Structural Plasticity of Circuits in Cortical Neuropil
Open Access
- 20 August 2008
- journal article
- research article
- Published by Society for Neuroscience in Journal of Neuroscience
- Vol. 28 (34), 8477-8488
- https://doi.org/10.1523/jneurosci.2046-08.2008
Abstract
Learning and memory formation in the brain depend on the plasticity of neural circuits. In the adult and developing cerebral cortex, this plasticity can result from the formation and elimination of dendritic spines. New synaptic contacts appear in the neuropil where the gaps between axonal and dendritic branches can be bridged by dendritic spines. Such sites are termed potential synapses. Here, we describe a theoretical framework for the analysis of spine remodeling plasticity. We provide a quantitative description of two models of spine remodeling in which the presence of a bouton is either required or not for the formation of a new synapse. We derive expressions for the density of potential synapses in the neuropil, the connectivity fraction, which is the ratio of actual to potential synapses, and the number of structurally different circuits attainable with spine remodeling. We calculate these parameters in mouse occipital cortex, rat CA1, monkey V1, and human temporal cortex. We find that, on average, a dendritic spine can choose among 4–7 potential targets in rodents and 10–20 potential targets in primates. The potential of neuropil for structural circuit remodeling is highest in rat CA1 (7.1–8.6 bits/μm3) and lowest in monkey V1 (1.3–1.5 bits/μm3). We also evaluate the lower bound of neuron selectivity in the choice of synaptic partners. Postsynaptic excitatory neurons in rodents make synaptic contacts with >21–30% of presynaptic axons encountered with new spine growth. Primate neurons appear to be more selective, making synaptic connections with >7–15% of encountered axons.Keywords
This publication has 52 references indexed in Scilit:
- Synaptogenesis on mature hippocampal dendrites occurs via filopodia and immature spines during blocked synaptic transmissionJournal of Comparative Neurology, 2005
- A Study of Pyramidal Cell Structure in the Cingulate Cortex of the Macaque Monkey with Comparative Notes on Inferotemporal and Primary Visual CortexCerebral Cortex, 2004
- Class-Specific Features of Neuronal WiringNeuron, 2004
- Multiple synapse formation in the motor cortex opposite unilateral sensorimotor cortex lesions in adult ratsJournal of Comparative Neurology, 1999
- Cortical integration in the visual system of the macaque monkey: large-scale morphological differences in the pyramidal neurons in the occipital, parietal and temporal lobesProceedings Of The Royal Society B-Biological Sciences, 1999
- Mathematical Methods for Physicists, 4th ed.American Journal of Physics, 1999
- Critical assessment of the involvement of perforations, spinules, and spine branching in hippocampal synapse formationJournal of Comparative Neurology, 1998
- Analysis of dendritic spines in rat CA1 pyramidal cells intracellularly filled with a fluorescent dyeJournal of Comparative Neurology, 1995
- Map of the synapses formed with the dendrites of spiny stellate neurons of cat visual cortexJournal of Comparative Neurology, 1994
- Ferrier lecture - Functional architecture of macaque monkey visual cortexProceedings of the Royal Society of London. B. Biological Sciences, 1977