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Processing neuroelectric data
BOOK REVIEWS poh,s in i n d i v i d u a l p a t i e n t s at d i f f e r e n t times. T h i s possibility is n o t however excluded b y Delay a n d his colleagues, since none of t h e works t h e y considered, i n c l u d i n g their own, involved a n y serial R o r s c h a c h :,ml EEG e x a m i n a t i o n s . T h i s b r i n g s us b a c k to the m,t,d for rei)etition a i m e l a b o r a t i o n of H e h n a n ' s work.
763
Taken together these two books provide a fascinating excursion into a n e x t r a o r d i n a r y d i f f i c u l t r e a h n of i n t e r r e l a t i o n s b e t w e e n m i n d a n d b r a i n in epilepsy. To read t h e m is s t i m u l a t i n g , a n d t h e i r fiehl is little trod. T h e y o f f e r an e x c i t i n g clmllcnge ~o ncuropsychologists. A. C. MUNDY-(~As:rI.E
PROCESSING N E U R O E L E C T R I C DATA C o n m m n i e a t i o n s B i o p h y s i c s Group of R e s e a r c h L a b o r a t o r y of Electronics a n d W i l l i a m M. Siebert, M a s s a c h u s e t t s I n s t i t u t e of T e c h n o l o g y T e c h n i c a l R e p o r t 35l. T e c h n o l o g y P r e s s , M.I.T., 1959, 121 pp. Within the come:tot comp:,ss of this vohlmc m a y be f o u n d one of the m a s t d i s c e r n i n g a p p r a i s a l s of the p a s t decade of p r o b l e m s at the core of the m a n y h a r r a s s i n g d i l e m m a s c u r r e n t l y c o n f r o n t i n g the s t u & , n t of c e n t r ' d n e r v o u s f u n c t i o n . These s t u d i e s b ) the C o m m u n i c a t i o n s B i o p h y s i c s Group are in m a n y respects symbolic, in t h e experiences of this one g r o u p of b~vestigators, of the s t r u g g l e s , the a s p i r a t i o n s , and, indeed, in t h e i r successes a n d f a i l u r e s , of the p r o g r e s s of the n e u r o p h y s o i l o g i c a l a r t to the p o i n t where the veritable a v a l a n c h e of d a t a p o u r e d f o r t h on p a p e r a n d f i l m f r o m a single e x p e r i m e n t can o v e r w h c h n the i n v e s t i g a t o r a t t e m p t i n g even the silnplest analysis. The relative ease of electrical recording front the b r a i n a n d the complexities of its s p o n t a n e o u s a n d evoked a c t i v i t y have, in g r e a t m e a s u r e , beguiled the exi)erbnenter into a c c e p t i n g his m o u n t a i n s of d a t a as capable of only empiric a n d s u b j e c t i v e i n t e r p r e t a tion, with t h e d a n c i n g of his p e n - w r i t e r s revealing little more t h a n " a tale told by a n idiot, full of sound and fury, signifying nothing" I t is here t h t a , to even the c a s u a l reader, this report is of such f a s c i n a t i n g i n t e r e s t , for in it :ire ninny of the links b e t w e e n retrospect a n d prosln'ct. On +he b a s i s of this research by 1)r. Rosenblith and his colleagues, t h e r e is r e a s o n for s a n g u i n e hope t!mt a t t e m p t s to a p p l y t h e electronic :,nd m a t h e m a t i c a l a r t s of the c o m p u t e r e n g i n e e r to p r o b l e m s of br:dn f u n c t i o n n m y b e a r s i g n i f i c a n t f r u i t , a n d t h a t these initi:tl steps are indeed t h e b a s i s for a n cssenti:dly new f r a m e of r e f e r e n c e in the s t u d y of f u n d a m e n t a l b r a i n m e c h a n s h n s . M e t h o d s .',re described for the eXalnination of the c h a r a c t e r i s t i c s of evoked poten tials, a n d other e s s e n t i a l l y ~ ' t i m e - l o c k e d ' ' p h e n o m e n a a n d f o r t h e a n a l y s i s of " s p o n t a n e o u s " rhythmic processes, by techniques of auto- a n d cross-corre!ation. which reveal a s p e c t s of i n h e r e n t r h y t h m i c i t y , h i d d e n r h y t h m s a n d p h a s e r e l a t i o n s h i p s between different brain regions sharing a common rhythmic process.
M u c h e f f o r t h a s been devoted by these laves t i g a t o r s to the design "rod c o n s t r u c t i o n of "lppropriate c o m p u t i n g devices on the oneh and, and on the other, to the f o r m u l a t i o n if m a t h e m a t i c a l models of neural f u n c t i o n s . Now it is here t h a t the s t u d e n t af b r a i n f u n c t i o n s h a s f r e q u e n t l y felt some concern at his e n g i n e e r i n g colle.~gues ~ easy e x t r a p o l a t i o n to b r a i n mecht, n i s m s on the b a s i s of such nmthenmtica:, models, u s u a l l y built on digital, or~ a t host, pulse-coded considerations, or e n t h u s i a s t i c a d a p t a t i o n s f r o m spinal cord physiology. T h i s is indeed a t h o r n y p:lth, a n d the p h y s i o l o g i s t will take little e o m f m ' t front t h e stqtt, ntents in this volume t h a t t h e u s e f u l n e s s of "1 m a t h e m a t i c a l nlodcl m a y be Ine.tsured by i t . ability to predict r e s u l t s of p r o c e s s i n g the dat't in w a y s d i f f e r e n t f r o m those used to e s t i m a t e the i m r a m e t e r s of the model. "lad t h a t if a simple model " f i t s " the d:lta well, it m a y provide a n e f f i c i e n t w a y of chara c t c r i z i n g the data, a n d m a y s u g g e s t new e x p e r i m e n t s . T h i s is surely merely to s u b s t i t u t e one e m p i r i c i s m for another. One m i g h t doubt w h e t h e r such an a p p r o a c h t h r o u g h the m o d c l l e r ' s a r t could b r i n g us s i g n i f i c a n t l y closer to "m u m l e r s t - t n d i n g of the pr(icesses, p r e s u n m b l y g r a d e d , -rod f r e q u e n t l y u n a c c o m p a n i e d by a discernible pulse-coded o u t p u t , t h r o u g h which a greag deal of i n f o r m a t i o n m a y be i n t e g r a t e d in the c(,rebr:d cortex, qnd nu,y indeed be at the root of its c h a r a c t e r i s t i c a l l y r h y t h m i c processes. Y e t it can be unequivocally s t a t e d t h a t these i n v e s t i g a t o r s have steered a clear course between tlm Scylla of oversimplific'~tion of eerebr.fl physioh)gy a n d the C h a r y b d i s of excessive belief in the powers of c u r r e n t e n g i n e e r i n g t e c h n i q u e s to unr'tvel t h e complexities of b r a i n organiz'/tion. There is au ;dmost w i s t f u l a c k n o w l e d g m e n t t h a t ~ i t is nluch less easy to j u s t i f y t h e G a u s s i a n process as a " r t ! a l i s t i c " model for n e u r o p h y s i o l o g i c a l 1)henomemt t h a n it is for m a n y other p h y s i c a l p r o c e s s e s . " A g v i n , they have s q u a r e l y c o n f r o n t e d b o t h the p r o b l e m of analysis of t h e ' ( s p o n t a n e o u s " r h y t h m , a n d the occur-
764
BOOK R E V I E W S
renee of intrinsically variable evoked t)otentials on a background of spontaneous activity. I n striking contrast to those who would plunge the brain into the abyss of barbiturate anesthesia in an attempt to better define its frame of functional organization, there is here a serious contemplation of tile spontaneous background activity, and of the possibility that transients, or transitional regions marking tile beginrang or end of a wave-train~ or of an evoked response, may have much informational significance. Above all, there is a recognition of tile assumptions implicit in applying such techniques as Fourier analysis or correlation analysis to a particular experimental situation, and the price to be paid for their use. I t is "ts a signpost to the future that this volume may hopefully display a singular prescience. I t is obvious that significant progress in brain physiology, and particularly at the level of behavioral processes, is only likely on the basis of collaborative efforts between the biologist and the engineer. N a n y current requirements in analysis of l~europhysiological data would be met by development of ~'on-line" versions of the varied and ingenious computers contrived by these investigators. One might refer here to tim growth and timely flowering of an academic atmosphere in which these investigators were ,lrawn toget-
her in a common effort. The high cost by eomp:~rison with other biological techniques of development and engineering of computing devices has restricted their use to very few centers in this country. Even tile frequency-modulated tape recorder, an essential item to any studies in this field, has so far found its place on the budgets of very few who seek support from granting agencies. Whatever changes may be wrought in this attitude, it is likely that for a very long time, collaborative and consultative studies will require a ready interchange of taperecorded data with a few well-equipped centers in this country. I t is for this reason that the time m , y well be at hand for tile setting up of national, a,,t hopefully, internationM standards in such matters. This study has sharply focused our "~ttention on the need for collaboration between tile biologist and the engineer, not merely in the analysis of neuroeh,ctrie data on the basis of currently conceived exper iments, nor solely in tlle worthy pursuit by tl.~ engineer of more efficient means of dat~l .mnlysis. but also ill tile appropriate design of the w'ry expt,riments themselves. I t is here that tile gr,,atest t.h.llenge would scent to lie, it" we are to employ most fruitfully the many facets of the electronic art. "~V. I1. AD~:Y
10 micro volt
2 micro volt 3 cm/sec.
True size unretouched
HANS HOLLAND
v A N GOGH -
AMSTERDAM
LANGSOM -
RAYON
26, 18
ELECTROENCEPHALOGRAPH • 2 to 16 c h a n n e l s • Sensitivity of 1 m i c r o v o h p e r 5 m m • N o i s e level a n d zero drift u n d e r 1 m i c r o v o l t • Plug-in i n t e r c h a n g e a b l e a m p l i f i e r s • Central administration • 1 extra amplifier-unit for replacement purposes
"16-channel EEG with built-in 12-channel direct writing and integrating analyser and triggered photostlmulator"
763
Taken together these two books provide a fascinating excursion into a n e x t r a o r d i n a r y d i f f i c u l t r e a h n of i n t e r r e l a t i o n s b e t w e e n m i n d a n d b r a i n in epilepsy. To read t h e m is s t i m u l a t i n g , a n d t h e i r fiehl is little trod. T h e y o f f e r an e x c i t i n g clmllcnge ~o ncuropsychologists. A. C. MUNDY-(~As:rI.E
PROCESSING N E U R O E L E C T R I C DATA C o n m m n i e a t i o n s B i o p h y s i c s Group of R e s e a r c h L a b o r a t o r y of Electronics a n d W i l l i a m M. Siebert, M a s s a c h u s e t t s I n s t i t u t e of T e c h n o l o g y T e c h n i c a l R e p o r t 35l. T e c h n o l o g y P r e s s , M.I.T., 1959, 121 pp. Within the come:tot comp:,ss of this vohlmc m a y be f o u n d one of the m a s t d i s c e r n i n g a p p r a i s a l s of the p a s t decade of p r o b l e m s at the core of the m a n y h a r r a s s i n g d i l e m m a s c u r r e n t l y c o n f r o n t i n g the s t u & , n t of c e n t r ' d n e r v o u s f u n c t i o n . These s t u d i e s b ) the C o m m u n i c a t i o n s B i o p h y s i c s Group are in m a n y respects symbolic, in t h e experiences of this one g r o u p of b~vestigators, of the s t r u g g l e s , the a s p i r a t i o n s , and, indeed, in t h e i r successes a n d f a i l u r e s , of the p r o g r e s s of the n e u r o p h y s o i l o g i c a l a r t to the p o i n t where the veritable a v a l a n c h e of d a t a p o u r e d f o r t h on p a p e r a n d f i l m f r o m a single e x p e r i m e n t can o v e r w h c h n the i n v e s t i g a t o r a t t e m p t i n g even the silnplest analysis. The relative ease of electrical recording front the b r a i n a n d the complexities of its s p o n t a n e o u s a n d evoked a c t i v i t y have, in g r e a t m e a s u r e , beguiled the exi)erbnenter into a c c e p t i n g his m o u n t a i n s of d a t a as capable of only empiric a n d s u b j e c t i v e i n t e r p r e t a tion, with t h e d a n c i n g of his p e n - w r i t e r s revealing little more t h a n " a tale told by a n idiot, full of sound and fury, signifying nothing" I t is here t h t a , to even the c a s u a l reader, this report is of such f a s c i n a t i n g i n t e r e s t , for in it :ire ninny of the links b e t w e e n retrospect a n d prosln'ct. On +he b a s i s of this research by 1)r. Rosenblith and his colleagues, t h e r e is r e a s o n for s a n g u i n e hope t!mt a t t e m p t s to a p p l y t h e electronic :,nd m a t h e m a t i c a l a r t s of the c o m p u t e r e n g i n e e r to p r o b l e m s of br:dn f u n c t i o n n m y b e a r s i g n i f i c a n t f r u i t , a n d t h a t these initi:tl steps are indeed t h e b a s i s for a n cssenti:dly new f r a m e of r e f e r e n c e in the s t u d y of f u n d a m e n t a l b r a i n m e c h a n s h n s . M e t h o d s .',re described for the eXalnination of the c h a r a c t e r i s t i c s of evoked poten tials, a n d other e s s e n t i a l l y ~ ' t i m e - l o c k e d ' ' p h e n o m e n a a n d f o r t h e a n a l y s i s of " s p o n t a n e o u s " rhythmic processes, by techniques of auto- a n d cross-corre!ation. which reveal a s p e c t s of i n h e r e n t r h y t h m i c i t y , h i d d e n r h y t h m s a n d p h a s e r e l a t i o n s h i p s between different brain regions sharing a common rhythmic process.
M u c h e f f o r t h a s been devoted by these laves t i g a t o r s to the design "rod c o n s t r u c t i o n of "lppropriate c o m p u t i n g devices on the oneh and, and on the other, to the f o r m u l a t i o n if m a t h e m a t i c a l models of neural f u n c t i o n s . Now it is here t h a t the s t u d e n t af b r a i n f u n c t i o n s h a s f r e q u e n t l y felt some concern at his e n g i n e e r i n g colle.~gues ~ easy e x t r a p o l a t i o n to b r a i n mecht, n i s m s on the b a s i s of such nmthenmtica:, models, u s u a l l y built on digital, or~ a t host, pulse-coded considerations, or e n t h u s i a s t i c a d a p t a t i o n s f r o m spinal cord physiology. T h i s is indeed a t h o r n y p:lth, a n d the p h y s i o l o g i s t will take little e o m f m ' t front t h e stqtt, ntents in this volume t h a t t h e u s e f u l n e s s of "1 m a t h e m a t i c a l nlodcl m a y be Ine.tsured by i t . ability to predict r e s u l t s of p r o c e s s i n g the dat't in w a y s d i f f e r e n t f r o m those used to e s t i m a t e the i m r a m e t e r s of the model. "lad t h a t if a simple model " f i t s " the d:lta well, it m a y provide a n e f f i c i e n t w a y of chara c t c r i z i n g the data, a n d m a y s u g g e s t new e x p e r i m e n t s . T h i s is surely merely to s u b s t i t u t e one e m p i r i c i s m for another. One m i g h t doubt w h e t h e r such an a p p r o a c h t h r o u g h the m o d c l l e r ' s a r t could b r i n g us s i g n i f i c a n t l y closer to "m u m l e r s t - t n d i n g of the pr(icesses, p r e s u n m b l y g r a d e d , -rod f r e q u e n t l y u n a c c o m p a n i e d by a discernible pulse-coded o u t p u t , t h r o u g h which a greag deal of i n f o r m a t i o n m a y be i n t e g r a t e d in the c(,rebr:d cortex, qnd nu,y indeed be at the root of its c h a r a c t e r i s t i c a l l y r h y t h m i c processes. Y e t it can be unequivocally s t a t e d t h a t these i n v e s t i g a t o r s have steered a clear course between tlm Scylla of oversimplific'~tion of eerebr.fl physioh)gy a n d the C h a r y b d i s of excessive belief in the powers of c u r r e n t e n g i n e e r i n g t e c h n i q u e s to unr'tvel t h e complexities of b r a i n organiz'/tion. There is au ;dmost w i s t f u l a c k n o w l e d g m e n t t h a t ~ i t is nluch less easy to j u s t i f y t h e G a u s s i a n process as a " r t ! a l i s t i c " model for n e u r o p h y s i o l o g i c a l 1)henomemt t h a n it is for m a n y other p h y s i c a l p r o c e s s e s . " A g v i n , they have s q u a r e l y c o n f r o n t e d b o t h the p r o b l e m of analysis of t h e ' ( s p o n t a n e o u s " r h y t h m , a n d the occur-
764
BOOK R E V I E W S
renee of intrinsically variable evoked t)otentials on a background of spontaneous activity. I n striking contrast to those who would plunge the brain into the abyss of barbiturate anesthesia in an attempt to better define its frame of functional organization, there is here a serious contemplation of tile spontaneous background activity, and of the possibility that transients, or transitional regions marking tile beginrang or end of a wave-train~ or of an evoked response, may have much informational significance. Above all, there is a recognition of tile assumptions implicit in applying such techniques as Fourier analysis or correlation analysis to a particular experimental situation, and the price to be paid for their use. I t is "ts a signpost to the future that this volume may hopefully display a singular prescience. I t is obvious that significant progress in brain physiology, and particularly at the level of behavioral processes, is only likely on the basis of collaborative efforts between the biologist and the engineer. N a n y current requirements in analysis of l~europhysiological data would be met by development of ~'on-line" versions of the varied and ingenious computers contrived by these investigators. One might refer here to tim growth and timely flowering of an academic atmosphere in which these investigators were ,lrawn toget-
her in a common effort. The high cost by eomp:~rison with other biological techniques of development and engineering of computing devices has restricted their use to very few centers in this country. Even tile frequency-modulated tape recorder, an essential item to any studies in this field, has so far found its place on the budgets of very few who seek support from granting agencies. Whatever changes may be wrought in this attitude, it is likely that for a very long time, collaborative and consultative studies will require a ready interchange of taperecorded data with a few well-equipped centers in this country. I t is for this reason that the time m , y well be at hand for tile setting up of national, a,,t hopefully, internationM standards in such matters. This study has sharply focused our "~ttention on the need for collaboration between tile biologist and the engineer, not merely in the analysis of neuroeh,ctrie data on the basis of currently conceived exper iments, nor solely in tlle worthy pursuit by tl.~ engineer of more efficient means of dat~l .mnlysis. but also ill tile appropriate design of the w'ry expt,riments themselves. I t is here that tile gr,,atest t.h.llenge would scent to lie, it" we are to employ most fruitfully the many facets of the electronic art. "~V. I1. AD~:Y
10 micro volt
2 micro volt 3 cm/sec.
True size unretouched
HANS HOLLAND
v A N GOGH -
AMSTERDAM
LANGSOM -
RAYON
26, 18
ELECTROENCEPHALOGRAPH • 2 to 16 c h a n n e l s • Sensitivity of 1 m i c r o v o h p e r 5 m m • N o i s e level a n d zero drift u n d e r 1 m i c r o v o l t • Plug-in i n t e r c h a n g e a b l e a m p l i f i e r s • Central administration • 1 extra amplifier-unit for replacement purposes
"16-channel EEG with built-in 12-channel direct writing and integrating analyser and triggered photostlmulator"