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Midline section of the cat brain with sparing of the corpus callosum
Electroencephalography and Clinical Neurophysiology Elsevier Publishing Company, Amsterdam - Printed in The Netherlands
627
MIDLINE SECTION OF THE CAT BRAIN WITH SPARING OF THE CORPUS CALLOSUM K . - A . HOSSMANN
Max-Planck-lnstitut fiir Hirt~l'orschung, Abteilunc fiir Allgemeine Neurologie, K61n-Merhebn (W.-Germany) (Accepted for publication: September 30, 1968)
In recent years there have been published an increasing number of investigations on the interhemispheric transfer of information (Bureg and Buregovfi 1960; Mountcastle 1962; Ettlinger 1965; Bremer 1966; Bure~ov,fi etal. 19661. The corpus callosum plays in this process a significant role and this can be indirectly concluded from the functional defect after it has been sectioned (split-brain preparation) (Myers 1959; Sperry 1964; Gazzaniga et al. 1965; Gazzaniga 1967). Direct evidence of the activity conducted over the corpus callosum, and only over the corpus callosum, from one hemisphere to the other has, however, not yet been sought. Therefore, it appears to be desirable to develop an operative method by means of which all anatomical connections between the hemispheres can be severed with the exception of the corpus callosum ("corpus callosum preparation"). Such a method is described for the cat brain.
anatomical connection remains between the two hemispheres of the brain (Fig. 1).
METHOD Under ether narcosis the cerebellar vermis is first deflected and then the brain-stem rostral to the sensory trigeminal nucleus is transversely sectioned. When bilateral miosis develops the narcosis is interrupted. After fixation of the animal's head in a stereotactic frame, an 8 mm wide spatula is attached to an electrode holder permitting controlled movements in the anteroposterior, horizontal, and vertical planes. The spatula is adjusted in the midline and slowly introduced horizontally from behind the tentorium in the Horsley-Clarke plane H + 5 up to frontal 20. A section is obtained which lies in the horizontal plane and reaches 4 mm from the midline on both sides. The spatula is withdrawn and turned through 90", so that it comes to lie in the sagittal L 0 plane. After adjustment of its upper edge at the height H 5, it is again slowly advanced horizontally up to frontal 20, then lowered until its lower edge touches the base of the cranium and, with further lowering, withdrawn. The horizontal cut dissects the area septalis, including the columnae fornices. The vertical cut, reaching dorsally up to the horizontal cut and caudally down to the midbrain section, separates the anterior and posterior commisures, the massa intermedia and the crossing fibres of the mesencephalon. Thus, apart from the corpus callosum and the psalterium, virtually no
Fig. 1 Coronal sections of the cat brain at diencephalic and mesencephalic levels after stereotactic splitting of the midline with sparing of the corpus callosum. In general there is no severe haemorrhage. Nissl staining, × 3.5.
Electroenceph. clin. Neurophysiol. 1969, 26:627-629
628
K.-A. HOSSMANN
Although in carrying out this operation it is rare to get extensive haemorrhage, there frequently develops directly after the midline section a severe brain oedema, fiom which, in the first experiments, more than half the animals died or were useless for further investigation. The nrortality in new experiments was considerably lowered when, instead of blunt sectioning, electro-coagulation was used. The spatula was for this purpose insulated except for its tip and connected to a radio frequency lesion maker. We found it advantageous during the operation to infuse 100 ml of a 10°,/, dextrose solution. RESULTS Following thc pre-trigeminal section of the brainstem a typical sleep EEG is obtained. Stimulation of the fcrmatio reticularis mesencephali in the region of the Horsley-Clarke coordinates A 5/L 4/H 1 with square wave pulses of 0.2 mA, 0.3 msec duration and a frequency of 300/sec produces a bilateral arousal effect. After section in the midline with sparing of the corpus callosum, mesencephalic stimulation with the same current strength produces an arousal effect only in the ipsilateral hemisphere (Fig. 2)° Only with very high current strengths (about 1-2 mA) can the arousal effect spread over to the contralateral hemisphere, particularly to the frontal part. Before the midline section sleep spindles and slow waves at homologous points of the two hemispheres to a great extent synchronize. In the "corpus callosum cat" synchronization of the slow waves often remains;
the sleep spindles, however, at least in the acute experintents, are lost. The operation described here, which up to now has been successful in fifty-four cats, permits the direct investigation of the activity conducted across the corpus catlosum (Hossmann, in pressL The possibility of placing one or the other hemisphere alternately in sleep or the waking state makes a comparison possible of the transcallosal projection undcr different states of alertness. SUMMARY A method is described by means of which the midline of the cat brain can be split without severing the corpus callosum ("corpus callosum cat"). This procedure provides a preparation for the study of interhemispheric volleys, in which the only anatomical connection between the two hemispheres remains the corpus callosum. ZUSAMMENFASSUNG OPERATIVE MITTELLINIENDURCHTRENNUNG DES KATZENHIRNES UNTER AUSSPARUNG DES CORPUS CAI,kOSUM Es wird eine Operationsmethode beschrieben, mit Hilfe derer die Mittellinie des Katzenhirnes unter Aussparung des Balkens durchtrennt werden kann ("Corpus callosum-Katze"). Dieses Verfahren ermBglicht das Studium interhemispharischer Aktivit~iten an einem Pr~iparat, bei dem der Balken die einzige anatomische Verbindung:zwischen beiden 1-Iemisph~iren ist.
som.L SS.ant. aud..
.~
vis. som.r.
,
I~
SS.ant. aud. N;
'
lsec
Fig. 2 Lateralized arousal effect in electrocorticogram of the "corpus callosum cat" after electrical stimulation of the right forn'tatio reticularis mesencephali with 0.2 mA square wave pulses of 0.3 msec duration and frequency of 300/sec (duration of stimulation indicated by a dash). Monopolar, reference in frontal bone. Horizontal bar: 1 sec, vertical bar: 100 izV. sore: somato-motor cortex; SS. ant. : gyrus suprasylvius anterior; aud. : auditory cortex; vis. : visual cortex; I : left; r : right. Time constant: 0.3 sec; H.F. filter: 70 c/sec.
Electroenceph. c/in. NL,urophysiol., 1969, 26:627-629
CORPUS CALLOSUM CAT 1 am indebted to Professor Buser, Paris, for stimulating me to carry out this work. REFERENCES BREMER, F. l~tude 61ectrophysiologique d'un transfert interh6mispherique callosal. Arch. ital. Biol., 1966, 104: 1-29. BUREt, J. and BURE~OVA,O. The use of Le~,o's spreading cortical depression in research on conditioned reflexes. Electroenceph. clin. Neurophysiol., 1960, Suppl. 13: 359-376. BURE~OVA, O., BUREt, J. and LUKASZEWSKA, J. Stain differences in ietrieval of unilateral and bilateral engrams. Physiol. Behav., 1966, 1: 331-333. ETTLINGER, G. E. (Ed.). Functions of the corpus callosum. Little, Brown, Boston, 1965, 156 p.
629
GAZZANIGA,M. S. The split brain in man. Sci. Amer., 1967, 217: 24-29. GAZZANIGA, M. S., BOGEN, J. E. and SPERRY, R. W. Observations on visual perception after disconnexion of the cerebral hemispheres in man. Brain, 1965, 88: 221-236. HOSSMANN, K.-A. Untersuchungen fiber transcallosale Potentiale an der akuten Corpus callosum-Katze. Dtsch. Z. Nervenheilk. in press. MOUNTCAS+LE,V. B. (Ed.). Interhemispheric relations and cerebral dominance. Johns Hopkins Press, Baltimore, 1962, 294 p. MYERS, R. E. Localization of function in the corpus callosum. Arch. Neurol. (Chic.), 1959, !: 74-77. SPERRY, R. W. The great cerebral commissu re. Sci. A mer., 1964, 211: 2-12.
Reference: HOSSMANN,K.-A. Midline section of the cat brain with sparing of the corpus callosum. Electroenceph clin. Neurophysiol, 1969, 26: 627-629.
ANNOUNCEMENT
International Primatologieal Society Third International Congress of Primatology Z u r i c h , A u g u s t 2 - 5 , 1970
Der n~chste Kongress der IPS wird vom 2.-5.8.1970 in Zfirich durchgefiihrt. Die Organisation dieses Kongresses wurde dem Anthropologischen lnstitut der Universit~it Zfirich, Kfinstlergasse 15, 8001 Zfirich (Schweiz) fibertragen. Alle Auskfinfte erteilt das Kongress-Sekretariat des Institutes. The next congress of the IPS will be held in Zurich, August 2-5, 1970. The Anthropological Institute of the University of Zurich has been appointed the organizer of this congress. Please address all inquiries to the secretary's office at the Anthropological Institute, Kfinstlergasse 15, CH-8001 Zurich. Le prochain congr6s de I'IPS aura lieu du 2 au 5 aofit 1970/~ Zurich. L'Institut Anthropologique de l'Universit6 de Zurich a 6t6 charg6 de l'organisation de ce congr6s. Pour tous renseignements veuillez vous adresser au secr6tariat du Congr~s, l'lnstitut Anthropologique, Kiinstlergasse 15, CH-8001 Zurich.
Electroenceph. clin. Neurophysiol., 1969, 26:629
627
MIDLINE SECTION OF THE CAT BRAIN WITH SPARING OF THE CORPUS CALLOSUM K . - A . HOSSMANN
Max-Planck-lnstitut fiir Hirt~l'orschung, Abteilunc fiir Allgemeine Neurologie, K61n-Merhebn (W.-Germany) (Accepted for publication: September 30, 1968)
In recent years there have been published an increasing number of investigations on the interhemispheric transfer of information (Bureg and Buregovfi 1960; Mountcastle 1962; Ettlinger 1965; Bremer 1966; Bure~ov,fi etal. 19661. The corpus callosum plays in this process a significant role and this can be indirectly concluded from the functional defect after it has been sectioned (split-brain preparation) (Myers 1959; Sperry 1964; Gazzaniga et al. 1965; Gazzaniga 1967). Direct evidence of the activity conducted over the corpus callosum, and only over the corpus callosum, from one hemisphere to the other has, however, not yet been sought. Therefore, it appears to be desirable to develop an operative method by means of which all anatomical connections between the hemispheres can be severed with the exception of the corpus callosum ("corpus callosum preparation"). Such a method is described for the cat brain.
anatomical connection remains between the two hemispheres of the brain (Fig. 1).
METHOD Under ether narcosis the cerebellar vermis is first deflected and then the brain-stem rostral to the sensory trigeminal nucleus is transversely sectioned. When bilateral miosis develops the narcosis is interrupted. After fixation of the animal's head in a stereotactic frame, an 8 mm wide spatula is attached to an electrode holder permitting controlled movements in the anteroposterior, horizontal, and vertical planes. The spatula is adjusted in the midline and slowly introduced horizontally from behind the tentorium in the Horsley-Clarke plane H + 5 up to frontal 20. A section is obtained which lies in the horizontal plane and reaches 4 mm from the midline on both sides. The spatula is withdrawn and turned through 90", so that it comes to lie in the sagittal L 0 plane. After adjustment of its upper edge at the height H 5, it is again slowly advanced horizontally up to frontal 20, then lowered until its lower edge touches the base of the cranium and, with further lowering, withdrawn. The horizontal cut dissects the area septalis, including the columnae fornices. The vertical cut, reaching dorsally up to the horizontal cut and caudally down to the midbrain section, separates the anterior and posterior commisures, the massa intermedia and the crossing fibres of the mesencephalon. Thus, apart from the corpus callosum and the psalterium, virtually no
Fig. 1 Coronal sections of the cat brain at diencephalic and mesencephalic levels after stereotactic splitting of the midline with sparing of the corpus callosum. In general there is no severe haemorrhage. Nissl staining, × 3.5.
Electroenceph. clin. Neurophysiol. 1969, 26:627-629
628
K.-A. HOSSMANN
Although in carrying out this operation it is rare to get extensive haemorrhage, there frequently develops directly after the midline section a severe brain oedema, fiom which, in the first experiments, more than half the animals died or were useless for further investigation. The nrortality in new experiments was considerably lowered when, instead of blunt sectioning, electro-coagulation was used. The spatula was for this purpose insulated except for its tip and connected to a radio frequency lesion maker. We found it advantageous during the operation to infuse 100 ml of a 10°,/, dextrose solution. RESULTS Following thc pre-trigeminal section of the brainstem a typical sleep EEG is obtained. Stimulation of the fcrmatio reticularis mesencephali in the region of the Horsley-Clarke coordinates A 5/L 4/H 1 with square wave pulses of 0.2 mA, 0.3 msec duration and a frequency of 300/sec produces a bilateral arousal effect. After section in the midline with sparing of the corpus callosum, mesencephalic stimulation with the same current strength produces an arousal effect only in the ipsilateral hemisphere (Fig. 2)° Only with very high current strengths (about 1-2 mA) can the arousal effect spread over to the contralateral hemisphere, particularly to the frontal part. Before the midline section sleep spindles and slow waves at homologous points of the two hemispheres to a great extent synchronize. In the "corpus callosum cat" synchronization of the slow waves often remains;
the sleep spindles, however, at least in the acute experintents, are lost. The operation described here, which up to now has been successful in fifty-four cats, permits the direct investigation of the activity conducted across the corpus catlosum (Hossmann, in pressL The possibility of placing one or the other hemisphere alternately in sleep or the waking state makes a comparison possible of the transcallosal projection undcr different states of alertness. SUMMARY A method is described by means of which the midline of the cat brain can be split without severing the corpus callosum ("corpus callosum cat"). This procedure provides a preparation for the study of interhemispheric volleys, in which the only anatomical connection between the two hemispheres remains the corpus callosum. ZUSAMMENFASSUNG OPERATIVE MITTELLINIENDURCHTRENNUNG DES KATZENHIRNES UNTER AUSSPARUNG DES CORPUS CAI,kOSUM Es wird eine Operationsmethode beschrieben, mit Hilfe derer die Mittellinie des Katzenhirnes unter Aussparung des Balkens durchtrennt werden kann ("Corpus callosum-Katze"). Dieses Verfahren ermBglicht das Studium interhemispharischer Aktivit~iten an einem Pr~iparat, bei dem der Balken die einzige anatomische Verbindung:zwischen beiden 1-Iemisph~iren ist.
som.L SS.ant. aud..
.~
vis. som.r.
,
I~
SS.ant. aud. N;
'
lsec
Fig. 2 Lateralized arousal effect in electrocorticogram of the "corpus callosum cat" after electrical stimulation of the right forn'tatio reticularis mesencephali with 0.2 mA square wave pulses of 0.3 msec duration and frequency of 300/sec (duration of stimulation indicated by a dash). Monopolar, reference in frontal bone. Horizontal bar: 1 sec, vertical bar: 100 izV. sore: somato-motor cortex; SS. ant. : gyrus suprasylvius anterior; aud. : auditory cortex; vis. : visual cortex; I : left; r : right. Time constant: 0.3 sec; H.F. filter: 70 c/sec.
Electroenceph. c/in. NL,urophysiol., 1969, 26:627-629
CORPUS CALLOSUM CAT 1 am indebted to Professor Buser, Paris, for stimulating me to carry out this work. REFERENCES BREMER, F. l~tude 61ectrophysiologique d'un transfert interh6mispherique callosal. Arch. ital. Biol., 1966, 104: 1-29. BUREt, J. and BURE~OVA,O. The use of Le~,o's spreading cortical depression in research on conditioned reflexes. Electroenceph. clin. Neurophysiol., 1960, Suppl. 13: 359-376. BURE~OVA, O., BUREt, J. and LUKASZEWSKA, J. Stain differences in ietrieval of unilateral and bilateral engrams. Physiol. Behav., 1966, 1: 331-333. ETTLINGER, G. E. (Ed.). Functions of the corpus callosum. Little, Brown, Boston, 1965, 156 p.
629
GAZZANIGA,M. S. The split brain in man. Sci. Amer., 1967, 217: 24-29. GAZZANIGA, M. S., BOGEN, J. E. and SPERRY, R. W. Observations on visual perception after disconnexion of the cerebral hemispheres in man. Brain, 1965, 88: 221-236. HOSSMANN, K.-A. Untersuchungen fiber transcallosale Potentiale an der akuten Corpus callosum-Katze. Dtsch. Z. Nervenheilk. in press. MOUNTCAS+LE,V. B. (Ed.). Interhemispheric relations and cerebral dominance. Johns Hopkins Press, Baltimore, 1962, 294 p. MYERS, R. E. Localization of function in the corpus callosum. Arch. Neurol. (Chic.), 1959, !: 74-77. SPERRY, R. W. The great cerebral commissu re. Sci. A mer., 1964, 211: 2-12.
Reference: HOSSMANN,K.-A. Midline section of the cat brain with sparing of the corpus callosum. Electroenceph clin. Neurophysiol, 1969, 26: 627-629.
ANNOUNCEMENT
International Primatologieal Society Third International Congress of Primatology Z u r i c h , A u g u s t 2 - 5 , 1970
Der n~chste Kongress der IPS wird vom 2.-5.8.1970 in Zfirich durchgefiihrt. Die Organisation dieses Kongresses wurde dem Anthropologischen lnstitut der Universit~it Zfirich, Kfinstlergasse 15, 8001 Zfirich (Schweiz) fibertragen. Alle Auskfinfte erteilt das Kongress-Sekretariat des Institutes. The next congress of the IPS will be held in Zurich, August 2-5, 1970. The Anthropological Institute of the University of Zurich has been appointed the organizer of this congress. Please address all inquiries to the secretary's office at the Anthropological Institute, Kfinstlergasse 15, CH-8001 Zurich. Le prochain congr6s de I'IPS aura lieu du 2 au 5 aofit 1970/~ Zurich. L'Institut Anthropologique de l'Universit6 de Zurich a 6t6 charg6 de l'organisation de ce congr6s. Pour tous renseignements veuillez vous adresser au secr6tariat du Congr~s, l'lnstitut Anthropologique, Kiinstlergasse 15, CH-8001 Zurich.
Electroenceph. clin. Neurophysiol., 1969, 26:629