- Email: [email protected]
Differential labeling of neural pathways converging on the ventrobasal complex of cat thalamus
342
Brain Research, 66 (1974) 342-348 O Elsevier ScientificPublishing Company, Amsterdam - Printed in The Netherlands
Differential labeling of neural pathways converging on the ventrobasal complex of cat thalamus
KAREN J. BERKLEY Department of Psychology, Florida State University, Tallahassee, Fla. 32306 (U.S.A.)
(Accepted October 9th, 1973)
Several experiments on the cat have demonstrated that cells in the dorsal column nuclei (DCN) project to the ventrobasal nuclear complex of the thalamus (VB) 1,10,14. These projections are contralateral, involve large-diameter axons, and terminate in a patchy pattern within VB. Electron microscopic evidence shows that the synaptic endings of these fibers are large (3-5 # m diameter) and contain round vesicles 14. Each terminal makes multiple synaptic contacts usually with the larger, more proximal portions of the dendritic tree8,1~,14,16. Other experiments on the cat have demonstrated that cells in the second somatosensory region of the cerebral cortex ($2), like those in DCN, also project to VB 4,9,10, ~,~a. These corticothalamic projections are ipsilateral, involve small-diameter axons, and terminate diffusely within VB. Electron microscope evidence shows that the synaptic endings of these fibers are small (1-2/zm diameter) and contain round vesicles 9A5. Each terminal forms synaptic contacts (usually only one) with a peripheral branch o f the dendritic tree8, 9A5,16. The reports mentioned above are based on the use of a single method o f 'labeling' pathways in the nervous system. This method makes use of the fact that degenerating neural tissue 'looks' different from normal tissue - - both under the electron and the light microscope. Taken together, these experiments suggest that, although the distribution and synaptic morphology of D C N and $2 terminals are different, both D C N and $2 cells send axons which converge on the same regions within VB, and possibly on the same cells. This suggestion of input convergence, however, has not yet been demonstrated directly. In order to provide such direct evidence it would be necessary to 'label' differentially in the same preparation the pathway from D C N to VB and the pathway from $2 to VB. Since the degeneration method of labeling has, until recently, been the only one available to neuroanatomists, it has been impossible to demonstrate directly the existence of convergence anywhere within the nervous system. A new method for 'labeling' pathways in the nervous system has been reported recently by Lasek et al. 1~ and by Cowan et al. 3. The method makes use of the normal transport system of the nerve cell in which proteins synthesized in the soma are
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transported distally to the terminals 13. Using this method, one injects a radioactively labeled amino acid precursor of proteins into a cell group and then searches by autoradiographic procedures a for the transported protein that identifies its efferent connections. Thus, while the degeneration method of labeling depends on cell damage, the autoradiographic method depends on cell transport for its success. Since there are now two different methods available for labeling pathways in the nervous system, it seemed feasible to use these two methods simultaneously in the same preparation in order to demonstrate directly the predicted convergence of D C N and $2 terminals on the same regions of VB. One could also use the preparation to demonstrate lack of convergence. For example, whereas the dorsal portion of the inferior olive has been shown to receive a projection from D C N 5, experimental studies by fiber-degeneration methods have failed to demonstrate cortico-olivary fibers arising in $2 2 (unpublished observations). Thus, the evidence suggests that fibers from $2 and D C N do not converge on the dorsal portion of the inferior olive. Furthermore, since the D C N and $2 projections are completely lateralized, it is also possible to use the same preparation as its own control (see below). To these ends, one could inject a radioactively labeled amino acid into $2 on one side (left) and ablate D C N on the other (right). Adjacent sections through the brain stem could then be processed using autoradiographic 3,7 and degeneration (Fink-
LEFT
RIGHT
DCN Fig. 1. Schematic diagram of the quadruple experimental manipulations and expected results of this study. (See text for details.) DCN, dorsal column nuclei: IOd, dorsal inferior olive; $2, second somatosensory region of cerebral cortex; VB, ventrobasal nuclear complex of thalamus. Dots indicate the presence of radioactively labeled protein (injection and termination sites). Slashes indicate sites of ablation or signs of degeneration.
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Fig. 2. Ablations and injections. The 4 procedures illustrated here were performed on the same day on the same cat observing aseptic precautions. Four days following surgery, the cat was anesthetized and perfused through the heart with 0.9)/o NaC1 and 10)o formaldehyde. The brain was removed and stored in sugar-formalin 6. The cortex and brain stem were frozen and cut in serial, 20/~m, coronal sections. Cortical sections at 240 #m intervals through the $2 region were processed using autoradiographic procedures3, v. Adjacent sections at 240/~m intervals through the brain stem from the level of D C N to anterior thalamus were processed using autoradiographic 3,v and Fink-Heimer 16 silver staining procedures, a: autoradiogram of a section cut through the left anterior ectosylvian gyrus ($2). The section was coated with diluted Kodak NTB-2 emulsion, exposed for 2 weeks, developed in D19 and stained with cresyl violet. Four injections of tritiated proline were made in the gyrus using a 1 #1 Hamilton syringe. Each injection of 0.2/d took 10 min to deliver. The isotope, obtained from New England Nuclear Corp., was dried under a nitrogen flow and redissolved in double-distilled water to a final concentration of 10/tCi//d. Note the heavier concentration of silver grains in the injection site (dotted line), b: coronal section through the ablated right anterior ectosylvian gyrus. The section was treated like the section in a. c: high power photomicrograph of the injected left cortical region shown in a. Note the heavy concentration of silver grains over the cell bodies. Calibration here and in d is 20/ma. d: high power photomicrograph, similar to c, but of the injected region in the left dorsal column nucleus shown in e. e: coronal section through the dorsal column nuclei. Two 0.3/~1 injections were made in the left D C N (one rostral and one caudal to the obex) with the same solution and at the same rate as in the left $2 cortex. The injections were followed by removal of most of the rostral-caudal extent of the right DCN. This section was treated like those shown in a and b. Note the heavy concentration of silver grains over cells in the left D C N injection site (dotted line) and the ablation of the right DCN.
H e i m e r ) 6 m e t h o d s . I n a specified r e g i o n o f
left
VB, o n e w o u l d e x p e c t to find l a b e l e d
p r o t e i n ( f r o m ipsilateral $2) in o n e s e c t i o n a n d signs o f t e r m i n a l d e g e n e r a t i o n ( f r o m c o n t r a l a t e r a l D C N ) in the a d j a c e n t section. By c o n t r a s t , l o o k i n g in the a p p r o p r i a t e region of the
left
d o r s a l i n f e r i o r olive, o n e w o u l d e x p e c t to find t e r m i n a l d e g e n e r a t i o n
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(from contralateral DCN) but, in the adjacent section, no radioactive label transported from $2. Next, one could apply the reverse strategy on the other side in the same animal - - e.g. ablate the right $2 and inject the left DCN. Of this procedure one would expect the opposite results. Such reversal of experimental procedures provides a control for the problems of retrograde degeneration inherent in the degeneration methods. Since the autoradiographic method labels fibers in only the orthograde direction11, orthograde (i.e. input) convergence would be clearly demonstrated only when both labeled protein a n d signs of degeneration are found in both the right and the left VB. This quadruple procedure and the expected results are schematized in Fig. 1. The ablations and injections of tritiated proline are illustrated and described in detail in Fig. 2. The predicted results were confirmed and are shown in Fig. 3. It should be noted that although the findings in only one experiment are shown and discussed in this paper, all of the results have been confirmed in 41 other cats subjected to either ablation of, and/or tritiated-proline injection in $2 or DCN. The photomicrographs in Fig. 3 confirm the predictions made above of (a) convergence of input from $2 and DCN fibers on the same region within VB and (b) lack of convergence of the two sets of fibers on the dorsal inferior olive. The results, moreover, are also consistent with electron microscopic evidence for a difference in the distribution and synaptic morphology of DCN and $2 terminals in VB. The autoradiograms in Fig. 4a and b show the distribution of labeled protein in VB. Much of this protein has presumably accumulated predominantly in the $2 and DCN terminals3. Fig. 4a shows that the labeled protein transported from $2 is distributed diffusely between the cells, far from the cell bodies in indistinct clusters about 5-10 #m in diameter. This distribution is consistent with electron microscopic evidence indicating that the small, 1-2/~m terminals from $2 are distributed diffusely in clusters on peripheral dendrites 9. (Measurements made on the electron micrographs in Figs. 1 and 2 of ref. 9 indicate that these clusters are about 7 #m in diameter.) Fig. 4b shows that the labeled protein transported from DCN is distributed in VB in disparate 'clumps', each of which is about 5/zm in diameter. These clumps occur in random relationship to the cell bodies. Electron microscopic evidence indicates that the terminals from DCN are 3-5 #m in diameter and form multiple synaptic contacts on various parts of the dendrites12,14,15. It thus seems possible that each of the 'clumps' of radioactive label appearing in the autoradiograph might correspond to a single DCN-axon terminal. In conclusion, it appears that the new autoradiographic-labeling method provides an excellent means for studying converging synaptic connections in the nervous system when it is combined with the older degeneration-labeling method. Although this study has focused on observations in the light microscope, the combined approach should be even more powerful when the electron microscope is used. It will then be possible to specify directly the convergence of several inputs on a single recipient structure (e.g. cell body, dendrite, axon). Supported by Grants PHS NS 02992, MH 11218, NB 7468, and NSF GU 2612.
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Fig. 4. Autoradiograms of $2 (a) and D C N (b) projections to VB. Calibration is 20/tm. a and b are from opposite sides of the same section in the same region of anterior VB. (See Fig. 3.) The arrows point to possible 'clusters' of $2 terminals in a and 'clumps' of D C N terminals in b. (See text for details.)
I t h a n k D r s . W. J. H . N a u t a a n d W. M . C o w a n f o r p e r m i t t i n g m e to visit t h e i r l a b o r a t o r i e s a n d o b s e r v e t h e i r r e s p e c t i v e t e c h n i q u e s . I t h a n k D r . J o h n E l a m f o r inv a l u a b l e advice. I t h a n k Drs. M . A. B e r k l e y a n d D . R. K e n s h a l o f o r t h e i r c o m m e n t s o n e a r l i e r d r a f t s o f this p a p e r . F i n a l l y , I t h a n k M r . R. P a r m e r f o r r e l i a b l e a n d c a p a b l e t e c h n i c a l assistance.
1 BolvIE, J., The termination in the thalamus and zona incerta of fibres from the dorsal column nuclei (DCN) in the cat. An experimental study with silver impregnation methods, Brain Research, 28 (1971) 459-490. 2 BRODAL,P., The corticopontine projection in the cat. Demonstration of a somatotopically organized projection from the second somatosensory cortex, Arch. ital. BioL, 106 (1968) 310-332. 3 COWAN, W. M., GOTTLIEB,D. I., HENDRICKSON, A. E., PRICE, J. L., AND WOOLSEY, T. A., The autoradiographic demonstration of axonal connections in the central nervous system, Brain Research, 37 (1972) 21-51. 4 DEVITO,J. L., Thalamic projection of the anterior ectosylvian gyrus (Somatic area II) in the cat, J. comp. Neurol., 131 (1967) 67-78. 5 EBBESSON,S. O. E., A connection between the dorsal column nuclei and the dorsal accessory olive, Brain Research, 8 (1968) 393-397. 6 FINK, R. P., AND HEIMER, L., Two methods for selective silver impregnation of degenerating axons and their synaptic endings in the central nervous system, Brain Research, 4 (1967) 369-374.
Fig. 3. Sign3 of degeneration and cell transport in VB and the dorsal inferior olive. Compare these photomicrographs with the diagram in Fig. 1. a, c, e, g are from the left; b, d, f, h are from the right side of the brain, a, b, c, d are from the same portion of anterior VB. e, f, g, h are from the same portion of dorsal inferior olive, a and b are from opposite sides of the same section; similarly for c and d, e and f, g and h. The section in c and d was adjacent (20/~m) to the section in a and b; similarly for e and f, g and h. All calibrations are 20 #m. a: degeneration in left VB of coarse fibers and terminals from the contralateral (right) DCN. b: degeneration in right VB of fine fibers and terminals from the ipsilateral (right) $2. c: silver grains in the left VB neuropil indicate transport from cells in the ipsilateral (left) $2. d: silver grains in the right VB neuropil indicate transport from cells in the contralateral (left) DCN. e: degeneration in left dorsal inferior olive of fine fibers and terminals from the contralateral (right) DCN. f: absence of degeneration in right dorsal inferior olive (no $2 projections). g: absence of silver grains in the neuropil of the left dorsal inferior olive (no $2 projections), h: silver grains in the neuropil of the right dorsal inferior olive indicate transport from cells in the contralateral (left) DCN.
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7 HENDRICKSON, A., MOE, L., AND NOBLE, B., Staining for autoradiography of the central nervous system, Stain Technol., 47 (1972) 283 290. 8 JONES, E. G., AND POWELL, T. P. S., Electron microscopy of synaptic glomeruli in the thalamic relay nuclei of the cat, Proc. roy. Soc. B, 172 (1969) 153-171. 9 JONES, E. G., AND POWELL, T. P. S., An electron microscopic study of the mode of termination of cortico-thalamic fibers within the sensory relay nuclei of the thalamus, Proc. roy. Soc. B, 172 (1969) 173-185. 10 JONES, E. G., AND POWELL, T. P. S., An analysis of the posterior group of thalamic nuclei on the basis of its afferent connections, J. comp. Neurol., 143 (1971) 185-215. 11 LASEK, R., JOSEPH, B. S., AND WHITLOCK,D. G., Evaluation of radioautographic neuroanatomical tracing method, Brabl Research, 8 (1968) 319-336. 12 LIEBERMAN,A. R., AND SPACEK,J., Synaptic glomeruli in the thalamus of the rat: Three-dimensional relationships between glomerular components, Experientia (Basel), 27 (1971) 788-789. 13 OCHS, S., Fast axoplasmic transport of materials in mammalian nerve and its integrative role, Ann. N.Y. Acad. Sci., 193 (1972) 43-58. 14 RALSTON, III, H. J., The synaptic organization of lemniscal projections to the ventrobasal thalamus of the cat, Brain Research, 14 (1969) 99-115. 15 RALSTON, III, H. J., The synaptic organization in the dorsal horn of the spinal cord and in the ventrobasal thalamus in the cat. In R. DUBNER AND Y. KAWAMURA(Eds.), Oral-facial Sensory and Motor Mechanisms, Appleton-Century-Crofts, New York, 1971, pp. 229-250. 16 RALSTON,III, H. J., AND HERMAN, M. M., The fine structure of neurons and synapses in the ventrobasal thalamus of the cat, Brain Research, 14 (1969) 77-97. 17 RINVIK, E., The corticothalamic projection from the second somatosensory cortical area in the cat. An experimental study with silver impregnation methods, Exp. Brain Res., 5 (1968) 153-172.
Brain Research, 66 (1974) 349-370
349
© Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
ABSTRACTS OF PAPERS presented at the
5th A N N U A L MEETING OF THE EUROPEAN BRAIN A N D BEHAVIOUR SOCIETY
September 2-5, 1973 Rotterdam (The Netherlands)
(Editor: Prof. H. G. J. M.
KUYPERS)
ELSEVIER SCIENTIFIC PUBLISHING COMPANY AMSTERDAM
Brain Research, 66 (1974) 342-348 O Elsevier ScientificPublishing Company, Amsterdam - Printed in The Netherlands
Differential labeling of neural pathways converging on the ventrobasal complex of cat thalamus
KAREN J. BERKLEY Department of Psychology, Florida State University, Tallahassee, Fla. 32306 (U.S.A.)
(Accepted October 9th, 1973)
Several experiments on the cat have demonstrated that cells in the dorsal column nuclei (DCN) project to the ventrobasal nuclear complex of the thalamus (VB) 1,10,14. These projections are contralateral, involve large-diameter axons, and terminate in a patchy pattern within VB. Electron microscopic evidence shows that the synaptic endings of these fibers are large (3-5 # m diameter) and contain round vesicles 14. Each terminal makes multiple synaptic contacts usually with the larger, more proximal portions of the dendritic tree8,1~,14,16. Other experiments on the cat have demonstrated that cells in the second somatosensory region of the cerebral cortex ($2), like those in DCN, also project to VB 4,9,10, ~,~a. These corticothalamic projections are ipsilateral, involve small-diameter axons, and terminate diffusely within VB. Electron microscope evidence shows that the synaptic endings of these fibers are small (1-2/zm diameter) and contain round vesicles 9A5. Each terminal forms synaptic contacts (usually only one) with a peripheral branch o f the dendritic tree8, 9A5,16. The reports mentioned above are based on the use of a single method o f 'labeling' pathways in the nervous system. This method makes use of the fact that degenerating neural tissue 'looks' different from normal tissue - - both under the electron and the light microscope. Taken together, these experiments suggest that, although the distribution and synaptic morphology of D C N and $2 terminals are different, both D C N and $2 cells send axons which converge on the same regions within VB, and possibly on the same cells. This suggestion of input convergence, however, has not yet been demonstrated directly. In order to provide such direct evidence it would be necessary to 'label' differentially in the same preparation the pathway from D C N to VB and the pathway from $2 to VB. Since the degeneration method of labeling has, until recently, been the only one available to neuroanatomists, it has been impossible to demonstrate directly the existence of convergence anywhere within the nervous system. A new method for 'labeling' pathways in the nervous system has been reported recently by Lasek et al. 1~ and by Cowan et al. 3. The method makes use of the normal transport system of the nerve cell in which proteins synthesized in the soma are
SHORT COMMUNICATIONS
343
transported distally to the terminals 13. Using this method, one injects a radioactively labeled amino acid precursor of proteins into a cell group and then searches by autoradiographic procedures a for the transported protein that identifies its efferent connections. Thus, while the degeneration method of labeling depends on cell damage, the autoradiographic method depends on cell transport for its success. Since there are now two different methods available for labeling pathways in the nervous system, it seemed feasible to use these two methods simultaneously in the same preparation in order to demonstrate directly the predicted convergence of D C N and $2 terminals on the same regions of VB. One could also use the preparation to demonstrate lack of convergence. For example, whereas the dorsal portion of the inferior olive has been shown to receive a projection from D C N 5, experimental studies by fiber-degeneration methods have failed to demonstrate cortico-olivary fibers arising in $2 2 (unpublished observations). Thus, the evidence suggests that fibers from $2 and D C N do not converge on the dorsal portion of the inferior olive. Furthermore, since the D C N and $2 projections are completely lateralized, it is also possible to use the same preparation as its own control (see below). To these ends, one could inject a radioactively labeled amino acid into $2 on one side (left) and ablate D C N on the other (right). Adjacent sections through the brain stem could then be processed using autoradiographic 3,7 and degeneration (Fink-
LEFT
RIGHT
DCN Fig. 1. Schematic diagram of the quadruple experimental manipulations and expected results of this study. (See text for details.) DCN, dorsal column nuclei: IOd, dorsal inferior olive; $2, second somatosensory region of cerebral cortex; VB, ventrobasal nuclear complex of thalamus. Dots indicate the presence of radioactively labeled protein (injection and termination sites). Slashes indicate sites of ablation or signs of degeneration.
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Fig. 2. Ablations and injections. The 4 procedures illustrated here were performed on the same day on the same cat observing aseptic precautions. Four days following surgery, the cat was anesthetized and perfused through the heart with 0.9)/o NaC1 and 10)o formaldehyde. The brain was removed and stored in sugar-formalin 6. The cortex and brain stem were frozen and cut in serial, 20/~m, coronal sections. Cortical sections at 240 #m intervals through the $2 region were processed using autoradiographic procedures3, v. Adjacent sections at 240/~m intervals through the brain stem from the level of D C N to anterior thalamus were processed using autoradiographic 3,v and Fink-Heimer 16 silver staining procedures, a: autoradiogram of a section cut through the left anterior ectosylvian gyrus ($2). The section was coated with diluted Kodak NTB-2 emulsion, exposed for 2 weeks, developed in D19 and stained with cresyl violet. Four injections of tritiated proline were made in the gyrus using a 1 #1 Hamilton syringe. Each injection of 0.2/d took 10 min to deliver. The isotope, obtained from New England Nuclear Corp., was dried under a nitrogen flow and redissolved in double-distilled water to a final concentration of 10/tCi//d. Note the heavier concentration of silver grains in the injection site (dotted line), b: coronal section through the ablated right anterior ectosylvian gyrus. The section was treated like the section in a. c: high power photomicrograph of the injected left cortical region shown in a. Note the heavy concentration of silver grains over the cell bodies. Calibration here and in d is 20/ma. d: high power photomicrograph, similar to c, but of the injected region in the left dorsal column nucleus shown in e. e: coronal section through the dorsal column nuclei. Two 0.3/~1 injections were made in the left D C N (one rostral and one caudal to the obex) with the same solution and at the same rate as in the left $2 cortex. The injections were followed by removal of most of the rostral-caudal extent of the right DCN. This section was treated like those shown in a and b. Note the heavy concentration of silver grains over cells in the left D C N injection site (dotted line) and the ablation of the right DCN.
H e i m e r ) 6 m e t h o d s . I n a specified r e g i o n o f
left
VB, o n e w o u l d e x p e c t to find l a b e l e d
p r o t e i n ( f r o m ipsilateral $2) in o n e s e c t i o n a n d signs o f t e r m i n a l d e g e n e r a t i o n ( f r o m c o n t r a l a t e r a l D C N ) in the a d j a c e n t section. By c o n t r a s t , l o o k i n g in the a p p r o p r i a t e region of the
left
d o r s a l i n f e r i o r olive, o n e w o u l d e x p e c t to find t e r m i n a l d e g e n e r a t i o n
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(from contralateral DCN) but, in the adjacent section, no radioactive label transported from $2. Next, one could apply the reverse strategy on the other side in the same animal - - e.g. ablate the right $2 and inject the left DCN. Of this procedure one would expect the opposite results. Such reversal of experimental procedures provides a control for the problems of retrograde degeneration inherent in the degeneration methods. Since the autoradiographic method labels fibers in only the orthograde direction11, orthograde (i.e. input) convergence would be clearly demonstrated only when both labeled protein a n d signs of degeneration are found in both the right and the left VB. This quadruple procedure and the expected results are schematized in Fig. 1. The ablations and injections of tritiated proline are illustrated and described in detail in Fig. 2. The predicted results were confirmed and are shown in Fig. 3. It should be noted that although the findings in only one experiment are shown and discussed in this paper, all of the results have been confirmed in 41 other cats subjected to either ablation of, and/or tritiated-proline injection in $2 or DCN. The photomicrographs in Fig. 3 confirm the predictions made above of (a) convergence of input from $2 and DCN fibers on the same region within VB and (b) lack of convergence of the two sets of fibers on the dorsal inferior olive. The results, moreover, are also consistent with electron microscopic evidence for a difference in the distribution and synaptic morphology of DCN and $2 terminals in VB. The autoradiograms in Fig. 4a and b show the distribution of labeled protein in VB. Much of this protein has presumably accumulated predominantly in the $2 and DCN terminals3. Fig. 4a shows that the labeled protein transported from $2 is distributed diffusely between the cells, far from the cell bodies in indistinct clusters about 5-10 #m in diameter. This distribution is consistent with electron microscopic evidence indicating that the small, 1-2/~m terminals from $2 are distributed diffusely in clusters on peripheral dendrites 9. (Measurements made on the electron micrographs in Figs. 1 and 2 of ref. 9 indicate that these clusters are about 7 #m in diameter.) Fig. 4b shows that the labeled protein transported from DCN is distributed in VB in disparate 'clumps', each of which is about 5/zm in diameter. These clumps occur in random relationship to the cell bodies. Electron microscopic evidence indicates that the terminals from DCN are 3-5 #m in diameter and form multiple synaptic contacts on various parts of the dendrites12,14,15. It thus seems possible that each of the 'clumps' of radioactive label appearing in the autoradiograph might correspond to a single DCN-axon terminal. In conclusion, it appears that the new autoradiographic-labeling method provides an excellent means for studying converging synaptic connections in the nervous system when it is combined with the older degeneration-labeling method. Although this study has focused on observations in the light microscope, the combined approach should be even more powerful when the electron microscope is used. It will then be possible to specify directly the convergence of several inputs on a single recipient structure (e.g. cell body, dendrite, axon). Supported by Grants PHS NS 02992, MH 11218, NB 7468, and NSF GU 2612.
346
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Fig. 4. Autoradiograms of $2 (a) and D C N (b) projections to VB. Calibration is 20/tm. a and b are from opposite sides of the same section in the same region of anterior VB. (See Fig. 3.) The arrows point to possible 'clusters' of $2 terminals in a and 'clumps' of D C N terminals in b. (See text for details.)
I t h a n k D r s . W. J. H . N a u t a a n d W. M . C o w a n f o r p e r m i t t i n g m e to visit t h e i r l a b o r a t o r i e s a n d o b s e r v e t h e i r r e s p e c t i v e t e c h n i q u e s . I t h a n k D r . J o h n E l a m f o r inv a l u a b l e advice. I t h a n k Drs. M . A. B e r k l e y a n d D . R. K e n s h a l o f o r t h e i r c o m m e n t s o n e a r l i e r d r a f t s o f this p a p e r . F i n a l l y , I t h a n k M r . R. P a r m e r f o r r e l i a b l e a n d c a p a b l e t e c h n i c a l assistance.
1 BolvIE, J., The termination in the thalamus and zona incerta of fibres from the dorsal column nuclei (DCN) in the cat. An experimental study with silver impregnation methods, Brain Research, 28 (1971) 459-490. 2 BRODAL,P., The corticopontine projection in the cat. Demonstration of a somatotopically organized projection from the second somatosensory cortex, Arch. ital. BioL, 106 (1968) 310-332. 3 COWAN, W. M., GOTTLIEB,D. I., HENDRICKSON, A. E., PRICE, J. L., AND WOOLSEY, T. A., The autoradiographic demonstration of axonal connections in the central nervous system, Brain Research, 37 (1972) 21-51. 4 DEVITO,J. L., Thalamic projection of the anterior ectosylvian gyrus (Somatic area II) in the cat, J. comp. Neurol., 131 (1967) 67-78. 5 EBBESSON,S. O. E., A connection between the dorsal column nuclei and the dorsal accessory olive, Brain Research, 8 (1968) 393-397. 6 FINK, R. P., AND HEIMER, L., Two methods for selective silver impregnation of degenerating axons and their synaptic endings in the central nervous system, Brain Research, 4 (1967) 369-374.
Fig. 3. Sign3 of degeneration and cell transport in VB and the dorsal inferior olive. Compare these photomicrographs with the diagram in Fig. 1. a, c, e, g are from the left; b, d, f, h are from the right side of the brain, a, b, c, d are from the same portion of anterior VB. e, f, g, h are from the same portion of dorsal inferior olive, a and b are from opposite sides of the same section; similarly for c and d, e and f, g and h. The section in c and d was adjacent (20/~m) to the section in a and b; similarly for e and f, g and h. All calibrations are 20 #m. a: degeneration in left VB of coarse fibers and terminals from the contralateral (right) DCN. b: degeneration in right VB of fine fibers and terminals from the ipsilateral (right) $2. c: silver grains in the left VB neuropil indicate transport from cells in the ipsilateral (left) $2. d: silver grains in the right VB neuropil indicate transport from cells in the contralateral (left) DCN. e: degeneration in left dorsal inferior olive of fine fibers and terminals from the contralateral (right) DCN. f: absence of degeneration in right dorsal inferior olive (no $2 projections). g: absence of silver grains in the neuropil of the left dorsal inferior olive (no $2 projections), h: silver grains in the neuropil of the right dorsal inferior olive indicate transport from cells in the contralateral (left) DCN.
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© Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
ABSTRACTS OF PAPERS presented at the
5th A N N U A L MEETING OF THE EUROPEAN BRAIN A N D BEHAVIOUR SOCIETY
September 2-5, 1973 Rotterdam (The Netherlands)
(Editor: Prof. H. G. J. M.
KUYPERS)
ELSEVIER SCIENTIFIC PUBLISHING COMPANY AMSTERDAM