Journal of Computational Neuroscience

, Volume 10, Issue 1, pp 71–77 | Cite as

Brain Size and Number of Neurons: An Exercise in Synthetic Neuroanatomy

  • Valentino Braitenberg


Certain remarkable invariances have long been known in comparative neuroanatomy, such as the proportionality between neuronal density and the inverse of the cubic root of brain volume or that between the square root of brain weight and the cubic root of body weight. Very likely these quantitative relations reflect some general principles of the architecture of neuronal networks. Under the assumption that most of brain volume is due to fibers, we propose four abstract models: I, constant fiber length per neuron; II, fiber length proportionate to brain diameter; III, complete set of connections between all neurons; IV, complete set of connections between compartments each containing the square root of the total number of neurons. Model I conforms well to the cerebellar cortex. Model II yields the observed comparative invariances between number of neurons and brain size. Model III is totally unrealistic, while Model IV is compatible with the volume of the hemispheric white substance in different mammalian species.

comparative neuroanatomy allometric relations brain volume 


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Copyright information

© Kluwer Academic Publishers 2001

Authors and Affiliations

  • Valentino Braitenberg
    • 1
    • 2
    • 3
  1. 1.Max-Planck Institute for Biological Cybernetics
  2. 2.Institute of Medical Psychology of the University
  3. 3.Tübingen; Laboratorio di Scienze Cognitive dell'Università degli Studi di TrentoRovereto

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