Cortical minicolumn

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A cortical minicolumn is a vertical column through the cortical layers of the brain. Neurons within the microcolumn "receive common inputs, have common outputs, are interconnected, and may well constitute a fundamental computational unit of the cerebral cortex".[1] Minicolumns comprise perhaps 80–120 neurons, except in the primate primary visual cortex (V1), where there are typically more than twice the number. There are about 2×108 minicolumns in humans.[2] From calculations, the diameter of a minicolumn is about 28–40 µm.[citation needed] Minicolumns grow from progenitor cells within the embryo and contain neurons within multiple layers (2–6) of the cortex.[3]

Many sources support the existence of minicolumns, especially Mountcastle,[4] with strong evidence reviewed by Buxhoeveden and Casanova[5] who conclude "... the minicolumn must be considered a strong model for cortical organization" and "[the minicolumn is] the most basic and consistent template by which the neocortex organizes its neurones, pathways, and intrinsic circuits".

Cortical minicolumns can also be called cortical microcolumns.[6] Cells in 50 µm minicolumn all have the same receptive field; adjacent minicolumns may have different fields.[7]

Number of neurons[edit]

Estimates of number of neurons in a minicolumn range from 80–100 neurons.[5][4][8]

Jones[9] describes a variety of observations that may be interpreted as mini- or micro-columns and gives example numbers from 11 to 142 neurons per minicolumn.

Number of minicolumns[edit]

Estimates of the number of neurons in cortex or in neocortex are on the order of 2×1010.[10][11] Most[12] (perhaps 90%[citation needed]) of cortical neurons are neocortical neurons.

Johansson and Lansner[2] use an estimate of 2×1010 neurons in the neocortex and an estimate of 100 neurons per minicolumn, yielding an estimate of 2×108 minicolumns.

Sporns et al. give an estimate of 2×107 – 2×108 minicolumns[13] with no derivation.[citation needed]

Size[edit]

The minicolumn measures of the order of 40–50 µm in transverse diameter[4][5]; 35–60 µm;[14][15] 50 µm with 80 µm spacing,[16] or 30 µm with 50 µm.[17] Larger sizes may not be of human minicolumns, for example macaque monkey V1 minicolumns are 31 µm diameter, with 142 pyramidal cells (Peters, 1994) — 1270 columns per mm2. Similarly, the cat V1 has much bigger minicolumns, ~56 µm.[18]

The size can also be calculated from area considerations. If cortex (both hemispheres) is 1.27×1011 µm2 then if there are 2×108 minicolumns in the neocortex then each is 635 µm2, giving a diameter of 28 µm (if the cortex area were doubled to the commonly quoted value, this would rise to 40 µm). Johansson and Lansner[2] do a similar calculation and arrive at 36 µm (p51, last para).

Downwards projecting axons in minicolumns are ≈10 µm in diameter, periodicity and density similar to those within the cortex, but not necessarily coincident.[19]

See also[edit]

References[edit]

  1. ^ "Microcolumns in the Brain". www.physics.drexel.edu. Retrieved 2017-12-31. 
  2. ^ a b c Johansson, Christopher; Lansner, Anders. "Towards cortex sized artificial neural systems". Neural Networks. 20 (1): 48–61. doi:10.1016/j.neunet.2006.05.029. 
  3. ^ Jeff Hawkins, Sandra Blakeslee On Intelligence p. 94
  4. ^ a b c Mountcastle, V. B. (April 1997). "The columnar organization of the neocortex". Brain: A Journal of Neurology. 120 ( Pt 4): 701–722. ISSN 0006-8950. PMID 9153131. 
  5. ^ a b c Buxhoeveden, Daniel P.; Casanova, Manuel F. (May 2002). "The minicolumn hypothesis in neuroscience". Brain: A Journal of Neurology. 125 (Pt 5): 935–951. ISSN 0006-8950. PMID 11960884. 
  6. ^ "Microcolumns in the Brain". www.physics.drexel.edu. Retrieved 2017-12-31. 
  7. ^ Jones 2000.
  8. ^ Sporns O, Tononi G, Kötter R. The human connectome: A structural description of the human brain. PLoS Comput. Biol. 2005 Sep1(4):e42.
  9. ^ Jones, Edward G. (2000-05-09). "Microcolumns in the cerebral cortex" (harv). Proceedings of the National Academy of Sciences. 97 (10): 5019–5021. doi:10.1073/pnas.97.10.5019. ISSN 0027-8424. PMID 10805761. 
  10. ^ Pakkenberg, B., & Gundersen, H. J. G. (1997). Neocortical Neuron Number in Humans: Effect of Sex and Age. The Journal of Comparative Neurology, 384, 312–320.
  11. ^ Azevedo, F. A.C., Carvalho, L. R.B., Grinberg, L. T., Farfel, J. M., Ferretti, R. E.L., Leite, R. E.P., Filho, W. J., Lent, R. and Herculano-Houzel, S. (2009), Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain. J. Comp. Neurol., 513: 532–541. doi: 10.1002/cne.21974
  12. ^ Claudia Krebs MD PhD, Joanne Weinberg PhD, Elizabeth Akesson MSc. Lippincott’s Illustrated Reviews: Neuroscience, accessed Nov 10 2013. Chapter 13, II.A, "Histological organization of the cortex"
  13. ^ Sporns O, Tononi G, Kötter R. The human connectome: A structural description of the human brain. PLoS Comput. Biol. 2005 Sep1(4):e42
  14. ^ Schlaug 1995.
  15. ^ Buxhoeveden 1996, 2000, 2001
  16. ^ Buldyrev, 2000
  17. ^ Buxhoeveden, 2000
  18. ^ Peters 1991, 1993
  19. ^ DePhilipe, 1990

External links[edit]

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