411
l';h'clroencel)halogralJhy
(md CliJzical Neurophysioiogy, 1977, 4 2 : 4 1 4 416 g) Elsevier/Nortb-Ilolland Scientific Publishers Ltd.
Laboratory note SIMULTANEOUS
LAMINAR INTRACORTICAL RECORDINGS IN S E I Z U R E S
*
H. PETSCHE, O. P R O H A S K A , P. R A P P E L S B E R G E R , R. V O L L M E R and H. POCKBERGI~]II,
Brain Research lnslitu to, A ustrian Academy o f Sciences, and Neurophysiological h~stilu te o / t h e University, Vienna (Austria) ( A c c e p t e d for p u b l i c a t i o n : J u n e 25, 1976)
It has been assumed for a long t i m e that the cortex is the generator o f m o s t seizure p a t t e r n s r e c o r d e d f r o m the scalp. This idea was suggested by the observations o f phase reversals b e t w e e n e l e c t r o d e s p u t o n the cortical surface and in the white m a t t e r b e n e a t h the c o r t e x (Calvet and Scherrer 1961). F r o m these and o t h e r o b s e r v a t i o n s the presence of one or even m o r e vertical cortical dipoles was suggested (Calvet et al. 1964). With a d e q u a t e m i e r o e l e c t r o d e recording f r o m d i f f e r e n t cortical layers, however, it was f o u n d t h a t the c o n c e p t o f a phase reversal is only valid to a limited e x t e n t , since a true mirror image hardly ever occurs (Petsche et al. 1972; S p e c k m a n n et al. 1972). Moreover, c o h e r e n c e estimates b e t w e e n the two patterns are low ( R a p p e l s b e r g e r and Petsehe 1974); t h e r e f o r e the intracortical dipole h y p o t h e s i s does n o t entirely c o m p l y with the observed events. To elucidate this p r o b l e m o f low c o r r e l a t i o n bet w e e n surface and d e e p cortical activities, the multiple e l e c t r o d e s used h i t h e r t o , consisting o f b u n c h e s o f wires o f d i f f e r e n t lengths, were too coarse to yield sufficiently e x a c t results. T h e r e f o r e , a m u l t i e l e e t r o d e p r o b e was d e v e l o p e d (Prohaska et al. 1977) carrying, on a needle o f 0.3 m m diameter, 8 c o n t a c t s o f 50 × 50 p at 300 /J distances. The length o f this multielect r o d e (2100 p b e t w e e n the o u t e r m o s t c o n t a c t s ) is suf ficient to record from the entire w i d t h o f the r a b b i t ' s cortex.
Methods The m u l t i e l e c t r o d e p r o b e was inserted into the precentral and visual (striate) cortices of 8 u n a n a e s t h e tized, curarized rabbits (for p r e p a r a t i o n and recording m e t h o d s see Petsche and Sterc, 1968). S i m u l t a n e o u s
* This research was s u p p o r t e d by the F o n d s zur FSrd e r u n g der w i s s e n s c h a f t l i c h e n F o r s c h u n g (Nr. 2186 and M 3 / 1 7 2 6 ) and b y the E u r o p e a n Training Program in Brain and Behaviour Research.
serial bipolar and unipolar derivations (with nasal b o n e as c o m m o n reference) were r e c o r d e d by m e a n s of a 16channel EEG machine. Seizures were elicited electrically with a transverse c u r r e n t t h r o u g h the precentral areas (2 msec, 100/see, 10 see, 5--10 m A ) and by local application o f Na penicillin o n t o the cortex.
Results The results o b t a i n e d with the m u l t i e l e c t r o d e b o t h c o n f i r m and e x t e n d those previously o b t a i n e d with double m i c r o e l e c t r o d e s (Petsche et al. 1972). The different layers o f the c o r t e x were characterized by patterns w h o s e shapes, ewm from adjacent recording electrodes, were s o m e t i m e s st) d i f f e r e n t from one to ano t h e r that the discrimination by an e l e c t r o d e distance of 300 p was n o t sufficient to delineate the e x a c t dim e n s i o n o f the p o t e n t i a l fields (see for instance the s t e e p gradients o f the slow waves b e t w e e n c o n t a c t s 2 and 3 in the striate area (Fig. 1) and t h o s e b e t w e e n activities r e c o r d e d f r o m c o n t a c t s 3 and 4, and 4 and 5, respectively, in the precengral area (Fig. 2)). Since, with unipolar recording, only a m o s t careful inspection of the traces will elucidate the intricate s u p e r p o sitions o f the d i f f e r e n t fields o f d i f f e r e n t e x t e n t s , serial s i m u l t a n e o u s bipolar recording was also p e r f o r m ed. Since bipolar records not only reflect voltage h u t also phase differences, they make it easier to find oul w h e t h e r few or several d i f f e r e n t activities act t o g e t h e r in p r o d u c i n g the seizure p a t t e r n . The fairly h o m o g e n e o u s a p p e a r a n c e o f the bipolar records in Fig. 1 thus leads to the a s s u m p t i o n of one basic process o f slow waves s u p e r i m p o s e d by sharp t r a n s i e n t s o f an amplit u d e d i s t r i b u t i o n quite d i f f e r e n t from one a n o t h e r . A l t h o u g h the slow waves appear a p p r o x i m a t e l y phasereversed if only channels 1 and 8 are c o n s i d e r e d , they are far from being a true mirror-image. The m o s t p r o m i n e n t d i f f e r e n c e in shape, according to the bipolar records, is b e t w e e n c o n t a c t s 2 and 3. In c o n t r a s t to the fairly h o m o g e n e o u s bipolar pattern in the striate area, the precentral area (Fig. 2)
I N T R A C O R T I C A L R E C O R D I N G S IN S E I Z U R E S
415
5 J~L'/~+{'~.t',~7y,,,'~.'~,.~',\'..,t_',~
l';h'clroencel)halogralJhy
(md CliJzical Neurophysioiogy, 1977, 4 2 : 4 1 4 416 g) Elsevier/Nortb-Ilolland Scientific Publishers Ltd.
Laboratory note SIMULTANEOUS
LAMINAR INTRACORTICAL RECORDINGS IN S E I Z U R E S
*
H. PETSCHE, O. P R O H A S K A , P. R A P P E L S B E R G E R , R. V O L L M E R and H. POCKBERGI~]II,
Brain Research lnslitu to, A ustrian Academy o f Sciences, and Neurophysiological h~stilu te o / t h e University, Vienna (Austria) ( A c c e p t e d for p u b l i c a t i o n : J u n e 25, 1976)
It has been assumed for a long t i m e that the cortex is the generator o f m o s t seizure p a t t e r n s r e c o r d e d f r o m the scalp. This idea was suggested by the observations o f phase reversals b e t w e e n e l e c t r o d e s p u t o n the cortical surface and in the white m a t t e r b e n e a t h the c o r t e x (Calvet and Scherrer 1961). F r o m these and o t h e r o b s e r v a t i o n s the presence of one or even m o r e vertical cortical dipoles was suggested (Calvet et al. 1964). With a d e q u a t e m i e r o e l e c t r o d e recording f r o m d i f f e r e n t cortical layers, however, it was f o u n d t h a t the c o n c e p t o f a phase reversal is only valid to a limited e x t e n t , since a true mirror image hardly ever occurs (Petsche et al. 1972; S p e c k m a n n et al. 1972). Moreover, c o h e r e n c e estimates b e t w e e n the two patterns are low ( R a p p e l s b e r g e r and Petsehe 1974); t h e r e f o r e the intracortical dipole h y p o t h e s i s does n o t entirely c o m p l y with the observed events. To elucidate this p r o b l e m o f low c o r r e l a t i o n bet w e e n surface and d e e p cortical activities, the multiple e l e c t r o d e s used h i t h e r t o , consisting o f b u n c h e s o f wires o f d i f f e r e n t lengths, were too coarse to yield sufficiently e x a c t results. T h e r e f o r e , a m u l t i e l e e t r o d e p r o b e was d e v e l o p e d (Prohaska et al. 1977) carrying, on a needle o f 0.3 m m diameter, 8 c o n t a c t s o f 50 × 50 p at 300 /J distances. The length o f this multielect r o d e (2100 p b e t w e e n the o u t e r m o s t c o n t a c t s ) is suf ficient to record from the entire w i d t h o f the r a b b i t ' s cortex.
Methods The m u l t i e l e c t r o d e p r o b e was inserted into the precentral and visual (striate) cortices of 8 u n a n a e s t h e tized, curarized rabbits (for p r e p a r a t i o n and recording m e t h o d s see Petsche and Sterc, 1968). S i m u l t a n e o u s
* This research was s u p p o r t e d by the F o n d s zur FSrd e r u n g der w i s s e n s c h a f t l i c h e n F o r s c h u n g (Nr. 2186 and M 3 / 1 7 2 6 ) and b y the E u r o p e a n Training Program in Brain and Behaviour Research.
serial bipolar and unipolar derivations (with nasal b o n e as c o m m o n reference) were r e c o r d e d by m e a n s of a 16channel EEG machine. Seizures were elicited electrically with a transverse c u r r e n t t h r o u g h the precentral areas (2 msec, 100/see, 10 see, 5--10 m A ) and by local application o f Na penicillin o n t o the cortex.
Results The results o b t a i n e d with the m u l t i e l e c t r o d e b o t h c o n f i r m and e x t e n d those previously o b t a i n e d with double m i c r o e l e c t r o d e s (Petsche et al. 1972). The different layers o f the c o r t e x were characterized by patterns w h o s e shapes, ewm from adjacent recording electrodes, were s o m e t i m e s st) d i f f e r e n t from one to ano t h e r that the discrimination by an e l e c t r o d e distance of 300 p was n o t sufficient to delineate the e x a c t dim e n s i o n o f the p o t e n t i a l fields (see for instance the s t e e p gradients o f the slow waves b e t w e e n c o n t a c t s 2 and 3 in the striate area (Fig. 1) and t h o s e b e t w e e n activities r e c o r d e d f r o m c o n t a c t s 3 and 4, and 4 and 5, respectively, in the precengral area (Fig. 2)). Since, with unipolar recording, only a m o s t careful inspection of the traces will elucidate the intricate s u p e r p o sitions o f the d i f f e r e n t fields o f d i f f e r e n t e x t e n t s , serial s i m u l t a n e o u s bipolar recording was also p e r f o r m ed. Since bipolar records not only reflect voltage h u t also phase differences, they make it easier to find oul w h e t h e r few or several d i f f e r e n t activities act t o g e t h e r in p r o d u c i n g the seizure p a t t e r n . The fairly h o m o g e n e o u s a p p e a r a n c e o f the bipolar records in Fig. 1 thus leads to the a s s u m p t i o n of one basic process o f slow waves s u p e r i m p o s e d by sharp t r a n s i e n t s o f an amplit u d e d i s t r i b u t i o n quite d i f f e r e n t from one a n o t h e r . A l t h o u g h the slow waves appear a p p r o x i m a t e l y phasereversed if only channels 1 and 8 are c o n s i d e r e d , they are far from being a true mirror-image. The m o s t p r o m i n e n t d i f f e r e n c e in shape, according to the bipolar records, is b e t w e e n c o n t a c t s 2 and 3. In c o n t r a s t to the fairly h o m o g e n e o u s bipolar pattern in the striate area, the precentral area (Fig. 2)
I N T R A C O R T I C A L R E C O R D I N G S IN S E I Z U R E S
415
5 J~L'/~+{'~.t',~7y,,,'~.'~,.~',\'..,t_',~
