a n e o u s i n h i b i t o r y field o n t h e edge of the m a n d i b l e ; i n h i b i t i o n of t h e h y p e r k i n e s i s was achieved, h o w e v e r , w i t h s u b s e q u e n t h a b i t u a t i o n ; (2) in the case o f e x t e n s o r spasticity, bioelectrical activity c o r r e s p o n d i n g to t h e clonus o f t h e f o o t was applied to a c u t a n e o u s r e c e p t o r field of f l e x o r synreflexia. T h e i n h i b i t o r y c o m p o n e n t s o f t h e l a t t e r were used to suppress t h e activity of t h e e x t e n s o r s .
3. Visual e v o k e d p o t e n t i a l s in p a t i e n t s w i t h cortical d y s t r o p h y . - - B. Blazhev (Sofia). Visual e v o k e d p o t e n t i a l s were studied f r o m t w o b r o t h e r s w i t h Spiegel--Vogt cortical d y s t r o p h y a n d f r o m t h e i r p a r e n t s . T h e diagnosis of t h e t w o p a t i e n t s was d e t e r m i n e d a f t e r clinical e x a m i n a t i o n i n c l u d i n g b i o p s y o f t h e f r o n t a l c o r t e x . T h e p a r e n t s had n o c o m p l a i n t s or established diseases. T h e t w o p a t i e n t s were aged 16 a n d 22, t h e p a r e n t s 42 a n d 37. A mic r o e l e c t r o r e t i n o g r a m a n d c o n s i d e r a b l y r e d u c e d visual a c u i t y a n d p i g m e n t a r y d e g e n e r a t i o n of t h e r e t i n a were f o u n d in b o t h p a t i e n t s . T h e VEPs in t h e t w o p a t i e n t s revealed considerable d i s r u p t i o n o f f r o m , with a b s e n c e o f t h e early components, reduced amplitude a n d increased l a t e n c y of t h e late c o m p o n e n t s c o m p a r e d w i t h h e a l t h y s u b j e c t s f o r m t h e c o n t r o l g r o u p and t h e p a r e n t s . In t h e p a r e n t s t h e r e were n o d e v i a t i o n s in t h e
585
BULGARIAN EEG SOCIETY VEPs c o m p a r e d w i t h t h e c o n t r o l g r o u p of h e a l t h y subjects.
4. Visual e v o k e d p o t e n t i a l s in patients w i t h intracranial g r o w t h s . - B. Blazhev (Sofia). Visual e v o k e d p o t e n t i a l s were s t u d i e d in 20 h e a l t h y s u b j e c t s ( c o n t r o l g r o u p ) a n d 21 p a t i e n t s with i n t r a c r a n i a l g r o w t h s : 17 p a t i e n t s w i t h t u m o u r s , t w o patients with optico-chiasmal arachnoiditis, one p a t i e n t with an abscess a n d o n e p a t i e n t w i t h a cyst. An o p e r a t i v e or a n a t o m i c a l v e r i f i c a t i o n of t h e diagnosis was p e r f o r m e d in 19 p a t i e n t s . In the p a t i e n t s w i t h t u m o u r s t h e r e was an increase in t h e a m p l i t u d e a n d l a t e n c y of t h e VEPs, b o t h in t h e a f f e c t e d a n d in t h e u n a f f e c t e d h e m i s p h e r e s c o m p a r e d w i t h t h e sub-" jects in t h e c o n t r o l g r o u p (p ~< 0 . 0 5 ) a n d significant i n t r a h e m i s p h e r i c a s y m m e t r y , w i t h greater l a t e n c y a n d smaller a m p l i t u d e in the a f f e c t e d h e m i s p h e r e . Considerable a s y m m e t r y of t h e e v o k e d r e s p o n s e s was also f o u n d in t h e p a t i e n t s with abscess a n d cyst. T h e t w o p a t i e n t s w i t h o p t i c o - c h i a s m a l a r a c h n o i d i t i s s h o w e d an increase in t h e l a t e n c y a n d a decrease in the amplit u d e of t h e VEPs. VEPs can be m u c h m o r e i n f o r m a t i v e in s o m e cases t h a n t h e basic E E G w h e n d e t e r m i n i n g t h e a f f e c t e d h e m i s p h e r e a n d t h e l o c a t i o n of t h e lesion.
5. All-night p o l y g r a p h i c studies o f patients r h e u m a t i c e p i l e p s y . - - D. Daskalov (Sofia).
with
F o u r t e e n p a t i e n t s (nine female a n d five m a l e ) aged 2 2 - - 4 9 (average age 3 6 ) were e x a m i n e d clinically a n d by o n e all-night E E G ( c o m b i n e d w i t h EMG, E O G a n d E C G ) in o r d e r to s t u d y t h e n i g h t d y n a m i c s of the sleep~activated e p i l e p t o g e n i c focus. T h e p a t i e n t s h a d a h i s t o r y of various r h e u m a t i c diseases d u r i n g childh o o d , c o m p l i c a t e d in all cases b y h e a r t disease. Rare n o c t u r n a l epileptic seizures a p p e a r e d in all p a t i e n t s a f t e r t h e age of 21. M o r e o v e r , n i n e p a t i e n t s also m a n ifested focal seizures, p r e d o m i n a n t l y t e m p o r a l . In half of t h e p a t i e n t s t h e seizures o c c u r r e d m o r e t h a n five years a f t e r t h e h e a r t disease. T h e diurnal E E G d u r i n g w a k e f u l n e s s was n o r m a l in five p a t i e n t s a n d in n i n e p a t i e n t s it s h o w e d diffuse c h a n g e s , m a i n l y slight. No f o c u s or bilaterally s y n c h r o n o u s p a r o x y s m s were f o u n d in a n y p a t i e n t i m m e d i a t e l y b e f o r e t h e n i g h t test. T h e all-night E E G revealed f r o n t o - t e m p o r a l foci in eight p a t i e n t s . T h e foci were seen m o s t o f t e n d u r i n g t h e s e c o n d N R E M phase. During R E M t h e foci were i n h i b i t e d in all p a t i e n t s e x c e p t one. It was f o u n d t h a t d u r i n g the s a m e sleep phase t h e f o c u s was a c t i v a t e d to d i f f e r e n t degrees in t h e initial, m i d d l e a n d final periods of t h e night. T w o m a x i m a o f focal a c t i v a t i o n
b e c a m e o u t l i n e d -- a t t h e b e g i n n i n g a n d at t h e e n d o f t h e night. During the m i d d l e p e r i o d o f t h e n i g h t t h e focus was c o m p l e t e l y or p a r t l y suppressed. In conclusion, a c t i v a t i o n of t h e focus did n o t d e p e n d o n l y o n t h e N R E M a n d R E M phases, b u t also o n the three periods o f t h e n i g h t (initial, m i d d l e a n d final).
6. Changes in the s p o n t a n e o u s and e v o k e d activity in different brain structures after administration o f stimulants. - - V. D i m o v a and D. Tchavdarov (Sofia). In e x p e r i m e n t s o n cats a s t u d y was m a d e of t h e e f f e c t of l i t h i u m , a m p h e t a m i n e a n d c e n t r o p h e n o x i n e o n the s p o n t a n e o u s a n d e v o k e d electrical activity of the somatosensory cortex, the ascending activating reticular s y s t e m , t h a l a m u s and h y p o t h a l a m u s . U n d e r t h e e f f e c t o f l i t h i u m , t h e cortical activity b e c a m e m o r e regular, with m o d e r a t e increase in a m p l i t u d e . F a s t e r waves a n d r h y t h m s a p p e a r e d 1 h after the a d m i n i s t r a t i o n of l i t h i u m , and after t h e s e c o n d h o u r the c o r t i c o g r a m a p p r o a c h e d t h e initial activity. T h e changes in t h e t h a l a m u s a n d h y p o t h a l a m u s were analogous, b u t t h e y a p p e a r e d later. Initially the activity of t h e reticular s t r u c t u r e s was faster, f o l l o w e d b y a delay a f t e r t h e first h o u r . S t i m u l a t i o n of n u c l e u s ischiadicus c h a n g e d t h e r e s p o n s e s of t h e c o r t e x a n d the deep s t r u c t u r e s in l a t e n c y a n d c o n f i g u r a t i o n of the c o m p o n e n t s . A m p h e t a m i n e d e s y n c h r o n i z e t h e activity of the c o r t e x a n d reticular s t r u c t u r e s and resulted in high voltage slow waves in t h e t h a l a m u s . E l e c t r o s t i m u l a tion o f t h e reticular s t r u c t u r e s while r e c o r d i n g f r o m the s o m a t o s e n s o r y c o r t e x was a c c o m p a n i e d by t h e a p p e a r a n c e of a c h a r a c t e r i s t i c slow negative c o m p o nent. A f t e r c e n t r o p h e n o x i n e slow waves p r e d o m i n a t e d initially in t h e c o r t e x , t r a n s f o r m e d i n t o regular alphalike activity, w i t h parallel slight d e s y n c h r o n i z a t i o n of t h e reticular s t r u c t u r e s .
7. C h a n g e s in C N V in d r o w s i n e s s induced b y m o n o t o n o u s noise. - - E. Dincheva and N. Tsaneva (Sofia). T h e CNV was studied in t h e classical p a r a d i g m : S 1-1.5 sec--S2--MR in seven t r a i n e d subjects. E E G activity was r e c o r d e d f r o m v e r t e x / m a s t o i d d e r i v a t i o n s w i t h a 6 sec time c o n s t a n t . A f t e r r e c o r d i n g c o n t r o l data a s t a t e o f m o n o t o m y was achieved by a p p l y i n g c o n t i n u o u s w h i t e noise w i t h 65 d B i n t e n s i t y . T h e a m p l i t u d e values of t h e s u m m a t e d C N V were m e a s u r e d at intervals of 200 msec. A p r o b a b i l i t y analysis o f t h e R T was p e r f o r m e d and a p o w e r s p e c t r u m o f the basic E E G activity was c o m p u t e d . In t h e c o n t r o l r e c o r d s t h e r e was a positive correla-
BULGARIAN EEG SOCIETY R e c o r d i n g o f t h e b a c k g r o u n d E E G a c t i v i t y was foll o w e d b y n o n - r h y t h m i c light stimuli (flash-~eries) a n d b y series r e q u i r i n g a rapid m o t o r r e s p o n s e a f t e r t h e stimulus. A significant increase in t h e n u m b e r o f slow waves ( t h e t a a n d d e l t a ) was f o u n d at t h e e n d o f t h e w o r k i n g day. T h e evoked p o t e n t i a l s t o flash w i t h motor r e s p o n s e m a n i f e s t an increase o f P200 a n d N160 c o m p a r e d w i t h EPs to flashes alone. T h e a m p l i t u d e of the e v o k e d p o t e n t i a l s decreased significantly at t h e e n d of t h e w o r k i n g d a y , while t h e R T increased. A positive c o r r e l a t i o n was established b e t w e e n t h e degree of a m p l i t u d e r e d u c t i o n o f P200 and t h e increase of t h e RT.
12. E f f e c t o f v o l u n t a r y m u s c l e activity o n the polys y n a p t i c reflexes e v o k e d b y electrical s t i m u l a t i o n o f n. suralis in m a n . - - L. G e r i l o w s k y , A. Gydikov, N. R a d i t c h e v a a n d N. T a n k o v (Sofia). A p o l y s y n a p t i c reflex p o t e n t i a l ( P S R P ) f r o m the muscles o f t h e ipsilateral leg w i t h b r i e f l a t e n c y ( 4 0 - 60 m s e c ) was e v o k e d b y s u p r a t h r e s h o l d electrical s t i m u l a t i o n o f n. suralis b y a series o f 12 pulses w i t h t o t a l d u r a t i o n o f 36 msec a n d 1 msec d u r a t i o n of each pulse. P r e c e d i n g s u p r a t h r e s h o l d s t i m u l a t i o n w i t h a similar series h a d a s t r o n g i n h i b i t o r y effect o n PSRP of t h e ipsilateral leg a n d a slight i n h i b i t o r y e f f e c t o n PSRP o f t h e c o n t r a l a t e r a l leg. P S R P was p o t e n t i a t e d s t r o n g l y in t h e interval 50 msec b e f o r e t h e v o l u n t a r y movement, S t r o n g electrical s t i m u l a t i o n of n. suralis b y a series of 12 pulses for 36 msec or 3 pulses for 10 msec was a c c o m p a n i e d by pain a n d e v o k i n g o f PSRP w i t h 8 0 - - 1 2 0 msec l a t e n c y in t h e muscles o f b o t h legs, as well as in o t h e r muscles of t h e b o d y ( b o t h m. trapezii). P r e l i m i n a r y s u b t h r e s h o l d s t i m u l a t i o n h a d an i n h i b i t o r y e f f e c t in this case as well. Before a n d during t h e v o l u n t a r y m o v e m e n t P S R P s w i t h l o n g l a t e n cies were a b s e n t in the t w o m, trapezii a n d were s t r o n g l y i n h i b i t e d in the leg muscles. T h e significance of t h e o b s e r v e d p h e n o m e n a for t h e r e g u l a t i o n of v o l u n t a r y m o v e m e n t , w h e n t h e m o v e m e n t was m a d e o n the b a c k g r o u n d of stimuli causing d e f e n c e reactions, is discussed.
13. V o l u m e - c o n d u c t e d p o t e n t i a l s o f m o t o r units in m. triceps surae in man. - - A. G y d i k o v , L. Geril o w s k y a n d G. D i m i t r o v (Sofia). T h e w o r k describes s o m e f e a t u r e s of t h e p o t e n t i a l s f r o m individual m o t o r u n i t s (MU) in m. triceps surae in m a n r e c o r d e d w i t h m o n o p o l a r a n d b i p o l a r surface e l e c t r o d e s w i t h a small leading-off area. In t h e distal part o f m. soleus t h e p o t e n t i a l s o r i g i n a t e f r o m pars p o s t e r i o r o f t h e same mLiscle. A b o v e ram. gastrocne-
587 mius lateralis and medialis t h e p o t e n t i a l s can b e l o n g e i t h e r to t h e s e muscles or t o pars p o s t e r i o r o f m. soleus. Very f r e q u e n t l y t h e e n d p l a t e s o f MUs in m. triceps surae are n o t in t h e m i d d l e o f t h e muscle fibres b u t closer t o o n e o f t h e i r ends. MUs in m. triceps surae are s h o r t a n d m a n y o f t h e m are n o t parallel to t h e skin surface. T h e p r o x i m a l MUs e n d s are deep in t h e distal part o f m. soleus, while t h e distal MUs e n d s are in t h e d e p t h o f the t w o ram. gastrocnemii. MUs along t h e edges of t h e distal part of m. soleus have curved fibres. These f e a t u r e s are in a g r e e m e n t w i t h the m o r p h o l o g i c a l data o n t h e l e n g h t a n d p o s i t i o n of t h e muscle fibres. T h e y c o n d i t i o n t h e specificities of shape, a m p l i t u t e a n d p r o p a g a t i o n velocity o f t h e negative m a x i m u m o f t h e p o t e n t i a l s in the volume conductor. 14. C o n d u c t i o n velocity in the m o t o r fibres o f nn. ulnaris, m e d i a n u s , fibularis and tibialis in patients w i t h hemiparesis after cerebral stroke. -- B. I s h p e k o v a (Sofia). C o m p a r i s o n is m a d e b e t w e e n t h e c o n d u c t i o n velocities in t h e p e r i p h e r a l nerves o n t h e paretic a n d o n t h e u n a f f e c t e d sides. It is e s t a b l i s h e d t h a t t h e m e a n c o n d u c t i o n velocity in t h e nerves t e s t e d is sign i f i c a n t l y decreased o n the paretic side (P < 0.001). The d i f f e r e n c e s in t h e m e a n distal t i m e s b e t w e e n u n a f f e c t e d and paretic sides is smaller. A n o t h e r c o m parison shows t h a t t h e c o n d u c t i o n velocity o n t h e h e a l t h y side is significantly lower t h a n in h e a l t h y c o n t r o l subjects, this b e i n g valid for all f o u r nerves. This is an i n t e r e s t i n g fact w h i c h i n d i c a t e s t h a t t h e unilateral a f f e c t i o n of t h e p y r a m i d a l t r a c t is n o t t h e o n l y f a c t o r for t h e decreased c o n d u c t i v i t y .
15. V e c t o r e l e c t r o m y o g r a p h i c studies o f antagonist muscles. - - D. Kosarov (Sofia). T h e so-called " c r o s s e d e l e c t r o d e s " were used for a vector e l e c t r o m y o g r a p h i c s t u d y o f t h e bioelectrical activity of t h e f o l l o w i n g pairs of a n t a g o n i s t muscles: biceps a n d triceps brachii, flexors a n d e x t e n s o r s o f t h e wrist, a b d u c t o r s a n d a d d u c t o r s o f t h e wrist. T h e s t u d y o f t h e biceps-triceps pair allowed e v a l u a t i o n of the e x t e n t o f c o a c t i v a t i o n o f the a n t a g o n i s t in the p e r f o r m a n c e of a m o v e m e n t or o n increasing t h e muscle t e n s i o n t o t h e m a x i m u m . It was f o u n d t h a t c o i n c i d e n c e of impulses f r o m a m o t o r u n i t b e l o n g i n g to each muscle o c c u r s a c c i d e n t a l l y r a t h e r t h a n as a result of s y s t e m i c s y n c h r o n i z a t i o n o f t h e i r impulse activities. In p a t i e n t s w i t h slight h e m i p a r e s i s t h e electrical activity d u r i n g a m o v e m e n t originated f r o m the agonist. In p a t i e n t s w i t h severe h e m i p a r e s i s t h e electrical activity m i g h t originate o n l y in t h e a n t a g o n i s t in a n a t t e m p t e d m o v e m e n t .
588
SOCIETY PROCEEDINGS
A s t u d y was m a d e of t h e muscles o f t h e f o r e a r m in a g o n i s t - a n t a g o n i s t pairs d u r i n g o n e of t h e wrist m o v e m e n t s : flexion, e x t e n s i o n , a b d u c t i o n a n d a d d u c t i o n . T h e relative c o a c t i v a t i o n o f t h e radial a n d u l n a r flexor a n d o f t h e radial a n d u l n a r e x t e n s o r in each m o v e m e n t p e r f o r m e d was s h o w n .
r a t i o of t h e largest a m p l i t u d e d o i n g light a d a p t a t i o n to t h e highest value d u r i n g dark a d a p t a t i o n , was smaller in p a t i e n t s w i t h a h i s t o r y o f cerebral ictus a n d greater o n t h e side of t h e b r a i n lesion. It was n o r m a l in t h e cases in w h i c h n o focal n e u r o l o g i c a l s y m p t o m s were o b s e r v e d .
16. Study o f the motor potential during v o l u n t a r y recurrent movement. -- R. Kristeva (Sofia).
18. Visual a n d auditory evoked potentials during therapeutic electroshocks and e l e c t r o c o n v u l s i v e therapy (ECT). - - Ch. M e r d z h a n o v , L. Peneva, D. Gadjev and D. T c h a v d a r o v (Sofia).
A s t u d y was m a d e o f t h e m o r p h o l o g y of t h e m o tor p o t e n t i a l d u r i n g r e c u r r e n t v o l u n t a r y m o v e m e n t (pressing a b u t t o n ) w i t h i n t h e f r a m e w o r k o f a 1 h e x p e r i m e n t w i t h nine r i g h t - h a n d e d e x p e r i m e n t a l subjects. T h e records were m a d e f r o m C3 a n d f r o m an area 2 c m a b o v e t h e inion. T h e p o t e n t i a l changes prec e d i n g and a c c o m p a n y i n g t h e m o v e m e n t were o b s e r v e d in all nine subjects. In seven of t h e m t h e r e was a r e d u c t i o n in t h e a m p l i t u d e of t h e negativity of t h e m o t o r p o t e n t i a l in t h e course o f t h e e x p e r i m e n t and this r e d u c t i o n m i g h t a m o u n t to disappearance. Positivity o c c u r e d in t w o cases. T h e decrease in t h e negative a m p l i t u d e b e g a n b e t w e e n t h e 8 t h a n d 1 5 t h rain of t h e e x p e r i m e n t . In five o f t h e s u b j e c t s t h e r e was a t e n d e n c y t o w a r d s decreased l a t e n c y of t h e b e g i n n i n g o f negativity. T h e spectral d e n s i t y curve of t h e E E G in t h r e e s u b j e c t s s h o w e d a s h i f t to t h e left of t h e d o m i n a n t f r e q u e n c y b y a b o u t 1 Hz a n d appearance o f periods w i t h low f r e q u e n c y waves. T h e decrease in t h e negative a m p l i t u d e o f t h e motor p o t e n t i a l c o u l d be associated w i t h a r e d u c t i o n of t h e a s c e n d i n g a c t i v a t i n g effects o f t h e reticular form a t i o n as a result o f t h e h a b i t u a t i o n process developing d u r i n g t h e r e c u r r e n t v o l u n t a r y m o v e m e n t .
17. Electrooculographic studies o f patients with hypertonic disease and a t h e r o s c l e r o s i s . - M. Matev, G. Zapryanov and D. Daskalov (Sofia). E l e c t r o o c u l o g r a p b i c studies are m a d e in 25 p a t i e n t s w i t h h y p e r t o n i c disease and atherosclerosis. No focal n e u r o l o g i c a l s y m p t o m s were f o u n d in t e n of t h e cases, t h e r e m a i n i n g cases b e i n g in a post-ictal s t a t e ( n o n - o b t u r a t i n g cerebral s o f t e n i n g ) . T h e t i m e for d a r k r e d u c t i o n (the t i m e necessary to a t t a i n t h e lowest a m p l i t u d e d u r i n g d a r k a d a p t a t i o n ) , t h e absolute r e d u c t i o n (the d i f f e r e n c e b e t w e e n t h e m e a n a m p l i t u d e at t b e 3rd rain a n d t h e average m i n i m u m d e f l e x i o n d u r i n g d a r k a d a p t a t i o n ) a n d t h e relative r e d u c t i o n (the r a t i o o f t h e a b s o l u t e r e d u c t i o n a n d t h e m e a n a m p l i t u d e at t h e 3rd r a i n ) s h o w e d lower average values in t h e p a t i e n t s a f t e r cerebral ictus c o m p a r e d w i t h t h o s e in w h o m n o focal neurological s y m p t o m s were f o u n d . T h e values o f t h e a b o v e indices were l o w e r o n t h e side o f the b r a i n lesion. T h e
Series of 32 r e s p o n s e s (analysis e p o c h 500 m s e c ) to light a n d s o u n d stimuli were averaged 1, 5, 15, 30, 60, 90 a n d 120 m i n after bilateral or unilateral ECT. In t h e first m i n u t e s of t h e p o s t c o n v u l s i v e p e r i o d t h e early c o m p o n e n t s of t h e EP were f o l l o w e d b y a high voltage negative wave with d u r a t i o n of 3 0 0 - - 3 5 0 msec. S m o o t h i n g a n d s i m p l i f i c a t i o n of t h e r e s p o n s e c o n f i g u r a t i o n were o b s e r v e d b e t w e e n t h e 5 t h a n d t h e 3 0 t h m i n w h e n a smaller n u m b e r of high voltage c o m p o n e n t s were r e c o r d e d . R h y t h m i c high voltage oscillations w i t h 8 0 - - 1 0 0 msec l a t e n c y a p p e a r e d b e t w e e n the 6 0 t h a n d t h e 1 2 0 t h min. Individual differences in t h e i n t e n s i t y a n d t i m e - c o u r s e of t h e changes in t h e evoked activity were o b s e r v e d in t h e d i f f e r e n t subjects. U n t i l t h e 1 2 0 t h rain n o t all subjects h a d reverted t o the pre-ECT p a t t e r n of the EPs. Differences in t h e c o n f i g u r a t i o n of t h e evoked p o t e n tials f r o m t h e t w o h e m i s p h e r e s were f o u n d in t h e case of u n i l a t e r a l ECT. T h e average a m p l i t u d e valus o f visual a n d a u d i t o r y r e s p o n s e s were e s t i m a t e d for t h e periods: 0 - - 9 0 msec (A), d e r a b l y higher average increases for B a n d C c o m p a r e d w i t h A; (2) t h e amp l i t u d e changes for A a n d B were u n i d i r e c t i o n a l in m o s t cases and reciprocal in t h e r e m a i n i n g cases. The possible m e c h a n i s m s o f t h e changes in t h e e v o k e d p o t e n t i a l s following bilateral or u n i l a t e r a l E C T are discussed.
19. Neurocybernetic aspects o f cerebral electrogenesis in the postconvulsive state -- Ch. Merdzhanov and M. Gospodinov (Sofia). T h e p o s t c o n v u l s i v e s t a t e is c o n s i d e r e d f r o m t h e standpoint of cybernetics, with determination of the information and autoregulation characteristics of the cerebral electrogenesis. T h e q u a n t i t a t i v e a s s e s s m e n t of t h e l a t t e r ( i r o n t a l a n d occipital region u p to 2 h o u r s a f t e r E C T ) was achieved b y f r e q u e n c y - a m p l i t u d e analysis. T h e i n f o r m a t i o n characteristics were d e t e r m i n e d on the basis of t h e p r o b a b i l i t y o f appearance o f d i f f e r e n t f r e q u e n c y ranges (beta, alpha, theta a n d delta waves). In t h e p o s t c o n v u l s i v e s t a t e t h e t o t a l e n t r o p y (H) was increased while t h e c o e f f i c i e n t o f
BULGARIAN EEG SOCIETY redundancy (R) decreased. The autoregulation characteristics were found on the basis of t h i r d ~ r d e r differential equations describing the dynamics of the average frequencies. The stability reserves were determined with respect to phase and amplitude for the different frequencies of the bioelectrical activity. The largest stability reserve with respect to phase and amplitude was found for the theta waves.
20. Comparative analysis o f t h e variance o f s p o n t a n e ous and e v o k e d EEG-activity. -- I. Mezan, N. Vrabchev and M. Matveev (Sofia).
The problem of dividing the variance of EEG signals into components corresponding to the variance of spontaneous activity and that of evoked potentials is dealt with. The evoked activity was obtained by visual stimulation and data were recorded of the preceding as well as the evoked activity from occipital and parietal derivations. The variance of each epoch and derivation, including spontaneous and evoked activity, was determined with respect to the averaged signal, using a specially developed algorithm for an ensemble of 32 epochs. The hypothesis of differentiation between variances of epochs of spontaneous activity and epochs containing evoked potentials was verified by variance analysis. In order to obtain a better accuracy, the experimental design included three factors. The remaining two were correspondingly the derivations and the experimental repetitions. The variances of the epochs of spontaneous activity and those of evoked potentials proved to be statistically indistinguishable, with a high degree of reliability, which proves the hypothesis that the variance of the epoch with evoked activity is due in a considerable degree to the variance of the spontaneous activity. The recording and treatment of the data were performed by a closed cycle of a laboratory experiment, a minicomputer and its programming included.
21. Motor unit firing pattern during f l e x o r reflex in dogs. -- N. Raditcheva and N. Tankov (Sofia). A study was made of the changes in the transient processes of the momentary frequency of discharge of previously active motor units (MU) in m. gastrocnemius and m. semitendinosus in dogs with flexor reflex elicited by electrical stimulation. Surface selective electrodes were used for recording the activity of the different MUs. Five types of transient process are described, mainly depending on the intensity of stimulation. A lower stimulus intensity led to an increase in the momentary frequency of the discharges of MUs 60 msec after its application, followed by a decrease and later by another increase in the frequency. The
589 strongest stimulation first lowered the frequency of firing of MUs for about 150 msec, then increased the frequency. The mechanisms of recurrent inhibition and the role of some afferent inputs of the flexor reflex are taken into account in the interpretation of these data.
22. E l e c t r o p h y s i o l o g i c a l e x p l o r a t i o n o f the sensory f u n c t i o n o f the sural nerve in diabetic patients. - D. Stanchev and N. Nikoevski (Sofia).
The exploration was carried out with an original electrode constructed in the authors' laboratory. The population comprised 106 diabetic patients (average age 56.6) and 50 healthy subjects (average age 56.9) equally distributed in age and sex, as for the first group. A highly significant disturbance of the sensory function of the sural nerve was found in diabetic patients (P < 0.001). The latency demonstrated considerable variability, which limited its value for diagnosis (59.05%). This shortcoming was compensated considerably if expressed as a velocity (67.61%). The changes in amplitude made it possible to determine objectively the disturbances in the highest percentage of patients (81.8%). An important advantage of the parameter is illustrated by examination of diabetic patients without clinical indications of neuropathy. Recording of the amplitude in these cases made it possible to discover subclinical functional disturbances of the sural nerve in 74.1% of the cases.
23. C o n t r i b u t i o n t o the e l e c t r o p h y s i o l o g i c a l assessm e n t o f m o t o r f u n c t i o n o f peripheral nerves in diabetic patients. - - D. Stancbev and N. Uzunov (Sofia).
The recording of changes in the distal latencies and conduction velocities of excitation is routine practice in the electrophysioiogical tests of the motor function of peripheral nerves in diabetic patients. Recently certain important shortcomings were discovered with respect to early electrodiagnosis. The study of changes in the percentage ratio of the amplitudes of the M responses after proximal and distal stimulation of the peroneal nerve in 30 diabetic patients and 23 healthy subjects permitted and expansion of the diagnostic possibilities of the method by about 20%. The ratio reflects most comprehensively the specific structural and functional disturbances in diabetic neuropathy. Its advantage is that it makes objective the changes in a wider range of the m o t o r fibres, including patients with a less serious clinical form of the complications. The above parameter permits the elimination of the effect of changes in the condition and number of the muscle fibres, of the differences in
590 t h e d e v e l o p m e n t of t h e s u b c u t a n e o u s tissues a n d of d i f f e r e n c e s in t h e e l e c t r o d e s used. Our d a t a e m p h a s i z e t h e a b o v e p a r a m e t e r as t h e m o s t sensitive c r i t e r i o n for t h e o b j e c t i v e assessment of early d i s t u r b a n c e s o f m o t o r f u n c t i o n .
24. H reflex in diabetic patients. -- D. S t a n c h e v , N. U z u n o v and N. Nikoevski (Sofia). Only a few studies o f t h e H reflex b a s e d o n a limited n u m b e r of d i a b e t i c p a t i e n t s are r e p o r t e d in t h e l i t e r a t u r e . T h e r e are n o d a t a o n t h e changes in t h e various e l e c t r o p h y s i o l o g i c a l p a r a m e t e r s o f t h e reflex d e p e n d i n g o n t h e clinical m a n i f e s t a t i o n o f t h e diabetic polyneuropathy. For the purpose experiments were m a d e involving 106 d i a b e t i c p a t i e n t s (average age 5 6 . 6 ) a n d 50 h e a l t h y s u b j e c t s (average age 56.9), equally d i s t r i b u t e d a c c o r d i n g to age a n d sex. Our results revealed a significant d i s t u r b a n c e in t h e funct i o n o f t h e Ia a f f e r e n t fibres in d i a b e t i c p a t i e n t s (P < 0.001). A m a r k e d variability of t h e reflex a m p l i t u d e was e s t a b l i s h e d , causing difficulties o f i n t e r p r e t a t i o n . R e c o r d i n g t h e changes in iatencies m a d e it possible to assess o b j e c t i v e l y t h e d i s t u r b a n c e s in 4 5 . 2 8 % of t h e p a t i e n t . C o m p a r a t i v e clinical a n d e l e c t r o p h y s i o l o g i c a l studies illustrate t h e low value of t h e a b o v e p a r a m e t e r for t h e p u r p o s e s of early diagnosis. T h e e x p l o r a t i o n of t h e H reflex was f o u n d t o b e o f i m p o r t a n c e in t h e cases of a b s e n c e o f a s e n s o r y nerve p o t e n t i a l f r o m t h e sural nerve as the result o f a m o r e p r o n o u n c e d disturb a n c e of s e n s o r y f u n c t i o n . T h e significance of t h e H reflex is also d e t e r m i n e d b y t h e fact t h a t it is the o n l y m e t h o d t o assess t h e c o n d i t i o n o f t h e Ia a f f e r e n t fibres.
25. On the s y n d r o m e of the anterior tibial artery: report o f three cases e x a m i n e d clinically and electromyographically. -- K. Subev, B. Ishpekova and R. Rasher (Sofia). T h e significance o f excessive t e n s i o n of t h e calf muscle a n d local tissue c h a n g e s r e s u l t i n g in c o m p r e s sion of t h e same a r t e r y , as f a c t o r s for t h e a p p e a r a n c e of t h e s y n d r o m e o f t h e a n t e r i o r tibial a r t e r y , are well k n o w n . M u l t i p l e e l e c t r o m y o g r a p h i c tests were perf o r m e d a n d the clinical c o u r s e o f t h e disease was foll o w e d in t h r e e cases for periods of 1--2.5 years. All cases m a n i f e s t e d c o m m o n clinical s y m p t o m s : t e n s i o n o f t h e tibial muscles w i t h p r o b a b l e c o m p r e s s i o n of t h e a n t e r i o r tibial a r t e r y a n d a s u b s e q u e n t i m m e d i a t e d e v e l o p m e n t of paralysis o f t h e ipsilateral p e r o n e a l nerve. A c o m m o n f e a t u r e in t h e e l e c t r o m y o g r a p h i c p a t t e r n was t h e i n d i c a t i o n o f d a m a g e t o t h e d e e p b r a n c h o f t h e p e r o n e a l nerve, very p r o n o u n c e d in all t h r e e cases. T h e a i m o f t h e p r e s e n t w o r k is t o f o c u s
SOCIETY PROCEEDINGS a t t e n t i o n o n a s y n d r o m e n o t so m u c h i n f r e q u e n t as s e l d o m diagnosed. T h e great significance of t h e elect r o m y o g r a p h i c tests for t h e c o r r e c t diagnosis was emphasized.
26. E E G in u n i l a t e r a l a n d bilateral e l e c t r o c o n v u l s i v e therapy (ECT). -- D. T c h a v d a r o v , Ch. M e r d z h a nov, N. Peneva and S. P o p o v (Sofia). C o m p a r a t i v e E E G tests (visual analysis, a m p l i t u d e , period analysis a n d p o w e r s p e c t r a ) were p e r f o r m e d on symmetrical temporo~ecipital and temporo-frontal records in m e n t a l p a t i e n t s after bilateral a n d unilateral e l e c t r o c o n v u l s i v e t h e r a p y (ECT). Slowing of t h e E E G was o b s e r v e d in bilateral E C T ; t h e differences b e t w e e n right a n d left were insignificant w i t h respect t o t h e d o m i n a n t f r e q u e n c y , t h e r e c o v e r y t i m e being d e p e n d e n t t o a large e x t e n t o n t h e o r g a n i z a t i o n o f t h e initial EEG. In t h e cases o f unilateral ECT s o m e s u b j e c t s displayed a bilaterally identical d o m i n a n t f r e q u e n c y and o t h e r s , a n 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 f r e q u e n c y c h a r a c t e r i s t i c s , w h i c h were m o r e f r e q u e n t a f t e r t h e 6 0 t h m i n . The a b n o r m a l m a n i f e s t a t i o n s a n d t h e n u m b e r of slow waves were c o n s i d e r a b l y less p r o n o u n c e d in unilateral ECT t h a n in bilateral ECT. R i g h t h e m i s p h e r e ECT resulted in greater i n t e r h e m i s p h e r i c d i f f e r e n c e s in t h e f r e q u e n c y a m p l i t u d e o r g a n i z a t i o n of t h e activity. No bioelectrical silence was o b s e r v e d a f t e r unilateral ECT. Considerable d i f f e r e n c e s in t h e E E G o r g a n i z a t i o n o f t h e t w o h e m i s p h e r e s were o b s e r v e d for a s h o r t t i m e a f t e r a b s e n c e s caused b y u n i l a t e r a l l y placed e l e c t r o d e s .
27. EEG changes in migraine patients treated with acupuncture. -- R. Tsikalova, M. Tsekova and L. Ivanova (Sofia). This w o r k studies t h e e f f e c t o f a single a c u p u n c ture p r o c e d u r e o n t h e brain activity. In 24 p a t i e n t s suffering f r o m m i g r a i n e EEGs were r e c o r d e d f r o m t h e occipital part of the side a f f e c t e d by t h e h e a d a c h e . An analysis was m a d e o f t h e E E G changes as a result of a c u p u n c t u r e b o t h at rest and after a c t i v a t i o n w i t h 0.25 m g N i t r o m i n t a n d h y p e r v e n t i l a t i o n . (1) At t h e 1 5 t h rain a f t e r t h e needles were placed d e s y n c h r o n i z a t i o n a c c o m p a n y i n g t h e pain r e a c t i o n was o b s e r v e d . R e m o v a l o f t h e needles r e s u l t e d in a tendency towards synchronization of the record with a statistically significant increase in t h e m e a n amplit u d e (P < 0.05). (2) T h e changes in the first a n d last 10 sec of a 1 m i n r e c o r d a f t e r h y p e r v e n t i l a t i o n h a d a phasic course a n d were c h a r a c t e r i z e d b y an initial decrease of t h e average f r e q u e n c y (P < 0.01), f o l l o w e d b y an increase in t h e f r e q u e n c y d u r i n g t h e s e c o n d phase.
B UL GAR I AN EEG SOCIETY The changes had the same dynamics and were more pronounced after acupuncture. (3) The studies of the Nitromint effect showed a statistically significant increase in the average frequency (P < 0.001) and an insignificant decrease in the average amplitude. The changes reached their maximum between the 3rd and 5th min after its administration. The effect of Nitroming was reduced after acupuncture. The results show that acupuncture has an effect on the brain structures. Most probably non-specific mechanisms leading to improvement of the vascular regulation participate in this reaction.
28. Rheoencephalographic studies in post-ictal patients before and after application o f rehabilitation procedures. - - N. Tsolov and S. Merdzhanova (Sofia). Quantitative and qualitative rheoencephalographic studies were performed in 50 patients with cerebral ictus. In most patients the stroke had occurred more than one year previously. The rehabilitating procedures involved regimen, vitamins, passive and active movements for the hemiparetic limbs, massage, kinesitherapy, paraffin applications, partial water iodine baths, etc. Drug therapy was completely excluded. After the end of the procedures there was a slight decrease in the tone of the peripheral and cerebral blood vessels. A drop in the systolic and diastolic blood pressure was found. Both in the "healthy" and in the "affected" hemisphere there was a rise in amplitude of the rheographic wave, a decrease in the relative share of the anacrotic part and dicrotic index with an insignificant increase in the hemispheral blood flow (estimated after the method of D. Hadjiev). All rheoencephalographic changes were more pronounced over the "healthy" hemispheres.
29. Study of m ot o r potentials in pre-school children. - - G. Vladimirova, R. Kristeva and G.M. Gantchev
(Sofia). The motor potentials from C3 (mastoid reference) were investigated in 21 children aged 6 to 6 11/12
591 years w h o were asked to press a button with the right thumb at an arrhythmic rate. T w o series of 100 trials each were averaged with analysis time of 2 sec (1.5 sec before and 0.5 sec after the movement). Type P motor potentials (after Timsit-Berthier et al. 1973) were found in 2 4 % of the children. In the remaining cases in which type N was recorded, it was not always possible to distinguish every component of the motor potential. Thus, the readiness potential could be seen clearly in only 4 7 % of the cases; N2 and P2 were the most frequent components. Comparing the data from both series it could be seen that N2 was the most invariable component of the motor potential at this age.
30. Electrooculographic
studies of Farkinsonian patients. - - G. Zapryanov, M. Matev and D. Daskalov (Sofia).
Electrooculographic studies were made in 32 patients with Parkinsonian syndrome and in a control group of 12 practically healthy subjects. It was found that the absolute drop (the difference between the average amplitude at the 3rd rain and the average m i n i m u m deflection during dark adaptation) showed insignificant differences between the two groups (P > 0.05). The relative drop (the ratio between the absolute drop and the mean amplitude at the 3rd rain) showed almost identical values in Parkinsonians and in healthy subjects, 15.4 and 15.2% respectively (P > 0.05). The rise-time was greatest at 8,80 rain after light adaptation for Parkinsonians, while in the control group it was at 7.40 rain (P < 0.05). The ratio of the largest amplitude during light adaptation to the lowest value during dark adaptation in parkinsonians was 160.8% and 195.4% in the control group. The experiments indicate the existence of certain changes in the functional state of the retina of Parkinsonians.