Abstract
In this study we investigated the arrangement of synapses on local axon collaterals of Golgi-stained pyramidal neurons in the mouse cerebral cortex. As synaptic markers we considered axonal swellings visible at high magnification under the light microscope. Such axonal swellings coincide with synaptic boutons, as has been demonstrated in a number of combined light and electron microscopic studies. These studies also indicated that, in most cases, one bouton corresponds precisely to one synapse. Golgi-impregnated axonal trees of 20 neocortical pyramidal neurons were drawn with a camera lucida. Axonal swellings were marked on the drawings. Most swellings were ‘en passant’; occasionally, they were situated at the tip of short, spine-like processes. On axon collaterals, the average interval between swellings was 4.5 μm. On the axonal main stem, the swellings were always less densely packed than on the collaterals. Statistical analysis of the spatial distribution of the swellings did not reveal any special patterns. Instead, the arrangement of swellings on individual collaterals follows a Poisson distribution. Moreover, the same holds to a large extent for the entire collection of pyramidal cell collaterals. This suggests that a single Poisson process, characterized by only one rate parameter (number of synapses per unit length), describes most of the spatial distribution of synapses along pyramidal cell collaterals. These findings do not speak in favour of a pronounced target specificity of pyramidal neurons at the synaptic level. Instead, our results support a probabilistic model of cortical connectivity.
Similar content being viewed by others
References
Abeles M (1982) Local cortical circuits. Springer, Berlin Heidelberg New York
Abeles M (1991) Corticonics. Neural circuits of the cerebral cortex. Cambridge University Press, Cambridge, UK
Aertsen AMHJ, Gerstein GL (1991) Dynamic aspects of neuronal cooperativity: fast stimulus-locked modulations of ‘effective connectivity’. In: Krüger J (ed) Neuronal cooperativity. Springer, Berlin Heidelberg New York, pp 52–67
Aertsen A, Preissl H (1991) Dynamics of activity and connectivity in physiological neuronal networks. In: Schuster H (ed) Nonlinear dynamics and neuronal networks. VCH, Weinheim
Aertsen A, Erb M, Palm G (1994) Dynamics of functional coupling in the cerebral cortex: an attempt at a model-based interpretation. Physica D (in press)
Amir Y, Harel M, Malach R (1993) Cortical hierarchy reflected in the organization of intrinsic connections in macaque monkey visual cortex. J Comp Neurol 334:19–46
Blue ME, Parnavelas JG (1983) The formation and maturation of synapses in the visual cortex of the rat. II. Quantitative analysis. J Neurocytol 12:697–712
Braitenberg V (1978a) Cortical architectonics: general and areal. In: Brazier MAB, Petsche H (eds) Architectonics of the cerebral cortex. Raven Press, New York
Braitenberg V (1978b) Cell assemblies in the cerebral cortex. In: Heim R, Palm G (eds) Theoretical approaches to complex systems. (Lecture Notes in Biomathematics, vol 21). Springer, Berlin Heidelberg New York, pp 171–188
Braitenberg V, Schüz A (1991) Anatomy of the cortex. Statistics and geometry. Springer, Berlin Heidelberg New York
Callaway EM, Katz LC (1990) Emergence and refinement of clustered horizontal connections in cat striate cortex. J Neurosci 10:1134–1153
Colonnier M (1964) The tangential organization of the visual cortex. J Anat 98:327–344
Cox DR, Lewis PAW (1966) The statistical analysis of series of events. Methuen, London
Cragg BG (1967) The density of synapses and neurones in the motor and visual areas of the cerebral cortex. J Anat 101:639–654
DeFelipe J, Fairén A (1988) Synaptic connections of an interneuron with axonal arcades in the cat visual cortex. J Neurocytol 17:313–323
DeFelipe J, Conley M, Jones EG (1986) Long-range focal collateralization of axons arising from corticocortical cells in monkey sensorymotor cortex. J Neurosci 6:3749–3766
Feller W (1957) An introduction to probability theory and its applications. Wiley, New York
Foh E, Haug H, König M, Rast A (1973) Quantitative Bestimmung zum feineren Aufbau der Sehrinde der Katze, zugleich ein methodischer Beitrag zur Messung des Neuropils. Microsc Acta 75:148–168
Freund TF, Martin KAC, Smith AD, Somogyi P (1983) Glutamate decarboxylase-immunoreactive terminals of Golgi-impregnated axoaxonic cells and of presumed basket cells in synaptic contact with pyramidal neurons of the cat's visual cortex. J Comp Neurol 221:263–278
Gabbott PLA, Martin KAC, Whitteridge D (1987) Connections between pyramidal neurons in layer 5 of cat visual cortex (area 17). J Comp Neurol 259:364–381
Gilbert CD, Wiesel TN (1983) Clustered intrinsic connections in cat visual cortex. J Neurosci 3:1116–1133
Glaser EM, Ruchkin DS (1976) Principles of neurobiological signal analysis. Academic Press, New York
Greilich H (1984) Quantitative Analyse der cortico-corticalen Fernverbindungen bei der Maus. Thesis, University of Tübingen
Hebb D (1949) The organization of behavior. A neuropsychological theory. Wiley, New York
Hellwig B (1992) Dichte und Verteilung präsynaptischer Boutons auf Golgi-gefärbten Axonen. Ein Beitrag zur Synaptologie der Großhirnrinde. Thesis, University of Tübingen
Hellwig B, Schüz A (1989) Density and distribution of presynaptic boutons on Golgi-stained axons in the cerebral cortex of the mouse. In: Elsner N, Singer W (eds) Dynamics and plasticity in neuronal systems. Proceedings of the 17th Göttingen Neurobiology Conference. Thieme, Stuttgart
Hubel DH, Wiesel TN (1962) Receptive fields, binocular interaction and functional architecture in the cat's visual cortex. J Physiol 160:106–154
Kisvárday ZF (1992) An example for specific connections in the visual cortex. In: Aertsen A, Braitenberg V (eds) Information processing in the cortex. Experiments and theory. Springer, Berlin, Heidelberg New York, pp 23–27
Kisvárday ZF, Martin KAC, Freund TF, Maglóczky ZF, Whitteridge D, Somogyi P (1986) Synaptic targets of HRP-filled layer III pyramidal cells in the cat striate cortex. Exp Brain Res 64:541–552
Kisvárday ZF, Martin KAC, Friedlander MJ, Somogyi P (1987) Evidence for interlaminar inhibitory circuits in the striate cortex of the cat. J Comp Neurol 260:1–19
Leuchtenberg P, Aertsen A, Lohmann H, Nelken I (1993) A stochastical model of axonal branching patterns in the cortex. In: Elsner N, Heisenberg M (eds) Gene-brain-behaviour. Proceedings of the 21st Göttingen Neurobiology Conference. Thieme, Stuttgart, p 474
Lohmann H (1992) Axon collaterals of pyramidal cells in extrastriate visual cortex of the rat. In: Elsner N, Richter DW (eds) Rhythmogenesis in neurons and networks. Thieme, Stuttgart, p 348
Lund JS, Boothe RG (1975) Interlaminar connections and pyramidal neuron organisation in the visual cortex, area 17, of the macaque monkey. J Comp Neurol 159:305–334
Martin KAC, Whitteridge D (1984) Form, function and intracortical projections of spiny neurones in the striate visual cortex of the cat. J Physiol (Lond) 353:463–504
Matthews DA, Cotman C, Lynch G (1976) An electron microscopic tudy of lesion-induced synaptogenesis in the dentate gyrus of the adult rat. II. Reappearance of morphologically normal synaptic contacts. Brain Res 115:23–31
McGuire BA, Hornung JP, Gilbert CD, Wiesel TN (1984) Patterns of synaptic input to layer 4 of cat striate cortex. J Neurosci 4:3021–3033
McGuire BA, Gilbert CD, Rivlin PK, Wiesel TN (1991) Targets of horizontal connections in macaque primary visual cortex. J Comp Neurol 305:370–392
Nelken I (1992) A probabilistic approach to the analysis of propagation delays in large cortical axon trees. In: Aertsen A, Braitenberg V (eds) Information processing in the cortex. Experiments and theory. Springer, Berlin Heidelberg New York, pp 29–49
Ojima H, Honda CN, Jones EG (1991) Patterns of axon collateralization of identified supragranular pyramidal neurons in the cat auditory cortex. Cerebral Cortex 1:80–94
Pandya DN, Yeterian EH (1985) Architecture and connections of cortical association areas. In: Peters A, Jones EG (eds) Cerebral cortex. Association and auditory cortices. Plenum Press, New York, pp 3–61
Peters A (1970) The fixation of central nervous tissue and the analysis of electron micrographs of the neuropil, with special reference to the cerebral cortex. In: Nauta WJH, Ebbesson SOE (eds) Contemporary research methods in neuroanatomy. Springer, Berlin Heidelberg New York, pp 56–76
Peters A, Feldman ML (1976) The projection of the lateral geniculate nucleus to area 17 of the rat cerebral cortex. I. General description. J Neurocytol 5:63–84
Peters A, Jones EG (1984) Classification of cortical neurons. In: Peter A, Jones EG (eds) Cerebral cortex, Vol I Cellular components of the cerebral cortex. Plenum Press, New York, pp 107–121
Peters A, Proskauer CC (1980) Synaptic relationships between a multipolar stellate cell and a pyramidal neuron in the rat visual cortex. A combined Golgi-electron microscope study. J Neurocytol 9:163–183
Ramón y Cajal S (1911) Histologie du Système Nerveux de l'Homme et des Vertébrés, (translated by L. Azoulay). Consejo superior de investigaciones cientificas, Instituto Ramón y Cajal, Madrid, 1972
Rockland KS, Lund JS (1983) Intrinsic laminar lattice connections in primate visual cortex. J Comp Neurol 216:303–318
Schüz A (1989) Untersuchungen zur Verknüpfungsstruktur der Grohirnrinde. Quantitative Studien am Cortex der Maus. Thesis, University of Tübingen
Schüz A (1992) Randomness and constraints in the cortical neuropil. In: Aertsen A, Braitenberg V (eds) Information processing in the cortex. Experiments and theory. Springer, Berlin Heidelberg New York, pp 3–21
Schüz A, Münster A (1985) Synaptic density on the axonal tree of a pyramidal cell in the cortex of the mouse. Neuroscience 15:33–39
Schüz A, Palm G (1989) Density of neurons and synapses in the cerebral cortex of the mouse. J Comp Neurol 286:442–455
Sholl DA (1956) The organization of the cerebral cortex. Wiley, New York
Somogyi P (1978) The study of Golgi stained cells and experimental degeneration under the electron microscope: a direct method for the identification in the visual cortex of three successive links in a neuron chain. Neuroscience 3:167–180
Somogyi P, Cowey A (1981) Combined Golgi and electron microscopic study on the synapses formed by double bouquet cells in the visual cortex of the cat and monkey. J Comp Neurol 195:547–566
Somogyi P, Hodgson AJ, Smith AD (1979) An approach to tracing neuron networks in the cerebral cortex and basal ganglia. A combination of Golgi staining, retrograde transport of horseradish peroxidase and anterograde degeneration of synaptic boutons in the same material. Neuroscience 4:1805–1852
Somogyi P, Nunzi MG, Gorio A, Smith AD (1983a) A new type of specific interneuron in the monkey hippocampus forming synapses exclusively with the axon initial segments of pyramidal cells. Brain Res 259:137–142
Somogyi P, Kisvárday ZF, Martin KAC, Whitteridge D (1983b) Synaptic connections of morphologically identified and physiologically characterized large basket cells in the striate cortex of cat. Neuroscience 10:261–294
Vaadia E, Aertsen A (1992) Coding and computation in the cortex: single-neuron activity and cooperative phenomena. In: Aertsen A, Braitenberg V (eds) Information processing in the cortex. Experiments and theory. Springer, Berlin Heidelberg New York, pp 81–121
Valverde F (1970) The Golgi method. A tool for comparative structural analysis. In: Nauta WJH, Ebbesson SOE (eds) Contemporary research methods in neuroanatomy. Springer, Berlin Heidelberg New York
Vrensen G, deGroot D (1975) The effect of monocular deprivation on synaptic terminals in the visual cortex of rabbits. A quantitative electron microscopic study. Brain Res 93:15–24
White EL (1989) Cortical circuits. Synaptic organization of the cerebral cortex. Structure, function, and theory. Birkhäuser, Boston
White EL, Hersch SM (1981) Thalamocortical synapses of pyramidal cells which project from SmI to MsI in the mouse. J Comp Neurol 198:167–181
White EL, Keller A (1987) Intrinsic circuitry involving the local axon collaterals of corticothalamic projection cells in mouse SmI cortex. J Comp Neurol 262:13–26
Winfield DA, Brooke RNL, Sloper JJ, Powell TPS (1981) A combined Golgi-electron microscopic study of the synapses made by the proximal axon and recurrent collaterals of a pyramidal cell in the somatic sensory cortex of the monkey. Neuroscience 6:1217–1230
Wolff JR (1976) Quantitative analysis of topography and development of synapses in the visual cortex. Exp Brain Res [Suppl] 1:259–263
Zeki S, Shipp S (1989) Modular connections between areas V2 and V4 of macaque monkey visual cortex. Eur J Neurosci 1:494–506
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Hellwig, B., Schüz, A. & Aertsen, A. Synapses on axon collaterals of pyramidal cells are spaced at random intervals: a Golgi study in the mouse cerebral cortex. Biol. Cybern. 71, 1–12 (1994). https://doi.org/10.1007/BF00198906
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00198906