Proc. 6th Symp. Int. Soc. Res. Stereoencephalotomy, Tokyo 1973, part II Confinia neurol. 37: 120-127 (1975)
Efferent Connections of the Centromedian Nucleus and the Magnocellular Part of the Medial Geniculate Body in Cats R. K uroda, H. M urui, K. A kagi, K. K amikawa and H. M ogami Department of Neurosurgery, Osaka University Medical School, Osaka
Introduction With the development of the stereotaxic thalamotomy, it has been clarified that the therapeutic destruction of the centromedian nucleus (CM) and the parafascicular nucleus (Pf) are effective for the alleviation of the intractable pain. M ehler [9] pointed out that the posterior nuclei group (PO) of the thalamus, including the magnocellular part of the medi al geniculate body (MGmc) is a relay of protopathic diffuse pain in the thalamus, and attached the importance to those rather than the CM and the intralaminar nuclei. Previously, we have reported that a certain amount of the secondary trigeminal fibers arising from the nucleus caudalis of the spinal trigeminal nucleus terminated in the ventrobasal and the intralaminar nuclei of the thalamus in cat [10]. Stewart and K ing [18] have also described the termination of those fibers in MGmc. Be sides the secondary trigeminal tract, the spinothalamic tract, the medial lemniscal afferent and some of the other afferent fibers have been report ed to terminate in MGmc. However, the evidence that the spinothalamic tract and secondary trigeminal tract terminated in the CM was not ob tained in our experiments. The degenerating axons seen in the CM were only passing fibers. This fact has been recognized by N auta and K uypers [12] and M ehler et al. [7, 8], The purpose of our report is to clarify the efferent connections from CM and MGmc in cats anatomically.
Materials and Methods
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Under Nembutal anesthesia and with aseptic precautions, small electrolytic le sions were placed stereotaxically on the thalamus and MG in cats. In all animals the
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K uroda/M urui /A kagi/K amikawa/M ogami
121
electrodes were introduced vertically through the ipsilatcral hemisphere according to the coordinates of Snider and N iemer’s atlas [17J. After survival periods of 7-10 days, the animals were perfused with saline and then lOVo formalin solution under deep anesthesia. The brains were removed and fixed in formalin for a few months. Serial coronal sections of 35 iim in thickness were cut on a freezing microtome and every third of fifth section was stained by Nauta-Gygax method. The lesions were ascertained by Nissl slain preparations.
Results
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1. MG me Lesions and their Efferent Connections In three cats (C21, 22, 23) lesions were placed on the MGmc. As con trol studies, the lesion on the parvocellular part (MGp) was made in a cat (C24), and only a needle track was made in another (C25). Figure 1 shows the distribution of the degenerating axons from the le sion in cat C23. The degenerating fibers from the lesion (at B) projected dorsomedially or medially and cranially. In the case with the lesion placed out of MGmc, the degenerating fine particles were not observed in the posterior nucleus, while preterminal degenerations were observed in the posterior lateral nucleus and the suprageniculate nucleus. As to the in terthalamic connections, the MGmc most probably projects fibers to the nucleus posterior of Snider-Niemer’s atlas which appears to correspond to the nucleus limitans or its caudal extension of R ioch [15], and others [4, 5]. The suprageniculate nucleus also would probably receive the afferent fibers from the MGmc. As to the cortical projections from the MGmc, the anterior ectosylvian gyrus was noteworthy. In three cases (C21, 22, 23) with an MGmc lesion the degenerating fibers were abundant in the dorsal part of the anterior ectosylvian gyrus. A case C24 with lesion in MGp showed a few degener ating axons in the anterior part of the anterior ectosylvian gyrus in addi tion to the projection to the dorsal part of it (A II). The degenerating axons in the anterior part of the anterior ectosylvian gyrus were thought to originate from the unintentional lesion in the ventrobasal nucleus. In consequence of analysis of the cases the corticopetal fibers from the MGmc terminated in the anterior ectosylvian gyrus. Most of the relevant fibers terminated in the dorsal part of the anterior ectosylvian gyrus which corresponded to the dorsal part of the second somatosensory area (S II), or the transitional area to the second acoustic area (A II), while the anterior and middle part of the S II received a small amount of them.
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Downloaded by: Vanderbilt University Library 129.59.95.115 - 10/29/2017 3:57:01 AM
Fig. 1. Diagrams of representative levels of the subcortical structure to show the distributions of degenerating axons (dot) from the lesion (solid black) of the MGmc in cat C23.
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2. CM Lesions and their Efferent Connections In four cats (Cl, 2, 5, 6) the lesions were placed in the CM selectively, and in three cats other thalamic lesions of the CM were made as control. Figure 2 shows the distribution of the degenerating axons from the le sion in cat C5. A small number of fibers passed through the massa inter media and terminated in the contralateral CM, Pf, the central lateral nu cleus (CL), the paracentral nucleus (Pc) and the ventral posteromedial nucleus (VPM). In addition, some of them terminated in the midline nu cleus on the way to the contralateral side. In the homolateral side, many fibers terminated in the intralaminar nuclei, CL, Pc, and Pf. The CM had probably close fiber connections with every ventral nuclei. Some of the efferent fibers terminated in the ventromedial part of the reticular nucle us. The CM projected fibers to the head of the caudate nucleus and the rostral putamen. As to the cortical termination, the CM projected some of the corticopetal fibers to the anterior ectosylvian gyrus, the anterior and poterior sig moid gyrus, the coronal gyrus and probably the anterior sylvian gyrus. However, these corticopetal fibers were only sustaining collateral and not the essential one. Discussion
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Various efferent connections to the MGmc have been proved anatomi cally and also supported by electrophysiological studies [13, 21, 22]. As to the efferent connections from the MGmc, many studies were reported, however, there were some controversies among them. It was because those conclusions were drawn from the various findings of retrograde de generations in the MGmc following cortical excision. Recently, the corti cal projection of the degenerating fibers arising from MGmc lesions have been investigated by NAUTA-Gygax stain. Mehler [9] has insisted on the efferent projections from the MGmc to the anterior ectosylvian gyrus. As to the corticothalamic projection from S II, R invic [14], deV ito [3] and K usama and K awana [6] have agreed with the fiber connection between the S II and the MGmc. In our experiments, the efferent fibers from the MGmc to the anterior ectosylvian gyrus were analyzed and compared to control experiments. As to the thalamic connections from the MGmc, it was difficult to draw a conclusion because the needle insersion caused the degenerating axons
124
K uroda / M u ru i /A kagi /K a m ik a w a /M ogami
(284)
Downloaded by: Vanderbilt University Library 129.59.95.115 - 10/29/2017 3:57:01 AM
Fig. 2. Diagrams of representative levels to show the distributions of degenerat ing axons (dot) from the lesion (solid black) of the CM in cat C5.
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which projected to the cortex. At the level of the meso-diencephalic junc tion, many degenerating fibers and preterminals were observed in the pulvinar, the pretectal nucleus, the posterior lateral nucleus, the suprageniculate nucleus and the posterior nucleus. The terminations in the pulvinar and the pretectal area are not yet clarified, because unintentional small lesions were made in the pulvinar in addition to the needle tracks in the optic tract. In our cats with lesions in the MGmc and its adjacent area, a certain number of terminations were found in the posterior nuclei complex, in cluding the suprageniculate nucleus. M orest [11] has also ascertained the efferent connections from the MGmc to the suprageniculate nucleus by Golgi stain. Therefore, the MGmc seemed to connect to the posterior nu cleus of the Snider and N iemer atlas and the suprageniculate nucleus. The CM is one of the most effective target points for the alleviation of pain. However, there are no direct afferent connections in the CM from the spinothalamic tract and the secondary trigeminal tract. The intrathalamic fiber connections and the cortical projections of the CM efferents have long been discussed. The degenerating fibers originated from the CM were distributed diffusely in almost every thalamic nuclei. Different findings were reported as to the small number of commissur al fibers through the massa intermedia and the termination in the ventro medial part of the reticular nucleus. C lark and B oggon [2] and W ells [20] noticed these commissural fibers via the massa intermedia in their study of the MD lesion, but their origin remained unknown. According to the Golgi study by Scheibel and Scheibel [16], the CM-Pf complex with a richly branching system projected to virtually every thalamic field. These axons spread to the neuropil field of most midline nuclei, medial nuclei of both sides and to the portions of the ventral lateral nucleus (VL), the ventral anterior nucleus (VA), the dorsomedial nucleus (MD) and reticular nucleus. Terminal degenerations were observed in the hom olateral MD, CM, Pf, Pc, CL, VPM, VL and VA. These terminal degen erations were supposed to be attributed to the CM lesion, but we could not deduce definite conclusion from our materials. Concerning the cortical projection of the CM, recently B owsher [[1] and T otibadze and M oniava [19] reported that the CM projected to the motorsensory cortex. But these reports also have some limitations owing to the inevitable lesions, such as the needle track. Therefore, these reports have involved some controversies. To clarify the cortical projection from the CM, various approaches to the CM should be attempted.
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References
Downloaded by: Vanderbilt University Library 129.59.95.115 - 10/29/2017 3:57:01 AM
1 Bowsher , D.: Some afferent and efferent connections of the parafascicular-center median complex; in P urpura The thalamus, pp. 99-108 (Columbia University Press, New York 1966). 2 C lark, W. E. L. and Boggon , R. H.: On the connections of the medial cell groups of the thalamus. Brain 56: 83-98 (1933). 3 DeVito, J. L.: Thalamic projection of the anterior ectosylvian gyrus (somatic area II) in the cat. J. comp. Neurol. 131: 462-475 (1969). 4 H irokawa, S.: Uber die Thalamuskerne der Katze. J. med. Sei. 9: 119-147 (1941). 5 J asper, H. H. and A jmone -M arsan, C.: A stereotaxic atals of the diencephalon of the cat (National Research Council of Canada, Ottawa 1960). 6 K usama, T. and K awana, E.: Projections of motor and somatic sensory cortices to subcortical nuclei, especial to thalamus. Recent Adv. neurol. Sei. 12: 325-340 (1968). 7 M ehler , W. A.; F eferman , M. E., and N auta, W. J. H.: Ascending axon degen eration following anterolateral cordotomy. An experimental study in the mon key. Brain 83: 718-750 (1960). 8 M ehler , W. A.: Further notes on the center median nucleus of Luys; in P ur pura The thalamus, pp. 109-127 (Columbia University Press, New York 1966). 9 M ehler , W. A.: Some observations on secondary ascending afferent systems in the central nervous system. Pain, Int. Symp. on Pain, pp. 11-32 (Little, Brown, Boston 1966). 10 M ogami, H.; K uroda, R.; H ayakawa, T.; Kanai, N., and Yamada, R.: Ascending pathways from nucleus caudalis of spinal trigeminal nucleus in cat. With special references to pain conducting pathways. Med. J. Osaka Univ. 19: 49-70 (1968). 11 M orest, D. K.: The neuronal architecture of the medial geniculate body of the cat. J. Anat., Lond. 98: 611-630 (1964). 12 N auta, W. J. H. and K uypers, H. G. H.: Some ascending pathways in the brain reticular formation. Reticular formation of the brain, pp. 1-20 (Little, Brown, Boston 1958). 13 P oggio , G. F. and M ountcastle, V. B.: A study of the functional contributions of the lemniscal and spinothalamic systems to somatic sensibilities. Central nerv ous mechanisms in pain. Johns Hopk. Hosp. Bull. 106: 266-316 (1960). 14 R invik , E.: The corticothalamic projection from the second somatosensory corti cal area in the cat. An experimental study with silver impregnation methods. Brain Res. 5: 153-172 (1968). 15 Rioch, D. M.: Studies on the diencephalon of carnivora. J. comp. Neurol. 49: 1-119 (1929). 16 Scheibel , M. E. and Scheibel , A. B.: Patterns of organization in specific and nonspecific thalamic fields; in P urpura The thalamus, pp. 13—46 (Columbia Uni versity Press, New York 1966). 17 Snider , R. S. and N iemer , W. T.: A stereotaxic atlas of cat brain (University of Chicago Press, Chicago 1961).
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18 Stewart , W. A. and K ing , R. B.: Fiber projections from the nucleus caudalis of the spinal trigeminal nucleus. J. comp. Neurol. 121: 271-286 (1963). 19 T otibadze, N. K. and M oniava, E. S.: On the direct cortical connections of the nucleus centrum medianum thalamic. J. comp. Neurol. 137: 347-360 (1960). 20 W ells , J.: The pathway from the dorsomedial thalamus to the frontal lobe. Exp. N eurol. 14: 338-351 (1966). 21 W hitlock , D. G. and Perl, E. R.: Afferent projections through ventrolateral
funiculi to thalamus of cat. J. Neurophysiol. 22: 133-148 (1959). 22 W hitlock , D. G. and P erl, E. R.: Thalamic projections of spinothalamic path ways in monkey. Exp. Neurol. 3: 240-255 (1961).
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Request reprints from: Dr. R. K uroda, Department of Neurosurgery, Osaka Uni versity Medical School, Osaka (Japan)
Efferent Connections of the Centromedian Nucleus and the Magnocellular Part of the Medial Geniculate Body in Cats R. K uroda, H. M urui, K. A kagi, K. K amikawa and H. M ogami Department of Neurosurgery, Osaka University Medical School, Osaka
Introduction With the development of the stereotaxic thalamotomy, it has been clarified that the therapeutic destruction of the centromedian nucleus (CM) and the parafascicular nucleus (Pf) are effective for the alleviation of the intractable pain. M ehler [9] pointed out that the posterior nuclei group (PO) of the thalamus, including the magnocellular part of the medi al geniculate body (MGmc) is a relay of protopathic diffuse pain in the thalamus, and attached the importance to those rather than the CM and the intralaminar nuclei. Previously, we have reported that a certain amount of the secondary trigeminal fibers arising from the nucleus caudalis of the spinal trigeminal nucleus terminated in the ventrobasal and the intralaminar nuclei of the thalamus in cat [10]. Stewart and K ing [18] have also described the termination of those fibers in MGmc. Be sides the secondary trigeminal tract, the spinothalamic tract, the medial lemniscal afferent and some of the other afferent fibers have been report ed to terminate in MGmc. However, the evidence that the spinothalamic tract and secondary trigeminal tract terminated in the CM was not ob tained in our experiments. The degenerating axons seen in the CM were only passing fibers. This fact has been recognized by N auta and K uypers [12] and M ehler et al. [7, 8], The purpose of our report is to clarify the efferent connections from CM and MGmc in cats anatomically.
Materials and Methods
Downloaded by: Vanderbilt University Library 129.59.95.115 - 10/29/2017 3:57:01 AM
Under Nembutal anesthesia and with aseptic precautions, small electrolytic le sions were placed stereotaxically on the thalamus and MG in cats. In all animals the
(281)
K uroda/M urui /A kagi/K amikawa/M ogami
121
electrodes were introduced vertically through the ipsilatcral hemisphere according to the coordinates of Snider and N iemer’s atlas [17J. After survival periods of 7-10 days, the animals were perfused with saline and then lOVo formalin solution under deep anesthesia. The brains were removed and fixed in formalin for a few months. Serial coronal sections of 35 iim in thickness were cut on a freezing microtome and every third of fifth section was stained by Nauta-Gygax method. The lesions were ascertained by Nissl slain preparations.
Results
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1. MG me Lesions and their Efferent Connections In three cats (C21, 22, 23) lesions were placed on the MGmc. As con trol studies, the lesion on the parvocellular part (MGp) was made in a cat (C24), and only a needle track was made in another (C25). Figure 1 shows the distribution of the degenerating axons from the le sion in cat C23. The degenerating fibers from the lesion (at B) projected dorsomedially or medially and cranially. In the case with the lesion placed out of MGmc, the degenerating fine particles were not observed in the posterior nucleus, while preterminal degenerations were observed in the posterior lateral nucleus and the suprageniculate nucleus. As to the in terthalamic connections, the MGmc most probably projects fibers to the nucleus posterior of Snider-Niemer’s atlas which appears to correspond to the nucleus limitans or its caudal extension of R ioch [15], and others [4, 5]. The suprageniculate nucleus also would probably receive the afferent fibers from the MGmc. As to the cortical projections from the MGmc, the anterior ectosylvian gyrus was noteworthy. In three cases (C21, 22, 23) with an MGmc lesion the degenerating fibers were abundant in the dorsal part of the anterior ectosylvian gyrus. A case C24 with lesion in MGp showed a few degener ating axons in the anterior part of the anterior ectosylvian gyrus in addi tion to the projection to the dorsal part of it (A II). The degenerating axons in the anterior part of the anterior ectosylvian gyrus were thought to originate from the unintentional lesion in the ventrobasal nucleus. In consequence of analysis of the cases the corticopetal fibers from the MGmc terminated in the anterior ectosylvian gyrus. Most of the relevant fibers terminated in the dorsal part of the anterior ectosylvian gyrus which corresponded to the dorsal part of the second somatosensory area (S II), or the transitional area to the second acoustic area (A II), while the anterior and middle part of the S II received a small amount of them.
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K uroda/M urui /A kagi/K amikawa/M ogami
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Downloaded by: Vanderbilt University Library 129.59.95.115 - 10/29/2017 3:57:01 AM
Fig. 1. Diagrams of representative levels of the subcortical structure to show the distributions of degenerating axons (dot) from the lesion (solid black) of the MGmc in cat C23.
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2. CM Lesions and their Efferent Connections In four cats (Cl, 2, 5, 6) the lesions were placed in the CM selectively, and in three cats other thalamic lesions of the CM were made as control. Figure 2 shows the distribution of the degenerating axons from the le sion in cat C5. A small number of fibers passed through the massa inter media and terminated in the contralateral CM, Pf, the central lateral nu cleus (CL), the paracentral nucleus (Pc) and the ventral posteromedial nucleus (VPM). In addition, some of them terminated in the midline nu cleus on the way to the contralateral side. In the homolateral side, many fibers terminated in the intralaminar nuclei, CL, Pc, and Pf. The CM had probably close fiber connections with every ventral nuclei. Some of the efferent fibers terminated in the ventromedial part of the reticular nucle us. The CM projected fibers to the head of the caudate nucleus and the rostral putamen. As to the cortical termination, the CM projected some of the corticopetal fibers to the anterior ectosylvian gyrus, the anterior and poterior sig moid gyrus, the coronal gyrus and probably the anterior sylvian gyrus. However, these corticopetal fibers were only sustaining collateral and not the essential one. Discussion
Downloaded by: Vanderbilt University Library 129.59.95.115 - 10/29/2017 3:57:01 AM
Various efferent connections to the MGmc have been proved anatomi cally and also supported by electrophysiological studies [13, 21, 22]. As to the efferent connections from the MGmc, many studies were reported, however, there were some controversies among them. It was because those conclusions were drawn from the various findings of retrograde de generations in the MGmc following cortical excision. Recently, the corti cal projection of the degenerating fibers arising from MGmc lesions have been investigated by NAUTA-Gygax stain. Mehler [9] has insisted on the efferent projections from the MGmc to the anterior ectosylvian gyrus. As to the corticothalamic projection from S II, R invic [14], deV ito [3] and K usama and K awana [6] have agreed with the fiber connection between the S II and the MGmc. In our experiments, the efferent fibers from the MGmc to the anterior ectosylvian gyrus were analyzed and compared to control experiments. As to the thalamic connections from the MGmc, it was difficult to draw a conclusion because the needle insersion caused the degenerating axons
124
K uroda / M u ru i /A kagi /K a m ik a w a /M ogami
(284)
Downloaded by: Vanderbilt University Library 129.59.95.115 - 10/29/2017 3:57:01 AM
Fig. 2. Diagrams of representative levels to show the distributions of degenerat ing axons (dot) from the lesion (solid black) of the CM in cat C5.
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Connections of the Centromcdian Nucleus and Medial Geniculate
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which projected to the cortex. At the level of the meso-diencephalic junc tion, many degenerating fibers and preterminals were observed in the pulvinar, the pretectal nucleus, the posterior lateral nucleus, the suprageniculate nucleus and the posterior nucleus. The terminations in the pulvinar and the pretectal area are not yet clarified, because unintentional small lesions were made in the pulvinar in addition to the needle tracks in the optic tract. In our cats with lesions in the MGmc and its adjacent area, a certain number of terminations were found in the posterior nuclei complex, in cluding the suprageniculate nucleus. M orest [11] has also ascertained the efferent connections from the MGmc to the suprageniculate nucleus by Golgi stain. Therefore, the MGmc seemed to connect to the posterior nu cleus of the Snider and N iemer atlas and the suprageniculate nucleus. The CM is one of the most effective target points for the alleviation of pain. However, there are no direct afferent connections in the CM from the spinothalamic tract and the secondary trigeminal tract. The intrathalamic fiber connections and the cortical projections of the CM efferents have long been discussed. The degenerating fibers originated from the CM were distributed diffusely in almost every thalamic nuclei. Different findings were reported as to the small number of commissur al fibers through the massa intermedia and the termination in the ventro medial part of the reticular nucleus. C lark and B oggon [2] and W ells [20] noticed these commissural fibers via the massa intermedia in their study of the MD lesion, but their origin remained unknown. According to the Golgi study by Scheibel and Scheibel [16], the CM-Pf complex with a richly branching system projected to virtually every thalamic field. These axons spread to the neuropil field of most midline nuclei, medial nuclei of both sides and to the portions of the ventral lateral nucleus (VL), the ventral anterior nucleus (VA), the dorsomedial nucleus (MD) and reticular nucleus. Terminal degenerations were observed in the hom olateral MD, CM, Pf, Pc, CL, VPM, VL and VA. These terminal degen erations were supposed to be attributed to the CM lesion, but we could not deduce definite conclusion from our materials. Concerning the cortical projection of the CM, recently B owsher [[1] and T otibadze and M oniava [19] reported that the CM projected to the motorsensory cortex. But these reports also have some limitations owing to the inevitable lesions, such as the needle track. Therefore, these reports have involved some controversies. To clarify the cortical projection from the CM, various approaches to the CM should be attempted.
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K uroda/M urui /A kagi/K amikawa/M ogami
(286)
References
Downloaded by: Vanderbilt University Library 129.59.95.115 - 10/29/2017 3:57:01 AM
1 Bowsher , D.: Some afferent and efferent connections of the parafascicular-center median complex; in P urpura The thalamus, pp. 99-108 (Columbia University Press, New York 1966). 2 C lark, W. E. L. and Boggon , R. H.: On the connections of the medial cell groups of the thalamus. Brain 56: 83-98 (1933). 3 DeVito, J. L.: Thalamic projection of the anterior ectosylvian gyrus (somatic area II) in the cat. J. comp. Neurol. 131: 462-475 (1969). 4 H irokawa, S.: Uber die Thalamuskerne der Katze. J. med. Sei. 9: 119-147 (1941). 5 J asper, H. H. and A jmone -M arsan, C.: A stereotaxic atals of the diencephalon of the cat (National Research Council of Canada, Ottawa 1960). 6 K usama, T. and K awana, E.: Projections of motor and somatic sensory cortices to subcortical nuclei, especial to thalamus. Recent Adv. neurol. Sei. 12: 325-340 (1968). 7 M ehler , W. A.; F eferman , M. E., and N auta, W. J. H.: Ascending axon degen eration following anterolateral cordotomy. An experimental study in the mon key. Brain 83: 718-750 (1960). 8 M ehler , W. A.: Further notes on the center median nucleus of Luys; in P ur pura The thalamus, pp. 109-127 (Columbia University Press, New York 1966). 9 M ehler , W. A.: Some observations on secondary ascending afferent systems in the central nervous system. Pain, Int. Symp. on Pain, pp. 11-32 (Little, Brown, Boston 1966). 10 M ogami, H.; K uroda, R.; H ayakawa, T.; Kanai, N., and Yamada, R.: Ascending pathways from nucleus caudalis of spinal trigeminal nucleus in cat. With special references to pain conducting pathways. Med. J. Osaka Univ. 19: 49-70 (1968). 11 M orest, D. K.: The neuronal architecture of the medial geniculate body of the cat. J. Anat., Lond. 98: 611-630 (1964). 12 N auta, W. J. H. and K uypers, H. G. H.: Some ascending pathways in the brain reticular formation. Reticular formation of the brain, pp. 1-20 (Little, Brown, Boston 1958). 13 P oggio , G. F. and M ountcastle, V. B.: A study of the functional contributions of the lemniscal and spinothalamic systems to somatic sensibilities. Central nerv ous mechanisms in pain. Johns Hopk. Hosp. Bull. 106: 266-316 (1960). 14 R invik , E.: The corticothalamic projection from the second somatosensory corti cal area in the cat. An experimental study with silver impregnation methods. Brain Res. 5: 153-172 (1968). 15 Rioch, D. M.: Studies on the diencephalon of carnivora. J. comp. Neurol. 49: 1-119 (1929). 16 Scheibel , M. E. and Scheibel , A. B.: Patterns of organization in specific and nonspecific thalamic fields; in P urpura The thalamus, pp. 13—46 (Columbia Uni versity Press, New York 1966). 17 Snider , R. S. and N iemer , W. T.: A stereotaxic atlas of cat brain (University of Chicago Press, Chicago 1961).
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18 Stewart , W. A. and K ing , R. B.: Fiber projections from the nucleus caudalis of the spinal trigeminal nucleus. J. comp. Neurol. 121: 271-286 (1963). 19 T otibadze, N. K. and M oniava, E. S.: On the direct cortical connections of the nucleus centrum medianum thalamic. J. comp. Neurol. 137: 347-360 (1960). 20 W ells , J.: The pathway from the dorsomedial thalamus to the frontal lobe. Exp. N eurol. 14: 338-351 (1966). 21 W hitlock , D. G. and Perl, E. R.: Afferent projections through ventrolateral
funiculi to thalamus of cat. J. Neurophysiol. 22: 133-148 (1959). 22 W hitlock , D. G. and P erl, E. R.: Thalamic projections of spinothalamic path ways in monkey. Exp. Neurol. 3: 240-255 (1961).
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Request reprints from: Dr. R. K uroda, Department of Neurosurgery, Osaka Uni versity Medical School, Osaka (Japan)
