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Olfactory arousal reactions in the “cerveau isolé” cat
OLFACTORY AROUSAL REACTIONS "CERVEAU ISOLE" CAT 1
IN
THE
A. A R D U ~ , M.D. and G. MoRuzzl, M.D. lstituto di Fislologia, Universith di Pisa, Italy
Bremer's (1935, 1937, 1938) fundamen- pulses is thoroughly unable of disorganising tal discovery, showing that the E E G patterns the E E G sleep rhythms of the "cerveau occuring during natural sleep or under bar- isol~", either because its intensity is too biturate anaesthesia were duplicated by a small or because the sleep is too deep in this midbrain transection ("cerveau isol~" cat), preparation. The activation patterns so frewas regarded as the conclusive proof that quently observed in the "enc~phale isol~" natural sleep was due to functional deaf- cat, must be due, therefore, to some awakenferentation of the brain. This hypothesis ing influence arising from rhombencephalic was substantiated by another of Bremer's structures. Recent experiments' have localiz(1936) findings, namely that E E G activa- ed in the brain stem reticular formation the tion patterns prevailed when the transection structures which are responsible for the E E G was made at a much lower level (C1: "enc~- arousal reaction and for the alertness observphale isol~" cat), thus sparing the connec- ed in the awake animal. tions between cerebrum and cranial sensory The aim of the present experiments was nerves. to investigate if the lower part of the brain It is true that the deafferentation of the stem reticular system had some influence "cerveau isol~" was far from being com- on the arousal reactions elicited by intenplete, since both olfactory and visual im- tional olfactory and visual stimulations, i.e. pulses still reached the brain. Bremer (1938) by impulses impinging upon higher levels of found, however, that visual stimuli, evoking the central nervous system. An attempt was on and off responses in the area striata, were made to compare the arousal reaction elicited unable to block the sleep patterns of the by these sensory stimulations in "ene~phale "cerveau isol~". Incidentally this observa- isol~" and "cerveau isol~" cats. tion could hardly be reconciled with the METHODS assumption, prevailing at the time Bremer's discovery was made, that the visual arousal "Enc~phale isol~" and "cerveau isol~" reaction was due to the disorganizing in- cats were prepared under ether anaesthesia. fluence of impulses spreading through intra- In the "enc~phale isol~" cat, ephedrine was cortical paths from the area striata to other given intravenously immediately after spinal cortical regions. Bremer did not investigate transection at C~. Local application of novothe influence of the olfactory impulses on caine prevented pain arising from wounds or the E E G of the isolated brain, but he pointed from compression produced by the Horsleyout (1935) that the olfactory pupillary re- Clarke machine, thereby allowing animal's flex was absent in his preparation. relaxation and occasionally appearence of The obvious conclusion to be drawn from E E G and behavioural sleep patterns. In the Bremer's experiments is that the uninter- "cerveau isol~" cat, one eyeball was often rupted inflow of olfactory and retinal ira- removed, so as to expose the lateral surface 1 These experiments were supported by a grantin-aid of the American Academy of Arts and Sciences (Boston) for the year 1951. Two preliminary notes were published in Boll. 8oc. it. Biol. sp., 1951, ~7: 1189-1190.
1 Moruzzi and Magoun 1949; Lindsley, Bowden and Magoun 1949; Lindsley, Sehreiner, Knowles and Magoun 1950; Starzl, Taylor and Magoun 1951 a,b. Reviews: Magoun 1950, 1952; Bremer 1951 and Moruzzi 1952.
[ 24a ]
244
A. A R D U I N I and G. MORUZZI
of the olfactory bulb and the lateral olfactory tract. The other eye was left in situ, since both extreme myosis and strong corneal reflex were routinely checked as reliable tests of the functional activity of the structures rostrad and caudad the midbrain transection. At least two hours elapsed, after the discontinuance of ether anaesthesia and before the experiment was begun. The methods for recording potentials from the dura overlying the olfactory bulb and from the skull as well as the technique for sensory activation and for stimulating, or recording from, thalamic midline nuclei have been reported in another paper (Ardnini and Moruzzi 1953, see p. 235). RESULTS
Synchronization in the unanaestheti~ed cerebral cortex. The arousal reactions should be tested, of course, upon a background of cortical synchronisation. This background is easily obtained with barbiturate anaesthesia, which however strongly depresses the excitability of the brain stem reticular system (Moruzzi and Magoun 1949) and thoroughly prevents the EEG arousal elicited by olfactory stimulations (Adrian 1942). Our preliminary experiments were devoted, therefore, to an attempt to synchronize the cortical neurones in the unanesthetized cerebrum. The "cerveau isol6" cat, whose EEG patterns are characterized by recurring spindles (Bremer 1935), is the obvious choice. After Bremer's (1938) failure in eliciting arousal reactions with visual stimuli, no attempt had been made to disorganize with sensory stimulations the brain rhythms of this preparation. A drawback is represented by the fact that both bulbo-reticular stimulations and the .arousal reactions elicited by acoustic and trigeminal stimuli are not available in the "cerveau isol~" preparation. The burst activity occuring after midbrain transection resembles that of the barbiturized cat (Dempsey and Morison 1942) in being triggered by low frequency (0.5-1./sec.) and disorganized by high frequency (30300/see.) stimulation of midline thalamic nuclei.
The "enc~phale isol~" cat is a preparation which might be also utilized for investigating the EEG arousal reaction. Cortical synchronization and behavioral sleep patterns are sometimes observed in this preparation (Bremer 1936), particularly if pain is prevented by local anaesthesia and if the animal is kept in the dark. However, synchronization is generally unconstant and unpredictable; moreover, the outbursts of spindle waves are irregularly spaced, thus providing an unsatisfactory background for investigating the arousal reaction. A uniform background of thalamically induced synchrony may be obtained in the "enc~phale isol~" by utilizin~ Morison and Dempsey's (1941) recruitment responses. These synchronous waves are clearly abolished by any kind of sensory stimulations, when both repetition rate and intensity of thalamic stimulation are just above threshold (Moruzzi and Magoun 1949). With slightly stronger stimuli the thalamieally induced synchronization is however so intense, that it cannot be overrun by natural stimulation of sensory receptors. •In the present experiments a background of synchronization which is more easily disorganized by sensory stimuli was brought about in two different ways. Dempsey and Morison (1941) reported that repetitive after-discharges sometimes oecured, in barbiturate eats, upon single shock stimuli delivered to the recruiting structures of the thalamus. Their findings were confirmed by Jasper (1949) and by Starzl and Magoun (1951) on "enc~phale isol6" cats. We have found that repetitive after-discharges may be constantly elicited in this preparation simply by increasing up to 5 reset, the duration of the single rectangular pulse. The optimum repetition rate for thalamie stimulation is .5-1/see. The repetitive after-discharges are constantly and easily blocked during the cortical arousal reaction (fig. 1, E, F). When the "ene6phale isol6" preparation is somewhat deteriorated the repetitive afterdischarge following single shocks or 0.5-1/see. stimulation may be lost, although repetition
OLFACTORY AROUSAL REACTIONS
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Fig. 1 Olfactory arousal reaction on sponlaneous and thalamieally induced synchronisation in the "enc@hale isold" cat
A - - B l o c k a d e of burst activity in the cerebral cortex and synchronous beatings in the olfactory bulb neurones ( A d r i a n ' s " i n d u c e d w a v e s " ) elicited by blowing air into the nostrils (4- - - ) B - - R e c o v e r y , 30 sec. a f t e r the end of the stimulus. C - Same preparation. The arousal reaction is elicited by an acoustic stimulation (Whistling 4- - - ) . D - - R e c o v e r y , 30 sec. a f t e r the end of the stimulus. E - - A n o t h e r "enc~phale isol~," cat. !nduced waves in the olfactory bulb and blockade of thalamically induced spindles (the square pulses of 7 ¥., 1/sec., 2 msec. pulse duration, applied to the i n t r a l a m i n a r nuclei, are marked by dots) elicited by blowing air into the nostrils ( 4 - ) . The arousal reactior, overlasts 7 sec. the end of the olfactory stimulation
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Few minutes a f t e r E. The blockade of the triggered spindles is elicited by an acoustic stimulation (whistling: 4-). I n all records L. olf. signifies: left olfactory bulb, L (R) sen-mot.: left (or right) sensory-motor cortex, L. temp.: left temporal areas. Vertical and horizontal b a r s : voltage (20(', #V) and time (1 see.) calibrations.
246
A. ARDUINI and G. MORUZZ[
rates of 6-8/see. still yield strong recruitment responses. A repetitive after-discharge may then be produced simply by shortening the duration of the recruiting stimulation, so that only three or four recruitment potentials are recorded. A f t e r the end of the last recruitment potentials, a repetitive afterdischarge is observed, which is much more sensitive to the blocking influence of the arousal reactions than the recruitment po~e~tials. Olfactory arousal reactions. Generalized E E G arousal reactions may be elicited by blowing room air into the nostrils of a "'eerveau isol~" preparation (figs. 2, 3). Although no smell could be appreciated by the human nose in the room air, there is no doubt that the arousal reaction was brought about by impulses arising in the receptors of the olfactory epithelium since (1) A d r i a n ' s induced waves (1942, 1949, 1950) were sinmltaneously recorded from the olfactory bulb (figs. l, 2) and ~2) stimulation of nasal trigeminal receptors was bound to be without effect on the brain waves, after complete midbrain transection. It is indeed possible - and it has actually been suggested by Adrian (1942) - - that the olfactory epithelium is mechanically stimulated by the air current and not by the odours contained in it. However, activation patterns were sometimes obtained simply by adding a strong odour (like gomenol or terpinol) to the inspired air, thereby increasing the strength of the chemical stimulation but avoiding forcible introd u c t i o n ' o f air under positive pressure. The same concentrations of smell had no influence if the inspiration occured through the tracheal eanula. There is no doubt, therefore, that cortical arousal reactions may be elicited in the " c e r v e a n isol~" by purely olfactory stimulations. Repetitive and forcible introduction of air into the nostrils is nevertheless the best way of eliciting a barrage of olfactory impulses having a widespread disorganizing effect on brain rhythms. The inspiratory introduction of odours, during eupnoic breathing, is less effective, and no cortical activation occurs when room air is inspired through
the nose, as is the case during normal respiration. This might be the reason why uninterrupted sleep characterizes the E E G patterns of the " c e r v e a u isol6". With a single exception, we have been thoroughly unable of detecting significant E E G differences in " c e r v e a u isol6" cats breathing alternatively through the nose and through the tracheal canula. Both intensity and duration of the cortical arousal reactions, elicited by blowing air into the nostrils, are definitely weaker in the " c e r v e a u isol6" than in the "enc6phale isol6" preparation. This observation was substantiated by control experiments, in which air was blown into the nostrils of the same "enc6phale isol6" eat, before and after a midbrain transection (fig. 2). Sometimes startling nasal stimuli were altogether unable to disorganize the brain rhythms of the " e e r v e a u isol6", although the induced waves were clearly recorded from the olfactory bulb. In deteriorated preparations or whenever nasal stimuli were applied at short intervals, the arousal reactions were found to decrease steadily in intensity and duration in sharp contrast with the responses of the olfactory bulb, which remained unaffected. l~inally a selective suppression of the olfactory arousal reactions, leaving the induced waves of the olfactory bulb unaffected, followed the intravenous injection of small doses of Penthotal (m~. 2/kg.). The electrothalamogram of the diffuse projection system had been previously re(,orded in the "enc6phale isol6" preparation (Moruzzi and Magoun 1949). High voltage waves were led from intralaminar recruiting areas during recruitment responses or chloralosane anaesthesia ; their complete blockade was easily produced by bulbo-reticular stimulations. In the present experiments high voltage waves, synchronous with the cortical spindles, were led from thalamie recruiting areas of the " c e r v e a u isol6" cat. Both thalamic and cortical rhythms were disorganized by blowing air into the nostrils (fig. 3, C and D.). Curiously enough, these generalized arousal reactions, affecting both eortieal and subeortieal structures, did not
OLFACTORY AROUSAL REACTIONS DISCUSSION
i n f l u e n c e t h e p u p i l d i a m e t e r . The e x t r e m e myosis which characterises the "cerveau i s o l ~ " p r e p a r a t i o n was t h o r o u g h l y u n m o d i f i e d d u r i n g s t r o n g s t i m u l a t i o n of t h e olfactory epithelium. Visual arousal reaction. F l i c k e r i n g light, y i e l d i n g c o m p l e t e b l o c k a d e of t h e sleep r h y t h m s in t h e " e n c ~ p h a l e i s o l ~ " p r e p a r a tion, was u n e f f e c t i v e on t h e c o r t i c a l s p i n d l e s of the " c e r v e a u i s o l ~ " cat. The same nega t i v e r e s u l t s were o b t a i n e d a f t e r a t r o p i n i z a -
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Two s e n s o r y m o d a l i t i e s a r e still a v a i l a b l e in the " c e r v e a u i s o l ~ " p r e p a r a t i o n , b u t o n l y the o l f a c t o r y i m p u l s e s a r e able to evoke a g e n e r a l i z e d a r o u s a l r e a c t i o n . T h e f a i l u r e of v i s u a l i m p u l s e s is n o t s u r p r i s i n g since t h e i r a b i l i t y to p r o d u c e a r o u s a l is the l e a s t d e v e l o p ed in the series of s e n s o r y a c t i v a t i o n s w h i c h h a v e been t e s t e d so f a r ( G e l l h o r n 1952). Visual arousal reactions are easily obtained in t h e i n t a c t , u n a n e s t h e t i z e d r a b b i t ( E e -
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Olfactory arousal reactions after cervical and ~nidbrain transections
A - - " E n c ~ p h a l e isol~", showing high voltage slow waves, most pronounced in the sensorymotor cortices, blocked by blowing air into the left nostril. During the stimulation ( - ~ - - ) , Adrian's induced wu,,es were led from the ipsilateral olfactory bulb. B - Shows that the arousal reaction is still present 28 sec. after the end of the stimulation, although the "induced ~vaves" overlasted only 2 sec. the stimulation of the olfactory receptors. C--Recovery to rest synchronisation (53 sec. after the end of the stimulation). Then a midbrain transection was made and 90 rain. later the records D, E, F were taken. D - - S h o w s that the blockade of the high voltage slow waves, most pronounced in the sensory-motor cortices, is less strong and markedly delayed after midbrain section. E - - T h e arousal reaction appears only 6 sec. after the end of the stimulation, when the induced waves of the olfactory bulb have just disappeared. F - - S h o w s recovery to rest synchronis~tion (38 sec. after the end of the stimulation). Calibration: 200 #V.; .5 sec. tion of the eye. C o n t r o l e x p e r i m e n t s showed, c o n f i r m i n g B r e m e r ' s (1938) f i n d i n g s , t h a t " o n " a n d " o f f " r e s p o n s e s w e r e led, f o r t h e same i n t e n s i t y of v i s u a l s t i m u l a t i o n , f r o m t h e a r e a s t r i a t a of t h e i s o l a t e d b r a i n . C o n d u c t i o n in the specific p r o j e c t i o n v i s u a l p a t h w a y s m a y be dissociated, t h e r e f o r e , f r o m t h e visual arousal reaction.
t o r s 1936) a n d i n t h e " e n c ~ p h a l e i s o l ~ " cat ( B r e m e r 1936). H e n c e a f t e r m i d b r a i n t r a n s ection t h e r e s p o n s i v e n e s s of the i s o l a t e d b r a i n to a r o u s a l s t i m u l a t i o n s is s t r o n g l y d e c r e a s ed, so t h a t o n l y t h e most a c t i v e s e n s o r y m o d a l i t i e s a r e still able to p r o d u c e a wides p r e a d d i s o r g a n i z a t i o n of c o r t i c a l r h y t h m s . T h e o l f a c t o r y s y s t e m belongs to the l a t t e r
248
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Fig. 3 Olfactory
and thalamically
induced arousal reactions
in the ' ' eerveau isol~' ' cat
A - - " I n d u c e d waves" in the olfactory bulb and generalized blockade of cortical spindles following stimulation of the olfactory receptors (room air blown into the nostrils). B - Full recovery to rest synehronisation, 9 sec. after the end of the stimulation. C - - Another ' ' cerveau isol~" preparation. Blocking of both thalamie and cortical spindles during olfactory stimulation. The thalamie potentials were led through concentric electrodes from a recruiting area of the midline nuclei of the thalamus. D - Full recovery of thalamie and cortical synehronisation after 9 see. E--Electrical activation elicited by stimulating a recruiting intrathalamie region (300/see., I msee. pulse duration, 3 V.) in another ' 'cerveau isol6 ~' eat. F--Complete recovery of synehronisation after 9 see. Calibrations: 200 pV. ; 1 see.
category, at least in a macrosmatic animal like the cat. Both intensity and duration of the olf a c t o r y arousal reaction arc less marked in the " c e r v e a u isol~" cat that a f t e r spinal section a t C1. A p p a r e n t l y the pons a n d the medulla facilitate in some w a y the olfactory arousal reactions, although they certainly are not involved in the specific projections paths arising f r o m the olfactory bulb. The most obvious explanation of these findings is that the olfactory and the ascending reticular impulses converge on the cephalic portions of the brain stem activating system, i.e. either on the mesencephalic t e g m e n t u m or on the hypothalamus and the subthalamus. These structures are not between those yielding electric responses to single shocks (Rose a n d Woolsey 1943; Allen 1943; Fox, McKinley and Magoun 1944; K a a d a 1951; Berry, H a g a m e n and H i n s e y 1952) or to a sequence of three shocks (Bonvallet, Dell and Hugelin 1952) applied to the olfactory bulbs. However multisynaptic connections are likely to be overcome only through temporal sequence of m a n y impulses. Electrical recording f r o m olfactory system following prolonged natural stimulations, has been limited so f a r to rhinencephalic structures ( H a s a m a 1934; A d r i a n 1942; Allen 1943~, the electrical stimulation of which is followed sometimes (in the anaesthetized animal) b y generalized activation of the E E G ( K a a d a :1951). I f these responses are mediated through corticofugal projections to the cephalic portion of the ascending reticular system (see Sloan and J a s p e r 1950; K a a d a 1951; Jasper, Ajmone-Marsan and Stoll 1952), the generalized arousal reaction elicited by olf a c t o r y stimuli in the " c e r v e a u isol~" might be more easily understood. SUMMARY 1. The b u r s t activity of the cerebral cortex is blocked in the " c e r v e a u isol~" c a t by olfactory but not b y visual impulses.
OLFACTORY AROUSAL REACTIONS 2. T h e m o s t e f f e c t i v e w a y o f e l i c i t i n g a n olfactory arousal is given by blowing repetitively air into the nostrils. The disorganization of the brain rhythms overlasts, sometimes for many seconds, the end of the sensory stimulation and the disappearance of Adrian's induced waves from the olfactory bulb. An arousal from stimulated trigeminal r e c e p t o r s o f t h e n o s e is p r e v e n t e d b y t h e midbrain transection. 3. T h e o l f a c t o r y a r o u s a l is s h o r t e r a n d less i n t e n s e i n t h e " c e r v e a u i s o l ~ " t h a t a f t e r s p i n a l s e c t i o n a t C~. T h e h y p o t h e s i s is p u t forward that the olfactory and the reticular ascending impulses converge on the cephalic areas of the activating system. REFERENCES ADRIAN, E. D. Olfactory reactions in the brain of the hedgehog. J. Physiol., 1942, 100: 459-473. ADRLCN, E. D. The development of nerve cell rhythms. Arch. Psychiatr. Zeitschr. Neurol., 1949, 183: 197-205. ADRIAN, E. D. The electrical activity of the mammalian olfactory bulb. EEG Clin. Neurophysiol., 1950, 2: 377-388. ALLEN, W. F. Distribution of cortical potentials resulting from insufflation of vapors into the nostrils and from stimulation of the olfactory bulb and the pyriform lobe. Amer. J. Physiol., 1943, 135: 553-555. ARDUINI, A. and MORUZZI, G. Sensory and thalamic synchronization in the olfactory bulb. EEG Clin. Neurophysiol., 1953, 2: 235-242. BERRY, C. M., tIA~A)ZEN, W. D. and HINSEY, J. C. Distribution of potentials following stimulation of olfactory bulb in cat. J. Neurophysiol., 1952, 15: 139-148. BONVALLET, M., DELL, P. et I~IUGELIN, A. Projections olfactives, gustatives, viscerales, vagales, visuelles et auditives au niveau des formations grises du cerveau ant~rieur du chat. J. Physiologic, 1952, 44: 222-224. BaEMER, F. Ccrveau isol~ et physiologic du sommeil. C. R. Soc. Biol., Paris, 1935, 118: 1235-1242. BREMER, F. Nouvelles recherches sur le m~canisme du sommeil. C. R. Soc. Biol., Paris, 1936, lZ2: 460-464. BREMER, F. L'activit~ c~r~brale au cours du sommeil et de la narcose. Contribution ~ l'~tude du m~canisme du sommeil. Bull. Acad. Roy. Mdd., 1937, 4: 68-86. BRE.'~IER, F. L'activit~ ~lectrique de l'~corce c~r~brale e t ] e probl~me physiologique du sommeil. Boll. Soc. it. Biol. sp. 1938, 13: 271-290.
249
BREMER, F. Le probl~me physiologique du sommeil. Medicina, 1951, 1: 586-619. DEMPSEY, E. W. and MORISON, R. S. The production of rhythmically recurrent cortical potentials after localized thalamic stimulation. Amer. J. Physiol., 1941, 135: 293-300. ECTORS, L. Etude de l'activit~ ~lectrique du cortex e~r~bral chez le lapin non narcotis~ ni curarisd. Arch. int. Physiol., 1936, 43: 267-298. FOX, C. A., •C KINLEY, W. A. and MAGOUN, H. W. An oscillographic study of the olfactory system in cats. J. Neurophysiol., 1944, 7: 1-16. GELLHORN, E. Experimental contributions to the duplicity theory of consciousness and perception. Pfliigers Arch., 1952, 255: 75-92. HASAM, B. t~ber die elektrischen Begleiterscheinungen und der Reichsph~ire bei der Geruehsempfindung. Pfliigers Arch., 1934, 234: 748-755. JASPER, H. H. Diffuse projection system: the integrative action of the thalamic reticular system. EEG Clin. Ncurophysiol., 1949, 1: 405-419. JASPER, H., AJMONE-MARSAN, C. and STOLL, J. Corticofugal projections to the brain stem. Arch. Neurol. Psychiat., Chicago, 1952, 67: 155-171. KAADA, B. R. Somato-motor, autonomic and electrocorticographic responses to electrical stimulation of " r h i n e n c e p h a l i c " and other structures in primates, cat and dog. Acta Physiol. Scan&, 1951, 23: (suppl. 83): 1-285. ],INDSLEY, D. B., ]~OV*'DEN,J. W. and MAGOUN, H. W. Effect upon the E E G of acute injury to the brain stem activating system. EEG Clin. Neurophysiol., 1949, 1: 475-481. LINDSLEY, D. ]~., SCHREINER, L. H., KNOWLES, W. B. and MAGOUN, H. W. Behavioral and E E G changes following brain stem lesions in the cat. EEG Clin. Ncurophysiol., 1950, 2: 483-498. 5IAGOUN, H. W. Caudal and cephalic influences of the brain stem reticular formation. Physiol. Rev., 1950, 30: 455-474. MAGOUN, H. W. An ascending reticular activating system in the brain stem. Arch. Ncurol. Psychiat., Chicago, 1952, 67: 145-154. MORISO~, R. S. and DEMPSEY, E. W. A study of thalamocortical relations. Amer. J. Physiol., 1941, 35: 281-292. MORUZZb G. and ]VIAGOUN,H. W. Brain stem reticular formation and activation of the EEG. EEG Clin. Ne~rophysiol., 1949, 1: 455-473. MORUZZI, G. I1 risveglio della corteccia cerebrale. Medicina 1952, 2: 577-596. ROSE, J. E. and WOOLSEY, C. N. Potential changes in the olfactory bulb produced by electrical stimulation of the olfactory bulb. Fed. Proe., 1943, 2 : 42. SLOAN, N. and JASPER, H. Studies of the regulatory functions of the limbic cortex. EEG Clin. Neurophysiol., 1959, 2: 317-327. STARZL, T. E. and MAGOUN, H. W. Organization of the diffuse thalamic projection system. J. Neuropl~ysiol., 1951, 14: 133-146.
250
A. ARDUINI and G. MORUZZI
STARZL, T. E., TAYLOR, C. W. and MAGOUN, H. W. Ascending conduction in reticular activating system, with special reference to the diencephalen. J. Neurophysiol., 1951 a, 14: 461-477.
ST~ZL, T. E., TAYLOR, C. W. and MA6OU~, H. W. Collateral afferent excitation of reticular formation of brain stem. J. Neurophysiol., 1951 b, 14: 479-496.
l~efcrence: ARDUINI, A. and •ORUZZI, (~. Olfactory arousal reactions in the "cerveau isol6" cat. ]EEG Clin. Neurophysiol., 1963, ~: 243-250.
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IN
THE
A. A R D U ~ , M.D. and G. MoRuzzl, M.D. lstituto di Fislologia, Universith di Pisa, Italy
Bremer's (1935, 1937, 1938) fundamen- pulses is thoroughly unable of disorganising tal discovery, showing that the E E G patterns the E E G sleep rhythms of the "cerveau occuring during natural sleep or under bar- isol~", either because its intensity is too biturate anaesthesia were duplicated by a small or because the sleep is too deep in this midbrain transection ("cerveau isol~" cat), preparation. The activation patterns so frewas regarded as the conclusive proof that quently observed in the "enc~phale isol~" natural sleep was due to functional deaf- cat, must be due, therefore, to some awakenferentation of the brain. This hypothesis ing influence arising from rhombencephalic was substantiated by another of Bremer's structures. Recent experiments' have localiz(1936) findings, namely that E E G activa- ed in the brain stem reticular formation the tion patterns prevailed when the transection structures which are responsible for the E E G was made at a much lower level (C1: "enc~- arousal reaction and for the alertness observphale isol~" cat), thus sparing the connec- ed in the awake animal. tions between cerebrum and cranial sensory The aim of the present experiments was nerves. to investigate if the lower part of the brain It is true that the deafferentation of the stem reticular system had some influence "cerveau isol~" was far from being com- on the arousal reactions elicited by intenplete, since both olfactory and visual im- tional olfactory and visual stimulations, i.e. pulses still reached the brain. Bremer (1938) by impulses impinging upon higher levels of found, however, that visual stimuli, evoking the central nervous system. An attempt was on and off responses in the area striata, were made to compare the arousal reaction elicited unable to block the sleep patterns of the by these sensory stimulations in "ene~phale "cerveau isol~". Incidentally this observa- isol~" and "cerveau isol~" cats. tion could hardly be reconciled with the METHODS assumption, prevailing at the time Bremer's discovery was made, that the visual arousal "Enc~phale isol~" and "cerveau isol~" reaction was due to the disorganizing in- cats were prepared under ether anaesthesia. fluence of impulses spreading through intra- In the "enc~phale isol~" cat, ephedrine was cortical paths from the area striata to other given intravenously immediately after spinal cortical regions. Bremer did not investigate transection at C~. Local application of novothe influence of the olfactory impulses on caine prevented pain arising from wounds or the E E G of the isolated brain, but he pointed from compression produced by the Horsleyout (1935) that the olfactory pupillary re- Clarke machine, thereby allowing animal's flex was absent in his preparation. relaxation and occasionally appearence of The obvious conclusion to be drawn from E E G and behavioural sleep patterns. In the Bremer's experiments is that the uninter- "cerveau isol~" cat, one eyeball was often rupted inflow of olfactory and retinal ira- removed, so as to expose the lateral surface 1 These experiments were supported by a grantin-aid of the American Academy of Arts and Sciences (Boston) for the year 1951. Two preliminary notes were published in Boll. 8oc. it. Biol. sp., 1951, ~7: 1189-1190.
1 Moruzzi and Magoun 1949; Lindsley, Bowden and Magoun 1949; Lindsley, Sehreiner, Knowles and Magoun 1950; Starzl, Taylor and Magoun 1951 a,b. Reviews: Magoun 1950, 1952; Bremer 1951 and Moruzzi 1952.
[ 24a ]
244
A. A R D U I N I and G. MORUZZI
of the olfactory bulb and the lateral olfactory tract. The other eye was left in situ, since both extreme myosis and strong corneal reflex were routinely checked as reliable tests of the functional activity of the structures rostrad and caudad the midbrain transection. At least two hours elapsed, after the discontinuance of ether anaesthesia and before the experiment was begun. The methods for recording potentials from the dura overlying the olfactory bulb and from the skull as well as the technique for sensory activation and for stimulating, or recording from, thalamic midline nuclei have been reported in another paper (Ardnini and Moruzzi 1953, see p. 235). RESULTS
Synchronization in the unanaestheti~ed cerebral cortex. The arousal reactions should be tested, of course, upon a background of cortical synchronisation. This background is easily obtained with barbiturate anaesthesia, which however strongly depresses the excitability of the brain stem reticular system (Moruzzi and Magoun 1949) and thoroughly prevents the EEG arousal elicited by olfactory stimulations (Adrian 1942). Our preliminary experiments were devoted, therefore, to an attempt to synchronize the cortical neurones in the unanesthetized cerebrum. The "cerveau isol6" cat, whose EEG patterns are characterized by recurring spindles (Bremer 1935), is the obvious choice. After Bremer's (1938) failure in eliciting arousal reactions with visual stimuli, no attempt had been made to disorganize with sensory stimulations the brain rhythms of this preparation. A drawback is represented by the fact that both bulbo-reticular stimulations and the .arousal reactions elicited by acoustic and trigeminal stimuli are not available in the "cerveau isol~" preparation. The burst activity occuring after midbrain transection resembles that of the barbiturized cat (Dempsey and Morison 1942) in being triggered by low frequency (0.5-1./sec.) and disorganized by high frequency (30300/see.) stimulation of midline thalamic nuclei.
The "enc~phale isol~" cat is a preparation which might be also utilized for investigating the EEG arousal reaction. Cortical synchronization and behavioral sleep patterns are sometimes observed in this preparation (Bremer 1936), particularly if pain is prevented by local anaesthesia and if the animal is kept in the dark. However, synchronization is generally unconstant and unpredictable; moreover, the outbursts of spindle waves are irregularly spaced, thus providing an unsatisfactory background for investigating the arousal reaction. A uniform background of thalamically induced synchrony may be obtained in the "enc~phale isol~" by utilizin~ Morison and Dempsey's (1941) recruitment responses. These synchronous waves are clearly abolished by any kind of sensory stimulations, when both repetition rate and intensity of thalamic stimulation are just above threshold (Moruzzi and Magoun 1949). With slightly stronger stimuli the thalamieally induced synchronization is however so intense, that it cannot be overrun by natural stimulation of sensory receptors. •In the present experiments a background of synchronization which is more easily disorganized by sensory stimuli was brought about in two different ways. Dempsey and Morison (1941) reported that repetitive after-discharges sometimes oecured, in barbiturate eats, upon single shock stimuli delivered to the recruiting structures of the thalamus. Their findings were confirmed by Jasper (1949) and by Starzl and Magoun (1951) on "enc~phale isol6" cats. We have found that repetitive after-discharges may be constantly elicited in this preparation simply by increasing up to 5 reset, the duration of the single rectangular pulse. The optimum repetition rate for thalamie stimulation is .5-1/see. The repetitive after-discharges are constantly and easily blocked during the cortical arousal reaction (fig. 1, E, F). When the "ene6phale isol6" preparation is somewhat deteriorated the repetitive afterdischarge following single shocks or 0.5-1/see. stimulation may be lost, although repetition
OLFACTORY AROUSAL REACTIONS
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A - - B l o c k a d e of burst activity in the cerebral cortex and synchronous beatings in the olfactory bulb neurones ( A d r i a n ' s " i n d u c e d w a v e s " ) elicited by blowing air into the nostrils (4- - - ) B - - R e c o v e r y , 30 sec. a f t e r the end of the stimulus. C - Same preparation. The arousal reaction is elicited by an acoustic stimulation (Whistling 4- - - ) . D - - R e c o v e r y , 30 sec. a f t e r the end of the stimulus. E - - A n o t h e r "enc~phale isol~," cat. !nduced waves in the olfactory bulb and blockade of thalamically induced spindles (the square pulses of 7 ¥., 1/sec., 2 msec. pulse duration, applied to the i n t r a l a m i n a r nuclei, are marked by dots) elicited by blowing air into the nostrils ( 4 - ) . The arousal reactior, overlasts 7 sec. the end of the olfactory stimulation
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Few minutes a f t e r E. The blockade of the triggered spindles is elicited by an acoustic stimulation (whistling: 4-). I n all records L. olf. signifies: left olfactory bulb, L (R) sen-mot.: left (or right) sensory-motor cortex, L. temp.: left temporal areas. Vertical and horizontal b a r s : voltage (20(', #V) and time (1 see.) calibrations.
246
A. ARDUINI and G. MORUZZ[
rates of 6-8/see. still yield strong recruitment responses. A repetitive after-discharge may then be produced simply by shortening the duration of the recruiting stimulation, so that only three or four recruitment potentials are recorded. A f t e r the end of the last recruitment potentials, a repetitive afterdischarge is observed, which is much more sensitive to the blocking influence of the arousal reactions than the recruitment po~e~tials. Olfactory arousal reactions. Generalized E E G arousal reactions may be elicited by blowing room air into the nostrils of a "'eerveau isol~" preparation (figs. 2, 3). Although no smell could be appreciated by the human nose in the room air, there is no doubt that the arousal reaction was brought about by impulses arising in the receptors of the olfactory epithelium since (1) A d r i a n ' s induced waves (1942, 1949, 1950) were sinmltaneously recorded from the olfactory bulb (figs. l, 2) and ~2) stimulation of nasal trigeminal receptors was bound to be without effect on the brain waves, after complete midbrain transection. It is indeed possible - and it has actually been suggested by Adrian (1942) - - that the olfactory epithelium is mechanically stimulated by the air current and not by the odours contained in it. However, activation patterns were sometimes obtained simply by adding a strong odour (like gomenol or terpinol) to the inspired air, thereby increasing the strength of the chemical stimulation but avoiding forcible introd u c t i o n ' o f air under positive pressure. The same concentrations of smell had no influence if the inspiration occured through the tracheal eanula. There is no doubt, therefore, that cortical arousal reactions may be elicited in the " c e r v e a n isol~" by purely olfactory stimulations. Repetitive and forcible introduction of air into the nostrils is nevertheless the best way of eliciting a barrage of olfactory impulses having a widespread disorganizing effect on brain rhythms. The inspiratory introduction of odours, during eupnoic breathing, is less effective, and no cortical activation occurs when room air is inspired through
the nose, as is the case during normal respiration. This might be the reason why uninterrupted sleep characterizes the E E G patterns of the " c e r v e a u isol6". With a single exception, we have been thoroughly unable of detecting significant E E G differences in " c e r v e a u isol6" cats breathing alternatively through the nose and through the tracheal canula. Both intensity and duration of the cortical arousal reactions, elicited by blowing air into the nostrils, are definitely weaker in the " c e r v e a u isol6" than in the "enc6phale isol6" preparation. This observation was substantiated by control experiments, in which air was blown into the nostrils of the same "enc6phale isol6" eat, before and after a midbrain transection (fig. 2). Sometimes startling nasal stimuli were altogether unable to disorganize the brain rhythms of the " e e r v e a u isol6", although the induced waves were clearly recorded from the olfactory bulb. In deteriorated preparations or whenever nasal stimuli were applied at short intervals, the arousal reactions were found to decrease steadily in intensity and duration in sharp contrast with the responses of the olfactory bulb, which remained unaffected. l~inally a selective suppression of the olfactory arousal reactions, leaving the induced waves of the olfactory bulb unaffected, followed the intravenous injection of small doses of Penthotal (m~. 2/kg.). The electrothalamogram of the diffuse projection system had been previously re(,orded in the "enc6phale isol6" preparation (Moruzzi and Magoun 1949). High voltage waves were led from intralaminar recruiting areas during recruitment responses or chloralosane anaesthesia ; their complete blockade was easily produced by bulbo-reticular stimulations. In the present experiments high voltage waves, synchronous with the cortical spindles, were led from thalamie recruiting areas of the " c e r v e a u isol6" cat. Both thalamic and cortical rhythms were disorganized by blowing air into the nostrils (fig. 3, C and D.). Curiously enough, these generalized arousal reactions, affecting both eortieal and subeortieal structures, did not
OLFACTORY AROUSAL REACTIONS DISCUSSION
i n f l u e n c e t h e p u p i l d i a m e t e r . The e x t r e m e myosis which characterises the "cerveau i s o l ~ " p r e p a r a t i o n was t h o r o u g h l y u n m o d i f i e d d u r i n g s t r o n g s t i m u l a t i o n of t h e olfactory epithelium. Visual arousal reaction. F l i c k e r i n g light, y i e l d i n g c o m p l e t e b l o c k a d e of t h e sleep r h y t h m s in t h e " e n c ~ p h a l e i s o l ~ " p r e p a r a tion, was u n e f f e c t i v e on t h e c o r t i c a l s p i n d l e s of the " c e r v e a u i s o l ~ " cat. The same nega t i v e r e s u l t s were o b t a i n e d a f t e r a t r o p i n i z a -
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Two s e n s o r y m o d a l i t i e s a r e still a v a i l a b l e in the " c e r v e a u i s o l ~ " p r e p a r a t i o n , b u t o n l y the o l f a c t o r y i m p u l s e s a r e able to evoke a g e n e r a l i z e d a r o u s a l r e a c t i o n . T h e f a i l u r e of v i s u a l i m p u l s e s is n o t s u r p r i s i n g since t h e i r a b i l i t y to p r o d u c e a r o u s a l is the l e a s t d e v e l o p ed in the series of s e n s o r y a c t i v a t i o n s w h i c h h a v e been t e s t e d so f a r ( G e l l h o r n 1952). Visual arousal reactions are easily obtained in t h e i n t a c t , u n a n e s t h e t i z e d r a b b i t ( E e -
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Olfactory arousal reactions after cervical and ~nidbrain transections
A - - " E n c ~ p h a l e isol~", showing high voltage slow waves, most pronounced in the sensorymotor cortices, blocked by blowing air into the left nostril. During the stimulation ( - ~ - - ) , Adrian's induced wu,,es were led from the ipsilateral olfactory bulb. B - Shows that the arousal reaction is still present 28 sec. after the end of the stimulation, although the "induced ~vaves" overlasted only 2 sec. the stimulation of the olfactory receptors. C--Recovery to rest synchronisation (53 sec. after the end of the stimulation). Then a midbrain transection was made and 90 rain. later the records D, E, F were taken. D - - S h o w s that the blockade of the high voltage slow waves, most pronounced in the sensory-motor cortices, is less strong and markedly delayed after midbrain section. E - - T h e arousal reaction appears only 6 sec. after the end of the stimulation, when the induced waves of the olfactory bulb have just disappeared. F - - S h o w s recovery to rest synchronis~tion (38 sec. after the end of the stimulation). Calibration: 200 #V.; .5 sec. tion of the eye. C o n t r o l e x p e r i m e n t s showed, c o n f i r m i n g B r e m e r ' s (1938) f i n d i n g s , t h a t " o n " a n d " o f f " r e s p o n s e s w e r e led, f o r t h e same i n t e n s i t y of v i s u a l s t i m u l a t i o n , f r o m t h e a r e a s t r i a t a of t h e i s o l a t e d b r a i n . C o n d u c t i o n in the specific p r o j e c t i o n v i s u a l p a t h w a y s m a y be dissociated, t h e r e f o r e , f r o m t h e visual arousal reaction.
t o r s 1936) a n d i n t h e " e n c ~ p h a l e i s o l ~ " cat ( B r e m e r 1936). H e n c e a f t e r m i d b r a i n t r a n s ection t h e r e s p o n s i v e n e s s of the i s o l a t e d b r a i n to a r o u s a l s t i m u l a t i o n s is s t r o n g l y d e c r e a s ed, so t h a t o n l y t h e most a c t i v e s e n s o r y m o d a l i t i e s a r e still able to p r o d u c e a wides p r e a d d i s o r g a n i z a t i o n of c o r t i c a l r h y t h m s . T h e o l f a c t o r y s y s t e m belongs to the l a t t e r
248
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A - - " I n d u c e d waves" in the olfactory bulb and generalized blockade of cortical spindles following stimulation of the olfactory receptors (room air blown into the nostrils). B - Full recovery to rest synehronisation, 9 sec. after the end of the stimulation. C - - Another ' ' cerveau isol~" preparation. Blocking of both thalamie and cortical spindles during olfactory stimulation. The thalamie potentials were led through concentric electrodes from a recruiting area of the midline nuclei of the thalamus. D - Full recovery of thalamie and cortical synehronisation after 9 see. E--Electrical activation elicited by stimulating a recruiting intrathalamie region (300/see., I msee. pulse duration, 3 V.) in another ' 'cerveau isol6 ~' eat. F--Complete recovery of synehronisation after 9 see. Calibrations: 200 pV. ; 1 see.
category, at least in a macrosmatic animal like the cat. Both intensity and duration of the olf a c t o r y arousal reaction arc less marked in the " c e r v e a u isol~" cat that a f t e r spinal section a t C1. A p p a r e n t l y the pons a n d the medulla facilitate in some w a y the olfactory arousal reactions, although they certainly are not involved in the specific projections paths arising f r o m the olfactory bulb. The most obvious explanation of these findings is that the olfactory and the ascending reticular impulses converge on the cephalic portions of the brain stem activating system, i.e. either on the mesencephalic t e g m e n t u m or on the hypothalamus and the subthalamus. These structures are not between those yielding electric responses to single shocks (Rose a n d Woolsey 1943; Allen 1943; Fox, McKinley and Magoun 1944; K a a d a 1951; Berry, H a g a m e n and H i n s e y 1952) or to a sequence of three shocks (Bonvallet, Dell and Hugelin 1952) applied to the olfactory bulbs. However multisynaptic connections are likely to be overcome only through temporal sequence of m a n y impulses. Electrical recording f r o m olfactory system following prolonged natural stimulations, has been limited so f a r to rhinencephalic structures ( H a s a m a 1934; A d r i a n 1942; Allen 1943~, the electrical stimulation of which is followed sometimes (in the anaesthetized animal) b y generalized activation of the E E G ( K a a d a :1951). I f these responses are mediated through corticofugal projections to the cephalic portion of the ascending reticular system (see Sloan and J a s p e r 1950; K a a d a 1951; Jasper, Ajmone-Marsan and Stoll 1952), the generalized arousal reaction elicited by olf a c t o r y stimuli in the " c e r v e a u isol~" might be more easily understood. SUMMARY 1. The b u r s t activity of the cerebral cortex is blocked in the " c e r v e a u isol~" c a t by olfactory but not b y visual impulses.
OLFACTORY AROUSAL REACTIONS 2. T h e m o s t e f f e c t i v e w a y o f e l i c i t i n g a n olfactory arousal is given by blowing repetitively air into the nostrils. The disorganization of the brain rhythms overlasts, sometimes for many seconds, the end of the sensory stimulation and the disappearance of Adrian's induced waves from the olfactory bulb. An arousal from stimulated trigeminal r e c e p t o r s o f t h e n o s e is p r e v e n t e d b y t h e midbrain transection. 3. T h e o l f a c t o r y a r o u s a l is s h o r t e r a n d less i n t e n s e i n t h e " c e r v e a u i s o l ~ " t h a t a f t e r s p i n a l s e c t i o n a t C~. T h e h y p o t h e s i s is p u t forward that the olfactory and the reticular ascending impulses converge on the cephalic areas of the activating system. REFERENCES ADRIAN, E. D. Olfactory reactions in the brain of the hedgehog. J. Physiol., 1942, 100: 459-473. ADRLCN, E. D. The development of nerve cell rhythms. Arch. Psychiatr. Zeitschr. Neurol., 1949, 183: 197-205. ADRIAN, E. D. The electrical activity of the mammalian olfactory bulb. EEG Clin. Neurophysiol., 1950, 2: 377-388. ALLEN, W. F. Distribution of cortical potentials resulting from insufflation of vapors into the nostrils and from stimulation of the olfactory bulb and the pyriform lobe. Amer. J. Physiol., 1943, 135: 553-555. ARDUINI, A. and MORUZZI, G. Sensory and thalamic synchronization in the olfactory bulb. EEG Clin. Neurophysiol., 1953, 2: 235-242. BERRY, C. M., tIA~A)ZEN, W. D. and HINSEY, J. C. Distribution of potentials following stimulation of olfactory bulb in cat. J. Neurophysiol., 1952, 15: 139-148. BONVALLET, M., DELL, P. et I~IUGELIN, A. Projections olfactives, gustatives, viscerales, vagales, visuelles et auditives au niveau des formations grises du cerveau ant~rieur du chat. J. Physiologic, 1952, 44: 222-224. BaEMER, F. Ccrveau isol~ et physiologic du sommeil. C. R. Soc. Biol., Paris, 1935, 118: 1235-1242. BREMER, F. Nouvelles recherches sur le m~canisme du sommeil. C. R. Soc. Biol., Paris, 1936, lZ2: 460-464. BREMER, F. L'activit~ c~r~brale au cours du sommeil et de la narcose. Contribution ~ l'~tude du m~canisme du sommeil. Bull. Acad. Roy. Mdd., 1937, 4: 68-86. BRE.'~IER, F. L'activit~ ~lectrique de l'~corce c~r~brale e t ] e probl~me physiologique du sommeil. Boll. Soc. it. Biol. sp. 1938, 13: 271-290.
249
BREMER, F. Le probl~me physiologique du sommeil. Medicina, 1951, 1: 586-619. DEMPSEY, E. W. and MORISON, R. S. The production of rhythmically recurrent cortical potentials after localized thalamic stimulation. Amer. J. Physiol., 1941, 135: 293-300. ECTORS, L. Etude de l'activit~ ~lectrique du cortex e~r~bral chez le lapin non narcotis~ ni curarisd. Arch. int. Physiol., 1936, 43: 267-298. FOX, C. A., •C KINLEY, W. A. and MAGOUN, H. W. An oscillographic study of the olfactory system in cats. J. Neurophysiol., 1944, 7: 1-16. GELLHORN, E. Experimental contributions to the duplicity theory of consciousness and perception. Pfliigers Arch., 1952, 255: 75-92. HASAM, B. t~ber die elektrischen Begleiterscheinungen und der Reichsph~ire bei der Geruehsempfindung. Pfliigers Arch., 1934, 234: 748-755. JASPER, H. H. Diffuse projection system: the integrative action of the thalamic reticular system. EEG Clin. Ncurophysiol., 1949, 1: 405-419. JASPER, H., AJMONE-MARSAN, C. and STOLL, J. Corticofugal projections to the brain stem. Arch. Neurol. Psychiat., Chicago, 1952, 67: 155-171. KAADA, B. R. Somato-motor, autonomic and electrocorticographic responses to electrical stimulation of " r h i n e n c e p h a l i c " and other structures in primates, cat and dog. Acta Physiol. Scan&, 1951, 23: (suppl. 83): 1-285. ],INDSLEY, D. B., ]~OV*'DEN,J. W. and MAGOUN, H. W. Effect upon the E E G of acute injury to the brain stem activating system. EEG Clin. Neurophysiol., 1949, 1: 475-481. LINDSLEY, D. ]~., SCHREINER, L. H., KNOWLES, W. B. and MAGOUN, H. W. Behavioral and E E G changes following brain stem lesions in the cat. EEG Clin. Ncurophysiol., 1950, 2: 483-498. 5IAGOUN, H. W. Caudal and cephalic influences of the brain stem reticular formation. Physiol. Rev., 1950, 30: 455-474. MAGOUN, H. W. An ascending reticular activating system in the brain stem. Arch. Ncurol. Psychiat., Chicago, 1952, 67: 145-154. MORISO~, R. S. and DEMPSEY, E. W. A study of thalamocortical relations. Amer. J. Physiol., 1941, 35: 281-292. MORUZZb G. and ]VIAGOUN,H. W. Brain stem reticular formation and activation of the EEG. EEG Clin. Ne~rophysiol., 1949, 1: 455-473. MORUZZI, G. I1 risveglio della corteccia cerebrale. Medicina 1952, 2: 577-596. ROSE, J. E. and WOOLSEY, C. N. Potential changes in the olfactory bulb produced by electrical stimulation of the olfactory bulb. Fed. Proe., 1943, 2 : 42. SLOAN, N. and JASPER, H. Studies of the regulatory functions of the limbic cortex. EEG Clin. Neurophysiol., 1959, 2: 317-327. STARZL, T. E. and MAGOUN, H. W. Organization of the diffuse thalamic projection system. J. Neuropl~ysiol., 1951, 14: 133-146.
250
A. ARDUINI and G. MORUZZI
STARZL, T. E., TAYLOR, C. W. and MAGOUN, H. W. Ascending conduction in reticular activating system, with special reference to the diencephalen. J. Neurophysiol., 1951 a, 14: 461-477.
ST~ZL, T. E., TAYLOR, C. W. and MA6OU~, H. W. Collateral afferent excitation of reticular formation of brain stem. J. Neurophysiol., 1951 b, 14: 479-496.
l~efcrence: ARDUINI, A. and •ORUZZI, (~. Olfactory arousal reactions in the "cerveau isol6" cat. ]EEG Clin. Neurophysiol., 1963, ~: 243-250.
ANNOUNCEMENT
THE
AMERICAN
NEUROLOGICAL
ASSOCIATION
ANNOUNCES
The 78th A n n u a l Atlantic
City,
M e e t i n g to be h e l d a t t h e H o t e l C l a r e n d o n ,
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Jersey,
from
June
15th
to
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Secretary : H . HOUSTON" MERRITT, M.D. Neurological Institute 710 W e s t 168th S t r e e t - N e w Y o r k 32, N.Y.
1953.